Volume One May Be Consulted.

=201. Method of Boussingault.=—The official French method is essentially the original method of Boussingault with slight modifications. It is conducted as follows: In case the sample is ammonium sulfate about half a gram is placed in a flask of half a liter capacity, together with 300 cubic centimeters of distilled water and two grams of caustic magnesia. The flask is connected with a condenser of glass or metal which ends in a tube drawn out to a point and dipping beneath the set acid in the receiver in the usual way. The acid is colored with litmus or lacmoid tincture. The distillation is continued until about 100 cubic centimeters have gone over. The receiver is then removed with the usual precautions and the residual acid titrated. Suppose twenty cubic centimeters of normal acid have been employed and twelve and a half cubic centimeters of normal alkali be necessary to neutralize the excess of the acid. Then the nitrogen is found by the following equations: 20.0 - 12.5 = 7.5 and 7.5 × 0.014 = 0.105 gram = weight of nitrogen found. Then 0.105 × 100 ÷ 5 = 21.00 = per cent of nitrogen found.

The distilling apparatus of Aubin is preferred by the French chemists, an apparatus so arranged with a reflux partial condenser, that nearly all the aqueous vapor is returned in a condensed state to the flask while the ammonia, on account of its great volatility, is carried over into the receiver. To avoid the regurgitation which might be caused by the concentrated ammonia gas coming in contact with the acid the separable part of the condensing tube is expanded into a bulb large enough to hold all the acid which lies above its mouth. By the means of this apparatus the ammonia is all collected in the standard acid without greatly increasing its volume and the titration is thus rendered sharper. The employment of caustic magnesia has the advantage of not decomposing any organic matters or cyanids that may be present.

If the sample under examination hold part of its ammonia as ammonium magnesium phosphate it will be necessary first to treat it with sulfuric acid in order to set the ammonia free and then to use enough of the magnesium oxid to neutralize the excess of the sulfuric acid and still supply the two grams necessary for the distillation. When the sample contains a considerable quantity of organic matter it sometimes tends to become frothy towards the end of the distillation. This trouble can be avoided by introducing into the flask one or two grams of paraffin.

Where carbon dioxid is given off during the distillation the contents of the receiver must be boiled before titration, or else lacmoid must be used as an indicator instead of litmus.

=202. Determination of Thiocyanates in Ammoniacal Fertilizers.=—The extended use of ammonium sulfate as a fertilizer renders it important to determine the actual constituents which may be present in samples of this material. The following bodies have been found in commercial ammonium sulfates: Sulfuric acid, chlorin, ammonia, thiocyanic acid, potash, soda, lime and iron oxid. These are found in the soluble portions. In the insoluble portions have been found silica, sulfuric acid, lime, magnesia and iron oxid. A sample of commercial ammonium sulfate analyzed by Jumeau contained the following substances:

Per cent. Moisture 10.5109 Ammonium sulfate 67.8453 Ammonium thiocyanate 9.3935 Sodium sulfate 9.2429 Potassium sulfate 0.9774 Calcium sulfate 0.6800 Iron thiocyanate 0.5000 Magnesium chlorid traces Silica 0.0830 Undetermined 0.7670

The determination of the thiocyanic acid in the thiocyanate is generally made by the oxidation of the sulfur to sulfuric acid and its subsequent weighing in the form of barium sulfate. Jumeau has modified the method by determining the amount of the thiocyanate by means of a titrated liquid. The method is practiced as follows:

A solution of ammonium thiocyanate is prepared, containing eight grams of this salt per liter, and its exact content of thiocyanate is rigorously determined by titration with silver nitrate or by the weight of the barium sulfate produced after the oxidation of the sulfur. Ten cubic centimeters of the titrated liquor are taken and diluted with water to about 100 cubic centimeters and ten cubic centimeters of pure sulfuric acid added. Afterward, drop by drop, a solution of potassium permanganate is added, containing about ten grams of that salt per liter. The permanganate is instantly decolorized. There is an evolution of hydrocyanic acid as the thiocyanate passes to the state of sulfuric acid. A single drop in excess gives to the mixture the well-known rose coloration of the permanganate solution which persists for several hours. The number of cubic centimeters necessary to produce the persistent rose tint is noted and the same operation is carried on with from one-half to one gram of the unknown product which is to be assayed. A simple proportion indicates the content of the thiocyanate in the unknown body. The process is of great exactitude and permits the rapid determination of thiocyanic acid in the presence of chlorids, cyanids, etc., which remain without action upon the permanganate. In case chlorids and cyanids are absent the thiocyanate can be determined directly by silver nitrate either by weighing the precipitate or by the process of Volhardt based upon the precipitation of the silver by thiocyanate in the presence of a ferric salt. The end of the reaction is indicated by the red coloration which the liquid shows when the thiocyanate is in excess.

=203. Separation of Albuminoid from Amid and Other Forms of Nitrogen in Organic Fertilizers.=—It may be of interest to the dealer, farmer, and analyst, to discriminate between the albuminoid and other nitrogen in fertilizers, such as oil-cakes. The final value of the nitrogen for plant nourishment is not greatly different, but the immediate availability for nitrification is a matter of some importance. The most convenient process in such a case is the copper hydroxid separation process as improved by Stutzer. The process is conveniently carried out in accordance with the method prescribed by the official chemists.

Total Crude Protein.—Determine nitrogen as directed for nitrogen in fertilizers and multiply the result by 6.25 for the crude protein.

Determination of Albuminoid Nitrogen.—To from seven-tenths to eight-tenths gram of the substance in a beaker add 100 cubic centimeters of water, heat to boiling, or in the case of substances rich in starch, heat on the water-bath ten minutes, and add a quantity of cupric hydroxid mixture containing from one-half to six-tenths gram of the hydroxid; stir thoroughly, filter when cold, wash with cold water, and put the filter and its contents into the concentrated sulfuric acid for the determination of nitrogen. The filter-papers used must be practically free of nitrogen. Add sufficient potassium sulfid solution to completely precipitate all copper and mercury, and proceed as in the moist combustion process for nitrogen. If the substance examined consist of seed of any kind, or residues of seeds, such as oil-cake or anything else rich in alkaline phosphates, add a few cubic centimeters of a concentrated solution of alum just before adding the cupric hydroxid, and mix well by stirring. This serves to decompose the alkaline phosphates. If this be not done cupric phosphate and free alkali may be formed, and the protein-copper may be partially dissolved in the alkaline liquid.

Cupric Hydroxid.—Prepare the cupric hydroxid as follows: Dissolve 100 grams of pure cupric sulfate in five liters of water, and add twenty-five cubic centimeters of glycerol; add a dilute solution of sodium hydroxid until the liquid is alkaline; filter, rub the precipitate up with water containing five cubic centimeters of glycerol per liter, and then wash by decantation or filtration until the washings are no longer alkaline. Rub the precipitate up again in a mortar with water containing ten per cent of glycerol, thus preparing a uniform gelatinous mass that can be measured out with a pipette. Determine the quantity of cupric hydroxid per cubic centimeter of this mixture.

Amid Nitrogen.—The albuminoid nitrogen determined as above subtracted from the total, gives that part of the organic nitrogen existing in the sample as amids and in other allied forms.

=204. Separation of Nitric and Ammoniacal from Organic Nitrogen.=—The nitrogen being present in three forms, viz., organic, ammoniacal, and nitric, the separation of the latter two may be accomplished by the following procedure: One gram of the fertilizer is exhausted on a small filter with a two per cent solution of tannin, using from thirty to forty cubic centimeters in small portions. This is sufficient to dissolve all the nitrates and the greater portion of the ammoniacal salts, while the tannin renders insoluble all the organic nitrogenous compounds. The filter and its contents are treated for nitrogen by the kjeldahl process. When the distillation and titration are completed the solution obtained by the aqueous tannin is added to the distilling flask and the operation continued. This represents the ammoniacal nitrogen.

The nitric acid is estimated by the ferrous iron or other appropriate method in another portion of the substance.

This method can be used even when the fertilizer contains ammonium magnesium phosphate. In this case digest one gram for fifteen hours in dilute soda-lye solution, which easily dissolves the ammonium magnesium phosphate. Filter and wash the insoluble part with the tannin solution. The residue is treated as above. The filtered solution distilled with soda-lye furnishes the ammonia. The nitrates are estimated by one of the methods above mentioned.

=205. Nitric Nitrogen.=—The methods of estimating nitric nitrogen, both when present in weighable quantities and as mere traces have been sufficiently described in the first volume. For convenience, however, the standard methods of procedure will be given here. The moist combustion methods adapted to nitrates and the volumetric copper oxid process have already been described. Of the reduction methods the process of Ulsch is one of the easiest of application and also reliable. As practiced by the official chemists the manipulation is conducted as described in the first volume, page 539.

=206. Ulsch Method, Applicable to Mixed Fertilizers.=—The method of Ulsch which is found to give good results with pure nitrates or with nitrates in the absence of other forms of nitrogen may also be adapted to mixed fertilizers containing nitrogen in more than one form. Street has developed such a method and shown, by analytical data, that it is applicable in a great number of cases. The process is based on the substitution of magnesia for soda in the distillation and is carried on as follows:

Place one gram of the sample in a half liter flat-bottomed flask. Add about thirty cubic centimeters of water, one gram of reduced iron, and ten cubic centimeters of sulfuric acid diluted with an equal volume of water, shake well, and allow to stand for a short time. This will remove the danger of an explosion caused by the otherwise violent action which takes place. Close the neck of the flask with a rubber stopper through which passes a glass dropping-bulb filled with water. The flask having been stoppered, place it on a slab to which a moderate heat is applied. Allow the solution to come slowly to a boil and then boil for five minutes and cool. Add about 100 cubic centimeters of water, a little paraffin, and about five grams of magnesium oxid. Boil for forty minutes, after which time all the ammonia will be distilled, and collect the ammonia in set acid.

The magnesia causes a slight frothing, which can easily be controlled by adding a little paraffin and by bringing to a boil very gradually. Fully forty minutes are necessary to distil all the ammonia. Tests were made after thirty minutes boiling and traces of ammonia were still found; after forty minutes these traces entirely disappeared.

The method is a quick one. One man can easily do six determinations at a time, and these six determinations can be made in but a little over an hour. Magnesia gives results closely agreeing with theory and causes a very slight frothing, which can be easily controlled. One gram of reduced iron is sufficient in all ordinary complete fertilizers.

Magnesia is preferred to caustic soda in the distillation because it produces less frothing and by reason of the danger of some of the soda-lye being carried over mechanically and thus tending to produce an error of a plus nature. In the use of magnesia, assurance must be had that it is strongly in excess. Being less active in its effects a longer time for the distillation must be taken than when soda-lye is used. The modified ulsch method just described is recommended provisionally and with the expectation that each analyst will ascertain its true merits before allowing it to displace longer approved processes.

=207. Method of Schlösing-Wagner.=—The Schlösing-Wagner method for estimating nitrogen in the nitrates of fertilizers is carried out at the Halle Experiment Station as follows:

A flask, figure 14, of about 250 cubic centimeters capacity, is provided with a rubber stopper with two holes. Through one of them is passed the stem of a funnel carrying a glass stop-cock. The other carries a delivery-tube leading to the receiving vessel. The end of the delivery tube is bent so as to pass easily under the mouth of the measuring burette and is covered with a piece of rubber tubing.

Fifty cubic centimeters of saturated ferrous chlorid solution and the same quantity of ten per cent hydrochloric acid are placed in the flask. The ferrous chlorid solution is obtained by dissolving nails or other small pieces of iron in hot hydrochloric acid and it is kept in glass stoppered flasks, of about fifty cubic centimeters capacity, entirely filled. The content of one flask is enough for about twelve determinations and by using the whole content of a flask as soon as possible after opening, any danger of oxidation which would take place in a large flask frequently opened is avoided.

The contents of the flask are boiled until all the air is driven off. The delivery-tube is then placed under the measuring-tube, which is filled with forty per cent potash-lye. The measuring-tube is previously almost filled with potash-lye and then a few drops of water added and the tube covered with a piece of filter-paper. By a careful and quick inversion the measuring-tube can be brought into the vessel receiving it without any danger of air entering. The boiling is continued for some time and when no more air escapes, the end of the delivery-tube is brought into another freshly filled measuring-tube and the estimation is commenced.

Ten cubic centimeters of a normal saltpeter solution, containing two and a half grams of pure sodium nitrate in 100 cubic centimeters are placed in the funnel and, with continued boiling, allowed to pass, drop by drop, into the flask. When almost all has run out the funnel is washed three times with ten cubic centimeters of ten per cent hydrochloric acid and this is allowed to pass, drop by drop, into the flask. When no more nitric oxid is evolved the measuring-tube is transferred to a large jar filled with distilled water.

The solution of the substance to be examined should be taken in such quantity as will give about the same quantity of gas as is furnished by the ten cubic centimeters test nitrate solution before described; viz., about seventy cubic centimeters. Eight or ten determinations can be made, one following the other, and at the end another determination with normal sodium nitrate solution should be made as a check. At the end of the operation all of the measuring-tubes are in the large jar filled with distilled water. The temperature of the surrounding water will soon be imparted to the contents of each tube and the volume of nitric oxid is read by bringing the level within and without the measuring-tube to the same point. The percentages are calculated for the given temperature and barometer pressure in the usual way; or to avoid computation the volume can be compared directly with the volume furnished by a normal nitrate solution, which is a much simpler method.

=208. Schmitt’s Modified Method.=—The method is a modification of that already described by the author in which a mixture of powdered zinc and iron is used as a reducing agent. The process is carried out as follows: Ten grams of the nitrate are dissolved and the volume made up to half a liter. Ten cubic centimeters of glacial acetic acid and ten grams of the fine metallic powder, iron and zinc, are placed in a flask of a capacity of about three-quarters of a liter and twenty-five cubic centimeters of the solution of the nitrate added. The flask is covered during the reduction to prevent loss by spraying, and after the solution is complete, which is the case in about ten minutes, the contents of the flask are diluted with from 200 to 300 cubic centimeters of water, thirty cubic centimeters of caustic soda of 1.25 specific gravity added, and the whole distilled as in the kjeldahl process. It must be noted that it is essential that the iron be finely divided; it is mixed with the powdered zinc in equal parts. The total nitrogen can be determined in guanos and nitrate mixtures by the following simple alteration in procedure: One gram of the substance is dissolved in water, five cubic centimeters of glacial acetic acid, and from two to three grams of the mixed metallic powder added, and the whole gently heated for ten or fifteen minutes. After the contents of the flask have cooled, twenty-five cubic centimeters of sulfuric acid are cautiously added in small portions, undue frothing being restrained by the addition of a fragment of paraffin wax. The acetic acid is then driven off by heating, and the remaining contents of the flask boiled until the organic matter is completely decomposed, as in the kjeldahl process. About two hours boiling is required. Neutralization and distillation are then practiced as in the ordinary manner. The method is also applicable to the determination of nitrates in drinking water, provided nitrites and ammonia be absent.

=209. Krüger’s Method for Nitric Acid.=—About three-tenths gram of the substance dissolved in water is mixed with twenty cubic centimeters of a hydrochloric acid solution of stannous chlorid holding 150 grams of tin per liter. One and a half grams of spongy tin prepared by the action of zinc on stannous chlorid are added. The flask containing the mixture is heated until the tin is dissolved, by which time the nitric acid is completely reduced. The subsequent distillation and titration are accomplished as usual. In the case of nitro and nitroso compounds, after the solution of the tin, twenty cubic centimeters of sulfuric acid are added and heated until sulfuric vapors escape. After cooling, the amido substances formed are oxidized by potassium bichromate before the distillation takes place.

Krüger also estimates the nitrogen in benzol, pyridin, and chinolin derivatives by dissolving them in sulfuric acid, using from two-tenths to eight-tenths of a gram of the alkaloidal bodies and, after cooling the solution, oxidizing by adding finely powdered potassium bichromate. About half a gram more of the potassium bichromate should be used than is necessary for the oxidation of the substances in solution. The entire oxidation does not consume more than from fifteen to thirty minutes.

SODIUM NITRATE.

=210. Functions of Sodium Nitrate.=—Practically the only form of oxidized nitrogen which is of importance from an agronomic point of view is sodium nitrate, often known in commerce by the name Chile saltpeter. Applied to a growing crop it at once becomes dissolved at the first rainfall or by the natural moisture of the soil. It carries thus to the rootlets of plants a supply of nitrogen in the most highly available state. There is perhaps no other kind of plant food which is offered to the living vegetable in a more completely predigested state, and none to which a quicker response will be given. By reason of its high availability, however, it must be used with care. A too free use of such a stimulating food may have, in the end, an injurious effect upon the crop, and is quite certain to lead to the waste of a considerable portion of expensive material. For this reason sodium nitrate should be applied with extreme care, in small quantities at a time and only when it is needed by the growing crop. It would be useless, for instance, to apply this fertilizer in the autumn with the expectation of its benefitting the crop to a maximum degree the following spring. Again, if the application of this salt should be made just previous to a heavy rain almost or quite the whole of it would be removed beyond the reach of the absorbing organs of the plant.

When once the nitric acid has been absorbed by the living rootlet it is held with great tenacity. Living plants macerated in water give up only a trace of nitric acid, but if they be previously killed with chloroform the nitric acid they contain is easily leached out.

The molecule of sodium nitrate is decomposed in the process of the absorption of the nitric acid. The acid enters the plant organism and the soda is excreted and left to combine with the soil acids. The nascent soda may thus play a role of some importance in decomposing particles of minerals containing potash or phosphoric acid. It is probable that the decomposition of the sodium nitrate takes place in the cells of the absorbing plant organs for it is difficult to understand how it could be accomplished externally. While the soda therefore is of no importance as a direct plant food it can hardly be dismissed as of no value whatever in the process of fertilization. Many of the salts of soda as, for instance, common salt, are quite hygroscopic and serve to attract moisture from the air and thus become carriers of water between the plant and the air in seasons of drought; and sodium nitrate itself is so hygroscopic as not to be suited to the manufacture of gunpowder.

To recapitulate: The chief functions of sodium nitrate are to give to the plant a supply of oxidized nitrogen ready for absorption into its tissues and incidentally to aid, by the residual soda, in the decomposition of silt particles containing potash or phosphoric acid and in supplying to the soil salts of a more or less deliquescent nature.

=211. Commercial Forms of Chile Saltpeter.=—The Chile saltpeter of commerce may reach the farmer or analyst in the lumpy state in which it is shipped or as finely ground and ready for application to the fields. Unless the farmer is provided with means for grinding, the latter condition is much to be preferred. It permits of a more even distribution of the salt and thus encourages economy in its use. For the chemist also it is advantageous to have the finely ground material, which condition permits more easily a perfect sampling, a process which, with the unground salt, is attended with no little difficulty.

=212. Percentage of Nitrogen in Chile Saltpeter.=—Chemically pure sodium nitrate contains 16.49 per cent of nitrogen. The salt of commerce is never pure. It contains moisture, potash, magnesia, lime, sulfur, chlorin, iodin, silica and insoluble materials, and traces of other bodies. The value of the salt depends, therefore, not only on the market value of nitrogen at the time of sale, but also on its content of nitrogen. The nitrate of commerce varies greatly in its nitrogen content and is sold on a guaranty of its purity. The best grades range in nitrogen from fifteen to sixteen per cent. The content of nitrogen has long been estimated in the trade by determining the other constituents and counting the rest as nitrogen. This practice arose in former times when no convenient method was at hand for determining nitric nitrogen. The process is tiresome and unreliable because all errors of every kind are accumulated in the nitrogen content, but inasmuch as the method is still required by many merchants, the analyst should be acquainted with it, and it is therefore given further along. The usual methods for determining nitric nitrogen may be applied in all cases where samples of sodium nitrate are under examination, but some special processes are added for convenience.

=213. Adulteration of Chile Saltpeter.=—The analyst is the only protector of the farmer in guarding against the practice of adulteration of sodium nitrate aside from the honesty of the dealer. Even the honest dealer is compelled to protect himself against fraud, and therefore, the world over, commerce in this fertilizer is now conducted solely on the analyst’s certificate. Happily, therefore, adulteration is almost unknown because it is certain to be detected. Formerly, the saltpeter was adulterated with common salt, or low grade salts from the potash mines; but it is an extremely rare thing now to find any impurities in the salts other than those naturally present.

In every case the analyst may grow suspicious when he finds the content of nitrogen in a sample to fall below thirteen per cent. It must not be forgotten, however, that some potassium nitrate may be present in the sample, and since that salt contains only 13.87 per cent of nitrogen its presence would tend to lower the value of the fertilizer; but although the potash itself is a fertilizer of value it is not worth more than one-third as much as nitrogen. In all cases of suspected adulteration, it is advisable to make a complete analysis. The results of this work will, as a rule, lead the analyst to a correct judgment.

=214. The Halle Zinc-Iron Method.=—For determining the nitrogen in Chile saltpeter the reduction method is conducted at the Halle Station as follows: Ten grams of the nitrate are dissolved in one liter and fifty cubic centimeters of the solution corresponding to half a gram of the sample, taken for each determination. The apparatus employed is shown in Fig. 15. A mixture of five grams of zinc dust and an equal weight of iron filings is employed as the source of hydrogen. The reduction takes place in an alkaline medium secured by adding to the other materials mentioned, eighty cubic centimeters of soda-lye of 1.30 specific gravity. The respective quantities of iron and zinc may be measured instead of weighed, as exact proportions are not required. After the addition of all the materials the flask is allowed to stand for an hour at room temperature. The distillation is then commenced and continued until at least 100 cubic centimeters of distillate have been collected. The receiving flasks are ordinary erlenmeyers, each of which contains twenty cubic centimeters of set sulfuric acid, as in the usual kjeldahl process. The flasks are sealed with a few drops of water by the device shown in the figure. After the end of the operation the water in each one is washed back into its proper flask with freshly boiled water. During the vigorous evolution of hydrogen, at the beginning of the operation, some kind of a safety arrangement is necessary to prevent the particles of soda-lye being carried over by the bubbles of that gas. The siphon bulb shown in the figure is found effective for this purpose. In this operation better results are obtained by condensing the escaping steam, and for this reason the block tin tubes are conducted through a tank supplied with a current of cold water. The ends of the tubes should not dip below the surface of the liquid in the receivers. When the condensed liquid collects in considerable quantities in the safety tube the lamp should be extinguished under the flask, which permits the return of the liquid to the flask by means of the siphon. This should be done two or three times during the progress of the distillation to prevent a too high concentration of the soda-lye, thus endangering the flask. The excess of the acid in the receiver is determined by titration, as in the regular kjeldahl method. Blank determinations should be made, from time to time, and corrections made in harmony therewith.

=215. Method of the French Sugar Chemists.=—The nitrogen in Chile saltpeter is estimated by the French chemists according to the method of Schlösing, described in the first volume, page 500. In order to avoid the trouble of calculating the results from the volume of nitric oxid obtained, a determination is first made with a pure salt, sodium or potassium nitrate. The volume of gas obtained is read directly without correction and taken for direct comparison. The comparison is made as follows:

The solutions of the pure salts and of the sample to be analyzed are made of such a strength as to contain sixty-six grams of sodium nitrate, or eighty grams of potassium nitrate, in a liter. Five cubic centimeters of such a solution will yield a little less than 100 cubic centimeters of nitric oxid under usual conditions. Let the volume of gas obtained with the pure salt be v; and that with the sample be v′. The calculation is then made from the equation:

v′ x ---- = ----. v 100

Example: Let ninety-five cubic centimeters be the volume of gas from five cubic centimeters of the pure salt (sodium nitrate), and 91.5 cubic centimeters be the volume of gas from five cubic centimeters of the sample; then

91.5 x ---- = ----, whence x = 96.31. 95 100

Hence the sample analyzed contains 96.31 per cent of sodium nitrate. Since the pure sodium nitrate contains 16.47 per cent of nitrogen the sample under examination would contain

16.47 × 96.31 ------------- = 15.86 per cent. 100

It is evident that this comparative method is quite easy of application when the sample under examination has no other nitrate in it except that combined with the one base.

=216. Volumetric Method of Gantter.=—The process proposed by Gantter for determining the nitrogen, volumetrically, in Chile saltpeter and other nitrates is based on the following principles:

(1) If a nitrate be heated in contact with sulfuric and phosphorous acids, nitrous acid will be formed.

(2) If nitrous acid be boiled with ammonium chlorid, nitrogen will be quantitatively evolved from both compounds. These processes are illustrated by the following formulas:

(a) N₂O₅ + P₂O₃ = N₂O₃ + P₂O₅.

(b) N₂O₃ + 2NH₄Cl = 2N₂ + 3H₂O + 2HCl.

It is seen from the above that the nitrate will give, by this treatment, double the volume of nitrogen which it contains. In practice, the two reactions may be secured in one operation by warming the nitrate solution slowly with sulfuric and phosphorous acids and ammonium chlorid. The nitric acid, as it becomes free, gives a part of its oxygen to the phosphorous compound, and the nitrous acid, in a nascent state, is at once reduced by the ammonium chlorid. There are two sources of error which must be guarded against in the work; a portion of the nitrogen may escape reduction to the elementary state, or some of the nitrate may fail to be decomposed. These errors are easily avoided if the reaction be begun slowly, so that the evolution of gas may be gradual. The temperatures at first should, therefore, be kept as low as possible. The development of red fumes, showing the presence of undecomposed nitrogen oxids, shows that the results will be too low. It is necessary, also, to provide for the absorption of the hydrochloric acid which is formed. The reaction is very conveniently conducted in the apparatus shown in Fig. 16. The decomposition takes place in the flask A and the mixed gases pass into the absorption bulb C. The delivery-tube is very much expanded, as shown in the figure, so that no soda-lye can enter A during the cooling of the flask. The absorption bulb is connected with A and B by the tubes a and b as shown. The tube d connects the apparatus with the gasvolumeter. The bulb B serves as a pipette for the introduction of the decomposing acid. The operation is conducted as follows: Three cubic centimeters of the nitrate solution, containing no more than 300 milligrams of substance, are placed in the flask A with half a gram each of crystallized ammonium chlorid and phosphorous acid. In the bulb B are placed seven cubic centimeters of sulfuric acid to which has been added one-third its volume of water. Two cubic centimeters of acid are allowed to flow from B into A. The apparatus is brought to a constant temperature by being immersed in a large cylinder, E, containing water at a temperature which can easily be controlled. When this constant temperature has been reached the apparatus is taken from the cooling cylinder which contains also a smaller cylinder, D, nearly filled with water and connected through f′ with the measuring apparatus M. The barometer-tube F is half filled with colored water so that the pressure may be equalized before and after the operation. The flask A is warmed very gently at first, and the nitrogen evolved is conducted into D driving an equivalent volume of water into M. The evolution of the gas must be carefully controlled and the heat at once removed if it become too rapid. The appearance of a red color shows the evolution of oxids of nitrogen rendering the analysis inexact. When the evolution of nitrogen has nearly ceased the lamp is removed and some more sulfuric acid allowed to flow into A from B, after which A is again heated, this time to the boiling-point. All vapors of hydrochloric acid produced are absorbed by the soda-lye in C. The boiling is continued a few minutes, but not long enough to darken the liquid in A. After replacing the apparatus in the cylinder E and bringing both temperature and pressure to the same point as before the beginning of the operation, the volume of nitrogen evolved is determined by measuring the water in M.

The apparatus is first set by using pure potassium or sodium nitrate. Since the temperature and pressure do not vary much within an hour or two the volume of water obtained with a sample of white saltpeter can be compared directly with that given off by the same weight of a pure potassium or sodium nitrate without correction.

Example.—Two hundred and fifty milligrams of potassium nitrate, containing 34.625 milligrams of nitrogen, displaced in a given case sixty cubic centimeters of water; therefore one cubic centimeter of water equals 0.578 milligram of nitrogen. If 289 instead of 250 milligrams be taken then the number of cubic centimeters of water displaced divided by five will give the per cent of nitrogen.

=217. Method of Difference.=—In the analysis of Chile saltpeter by the direct method a variation of 0.25 per cent in the content of nitrogen is allowed from the dealers’ guaranty. This would allow a total variation in the content of sodium nitrate of 1.52 per cent. Dealers and shippers have always been accustomed to estimate the quantity of sodium nitrate in a sample by difference; i. e., by estimating the constituents not sodium nitrate and subtracting the sum of the results from 100. Chile saltpeter usually contains sodium nitrate, water, insoluble ferruginous matters, sodium chlorid, sodium sulfate, magnesium chlorid, sodium iodate, calcium sulfate and sometimes small quantities of potassium nitrate.

When the total sodium nitrate is to be estimated by difference the following procedure, arranged by Crispo, may be followed:

Water.—Dry ten grams of the finely powdered sample to constant weight at 150°-160°.

Chlorin.—The residue, after drying, is dissolved and the volume made up to one-fourth liter with water and the chlorin determined in one-fifth thereof and calculated as sodium chlorid.

Insoluble.—Twenty grams are treated with water until all soluble matter has disappeared, filtered on a tared gooch, and the filtrate dried to constant weight.

Sulfuric Acid.—The sulfuric acid is precipitated by barium chlorid in the slightly acid filtrate from the insoluble matter. The acidity is produced by a few drops of nitric acid. The rest of the process is conducted in the usual way.

Magnesia.—This is precipitated by ammonium sodium phosphate, filtered, ignited, and weighed as pyrophosphate. The magnesium is then calculated as chlorid. Magnesia is rarely found in excess of one-fourth per cent. When this amount is not exceeded the estimation of it may be neglected without any great error. As has already been said the chlorin is all calculated as sodium chlorid. If a part of it be combined with one-fourth per cent of magnesia it would represent 0.59 per cent of magnesium chlorid instead of 0.73 per cent sodium chlorid. In omitting the estimation of the magnesia therefore the importer is only damaged to the extent of 0.14 per cent of sodium nitrate.

Sodium Iodate.—This body, present only in small quantities, may also be neglected. In case the content of this body should reach one-fourth per cent the estimation of chlorin by titration using potassium chromate as indicator is impracticable. Such an instance, however, is rarely known.

Approximate Results.—When the determinations outlined above have been carefully made it is claimed that the result obtained by subtraction from 100 will not vary more than from two-tenths to three-tenths per cent from the true content of sodium nitrate. The method, however, cannot be considered strictly scientific and is much more tedious and chronophagous than the direct determination. In the direct determination, however, the analyst must assure himself that potassium is present in only appreciable quantities otherwise the per cent of sodium nitrate will be too low.

The presence of potassium nitrate is a detriment in this respect only; viz., that it contains a less percentage of nitrogen than the corresponding sodium salt. As a fertilizer, the value of Chile saltpeter may be increased by its content of potassium.

=218. The Application of Chile Saltpeter to the Soil.=—The analyst is often asked to determine the desirability of the use of sodium nitrate as a fertilizer and the methods and times of applying it. These are questions which are scarcely germane to the purpose of this work but which, nevertheless, for the sake of convenience may be briefly discussed. In the first place it may be said that the data of a chance chemical analysis will not afford a sufficiently broad basis for an answer. A given soil may be very rich in nitrogen as revealed by chemical analysis, and yet poor in an available supply. This is frequently the case with vegetable soils, containing, as they do, large quantities of nitrogen but holding it in practically an inert state. I have found such soils very rich in nitrogen, yet almost entirely devoid of nitrifying organisms. It is necessary therefore in reaching a judgment on this subject from analytical data to consider the different states in which the nitrogen may exist in a soil and above all the nitrifying power of the soil if the nitrogen be chiefly present in an organic state. Culture solutions should therefore be seeded with samples of the soil under examination and the beginning and rapidity of the nitrification carefully noted. In conjunction with this the nitrogen present in the soil in a nitric or ammoniacal form should be accurately determined. These determinations should be made according to the directions given in the first volume, pp. 448-548.

For the determination of nitrifying power we prefer the following method:

=219. Taking Samples of Soil in Sterilized Tubes.=—Brass tubes are prepared twenty centimeters in length and one and a half in diameter. One end is ground to a beveled edge and compressed in a mold so as to make the cutting edge slightly smaller in diameter than the internal diameter of the tube. It is then ground or filed until smooth and sharp. The blunt end of the tube is stoppered loosely with cotton and it is then sterilized by heating for an hour to 150°. Rubber caps are provided and each one has placed at the bottom a rubber ball to prevent the rubber from being cut by the edges of the brass tube. The caps should be of two distinct colors. Half of the rubber caps are sterilized by being boiled for an hour in water for three successive days. The caps cannot be heated to 150° dry heat with safety. On removing the brass tube from the sterilizing oven as soon as it is cool enough to handle, a sterilized rubber cap is slipped over its cutting end. An unsterilized cap is then slipped over the other end containing the cotton plug. Inasmuch as the cotton plug is never removed it is not necessary to sterilize the cap covering it. Large numbers of the tubes can thus be prepared for use and they can be safely transmitted to a distance by express or mail. For convenience, each tube is encased in a small cloth bag, which is tied with a cord carrying a tag on which the necessary data can be recorded at the time of taking the sample.

The tubes and their rubber caps thus carefully sterilized should not be removed from their cloth envelopes until the moment of taking each sample. After the sample has been taken and the cap replaced on the tube the latter should be immediately enclosed in the cloth sack and labeled with one of the tags therewith enclosed. The sample should be taken in two kinds of soil, in one instance in a cultivated soil, which is most characteristic of the locality, and in the second place a virgin soil of the same type. The virgin soil may be either soil which has been covered with grass or in forest. The spots at which the samples are to be taken having been previously selected, the tags for each tube should be prepared beforehand so as to avoid delay at the time of sampling. A pit with straight walls should be dug, the sides of which are at least two feet wide and even three feet would be better. The pit should be about forty-two inches deep. One of the sides having been made perfectly smooth and without allowing the loose fragments from the top to fall down and adhere to the walls below, the spots at which the samples are to be taken should be marked with a tape line at the following points; viz., three, fifteen, twenty-seven, and thirty-nine inches, respectively, below the surface. Beginning at the bottom point, carefully scrape off the surface of the wall over an area slightly larger than that of the end of the sample tube by means of a spatula, which, just previous to use, has been held for a moment or two in the flame of an alcohol or other convenient lamp. The sample tube having been removed from its sack, it will be noted that the end covered with black rubber is the one which is to be held in the hand, and this black rubber cap should be first removed being careful not to extract the plug of sterilized cotton which closes the end of the tube. Holding the tube firmly by the end, the fingers extending only about two inches from the end, remove the light-colored cap and push the tube with a turning motion into the side of the pit at the point where the surface has been removed with the sterilized spatula. When this is properly done the tube will be filled with a cylinder of soil equal to the length of the part of the tube penetrating the wall of the pit. The tube is then withdrawn, the light rubber cap first replaced, and then the black one. The light rubber cap should be held in the hand during the process in such a way that no dust or particles of soil are permitted to contaminate its inner walls. For this purpose the open end of the cap should be held downward. For the same reason after the removal of the light rubber cap the brass tube should be carefully preserved from dust or fragments, the open end, that is the cutting end, being held downward until ready for use. After one tube has been filled, capped, replaced in the sack and labeled, the spatula should be again sterilized and samples taken in regular order until the top one is finished.

=220. Directions for Taking Bulk Samples.=—From the sides of the pit described above, bulk samples should be taken as follows:

By means of a spade the soil should be removed from the four sides to the depth of six or nine inches or until the change of color between the soil and subsoil is noted; in all enough to make about 150 pounds of the air-dried soil. In the same way take a sample of the subsoil to the depth of nine additional inches. Remove all stones, large pebbles, sticks, roots, etc., and spread the samples in a sheltered place where they can be air-dried as rapidly as possible. The bulk samples should be taken both from the cultivated and virgin soils. In selecting the cultivated soil, preference should be given to those soils which have not been fertilized within a few years. If recent fertilization have been practiced the character and amount of it should be noted.

=221. The Nitrifiable Solution.=—The solution to test the nitrifying power of the samples collected as above described is conveniently made as follows:

Potassium phosphate, one gram per liter. Magnesium sulfate, half a gram per liter. Calcium chlorid, a trace. Ammonium sulfate, 200 milligrams of nitrogen per liter. Calcium carbonate, in excess.

One liter of the above solution is enough for ten samples, each of 100 cubic centimeters. This quantity is placed in an erlenmeyer, which is stoppered with cotton and sterilized by being kept at 100° for an hour on three successive days. The erlenmeyer should be sterilized beforehand by heating for an hour at 150°. The freshly precipitated and washed calcium carbonate should be sterilized separately and added to each erlenmeyer at the time of seeding. Enough should always be used to be in excess of the nitrous and nitric acids found. The seeding is accomplished by filling a sterilized spoon which holds approximately half a gram of the soil, from the contents of one of the brass tubes, lifting the plug in the erlenmeyer and transferring quickly to the flask. This should be done in a perfectly still room, preferably as high above the ground as possible and in a place free from dust and under cover. The cotton plug being replaced the erlenmeyer is shaken until the sample of soil added is thoroughly disintegrated and intimately mixed with its contents. With care and experience the seeding is easily accomplished without danger of accidental contamination.

At the end of each period of five days the beginning and progress of nitrification should be determined by some of the methods described in volume first. Either the ammonia can be determined by nesslerizing or the nitrous and nitric acids estimated. For nitrous acid we prefer the method described in volume first, paragraph =504=, and for nitric the one in same volume paragraphs =497= and =498=.

By supplementing the analysis of a soil by the above described experiments in nitrification the analyst will be able to judge with sufficient accuracy of its needs for nitric nitrogen.

=222. Quantity of Chile Saltpeter to be Applied.=—The quantities of Chile saltpeter which should be applied per acre vary with so many conditions as to make any definite statement impossible. On account of the great solubility of this salt no more should be used than is necessary for the nutrition of the crop. For each 100 pounds used, from fourteen to fifteen pounds of nitrogen will be added to the soil. Field crops, as a rule, will require less of the salt than garden crops. There is an economic limit to the application which should not be passed. As a rule 250 pounds per acre will prove to be a maximum dressing. The character of the crop must also be considered. Different amounts are required for sugar beets, tobacco, wheat, and other standard crops. It is rarely the case that a crop demands a dressing of Chile saltpeter alone. It will give the best effects, as a rule, when applied with phosphoric acid or potash. But this is a branch of the subject which cannot be entered into at greater length in this manual. The reader is referred to Stutzer’s work on Chile saltpeter for further information.

=223. Consumption of Chile Saltpeter.=—The entire consumption of sodium nitrate for manurial purposes in the whole world for 1894 was 992,150 metric tons, valued at $41,000,000. For the several countries using it the consumption was distributed as follows:

Germany 397,200 tons. France 187,100 “ England 117,000 “ Belgium 123,000 “ United States 100,000 “ Holland 56,700 “ Italy and Spain 5,200 “ Other countries 5,950 “ ------- Total 992,150 “

The above figures represent the actual commerce of each country in Chile saltpeter, and may not give the exact consumption. For instance, Germany exports sodium nitrate to Russia and Austria, but it imports this salt from Holland and Belgium. Belgium imports from France, but its exportation is greater than its importations from that country, so that its actual consumption on the farm probably falls considerably below that given on the table. Holland also exports larger quantities than are imported from neighboring states. The exports from England are inconsiderable compared with the quantities received, amounting only to about 5,000 tons a year, while the exportations from France reach nearly 10,000 tons.

Sodium nitrate has a moderate value at the factories where it is prepared for shipment in Chile. Its chief value at the ports where it is delivered for consumption comes from freights and profits of the syndicate. The factories, where it is prepared for the market, are at or near the deposits, and the freights thence to the sea coast are very high. The rail roads which have been constructed to the high plateaux which contain the deposits, have been built at a very great cost, and the freights charged are correspondingly high. There is also a tax of $1.20 levied on each ton exported. Deducting all costs of transportation and export duties the actual value of sodium nitrate at the factory, ready for shipment, is about sixteen dollars in gold a ton.

AUTHORITIES CITED IN PART SECOND.

American Chemical Journal, Vol. 13, No. 7.

Atwater: Report of the U. S. Commissioner of Fish and Fisheries, 1888, pp. 679-868.

American Naturalist, Vol. 14, p. 473.

Wiley: Retiring Address as President of American Chemical Society, Baltimore Meeting, Dec. 1893, Journal of the American Chemical Society, Vol. 16, pp. 17-20.

Vid. op. et. loc. cit. supra.

Vid. op. et. loc. cit. 4.

Vid. op. et. loc. cit. 4.

Vid. op. et. loc. cit. 4.

Bulletin No. 43, p. 343 (to paragraph =156=).

American Chemical Journal, Vol. 2, pp. 27, et seq.

Vid. op. et. loc. cit. supra.

Weather Bureau: Barometers and Measurements of Atmospheric Pressures.

Physikalisch-Chemische Tabellen Landolt und Börnstein, S. 32.

Battle and Dancy: Conversion Tables, p. 34.

Bulletin No. 43, p. 348 (to paragraph =169=).

Guide pour le dosage de l’Azote No. 3, p. 8.

Zeitschrift für analytische Chemie, Band 23, S. 557.

Chemiker Zeitung, Band 8, S. 1747.

Journal of the Chemical Society, Transactions, 1881, p. 87.

Bulletin No. 16, p. 51.

Bulletin No. 28, p. 193 (to paragraph =175=).

Journal Society of Chemical Industry, Vol. 2, p. 21.

Bulletin de l’Association des Chimistes de Sucrèrie, Tome 9, p. 598.

(bis p. 192) Journal Chemical Society; Transactions, Vol. 21, p. 161.

Zeitschrift für analytische Chemie, Band 22, S. 366.

Vid. op. cit. supra, pp. 370, et seq.

Vid. op. cit., 24. Band 24, S. 455.

Chemisches Centralblatt, 1886, S. 165.

Nederlandsche Staatscourant, Jan. 11, 1893.

Die Agricultur-Chemische Versuchs-Station, Halle a/S., S. 34.

(bis. p. 204) Bulletin No. 43, p. 345.

Bulletin No. 31, 142.

Fresenius, quantitative Analyse, 6th Auflage, S. 731.

Zeitschrift für Analytische Chemie, Band 24, S. 455.

Vid. op. cit. supra, Band 25, S. 149.

Archive der Pharmacie {3}, Band 23, S. 177.

Chemisches Centralblatt, 1886, S. 375.

Vid. op. cit. supra, S. 161.

Vid. op. cit. 35, S. 433.

Vid. op. et. loc. cit. 28.

Vid. op. cit. 29, S. 44.

Bulletin No. 16, p. 51.

Zeitschrift für analytische Chemie, Band 28, S. 188.

Bulletin No. 35, p. 68.

Bulletin No. 35, p. 202.

Bulletin No. 112, Connecticut Agricultural Experiment Station, and Bulletin No. 35, p. 96.

Guide pour le dosage de l’Azote, p. 14.

Revue de Chimie Analytique Appliquée, Tome 1, p. 51.

Chemiker Zeitung, Band 4, S. 360.

Bulletin No. 43, p. 361.

Bulletin de la Société Chimique, 1890, p. 324.

Bulletin No. 35, p. 88.

Die Agricultur-Chemische Versuchs-Station, Halle a/S., S. 50.

Vid., Vol. 1, p. 539.

Berichte der deutschen chemischen Gesellschaft, Band 27, S. 1633.

Vid. op. et. loc. cit. supra.

Vid. op. cit. 51, S. 48.

Zeitschrift für analytische Chemie, Band 34, S. 26.

Vid. op. cit. supra, Band 32, S. 553.

L’Engrais, Tome 9, p. 877.

Der Chile Saltpeter; Seine Bedeutung und Anwendung als Düngemittel.

L’Engrais, 5 Avril, 1895, p. 324.

PART THIRD.

POTASH IN FERTILIZING MATERIALS AND FERTILIZERS.

=224. Introduction.=—The potash present in unfertilized soils has been derived from the decay of rocks containing potash minerals. Among these potash producers feldspars are perhaps the most important. For a discussion of the nature of their decomposition and the causes producing it the first part of volume first may be consulted. Potash is quite as extensively distributed as phosphoric acid and no true soils are without it in some proportion. Its presence is necessary to plant growth and it forms, in combination with organic and mineral acids, an essential part of the vegetable organism, existing in exceptionally rich quantities in the seeds. It is possible that potash salts, such as the chlorid, sulfate, and phosphate may be assimilated as such, but, as with other compounds, we must not deny to the plant the remarkable faculty of being able to decompose its most stable salts and to form from the fragments thus produced entirely new compounds. This is certainly true of the potash compounds existing in plants in combination with organic acids. The potash which is assimilated by plants exists in the soil chiefly in a mineral state, and that added as fertilizer is chiefly in the same condition. That part of the potash in a soil arising directly from the decomposition of vegetable matters may exist partly in organic combination, but this portion, in comparison with the total quantity absorbed by the plant, is insignificant.

It is then safe to assume that at least a considerable part of the potash absorbed by the plant is decomposed from its original form of combination by the vegetable biochemical forces, and is finally incorporated in the plant tissues in forms determined by the same powerful forces of vegetable metabolism.

The analyst is not often called upon to investigate the forms in which the potash exists in plants, when engaged in investigation of fertilizers. It is chiefly found in combination with organic and phosphoric acids, and on ignition will appear as phosphate or carbonate in the ash.

=225. Forms in which Potash is Found in Fertilizers.=—The chief natural sources of potash used in fertilizer fabrication are: First, organic compounds, such as desiccated mineral matters, tobacco waste, cottonseed hulls, etc.; second, the ash derived from burning terrestrial plants of all kinds; third, the natural mineral deposits, such as Stassfurt salts.

All of these forms of potash may be found in mixed fertilizers. While the final methods of analyses are the same in all cases the preliminary treatment is very different, being adapted to the nature of the sample. For analytical purposes, it is highly important that the potash be brought into a soluble mineral form, and that any organic matters which the sample contains be destroyed. If the sample be already of a mineral nature, it may still be mixed with other organic matter and then it requires treatment as above, for it is not safe always to rely solely on the solubility of the potash mineral, and the solution, moreover, in such cases, is likely to contain organic matter. In some States, only that portion of the potash soluble in water is allowed to be considered in official fertilizer work. In these cases it is evident that the organic matter present should not be destroyed in the original sample, but only in the aqueous solution. Since, however, the potash occluded in organic matter becomes constantly available as the process of decay goes on, it is not just to exclude it from the available supply. It may not be so immediately available as when in a soluble mineral state, but it is not long before it becomes valuable. Experience has shown, moreover, that phosphorus, nitrogen, and potash are all more valuable finally when applied to the soil in an organic form. This fact is a corroboration of the theory already advanced that all mineral compound bodies are probably decomposed before they enter as component parts into the tissues of the vegetable organism.

It is highly probable, therefore, that the potash existing in organic compounds, finely divided and easily decomposed, is of equal, if not greater value to plant life than that already in a soluble mineral state. The organic matter, when present, is destroyed, either by ignition at a low temperature, or by moist combustion with an oxidizing agent before the potash is precipitated.

ORGANIC SOURCES OF POTASH.

=226. Tobacco Stems and Waste.=—Until within a few years tobacco stems and other waste from factories, were treated as a nuisance in this country, and burned or dumped into streams. By burning and saving the ash the potash contained in the stems and waste would be recovered in a form suitable for field use. The nitrogen, however, contained in these waste materials, both in the form of nicotin and of albuminoids would be lost. Ignition of this waste, therefore, should not be practiced. It should be prepared for use by grinding to a fine powder. Applied to the soil in this condition the powder may be useful as an insecticide as well as a fertilizer. Tobacco stems contain from twelve to twenty-seven per cent of moisture, and from twelve to twenty per cent of ash. The composition of the stems from two celebrated tobacco growing regions is subjoined:

Kentucky stems. Connecticut stems. Moisture 26.70 per cent. 13.47 per cent. Organic and volatile 60.18 “ “ 70.85 “ “ Ash 13.12 “ “ 15.68 “ “

The ash calculated to the original substance had the following composition:

Kentucky stems. Connecticut stems. Phosphoric acid 0.67 per cent. 0.53 per cent. Potash 8.03 “ “ 6.41 “ “

It is thus seen that about half the ash of tobacco stems is composed of potash. The stalks of the tobacco have almost the same composition as the stems, but the percentage of ash is not quite so great. In three samples analyzed at the Connecticut station the percentages of ash found in the water-free substance were 6.64, 7.00, and 7.46 respectively. The pure ash of the stalks was found to have the following composition:

Description of samples. Constituents Cut Aug. 22. Cut Sept. 17. Silica 0.82 per cent. 0.57 per cent. Iron and aluminum oxids 1.38 “ “ 1.38 “ “ Lime 14.01 “ “ 16.58 “ “ Magnesia 6.64 “ “ 7.36 “ “ Potash 56.34 “ “ 54.46 “ “ Soda 1.28 “ “ 1.16 “ “ Sulfuric acid 8.06 “ “ 6.75 “ “ Phosphoric acid 6.37 “ “ 6.27 “ “ Chlorin 6.55 “ “ 7.05 “ “ ------ ------ 101.45 “ “ 101.58 “ “ Deduct oxygen = chlorin 1.45 “ “ 1.58 “ “ ------ ------ 100.00 “ “ 100.00 “ “

The leaves of the tobacco contain more ash than the stalks or stems, but the percentage of potash therein is less. In eighteen samples analyzed at the Colorado station the percentages of moisture in the leaf varied from 6.08 to 28.00, and those of ash from 22.60 to 28.00. The percentages of potash in the ash varied from 15.20 to 26.30. In these data the carbon dioxid, sand, etc., are included, while in those quoted from the Connecticut station they were excluded.

=227. Cottonseed Hulls and Meal.=—A considerable quantity of potash is added to the soil in cottonseed meal and hulls. The practice of burning the hulls cannot be recommended, although it is frequently practiced, for the incineration does not increase the quantities of phosphoric acid and potash, while it destroys the availability of the nitrogen. Nevertheless the analyst will often have to deal with samples of the raw materials above mentioned, as well as with the ash of the hulls, in which the potash can be determined by some one of the standard methods to be described. In general it is found that the hulls of seeds and the bark and leaves of plants have a greater percentage of ash than the interior portions. In the case of cottonseed however, an exception is to be noted. The cottonseed meal in the air-dried state has about seven per cent of ash, while the hulls have only about three. When it is remembered, however, that the greater part of the oil has been removed from the meal it will be seen that in the whole seed in the fresh state the discrepancy is not so marked.

In the crude ash of the hulls the percentage of potash varies generally from twenty to twenty-five per cent, but in numerous cases these limits are exceeded. In twelve samples of cottonseed hull ashes examined by the Connecticut station the mean percentage of potash in the crude sample was 22.47, and the extremes 15.57 and 30.24 per cent respectively. In determining the value of the ash per ton the content of phosphoric acid must also be taken into account.

Cottonseed meal contains about 1.75 per cent of potash. Since the mean percentage of ash in the meal is seven, the mean content of potash in the crude ash is about twenty-five.

=228. Wood Ashes.=—Unleached wood ashes furnish an important quantity of potash fertilizer. The composition of the ash of woods is extremely variable. Not only do different varieties of trees have varying quantities of ash, but in the same variety the bark and twigs will give an ash quite different in quantity and composition from that furnished by the wood itself. In general the hard woods, such as hickory, oak, and maple, furnish a quality of ash superior for fertilizing purposes to that afforded by the soft woods, such as the pine and tulip trees.

The character of the unleached wood ashes found in the trade is indicated by the subjoined analyses. The first table contains the mean, maximum and minimum results of the analyses of ninety-seven samples by Goessmann.

Mean composition of wood ashes. Means. Maxima. Minima. Potash 5.5 10.2 2.5 Phosphoric acid 1.9 4.0 0.3 Lime 34.3 50.9 18.0 Magnesia 3.5 7.5 2.3 Insoluble 12.9 27.9 2.1 Moisture 12.0 28.6 0.7 Carbon dioxid and undetermined 29.9

In sixteen analyses made at the Connecticut station the data obtained are given below:

Means. Maxima. Minima. Potash 5.3 7.7 4.0 Phosphoric acid 1.4 1.8 0.9

In fifteen analyses of ashes from domestic wood-fires in New England stoves, the following mean percentages of potash and phosphoric acid were found:

Potash 9.63 Phosphoric acid 2.32

In leaching, ashes lose chiefly the potassium carbonate and phosphate which they contain. Leached and unleached Canada ashes have the following composition:

Unleached. Leached. Insoluble 13.0 per cent. 13.0 per cent. Moisture 12.0 “ “ 30.0 “ “ Calcium carbonate and hydroxid 61.0 “ “ 51.0 “ “ Potassium carbonate 5.5 “ “ 1.1 “ “ Phosphoric acid 1.9 “ “ 1.4 “ “ Undetermined 6.6 “ “ 3.5 “ “

In the wood ashes of commerce therefore, it is evident that the proportion of the potash to the lime is relatively low.

The number of parts by weight of the chief ingredients of the ash in ten thousand pounds of woods of different kinds is given in the table below together with the percentage composition of the pure ash, that is the crude ash deprived of carbon and carbon dioxid.

POUNDS OF THE INGREDIENTS NAMED IN TEN THOUSAND POUNDS OF WOOD.

------------------------+---------------+-------------+------------+ Dogwood.| Sycamore. | Post oak. | Ash. | Cornus | Platanus | Q. | F. | florida.|occidentalis.|obtusiloba.|Americana.| ------------------------+---------------+-------------+------------+ Potash | 9.02 | 18.06 | 16.85 | 14.94 | Phosphoric acid| 5.72 | 9.55 | 6.96 | 1.15 | Lime | 6.41 | 24.73 | 35.61 | 7.60 | Magnesia | 14.67 | .49 | 5.28 | .10 | ---------------+--------+---------------+-------------+------------+ ------------------------+------------+-------+--------------+ Red | Hickory. | White | Magnolia. | oak. | Carya | oak. | M. | Q. |tomentosa.| Q. |grandiflora.| rubra.| |alba.| | ---------------+--------+------------+-------+--------------+ Potash | 13.95 | 13.80 | 10.60 | 7.13 | Phosphoric acid| 5.98 | 5.83 | 2.49 | 3.19 | Lime | 27.40 | 18.40 | 7.85 | 14.21 | Magnesia | 3.05 | 4.86 | .90 | 2.94 | ---------------+--------+------------+-------+--------------+ ----------------------------+--------+--------+-----------+---------- Georgia | Yellow | Black | Chestnut. | Old field pine. | pine. | pine. |Castanea | pine. P. | P. |Picea |vesca or |P. mitis. palustris.|mitis.|nigra.|sativa. | ---------------+------------+--------+--------+-----------+---------- Potash | 5.01 | 4.54 | 3.02 | 2.90 | .79 Phosphoric acid| 1.24 | .96 | .92 | 1.09 | .73 Lime | 18.04 | 15.16 | 12.46 | 7.93 | 12.12 Magnesia | 2.03 | .74 | .10 | .34 | 1.17 ---------------+------------+--------+--------+-----------+----------

THE PURE ASHES OF THE WOODS CONTAIN THE FOLLOWING PER CENTS OF THE INGREDIENT NAMED.

------------------------+---------------+-------------+------------+ Dogwood.| Sycamore. | Post oak. | Ash. | Cornus | Platanus | Q. | F. | florida.|occidentalis.|obtusiloba.|Americana.| ------------------------+---------------+-------------+------------+ Potash | 28.04 | 23.17 | 21.92 | 46.04 | Phosphoric acid| 8.51 | 12.23 | 9.00 | 3.58 | Lime | 38.93 | 31.62 | 46.39 | 23.57 | Magnesia | 6.80 | .62 | 6.88 | .60 | ---------------+--------+---------------+-------------+------------+ ------------------------+------------+-------+--------------+ Red | Hickory. | White | Magnolia. | oak. | Carya | oak. | M. | Q. |tomentosa.| Q. |grandiflora.| rubra.| |alba.| | ---------------+--------+------------+-------+--------------+ Potash | 24.66 | 28.60 | 42.16 | 19.54 | Phosphoric acid| 10.55 | 11.97 | 9.48 | 8.75 | Lime | 48.26 | 37.94 | 29.85 | 38.94 | Magnesia | 5.38 | 10.04 | 3.43 | 8.05 | ---------------+--------+------------+-------+--------------+

----------------------------+--------+--------+-----------+---------- Georgia | Yellow | Black | Chestnut. | Old field pine. | pine. | pine. |Castanea | pine. P. | P. |Picea |vesca or |P. mitis. palustris.|mitis.|nigra.|sativa. | ---------------+------------+--------+--------+-----------+---------- Potash | 15.35 | 19.70 | 14.30 | 18.10 | 3.85 Phosphoric acid| 3.82 | 4.18 | 4.33 | 6.76 | 4.11 Lime | 55.24 | 65.53 | 58.98 | 49.18 | 67.73 Magnesia | 6.25 | 3.20 | .50 | 2.11 | 6.54 ---------------+------------+--------+--------+-----------+----------

=229. Fertilizing Value of Ashes.=—Primarily, the fertilizing value of wood-ashes depends on the quantity of plant food which they contain. With the exception of potash and phosphoric acid, however, the constituents of wood-ashes have little, if any, commercial value. The beneficial effects following the application of ashes, however, are greater than would be produced by the same quantities of matter added in a purely manurial state. The organic origin of these materials in the ash has caused them to be presented to the plant in a form peculiarly suited for absorption. Land treated generally with wood-ashes becomes more amenable to culture, is readily kept in good tilth, and thus retains moisture in dry seasons and permits of easy drainage in wet. These effects are probably due to the lime content of the ash, a property moreover favorable to nitrification and adapted to correcting acidity. Injurious iron salts, which are sometimes found in wet and sour lands, are precipitated by the ash and rendered innocuous or even beneficial. A good wood-ash fertilizer therefore is worth more than would be indicated by its commercial value calculated in the usual way.

=230. Molasses from Sugar-Beets.=—The residual molasses resulting after the extraction of all the crystallizable sugar in beet-sugar manufacture is very rich in potash. The molasses contains from ten to fifteen per cent of ash.

The composition of the ash varies greatly in the content of potash as well as of the other constituents. The content of potassium carbonate varies from twenty-two to fifty-five per cent and, in addition to this, some potassium sulfate and chlorid are usually present.

The following figures give the composition of a good quality of beet-molasses ash:

Potassium carbonate 45.30 per cent Sodium “ 13.86 “ Potassium chlorid 22.40 “ “ sulfate 8.00 “ Silica, lime, alumina, water, phosphoric acid, and undetermined 15.82 “

Thus, in 100 parts of such an ash over three-quarters are potash salts. The molasses may be applied directly to the soil or diluted and sprayed over the fields.

=231. Residue of Wineries.=—The pomace of grapes after being pressed or fermented for wine production contains considerable quantities of potash as crude argol or acid potassium tartrate. This material can be applied directly to the soil or first burned, when its potash will be secured in the form of carbonate.

The use of the winery refuse for fertilizing purposes has not assumed any commercial importance in this country.

=232. Destruction of Organic Matter by Direct Ignition.=—The simplest and most direct method for destroying organic matter is by direct ignition. The incineration may be conducted in the open air or in a muffle and the temperature should be as low as possible. In no case should a low red heat be exceeded. By reason of the moderate draft produced in a muffle and the more even heat which can be maintained this method of burning is to be preferred. With the exercise of due care, however, excellent results can be obtained in an open dish or one partly closed with a lid. At first, with many samples, the organic matter will burn of its own accord after it is once ignited, and during this combustion the lamp should be withdrawn. The ignition in most cases should be continued in a platinum dish but should the sample contain any reducible metal capable of injuring the platinum a porcelain vessel should be used. The lamp should give a diffused flame to avoid overheating of any portions of the dish and to secure more uniform combustion. In using a muffle the heat employed should be only great enough to secure combustion and the draft should be so regulated as to avoid loss due to the mechanical deportation of the ash particles.

=233. Ignition with Sulfuric Acid.=—The favorable action of sulfuric acid in securing a perfect incineration may also be utilized in the preparation of samples containing organic matter for potash determinations. In this case the bases which by direct ignition would be secured as carbonates are obtained as sulfates. In the method adopted by the official chemists it is directed to saturate the sample with sulfuric acid and to ignite in a muffle until all organic matter is destroyed. Afterwards, when cool the ash is moistened with a little hydrochloric acid and warmed, whereby it is the more easily detached from the dish. The potash is then determined by any one of the standard methods. This method has several advantages over the direct ignition. Where any chlorids of the alkalies are present in the ash there is danger of loss of potash from volatilization. This is avoided by the sulfate process. Moreover, there is not so much danger in this method of occluding particles of carbon in the ash.

=234. The Destruction of Organic Matter by Moist Combustion.=—In the process of ignition to destroy organic matter or remove ammonium salts in the determination of potash, there are often sources of error which may cause considerable loss. This loss, as has already been mentioned, may arise from the volatilization of the potash salts or mechanically from spattering. In order to avoid these causes of error de Roode has used aqua regia both for the destruction of the ammonium salts and for the oxidation of the organic matter at least sufficiently to prevent any subsequent reduction of the platinum chlorid. His method consists in boiling a sample of the fertilizer, or an aliquot portion of a solution thereof with aqua regia. The proposed method has not yet had a sufficient experimental demonstration to warrant its use, but analysts may find it profitable to compare this process with the standard methods. The organic matter may also be destroyed by combustion with sulfuric acid, as in the kjeldahl method for nitrogen. The residue, however, contains ammonium sulfate and a large excess of sulfuric acid, and for both reasons would not be in a fit condition for the estimation of potash.

It is suggested that the organic matter might also be destroyed by boiling with strong hydrochloric acid, to which from time to time, small quantities of sodium chlorate free of potash is added. Subsequently the solution could be boiled with addition of a little nitric acid and the ammonium salts be removed.

POTASH IN MINERAL DEPOSITS.

=235. Occurrence and History.=—The generally accepted theory of the manner in which potash has been collected into deposits suited to use as a fertilizer has already been described. The Stassfurt deposits, which have for many years been almost the sole source of potash in fertilizers, were first known as mines of rock salt. In 1839, having previously been acquired by the Prussian treasury, they were abandoned by reason of the more economical working of rock salt quarries in other localities. It was determined thereafter to explore the extent of these mines by boring, and a well was sunk to the depth of 246 meters, when the upper layer of the salt deposit was reached. The boring was continued into the salt to a total depth of 581 meters without reaching the bottom. The results of these experiments were totally unexpected. Instead of getting a brine saturated with common salt, one was obtained containing large quantities of potassium and magnesium chlorids. Shafts were sunk in other places, and with such favorable results, that in 1862 potash salts became a regular article of commerce from that locality. At first these salts were regarded as troublesome impurities in the brine from which common salt was to be made, but at this time the common salt has come to be regarded as the disturbing factor. At the present time the entire product is controlled by a syndicate of nine large firms located at Stassfurt and vicinity. Outside of the syndicate properties a shaft has been sunk at Anderbeck, (Halberstadt,) which, however, has produced only carnallit, since kainit has not been found there. Also at Sondershausen, potash salts have been discovered and a shaft is now sinking there.

It is thus seen that the potash deposits extend over a wide area in Germany, and there is little fear of the deposits becoming exhausted in many centuries. In this country no potash deposits of any commercial importance have been discovered; but the geological conditions requisite to these formations have not been wanting, and their future discovery is not improbable.

=236. Changes in Potash Salts in Situ.=—The deposits of potash salts are not all found at the present in the same condition in which they were first deposited from the natural brines. The layers of salt have been subjected to the usual upheavals and subsidences peculiar to geological history. The layers of salt were thus tilted and the edges often brought to the surface. Here they were exposed to solution, and the dissolved brine afterward separated its crystallizable salts in new combinations. For instance, kieserit and the potassium chlorid of the carnallit were first dissolved and there was left a salt compound chiefly of potassium and sodium chlorids, sylvinit. In some cases there was a mutual reaction between the magnesium sulfate and the potassium chlorid and the magnesium potassium sulfate, schönit, was thus produced. This salt is also prepared at the mines artificially. The most important of these secondary products however, from the agricultural standpoint, is kainit. This salt arose by the bringing together of potassium sulfate, magnesium sulfate, and magnesium chlorid, and was formed everywhere about the borders of the layers of carnallit wherever water could work upon them. In quantity the kainit, as might be supposed, is far less than the carnallit, the latter existing in immense deposits. There is however quite enough of it to satisfy all the demands of agriculture for an indefinite time. In fact for many purposes the carnallit can take the place of kainit without detriment to the growing crops. The relative positions and quantities of the layers of mineral matters in the potash mines, and the depth in meters at which they are found is shown in Fig. 17.

=237. Kainit.=—The most important of the natural salts of potash for fertilizing purposes is the mixture known as kainit. It is composed in a pure state of a molecule each of potassium sulfate, magnesium sulfate, magnesium chlorid, and water. Chemically it is represented by the symbols:

K₂SO₄·MgSO₄·MgCl₂·H₂O. Its theoretical percentage of potash (K₂O), oxygen = 16, is 23.2.

Pure kainit, however, is never found in commerce. It is mixed naturally as it comes from the mines with common salt, potassium chlorid, gypsum, and other bodies. The content of potash in the commercial salt is therefore only a little more than half that of the pure mineral. In general it may be taken at 12.5 per cent, of which more than one per cent is derived from the potassium chlorid present. The following analysis given by Maercker may be regarded as typical:

Potassium sulfate 21.3 per cent Magnesium “ 14.5 “ Magnesium chlorid 12.4 “ Potassium “ 2.0 “ Sodium “ 34.6 “ Calcium sulfate (gypsum) 1.7 “ Water 12.7 “ Alumina 0.8 “

Kainit occurs as a crystalline, partly colorless, partly yellow-red mass. When ground, in which state it is sent into commerce, it forms a fine, gray-colored mass containing many small yellow and red fragments. It is not hygroscopic and if it become moist it is due to the excess of common salt which it contains.

According to Maercker kainit was formerly regarded as a potassium magnesium sulfate. But this conception does not even apply to the pure salt much less to that which comes from the mines. If, therefore, the agronomist desire a fertilizer free from chlorin he would be deceived in choosing kainit which may sometimes contain nearly fifty per cent of its weight of chlorids.

Where a fertilizer free of chlorin is desired, as for instance, in the culture of tobacco, kainit cannot be considered. In many other cases, however, the chlorin content of this body instead of being a detriment may prove positively advantageous, the chlorids on account of their easy diffusibility through the soil serving to distribute the other ingredients.

By reason of the presence of common salt and magnesium chlorid the ground kainit delivered to commerce tends to harden into compact masses. To prevent this in Germany it is recommended to mix it with about two and a half per cent of fine-ground dry peat.

Such a mixture is recommended in all cases where the freshly ground kainit is not to be immediately applied to the soil.

=238. Carnallit.=—This mineral is a mixture of even molecules of potassium and magnesium chlorids crystallized with six molecules of water. It is represented by the symbols KCl·MgCl₂·6H₂O. As it comes from the mines it contains small quantities of potassium and magnesium sulfates and small quantities of other accidental impurities. Existing as it does in immense quantities it has been extensively used for the manufacture of the commercial potassium chlorid (muriate of potash). For many purposes in agriculture, for instance, fertilizing tobacco fields, it is not suited, and it is less widely used as a fertilizer in general than its alteration product kainit. Its direct use as a fertilizer however is rapidly increasing since later experience has shown that chlorin compounds are capable of a far wider application in agriculture without danger of injury than was formerly supposed. As it comes from the mines, the Stassfurt carnallit has the following composition:

Potassium chlorid 15.5 per cent. Magnesium “ 21.5 “ “ Magnesium sulfate 12.1 “ “ Sodium chlorid 22.4 “ “ Calcium sulfate 1.9 “ “ Water 26.1 “ “ Undetermined 0.5 “ “

Pure carnallit would have the following composition:

Chlorin 38.3 per cent. Potassium 14.0 “ “ Magnesium 8.7 “ “ Water 39.0 “ “

Equivalent to

Potassium chlorid 26.8 “ “ Magnesium “ 34.2 “ “ Water 39.0 “ “

The commercial article as taken from the mines, as is seen above, has less potash (K₂O) than kainit, the mean content being about nine and nine-tenths per cent. Those proposing to use this body for fertilizing purposes should bear in mind that it contains less potash and more chlorin than kainit.

Carnallit occurs in characteristic brown-red masses. On account of its highly hygroscopic nature it should be kept as much as possible out of contact with moist air and should not be ground until immediately before using.

By reason of the greater bulk in proportion to its content of potash and its hygroscopic nature and consequent increased difficulty in handling, the price per unit of potash in carnallit is less than in kainit.

In some localities small quantities of ammonium chlorid have been found with carnallit but not to exceed one-tenth per cent. It has therefore no practical significance to the farmer but may be of interest to the analyst.

=239. Polyhalit.=—Polyhalit is a mineral occurring in Stassfurt deposits and consisting of a mixture of potassium, magnesium, and calcium sulfates, with a small proportion of crystal water. This mineral, on account of its being practically free of chlorin, would be one especially desirable for use in those cases, as in the culture of tobacco, where chlorids are injurious. Unfortunately, it does not occur in sufficient quantities to warrant the expectation of its ever being found in masses large enough to become a general article of commerce. It is found only in pockets or seams among the other Stassfurt deposits, and there is no assurance given on finding one of these deposits of polyhalit that it will extend to any great distance. The composition of the mineral is shown by the following formula: K₂SO₄·MgSO₄·(CaSO₄)₂·H₂O. Its percentage composition is shown by the following numbers:

Potassium sulfate 28.90 per cent. Magnesium sulfate 19.93 “ “ Calcium sulfate 45.18 “ “ Water 5.99 “ “

The percentage of potash corresponding to the above formula is 15.62. It therefore contains a considerable excess of potash over kainit, and on account of its freedom from chlorids, would be preferred for many purposes.

=240. Krugit.=—This mineral occurs associated with polyhalit and differs from it only in containing four molecules of calcium sulfate instead of two. Its formula is: K₂SO₄·MgSO₄·(CaSO₄)₄·H₂O. As it comes from the mines it is frequently mixed with a little common salt. Its mean percentage composition as it comes from the mines is given in the following numbers:

Potassium sulfate 18.60 per cent. Magnesium sulfate 14.70 “ “ Calcium sulfate 61.00 “ “ Sodium chlorid 1.50 “ “ Water 4.20 “ “

The percentage of potash corresponding to the above formula is 10.05. It is therefore less valuable than kainit in so far as its content of potash is concerned. This salt also exists in limited quantities and is not likely to become an important article of commerce.

=241. Sylvin.=—One of the alteration products of carnallit is a practically pure potassium chlorid which, as it occurs in the Stassfurt mines is known as sylvin. The alteration of the carnallit arises from its solution in water from which, on subsequent evaporation, the potassium chlorid is deposited alone. This mineral is found in only limited quantities in the Stassfurt deposits and it therefore does not have any great commercial importance.

=242. Sylvinit.=—This mineral has been mined in recent years in considerable quantities. It is, in fact, only common salt carrying large quantities of potassium chlorid together with certain other accidental impurities. It was probably formed by the drying up of a saline mass in such a way as not to permit the complete separation of its mineral constituents. The average composition of sylvinit as it comes from the mines is given in the following table:

Potassium chlorid 30.55 per cent. Sodium chlorid 46.05 “ Potassium sulfate 6.95 “ Magnesium sulfate 4.80 “ Magnesium chlorid 2.54 “ Calcium sulfate 1.80 “ Water and insoluble 7.29 “

This salt is richer in chlorin than any other of the Stassfurt potash minerals, containing altogether 79.14 per cent of chlorids. Its potash content amounts to 23.04 per cent, but in proportion to the potash which it contains, it is relatively poorer in chlorin than kainit and carnallit. On account of its high content of potash the freights on a given weight thereof as contained in sylvanit are lower than for kainit and carnallit.

=243. Kieserit.=—The mineral kieserit is essentially magnesium sulfate and it does not necessarily contain any potash salts. Under the name of kieserit, however, or bergkieserit, there is mined a mixture of carnallit and kieserit, which is a commercial source of potash. The mixture contains the following average content of the bodies named:

Potassium chlorid 11.80 per cent. Magnesium sulfate 21.50 “ Magnesium chlorid 17.20 “ Sodium chlorid 26.70 “ Calcium sulfate 0.80 “ Water 20.70 “ Insoluble 1.30 “

This mixture contains only about seven per cent of potash and would not prove profitable when used at a distance from the mines on account of the cost of freights. It has proved valuable, however, for a top dressing for meadow lands in the vicinity of Stassfurt.

=244. Schönit.=—Among the Stassfurt deposits there occurs in small quantities a mineral, schönit, which is composed of the sulfates of potassium and magnesium. The quantity of the mineral occurring naturally is very small and therefore it has no commercial importance. When, however, kainit is washed with water the common salt and magnesium chlorid which it contains being more soluble are the first leached out, and the residue has approximately the composition of the pure mineral. This mixture, as prepared in the way mentioned above, has the following average composition:

Potassium sulfate 50.40 per cent. Magnesium sulfate 34.00 “ Sodium chlorid 2.50 “ Water 11.60 “

The percentage of potash corresponding to the above composition is 27.2. This substance being so rich in potash, and practically free of chlorids, is well suited to transportation to great distances and for general use in the field. Since, however, a considerable expense attends the manufacture of the artificial schönit, the advantages above named give it very little, if any, advantage in competition with the other potash salts as they come from the mines. It has, however, an especial value for the fertilization of tobacco and vineyards.

=245. Potassium Sulfate.=—Several grades of potassium sulfate are found in the market for fertilizing purposes, some of them quite pure, containing over ninety-seven per cent of the pure sulfate. The following data show the composition of a high grade and low grade potassium sulfate of commerce:

High grade. Low grade. Potassium sulfate 97.20 per cent. 90.60 per cent. Potassium chlorid 0.30 “ 1.60 “ Magnesium sulfate 0.70 “ 2.70 “ Magnesium chlorid 0.40 “ 1.00 “ Sodium chlorid 0.20 “ 1.20 “ Insoluble 0.20 “ 0.30 “ Water 0.70 “ 2.20 “

Naturally, high grade sulfates of this kind can only be prepared in chemical factories built especially for the work. The result is that the potash per unit is raised greatly in price. When, however, the fertilizers are to be transported to a great distance, the saving in freight often more than compensates for the higher price of the potash. It therefore happens that there are many places in this country where the actual price of potash per pound is less in high grade sulfates than in kainit or carnallit. When, in addition to this, the especial fitness of the high grade sulfates for certain forms of fertilization, especially tobacco growing, is considered, it is seen that at this distance from the mines these high grade salts are of no inconsiderable importance. The percentage of potash in the high grade sulfates often exceeds fifty.

=246. Potassium Magnesium Carbonate.=—This salt has lately been manufactured and used to a considerable extent, especially for tobacco fertilizing. As furnished to the trade it has the following average composition:

Potassium carbonate 35 to 40 per cent. Magnesium carbonate 33 to 36 “ Water of crystallization 25 “ Potassium chlorid, potassium sulfate, and insoluble 2 to 3 “

The content of potash, as is seen from the above formula, amounts to from seventeen to eighteen per cent. The compound is completely dry, is not hygroscopic, and is, therefore, always ready for distribution. It is especially to be recommended for all those intensive cultures where it is feared that chlorids and sulfates will prove injurious, especially in the cultivation of tobacco.

=247. Potash in Factory Residues.=—The residues from the potash factories in Stassfurt and vicinity contain considerable quantities of potash and attempts have been made to recover this waste and put it into form for fertilizing uses. The waste waters of the factories are sometimes collected and evaporated, and the residue incinerated. The content of potash in these residues is extremely variable, usually quite low, and they, therefore, cannot be recommended for fertilizing purposes, especially if they are to be transported to any distance.

=248. Quantity of Potash Salts Used.=—The total quantity of potash delivered to consumers from the Stassfurt mines in 1891, the last year for which complete statistics are at hand was 413,508 tons of kainit and sylvinit, 39,444 tons of carnallit, 18,078 tons of sulfate, and 12,453 tons of the potassium magnesium sulfate. Of the above quantities, 115,245 tons of kainit were shipped to North America, and of the high grade sulfate mentioned, 13,322 tons were sent to other countries, and of the potassium magnesium sulfate, 11,081 tons were exported.

METHODS OF ANALYSIS.

=249. Classification of Methods.=—To detect the presence of potash in a mixture the aid of the spectroscope may be invoked. In the scale of the spectrum divided into 170 parts, on which the sodium line falls at 50, potassium gives three faint rather broad bands, two red, falling at 17 and 27, and one plum-colored band, near the extreme right of the spectrum, at 153. Potassium, however, does not give brilliant and well-marked spectral bands, such as are afforded by its associates rubidium, caesium, sodium, and lithium. A convenient qualitative test which, for practical purposes will be quite sufficient, may be secured by dipping a platinum loop into a strong acid solution of the supposed potash compound, and viewing through a piece of cobalt glass, the coloration produced thereby when held in the flame of a bunsen. The red-purple tint thereby produced should be compared with that coming from a pure potash salt similarly treated. If a fertilizer sample give no indication of potash when treated as above it may be safely concluded that it does not contain any weighable quantity of potash.

For the estimation of the percentage of potash present in a given sample it may be safely assumed that all of value in agriculture will be given up to an aqueous or slightly acid solution if organic matter have been destroyed as indicated in a previous paragraph. In the case of minerals insoluble in a dilute acid the potash may be determined by some one of the processes given in the first volume. The potash having been obtained in an aqueous or slightly acid (hydrochloric) solution, it may be determined either by precipitation as potassium platinochlorid or as potassium perchlorate. The former method is the one which has been almost exclusively used by analysis in the past, but the latter one is coming into prominence and by reason of the greater economy attending its practice and the excellent results obtained by some analysts, demands a generous consideration.

=250. The Platinic Chlorid Method.=—The principle of this method rests on the great insolubility of the potassium platinochlorid in strong alcohol and the easy solubility of some of its commonly attending salts; viz., sodium, etc., in the same reagent. Before the precipitation of the potash it is necessary to remove the bases of the earths, sulfates, etc. Barium chlorid and hydroxid, ammonium oxalate or carbonate, sulfuric acid, etc., are used in conjunction or successively to effect these purposes in the manner hereinafter described. The filtrate and washings containing the potash are evaporated to dryness and gently ignited to expel excess of ammonium salts and in the residue taken up with water and acidulated with hydrochloric acid, the potash is precipitated with platinic chlorid solution. The best methods of executing the analysis follow.

=251. The Official Agricultural Method.=—This method is based on the processes at first proposed by Lindo and Gladding, and is given below as adapted to mixed fertilizers and mineral potash salts.

(1) In Superphosphates.—Boil ten grams with 300 cubic centimeters of water thirty minutes. To the hot solution add ammonia in slight excess, and then a sufficient quantity of ammonium oxalate to precipitate all the lime present; cool and make up to half a liter, mix thoroughly, and filter through a dry filter; evaporate fifty cubic centimeters, corresponding to one gram, nearly to dryness, add one cubic centimeter of dilute sulfuric acid (1 to 1), evaporate to dryness and ignite to whiteness. As all the potash is in form of sulfate, no loss need be apprehended by volatilization of potash, and a full red heat must be maintained until the residue is perfectly white. This residue is dissolved in hot water, plus a few drops of hydrochloric acid, and a slight excess of platinum solution is added. This solution is then evaporated to a thick paste in a small dish, and eighty per cent alcohol added. In evaporating, special precaution should be taken to prevent absorption of ammonia. The precipitate is washed thoroughly with alcohol by decantation and on the filter, as usual. The washing should be continued even after the filtrate is colorless. Ten cubic centimeters of the ammonium chlorid solution, prepared as hereinafter directed, are run through the filter, or the washing may be performed in the dish. The ten cubic centimeters will contain the bulk of the impurities, and are thrown away. Fresh portions of ten cubic centimeters of the ammonium chlorid are run through the filter several times (5 or 6). The filter is then washed thoroughly with pure alcohol, dried, and weighed as usual. Care should be taken that the precipitate is perfectly soluble in water. The platinum solution used contains one gram of metallic platinum in every ten cubic centimeters. To prepare the washing solution of ammonium chlorid, place in a bottle 500 cubic centimeters of water and 100 grams of ammonium chlorid and shake till dissolved. Now pulverize five or ten grains of potassium platinochlorid, put in the bottle and shake at intervals for six or eight hours; let settle over night, then filter off the liquid into a second bottle. The first bottle is then ready for preparation of a fresh supply when needed.

(2) Potassium Chlorids.—In the analysis of these salts an aliquot portion of the solution, containing a half gram, is evaporated with forty cubic centimeters of the platinum solution and a few drops of hydrochloric acid, and washed as before.

(3) Potassium Sulfate, Kainit, Etc.—In the analysis of kainit, dissolve ten grams of the pulverized salt in 300 cubic centimeters of boiling water, add ammonia to slight excess, then a sufficient quantity of ammonium oxalate to throw down all lime present; cool and make up to half a liter, mix thoroughly, and filter on a dry filter; from twenty-five cubic centimeters, corresponding to a half gram, proceed to remove the ammonia, as in the analysis of superphosphates; dissolve the residue in hot water, plus a few drops of hydrochloric acid, and add fifteen cubic centimeters of platinum solution. In the analysis of high-grade sulfate and of double-manure salt (potassium sulfate, magnesium sulfate, containing about twenty-seven per cent of potassium oxid), make up the solution as above, but omit the precipitation, evaporation, etc.; to an aliquot part equal to a half gram add fifteen cubic centimeters of platinum solution. In all cases special care must be taken in the washing with alcohol to remove all the double platinum sodium chlorid which may be present. The washing should be continued some time after the filtrate is colorless. Twenty-five cubic centimeters of the ammonium chlorid solution are employed instead of ten cubic centimeters, and the twenty-five cubic centimeters poured through at least six times to remove all sulfates and chlorids. Wash finally with alcohol; dry and weigh as usual.

=252. Alternate Method for Potash.=—Boil ten grams of the prepared sample for thirty minutes with 300 cubic centimeters of water, and, after cooling and without filtering, make up to one liter and filter through a dry filter. If the sample have ten per cent of potassium oxid, use fifty cubic centimeters of the filtrate; if less than ten per cent of potassium oxid (ordinary potash fertilizers), use 100 cubic centimeters of the filtrate. In each case make the volume up to 150 cubic centimeters, heat to 100°, and add, drop by drop with constant stirring, a slight excess of barium chlorid, and, without filtering, in the same manner add barium hydrate in slight excess. Filter while hot and wash until the precipitate is free of chlorids. Add to the filtrate one cubic centimeter of strong ammonium hydrate, and then a saturated solution of ammonium carbonate, until the excess of barium is precipitated. Heat and add, in fine powder, a half gram of pure oxalic acid or 0.75 gram of ammonium oxalate. Filter, wash free of chlorids, evaporate the filtrate to dryness in a platinum dish, and ignite carefully over the free flame, below red heat, until all volatile matter is driven off.

The residue is digested with hot water, filtered through a small filter, and washed with successive small portions of water until the filtrate amounts to thirty cubic centimeters or more. To this filtrate, add two drops of hydrochloric acid, in a porcelain dish, and from five to ten cubic centimeters of a solution of ten grams of platinic chlorid in 100 cubic centimeters of water. The mixture is evaporated on a water-bath to a thick sirup, as above, treated with alcohol of eighty per cent strength, washed by decantation, collected in a gooch or other form of filter, washed with strong alcohol, afterwards with five cubic centimeters of ether, dried for thirty minutes at 100°, and weighed.

It is desirable, if there be an appearance of foreign matter in the double salt, that it should be washed, according to the previous method, with ten cubic centimeters of the half-concentrated solution of ammonium chlorid, which has been saturated by shaking with potassium platinochlorid.

=253. Method of Solution for Organic Compounds.=—In case the potash is contained in organic compounds, like tobacco stems, cottonseed hulls, etc., weigh ten grams, saturate with strong sulfuric acid, and ignite in a muffle to destroy organic matter. Add a little strong hydrochloric acid to moisten the mass and warm slightly so as to loosen it in the dish. Proceed then as in the lindo-gladding or alternate method.

=254. Factors.=—The use of the factors 0.3056 for converting potassium platinochlorid to potassium chlorid and 0.19308 for converting it to potassium oxid is advised. The latter number is almost identical with that used by the Halle and Stassfurt chemists viz., 0.1927 and 0.1928 respectively.

=255. Methods Used at the Halle Station.=—(1) In Kainits and other Mineral Salts of Potash.—Five grams of the prepared sample are boiled for half an hour in a half liter flask with from twenty to thirty cubic centimeters of concentrated hydrochloric acid and 100 cubic centimeters of water, and afterwards as much water added as is necessary to fill the flask about three quarters full, and the sulfuric acid is then precipitated with barium chlorid. To avoid an excess of barium chlorid the solution used is of known strength and is added first in such quantity as would precipitate the sulfuric acid from a kainit of low sulfuric acid content. The mixture is then boiled, allowed to settle and tried with a dropping tube containing barium chlorid. If a further precipitate be given a few drops more of barium chlorid solution are added, again boiled and allowed to settle. This is continued until barium chlorid gives no precipitation. After the barium chlorid gives no more precipitate a drop of dilute sulfuric acid is added to test for excess of barium. The operation is continued with the sulfuric acid until it no longer gives a precipitate of barium sulfate. By the alternate use of the barium chlorid and sulfuric acid the exact neutral point can soon be secured. When this point is reached the liquid is allowed to cool, the flask is filled to the mark, its contents filtered, and of the filtrate fifty cubic centimeters, equal to half a gram of the substance, taken for further estimation.

This quantity is evaporated on a water-bath to a sirupy consistence in a porcelain dish with ten cubic centimeters of platinic chlorid. The platinic chlorid solution should contain one gram of platinum in each ten cubic centimeters. The residue is treated with eighty per cent alcohol and, with stirring, allowed to stand for an hour. The precipitate is then collected on a gooch, either of platinum or porcelain, washed about eight times with eighty per cent alcohol and the potassium platinochlorid dried for two hours at 100°. After weighing the precipitate is dissolved in hot water and the residue washed under pressure, first with hot water and then with alcohol. The crucible with the asbestos felt is dried at 100° and weighed. Any impurities which the double salt may have carried down with it are left on the filter and the weight of the original precipitate can thus be corrected. The weight of potassium platinochlorid is multiplied by 0.1927 and the product corresponds to the weight of K₂O in the sample taken.

(2) Estimation of Potash in Guanos and Other Fertilizers containing Organic Substances.—Ten grams of the substances are carefully incinerated at a low temperature in a platinum dish. After ignition the contents of the dish are placed in a half liter flask and boiled for an hour with hydrochloric acid and a few drops of nitric acid. The sulfuric acid can then be precipitated directly with barium chlorid, or better, allow the flask to cool, fill to the mark, filter and treat an aliquot part of the filtrate with barium chlorid as described above. The filtrate from the separated sulfate of barium is neutralized with ammonia and all the bases, with the exception of magnesia and the alkalies, precipitated with ammonium carbonate; boil, fill to the mark and filter. Of this filtrate evaporate from 100 to 200 cubic centimeters in a platinum dish. After evaporation the ammonium salts are driven off by careful ignition, the residue taken up with hot water and filtered through as small a filter as possible into a porcelain dish; the magnesia remaining in the precipitate. The filtrate is acidified with a few drops of hydrochloric acid, ten cubic centimeters of platinic chlorid added and the further determination conducted as with kainit.

=256. Dutch Method.=—The process used at the Royal Agricultural Station of Holland is almost identical with that employed at Halle.

A. Method for Stassfurt and other Potash Salts.—The necessary reagents are:

1. A dilute solution of barium chlorid:

2. A solution of platinic chlorid containing one gram of platinum in ten cubic centimeters: It must be wholly free from platinous chlorid and nitric acid, and partially freed from an excess of hydrochloric acid by repeated evaporations with water.

3. Alcohol of eighty per cent strength by the volume:

The methods of bringing the potash into solution and of precipitating the sulfuric acid are the same as for the Halle process described above.

Add then twenty cubic centimeters of the platinum solution and evaporate the mixture nearly to dryness. Add a sufficient quantity of eighty per cent alcohol and stir for some time. Allow to stand and then filter through a gooch dried at 120°. Finally wash with eighty per cent alcohol, dry at 120°, and weigh.

B. Method for Potash Superphosphate and other mixed Fertilizers.—The reagents necessary are the same as under A, and, in addition, a saturated solution of barium hydrate and a solution of ammonium carbonate mixed with ammonia.

Boil twenty grams of the substance with water for half an hour, cool, make up to half a liter and filter. Boil fifty cubic centimeters of the filtrate, and add barium chlorid till no more precipitate forms. Mix with baryta water to strong alkaline reaction, cool, make up to 100 cubic centimeters and filter. Raise fifty cubic centimeters of the filtrate to the boiling temperature and add ammonium carbonate solution till no more precipitate forms: Cool, make up to 100 cubic centimeters and filter. Transfer fifty cubic centimeters of the filtrate to a platinum dish, evaporate and heat the residue, avoiding too high a temperature, till the ammonia salts are expelled. Dissolve the residue in water, filter, and treat the filtrate as described under A.

=257. Swedish Methods.=—The Swedish chemists determine the potash in mineral salts by the platinum chlorid process, but with certain variations from the processes already given. The manipulation is conducted as follows:

Weigh one gram of the sample to be examined and pour about 300 cubic centimeters of hot water over it in a beaker and filter after complete solution; add one cubic centimeter of hydrochloric acid, heat nearly to boiling, add dilute barium chlorid solution from a pipette or burette in a very fine stream stirring, slowly and carefully, till all sulfuric acid is completely precipitated, and only a trace of the precipitant is in excess. If the precipitation be conducted in the way given the barium sulfate will come down in crystalline condition, and settle rapidly within a few minutes, and almost immediately after the precipitation is finished may be filtered clear. The filtrate and washings from the barium sulfate are brought into a liter flask; fill this to the mark, take out fifty cubic centimeters with a pipette, evaporate the greater portion on a water-bath in a porcelain dish, transfer the residue by means of ammonia-free water to a beaker of fifty cubic centimeters capacity, add ten cubic centimeters of platinic chlorid solution, stir well with a glass rod, evaporate on a water-bath to a sirupy condition, allow to cool, and if the residue be too dry, add a few drops of water to allow the sodium platinochlorid to take up crystal water with certainty, stir well, add alcohol after a few minutes, mix carefully, leave the mixture standing for a while in the beaker covered with a watch glass, stirring occasionally; finally decant the solution, which must be of a dark yellow color, through a very small filter, wash the precipitate in the beaker repeatedly with small quantities of alcohol and decant; then transfer the precipitate to the filter, wash with alcohol, dry the filter and the precipitate at a gentle heat till all alcohol has evaporated, carefully transfer the contents of the filter to a watch glass placed on white glazed paper; dissolve the potassium platinochlorid still remaining on the filter in small quantities of boiling water, evaporate the filtrate on a water-bath in an accurately weighed platinum dish to dryness and transfer the same to the main portion of the chlorid from the watch glass. In order to obtain the salt free of the corresponding combinations of sodium, barium, calcium, and magnesium, which salts, although soluble in alcohol, may make the salt impure, before weighing, treat the precipitate twice with small quantities of cold water which will dissolve these impurities; evaporate the solution after addition of one cubic centimeter of platinic chlorid nearly to dryness on a water-bath, treat the residue in the same way as given before, add the small quantity of potassium platinochlorid which is hereby obtained together with the main portion to the platinum dish, dry at 130°, and weigh. Only after having been treated in this way may the precipitated potassium platinochlorid be considered absolutely pure. The Stassfurt salts contain magnesia, often in large quantities and as a consequence the potassium platinochlorid precipitated directly is likely to be contaminated therewith.

=258. Methods for the Analysis of Carnallit, Kainit, Sylvinit, and Kieserit.=—The chemists of the German Potash Syndicate use the following methods in the analysis of the raw products mentioned above.

(1) Preparation of the Sample.—It is advisable to take from a large well mixed mass at least half a kilogram for the analytical sample and this should be ground to a fine powder in a mill or mortar.

(2) Estimation of the Potash by the Precipitation Method.—In a half liter flask are placed 35.70 grams of kainit or sylvinit, or 30.56 grams of carnallit or bergkieserit, which are boiled with 350 cubic centimeters of water after the addition of ten cubic centimeters of hydrochloric acid. After cooling the flask is filled to the mark with water, well shaken, and its contents filtered. Fifty cubic centimeters of the filtrate are treated in a 200 cubic centimeter flask with a solution of barium chlorid, the flask filled to the mark, well shaken, and its contents filtered. Twenty cubic centimeters of the filtrate, corresponding to 0.3570 or 0.3056 gram of the substance, are treated with five cubic centimeters of platinic chlorid solution and the potassium estimated according to the usual methods.

(3) Estimation of Potash (K₂O) in Raw Potash Salts.—(a) For the determination of potash alone in carnallit, kainit, and sylvinit one hundred grams of the well-mixed sample are put into a graduated flask holding one liter and dissolved by boiling with half a liter of water, acidulated with ten cubic centimeters of hydrochloric. The purpose of adding hydrochloric acid is to bring any polyhalit that might be present in the salts into solution and which it is difficult to dissolve in pure water. After dissolving and cooling the flask is filled up to the mark. The solution, after mixing, is filtered through a dry filter and 100 cubic centimeters of the filtrate, corresponding to ten grams substance, are put into a half liter flask by means of a pipette. After the addition of 200-300 cubic centimeters of water the solution is heated to boiling and the sulfuric acid accurately precipitated with normal barium chlorid solution, containing 104 grams of the dry salt in one liter. The volume of the precipitate is calculated from the amount of barium solution used and from the specific gravity of the barium sulfate. After cooling, the flask is filled up with water as far above the mark as equals the volume of the calculated barium precipitate, and, after thorough mixing, the solution is filtered again through a dry filter. Fifty cubic centimeters of this filtrate, corresponding to one gram substance, are evaporated upon the water-bath with a sufficient amount of platinic chlorid. The residue of potassium platinochlorid is washed with ninety per cent alcohol, dried at 120°, and weighed.

(b) If it be desired to determine separately the quantity of potash present in the form of sulfate and in the form of chlorid, as for example in kainit and in sulfate of potash, or if it is to be determined whether potassium sulfate is in combination with a proportionate amount of magnesium chlorid, as in kainit, or in combination with magnesium sulfate alone, as in schönit, it then becomes necessary to determine besides potash the percentages of chlorin, sulfuric acid, lime, magnesia, the total alkalies, water, and the residue insoluble in water. For this purpose 100 grams of the sample are dissolved, the solution is filtered, the filter washed, and the filtrate made up to one liter; a part of the liquid is taken for the determination of sulfuric acid; by precipitating with barium chlorid, and another part for the determination of lime and magnesia. For the determination of the alkali chlorids, 100 cubic centimeters of the solution, corresponding to ten grams substance, are acidulated with hydrochloric, and, after heating to boiling, the sulfuric acid is completely precipitated with barium chlorid, with the precaution of using not more of the barium solution than is necessary for the complete precipitation. Fifty cubic centimeters of the filtered solution, corresponding to one gram substance, are evaporated to dryness in order to drive off the hydrochloric acid. Magnesium chlorid is decomposed by igniting with oxalic acid or with mercuric oxid. After ignition, the residue is moistened with a little ammonium carbonate for the purpose of converting the calcium oxid that may have been formed into calcium carbonate. The alkali chlorids, which are entirely free of lime and magnesia, are weighed, and potassium chlorid is determined by means of platinic chlorid. The amount of sodium chlorid is obtained by deducting potassium chlorid from the mixed chlorids. For the water determination five grams of the sample are ignited and the loss of weight is determined. The ignited mass is dissolved in water, and for the purpose of determining the quantity of magnesium chlorid that may have been decomposed by the ignition the percentage of chlorin is determined by titration. The difference in the contents of chlorin before and after ignition is subtracted from the loss in weight, after allowance has been made for the absorption of oxygen and for the loss of hydrogen. The rest is water. The results obtained are calculated in the following manner: From the total amount of the sulfuric acid found, that portion is deducted which is combined with calcium as calcium sulfate; the rest of the sulfuric acid is divided into two equal parts for the purpose of calculating the contents of potassium sulfate and magnesium sulfate, according to the molecular proportion in which these salts are present in kainit and in schönit. If there be an excess of potash left uncombined with sulfuric acid, then it is in the form of potassium chlorid; likewise the amount of magnesia, uncombined with sulfuric acid, is to be reckoned as magnesium chlorid. The result of this calculation will tell how much potash is in the form of kainit (K₂SO₄, MgSO₄, MgCl₂ with 6H₂O) and how much of it is in the form of schönit (K₂SO₄, MgSO₄, with 6H₂O) and how much in the form of potassium chlorid. The sodium is reckoned as sodium chlorid.

(c) In calculating the contents of potash, of potassium chlorid, and of potassium sulfate from the weighed potassium platinochlorid, the factors 0.1928, 0.3056, and 0.3566 are used, assuming that the atomic weight of platinum is 197.18.

(d) The two methods which have been described under a and b, and which are in common use in the Stassfurt potash industry, i. e., the so-called precipitation method, and the oxalic acid method, give almost identical results. The first method, however, deserves preference on account of greater simplicity in cases where potash alone is to be determined. Finkner’s method likewise gives results which agree well with the results obtained by the customary methods. It consists in evaporating the salt solution with a sufficient quantity of platinic chlorid without previously removing the sulfuric acid, reducing the potassium platinochlorid, and weighing the metallic platinum.

The following are the results of comparative analyses:

1. After the precipitation method 22.02 per cent KCl 2. After the oxalic acid method 22.03 per cent KCl 3. After Finkner’s method 22.01 per cent KCl

In another sample of carnallit the following results were obtained:

1. After the precipitation method 17.88 per cent KCl 2. After the oxalic acid method 17.88 per cent KCl

In a third sample of carnallit the content of potassium chlorid was as follows:

1. After the precipitation method 18.44 per cent 2. After the oxalic acid method 18.38 per cent

The Anhalt chemists object to precipitating the sulfuric acid and alkaline earths with barium oxid and ammonium carbonate, and afterwards the potash with platinic chlorid. The results obtained with this method are, according to them, very inaccurate, and always too low. This is explained by the fact that it is impossible to precipitate sulfuric acid without at the same time precipitating some of the potash, unless it be in an acid solution.

A separation of the alkaline earths, if potash alone is to be determined, is superfluous, for the reason that calcium and magnesium platinochlorid are soluble in ninety per cent alcohol, even with more facility than sodium platinochlorid.

=259. Methods for Concentrated Potash Salts.=—In the preceding paragraphs have been given the methods used by the Stassfurt syndicate for the estimation of potash in the raw salts as they come from the mines. Following are the methods used by the same syndicate for the concentrated approximately pure compounds and the other salts which accompany them.

Potassium Chlorid.—The following process is used for the estimation of potassium and other constituents of the high grade chlorids of commerce. In a half liter flask are placed 7.6405 grams of the finely powdered sample, which is dissolved and made up to the mark. With salts which contain more than half a per cent of sulfuric acid the preliminary conversion of the sulfates into the corresponding chlorin compounds, by precipitation with barium chlorid solution, is necessary. Twenty cubic centimeters of the above solution, corresponding to 0.3056 gram of the salt, are placed in a flat porcelain dish having a diameter of about ten centimeters and, after the addition of five cubic centimeters of the platinic chlorid solution, evaporated on the water-bath with constant stirring until, after cooling, the sirupy liquid passes quickly into a fine crystalline condition. The residue is rubbed into a fine powder with a glass rod, mixed with twenty cubic centimeters of ninety-six per cent alcohol and dried at 120° to a constant weight. It is weighed while warm and brought on a moistened filter with alcohol, care being taken that the liquid does not touch the edge of the filter. The filtration can be carried on under a moderate pressure. The complete washing of the potassium platinochlorid can be easily accomplished upon the filter. The filter and the precipitate, after as much of the alcohol wash has been removed as is possible, are dried at 120° to constant weight and weighed while still warm. One milligram of the potassium platinochlorid thus obtained corresponds to a tenth per cent of potassium chlorid.

Estimation of Sodium Chlorid.—For the estimation of the sodium chlorid which may be present in the potassium chlorid twelve and a half grams of the latter salt are dissolved in a quarter liter flask with twenty-five cubic centimeters of boiling water after the addition of a little potassium carbonate for the purpose of converting the magnesium and calcium compounds into carbonates. After filtration 100 cubic centimeters corresponding to five grams of the salt are evaporated to dryness in a porcelain or platinum dish after the addition of a few drops of concentrated hydrochloric acid in order to convert any calcium carbonate which may be present into chlorid. The residue is gently ignited and weighed. In this mixture of potassium and sodium chlorids the potassium chlorid may be estimated in the usual way and the sodium chlorid determined by difference or the respective proportions of the two bases may be calculated after the determination of the total chlorin by precipitation with a standard solution of silver nitrate.

Estimation of Magnesium Chlorid.—In order to estimate the amount of magnesium chlorid in high grade muriate of potash, twenty-five grams of the latter salt are dissolved in a half liter flask and treated with ten cubic centimeters of a normal solution of potash lye. The flask is then filled to the mark with water, thoroughly shaken and its contents filtered. Fifty cubic centimeters of the filtrate are then titrated with one-tenth normal sulfuric acid. The calcium compounds which remain in solution do not influence the result. The quantity of magnesium chlorid originally present corresponds to the number of cubic centimeters of the normal potash lye which has disappeared in the operation. The reaction which takes place is represented by the following equation:

MgCl₂ + 2KOH = MgO₂H₂ + 2KCl.

Potassium Sulfate.—The quantity of potassium sulfate contained in the high grade sulfates of commerce is determined in the following manner: In a half liter flask are placed 8.9235 grams of the finely ground sample which is dissolved in about 350 cubic centimeters of boiling water after the addition of twenty cubic centimeters of hydrochloric acid. The sulfuric acid is thrown out by the addition, drop by drop, of a barium chlorid solution, the contents of the flask being kept boiling meanwhile and thoroughly stirred. From time to time the addition of the barium chlorid is stopped and the upper part of the liquid allowed to become clear by the subsidence of the barium sulfate. It is then noticed whether or not an additional drop of the barium chlorid solution produces a turbidity. Any excess of barium chlorid is removed by the careful addition of sulfuric acid. After the precipitation is complete and the contents of the flask are cooled, it is filled up to the mark with water and its contents filtered. Twenty cubic centimeters of the filtrate, corresponding to 0.357 gram of the original salt are precipitated by platinic chlorid in the usual manner and the resulting potassium platinochlorid collected and weighed. One milligram of the potassium platinochlorid thus obtained corresponds to one-tenth per cent of potassium sulfate in the original salt. To the percentage of potassium sulfate thus found three-tenths per cent are to be added for a correction when high grade potassium sulfate is taken. If the sample be a high grade sulfate of potassium and magnesium no correction should be applied.

Estimation of Potassium Chlorid and Potassium Sulfate in Calcined Manurial Salts.—In these salts 15.281 grams for potassium chlorid or 17.847 grams for potassium sulfate are dissolved in a half liter flask after the addition of ten cubic centimeters of hydrochloric acid. The flask is filled to the mark and its contents filtered and 250 cubic centimeters placed in a half liter flask and treated with barium chlorid solution as indicated above. The rest of the operation is exactly as has been described. In each case one milligram of the potassium platinochlorid corresponds to one-tenth per cent of the desired salt.

Estimation of Magnesium Sulfate in Kieserit.—Ten grams of the finely powdered kieserit are boiled for one hour in a half liter flask two-thirds full of water. After cooling, from fifty to sixty cubic centimeters of double normal potash lye and twenty cubic centimeters of a ten per cent neutral potassium oxalate solution are added, the flask filled to the mark, and after being well shaken and standing for a quarter of an hour, filtered. The reaction is represented by the formula

MgSO₄ + 2KOH = MgO₂H₂ + K₂SO₄.

Fifty cubic centimeters of the filtrate are then titrated with one-tenth normal sulfuric acid. To the percentage of magnesium sulfate found by this process two-tenths per cent are to be added as a correction.

Barium Chlorid Solution.—Dissolve 122 grams of crystallized barium chlorid in water in a liter flask. Add fifty cubic centimeters of hydrochloric acid and water to the mark and shake well.

=260. The Barium Oxalate Method.=—The principle of this process, worked out by Schweitzer and Lungwitz is based on the fact that in an ammoniacal solution, by means of barium oxalate, all the alkaline earths can be precipitated as oxalates, and sulfuric acid in similar circumstances can be thrown down as a barium salt and the iron and alumina as hydroxids. The reagents used to secure this precipitation are ammonia and barium oxalate.

For the determination of potash in a superphosphate the analytical process is conducted as follows: Ten grams of the superphosphate are mixed with half a liter of water and fifteen grams of barium oxalate dissolved in hydrochloric acid.

The mixture is boiled for twenty minutes and treated with some hydrogen peroxid to oxidize any ferrous iron that may be present. Afterwards the solution is made alkaline with ammonia. After cooling, it is made up to a given volume (half a liter) and filtered. An aliquot part of the filtrate is evaporated to dryness, ignited, extracted with hot water and, after the addition of a few drops of hydrochloric acid, the potassium is precipitated with platinic chlorid, and collected and weighed in the usual manner: Or the ignited residue may be dissolved directly in dilute hydrochloric acid and the rest of the process carried out as indicated.

In kainit the process is conducted as follows: Ten grams of the powdered sample are treated with a hydrochloric acid solution of the barium oxalate containing ten grams of the salt. The rest of the operation is conducted as described above. In the use of this method it is important that always enough of the barium oxalate solution be employed to fully saturate all the sulfuric acid which may be present.

=261. Method of DeRoode for Kainit.=—All the potash contained in kainit, according to de Roode, passes readily into aqueous solution. On evaporating this aqueous solution to a pasty condition with enough platinic chlorid to unite with all the halogens present all the other bodies can be washed out of the potassium platinochlorid by ammonium chlorid solution and the pure platinum salt thus obtained, which is washed and dried in the usual way. De Roode therefore asserts that it is quite useless to previously precipitate the solution of kainit with barium chlorid, ammonium oxalate, or carbonate. Before the addition of alcohol to the residue obtained by evaporation with platinic chlorid the sodium sulfate present renders the platinum salt sticky and difficult to wash, but the disturbing sodium compound can be readily removed by washing with ammonium chlorid solution.

The method of direct treatment has the advantage of avoiding the occlusion of potash in other precipitates and the danger of loss on ignition. The method as used by de Roode gives results about one-tenth per cent higher than are obtained by the official processes.

=262. The Calcium Chlorid Method.=—Huston has proposed the addition of calcium chlorid to the solution of a fertilizer in the determination of potash, in order to furnish sufficient calcium to form tricalcium phosphate with all the phosphoric acid present, and thereby permit of the use of platinum dishes in the lindo-gladding method. In testing this process de Roode found that when sufficient calcium chlorid was added to combine with all the phosphoric acid present and then ammonia added in excess and a portion of the solution filtered, no test for phosphoric acid could be obtained; but, that if in addition to the calcium chlorid and ammonia, some ammonium oxalate or carbonate was added, a filtered portion of the solution gave a test for phosphoric acid. This is accounted for by the fact that the calcium phosphate, which is precipitated by the ammonia, is changed by the ammonium oxalate or carbonate into calcium oxalate or carbonate and ammonium phosphate, so that the very object for which the calcium chlorid was added is defeated by the addition of the ammonium oxalate or carbonate. In order to make the use of calcium chlorid effective it is necessary to filter the liquid from the precipitate formed by the calcium chlorid and ammonia and then add the ammonium oxalate or carbonate to the filtrate. This necessitates two separate filtrations and makes the proposed method of Huston as long as the old process.

=263. Rapid Control Method for Potash Salts.=—For rapid control work where great accuracy is not required Albert recommends that the finely ground substance be placed in a liter flask and about 400 cubic centimeters of water added and three cubic centimeters of hydrochloric acid. After boiling, barium chlorid is added drop by drop as long as a precipitate is produced. After cooling, the flask is filled to the mark and shaken and its contents filtered through a dry filter. An aliquot portion of the filtrate is evaporated with platinum chlorid solution in a smooth porcelain dish almost to dryness and the mass treated with alcohol, filtered through a weighed filter, and well washed with alcohol. The filter is then dried in an air-bath to a constant weight. For the different kinds of potash materials on the market the following proportions are recommended:

Kainit or Carnallit.—Twenty grams in one liter: Fifty cubic centimeters of the filtrate are evaporated with forty of platinic chlorid solution. The weight of potassium platinochlorid obtained × 19.3 gives the per cent of K₂O.

Sulfate of Potash.—Fifteen grams in one liter: Twenty cubic centimeters of the solution are evaporated with fifteen of platinic chlorid. The weight of potassium platinochlorid obtained × 64.33 gives the per cent of K₂O.

Potassium Chlorid.—Ten grams in one liter: Twenty-five cubic centimeters are evaporated with fifteen of platinic chlorid solution. The weight of the precipitate obtained × 77.2 gives the per cent of K₂O.

=264. Weighing the Precipitate as Metallic Platinum.=—Hilgard calls attention to the difficulty of weighing the double chlorid of platinum and potash as such, although he acknowledges that in the gooch this weighing can be made with great accuracy. He prefers to estimate the platinum in the metallic state and uses for this purpose a platinum crucible the inside of which, half way up from the bottom, is coated with a layer of platinum sponge, which is conveniently prepared by the decomposition of a few decigrams of the platinum double salt by inclining the crucible and rotating it during the progress of the reduction, using about a quarter of an hour in all. The platinum sponge produced in this way greatly favors the decomposition of the double salt for analytical purposes. The decomposition of the salt takes place quickly and quietly and at conveniently low temperatures.

When the decomposition is ended the crucible is strongly heated so as to hold the platinum sponge, which is produced, together sufficiently to prevent its being removed in the subsequent washing of the crucible by decantation. By the ignition at a high temperature necessary to secure this, the greater part of the calcium chlorid is volatilized. After cooling, a few drops of concentrated hydrochloric acid are placed in the crucible and if the slightest yellow color be shown the acid is evaporated and the ignition repeated, with the addition of a little oxalic acid. In most cases the slight yellow color produced comes from a trace of iron and will therefore appear again after the second ignition. The crucible is subsequently washed by repeated decantations, finally with boiling water, and after drying is ignited and weighed.

The advantage of this process is that without further trouble the reduced metal is completely freed of any salts of the alkaline earths, etc., which have been carried down with it and also from any of the uncombined sodium chlorid which may not have been washed out by the alcohol. In fact, the results obtained in this way are nearly always lower than those obtained through the direct weighing of the double salt, and the wash water which is first poured off contains, as a rule, traces of the alkaline earths and almost without exception some sodium chlorid. Correction for the filter ash is unnecessary because the ash is completely dissolved by the treatment received. The platinum sponge which is collected in the crucible in this way is removed in case it does not adhere to the sides and the crucible is then ready for the next operation.

=265. Sources of Error in the Platinum Method.=—In the comparative work done in the determination of potash by the members of the Association of Official Agricultural Chemists there has been noted, from year to year, marked differences in the data obtained by different analysts. Such differences often are due to personal errors, or a failure to accurately follow the directions for manipulation. Sometimes, however, they are due to sources of error in the processes employed. In the platinum method these sources of error have been long known to exist. Chief among these is the remarkable facility with which potash becomes incorporated with the precipitates of other bodies. The character and magnitude of some of these errors have lately been studied by Robinson.

Many precipitates occlude potash and hold it so firmly that it cannot be washed out with hot water although the potash compounds present in the precipitate are perfectly soluble. It appears to be a kind of molecular adhesion. Barium sulfate has this property of attaching potash molecules in a high degree, and ferric and aluminic compounds only to a slightly less extent. To reduce the losses, consequent on the conditions just mentioned, to a minimum, the sulfuric acid and earthy bases should be very slowly precipitated, with violent agitation, at a boiling temperature.

Another source of loss in the platinum method arises from the use of a solution of ammonium chlorid for washing the potassium platinochlorid precipitate. There is danger here, not only of the solution of the impurities present in the precipitate, but also of a double decomposition by means of which some ammonium may be substituted for the potassium in the washed product. In the official method, moreover, there is danger of securing a final precipitate which may contain traces of calcium and magnesium sulfates when these bodies are abundantly present in the sample taken for analysis. The careful analyst must guard against these sources of error, but it is probably true that he will never secure a practically chemically pure precipitate of potassium platinochlorid when working on the mixed fertilizers found in commerce.

=266. Effect of Concentration on the Accuracy of Potash Analysis.=—Winton has also studied the sources of error in the determination of potash as platinochlorid, especially with reference to the effect of the concentration of the solution at the time of precipitation.

He finds that the method of precipitating in concentrated solutions and drying the potassium platinochlorid at 130°, depends for its accuracy upon the mutual compensation of three errors; viz., (1) to the solubility of the potassium salt in eighty per cent alcohol, (2) to the presence of water in the crystals which is not driven off at 130°, and (3) the use of a factor based on the wrong atomic weight of platinum.

He finds, further, that the error due to the presence of water occluded in the crystals can be reduced to a minimum, and the process of drying greatly simplified, by adding the solution of platinum chlorid to the potash solution in a dilute condition, not exceeding one per cent in strength. The potassium platinochlorid thus produced can be very effectively dried at 100°. The error due to the solubility of the salt in eighty per cent alcohol can also be greatly reduced by using ninety-five per cent alcohol. The error due to the wrong factor, based on the old atomic weight of platinum, viz., 0.3056, can be corrected by using the factor based on the recently determined atomic weight of platinum, viz., 195, which is 0.30688.

=267. Differences in Crystalline Form.=—Winton has also observed a distinct difference in the crystals of potassium platinochlorid when obtained from concentrated and dilute solutions. When platinic chlorid is added to a concentrated solution of potassium chlorid, a large part of the salt which is formed is precipitated in a pulverulent state, the remainder being deposited on evaporation. After treating with alcohol, filtering, and drying, the double salt is found in the state of a fine powder which, when examined under the microscope, is found to consist largely of radiating crystals. The characteristic form is one having six arms formed by the intersection, at right angles, of three bars. Numerous globular cavities in the crystals are observed in which mother liquid is enclosed. For this reason the salt is not easily dried at 100°, but when so dried loses additional moisture at 130°, and still more at 160°. The total additional loss, after drying at 100°, from this cause may amount to as much as six-tenths per cent of potassium chlorid.

When, however, the solution of the potassium salt is so dilute that no precipitate at all is formed on the addition of platinic chlorid, the double salt is all deposited, as well as formed slowly, during the evaporation and occurs exclusively as octahedra. These octahedra are comparatively free of cavities, and give up practically all their moisture when dried at 100°. A method of procedure therefore for potash determination, based on the above principle of the addition of the reagent to dilute solutions, and drying the double salt produced upon evaporation, after washing with ninety-five per cent alcohol at 100°, and using the factor 0.30688 for potassium chlorid and 0.1939 for potassium oxid, gives good results and is regarded as better than any of the methods which prescribe the addition of platinic chlorid to highly concentrated potash solutions.

=268. Factors for Potash Estimation.=—The factor now in use by the official chemists to convert potassium platinochlorid into potash (K₂O) is 0.19308, and for potassium chlorid 0.3056.

Wolfbauer gives the differences which may arise by computing the potash from its platino-double chlorid by the different values assigned to the atomic weight of platinum.

The common factor used to obtain potassium chlorid from potassium platinochlorid is based on the atomic weight 197.18 and is derived from the formula:

2(39.13 + 35.46) 149.18 ------------------------------ = ------ = 0.30557. 2 × 39.13 + 197.18 + 6 × 35.46 = 488.20

The variations arising from taking other assigned values for the atomic weight of platinum are shown in the following table:

Factor for potassium Relation to factor chlorid from 0.30557 in per cent Atomic Determined weight of or Potassium Potassium Platinum. calculated platino- Platinum. platino- Platinum. by chlorid. chlorid.

197.18 Berzelius 0.30557 0.75658 100.00 100.00 197.88 Andrews 0.30517 0.75390 99.86 99.65 195.06 Haberstadt 0.30690 0.76468 100.44 101.07 Seubert } 194.87 and Clark } 0.30700 0.76555 100.47 101.20

The factor 0.3056 is regarded as the best for the computation from potassium platinochlorid and 0.7566 from platinum. It is also suggested that it is better to make the computation from the reduced platinum than from the double salt.

=269. Recovery of the Platinum Waste and Preparation of the Platinic Chlorid Solution.=—(1) By Reduction in Alkaline Alcohol.—All filtrates containing platinic chlorid, all precipitates of potassium platinochlorid and all residues of metallic platinum should be carefully preserved and the platinum recovered therefrom by the following process: The platinum residues are placed in a large porcelain dish. Since these residues contain a large amount of alcohol they should be diluted with about one-third their volume of water, and when boiling treated with some sodium carbonate. The solid potassium platinochlorids should not be added until the liquid is boiling, and then only little by little. The heating on the water-bath is continued until the liquid floating over the platinum sponge is quite clear and only slightly yellow. The liquid is then poured off and the reduced platinum purified by boiling with hydrochloric acid and water. It is then dried and ignited to destroy any organic matter which may be present. It is advisable to boil the finely divided platinum once with strong nitric acid, and after this is poured off the solution of the platinum is effected in a large porcelain dish over a water-bath by adding about four times its weight of hydrochloric acid, warming, and adding nitric acid, little by little. After the platinum is in solution the evaporation is continued until a drop of the liquid, removed by a glass rod, quickly solidifies. The crystalline mass which is formed on cooling is taken up with water and filtered, and then a sufficient amount of water added so that each ten cubic centimeters will contain one gram of platinum. The specific gravity of this solution is 1.18 at ordinary temperatures. Special care must be taken that the solution contains neither platinous chlorid nor nitrogen compounds. If the first named compound be present it should be converted into platinic chlorid by treatment with fuming hydrochloric acid and a little nitric acid. The last mentioned compound may be removed by evaporating successively with hydrochloric acid and water. If the platinic chlorid be made from waste platinum, the danger of contamination with iridium must be considered. In such a case the platinum should be separated as ammonium platinochlorid, which can afterwards be reduced as above indicated. A convenient test of the purity of platinic chlorid solution is accomplished by the precipitation of a known weight of chemically pure potassium salt.

(2) By Reduction in Nascent Hydrogen.—The platinum residues, filtrates containing platinum, etc., are collected in a large flask and evaporated in a large dish on a water-bath, and reduced by means of zinc and hydrochloric acid to metallic platinum, the mass being warmed until all the zinc has been dissolved. The supernatant liquid standing over the spongy platinum is decanted and the spongy mass boiled twice with distilled water. The spongy platinum is then brought on a filter and washed till the filtrate shows no acid reaction. The filter and platinum sponge are next incinerated in a platinum dish and the residue weighed. The weighed mass of pure platinum is dissolved in hydrochloric acid, with the addition of as little nitric acid as possible, and, after cooling, filtered. The filtrate is afterwards evaporated in a porcelain dish on a water-bath to a sirupy consistence, taken up with water and filtered. To this filtrate enough water is now added to make the solution correspond to one gram of metallic platinum in ten cubic centimeters.

THE ESTIMATION OF POTASH AS PERCHLORATE.

=270. General Principles.=—By reason of the great cost of platinum chlorid analysts have sought for a reagent of a cheaper nature and yet capable of forming an insoluble compound with potash. Phosphomolybdic and perchloric acids are the reagents which have given the most promising results. The principle of the method with the latter salt is based on the insolubility of potassium perchlorate in strong alcohol containing a little perchloric acid and the comparative easy solubility of the other bases usually associated with potassium in water. The French chemists have stated that magnesia, when present in considerable quantities, interferes with the accuracy of the results. Since in soil analysis considerable quantities of magnesia are often found, this base, according to the French chemists, should previously be removed when present in any considerable quantity, by the process described in the first volume. Kreider, however, as will be seen further on, working in the presence of magnesia, did not notice any disturbing effects caused thereby. The method is applicable to the common potash salts of the trade and with certain precautions to mixed salts. As will be mentioned later on, sulfuric acid should be previously removed and this is likely to introduce an error on account of the tendency of barium sulfate to entangle particles of potash among its molecules and thus remove them from solution. The barium sulfate should be precipitated slowly and in a strongly acid (nitric or hydrochloric) solution. The loss, which is inevitable, is thus reduced to a minimum and does not seriously affect the value of the numbers found. It is important to have an abundant supply of pure perchloric acid, and as this is not readily obtainable in the market the best methods of preparing it are given below. The method, while it has not been worked out extensively, is one of merit, and seemingly is worthy of fair trial by analysts. The process is by no means a new one, but it will not be necessary to describe here its development any further than to refer to the methods proposed by Serullas, Schlösing, Kraut, and Bertrand, The method was fully developed by a committee appointed by the French agricultural chemists in 1887.

Wense has also described an improved method of estimating potash as perchlorate after the removal of sulfuric acid and also a process of preparing perchloric acid by distilling potassium perchlorate with sulfuric acid in a vacuum. He was also the first who proposed the plan of rendering potassium perchlorate insoluble in alcohol by dissolving a little perchloric acid therein. The best approved methods now known of preparing the perchloric acid and conducting the analysis will be described in the following paragraphs.

=271. Caspari’s Method for Preparing Perchloric Acid.=—A hessian crucible about fifteen centimeters high is filled with moderately well compressed pure potassium chlorate and gradually heated in a suitable furnace until the contents become fluid. The heat must then be carefully regulated to avoid loss by foaming due to the evolution of oxygen. The heat is continued until oxygen is no longer given off and the surface of the liquid becomes encrusted, which will take place in from one and a half to two hours.

After cooling, the contents of the crucible are pulverized and heated, with vigorous stirring, to boiling, with one and a half times their weight of water. By this process the potassium chlorid which has formed during the first reaction is dissolved and is thus removed. The residual salt is washed with additional quantities of cold water and finally dried. To remove the potassium salt from the crude potassium perchlorate obtained as above, recourse is had to hydrofluosilicic acid. The reaction is represented by the following formula: 2KClO₄ + H₂SiF₆ = K₂SiF₆ + HClO₄. In order to effect this decomposition the potassium perchlorate is dissolved in seven times its weight of hot water and an excess of hydrofluosilicic added to the boiling solution. The boiling is continued for about an hour until particles of potassium perchlorate can no longer be detected with addition of water to compensate for evaporation.

On cooling the gelatinous potassium silicofluorid is deposited and the perchloric acid separated therefrom as completely as possible by decantation. The residue is again boiled with water and a little hydrofluosilicic acid and the clear liquor thus obtained added to the first lot. Finally, any residual perchloric acid may be removed on an asbestos felt under pressure. The clear liquid thus obtained is evaporated on a steam-bath to the greatest possible degree of concentration and allowed to stand in a cool place for twenty-four hours, whereby is effected the separation of any remaining potassium silicofluorid or potassium perchlorate. The residual liquid when filtered through an asbestos felt should give a perfectly clear filtrate. In order to throw out the last traces of hydrofluosilicic acid and any sulfuric acid present an equal volume of water is added, and while cold small quantities of barium chlorid are successively added until the barium salt is present in a very slight excess. The clear supernatant liquid is poured off after a few hours and evaporated until the hydrochloric acid is all expelled and white fumes of perchloric acid are noticed. Any potassium perchlorate still remaining will now be separated and, in the cold, sodium perchlorate will also be separated in crystals. The clear residue is again diluted with an equal volume of water and any barium salts present carefully removed with sulfuric acid. The mass is allowed to stand for one or two days, and is then filtered through paper and is ready for use. The purity of the acid obtained depends chiefly on the purity of the hydrofluosilicic acid at first used. Hence to get good results this acid must be free from foreign bodies. If an absolutely pure product be desired the acid above obtained must be distilled in a vacuum.

=272. Method of Kreider.=—Kreider has worked out a simpler method of preparing perchloric acid which will make it easy for every analyst to make and keep a supply of this admirable yet unappreciated reagent. This method is conducted as follows:

A convenient quantity of sodium chlorate, from 100 to 300 grains, is melted in a glass retort or round-bottomed flask and gradually raised to a temperature at which oxygen is freely, but not too rapidly evolved, and kept at this temperature till the fused mass thickens throughout, indicating the complete conversion of the chlorate to the chlorid and perchlorate, which requires from one and one-half to two hours: or the retort may be connected with a gasometer and the end of the reaction determined by the volume of oxygen expelled, according to the equation

2NAClO₃ = NACl + NAClO₄ + O₂.

The product thus obtained is washed from the retort to a capacious evaporating dish where it is treated with sufficient hydrochloric acid to effect the complete reduction of the residual chlorate, which, if the ignition has been carefully conducted with well distributed heat, will be present in but small amount. It is then evaporated to dryness on the steam-bath, or more quickly over a direct flame, and with but little attention until a point near to dryness has been reached, when stirring will be found of great advantage in facilitating the volatilization of the remaining liquid and in breaking up the mass of salt. Otherwise the perchlorate seems to solidify with a certain amount of water and its removal from the dish, without moistening and reheating, is impossible.

After triturating the residue, easily accomplished in a porcelain mortar, an excess of the strongest hydrochloric acid is added to the dry salt, preferably in a tall beaker where there is less surface for the escape of hydrochloric acid and from which the acid can be decanted without disturbing the precipitated chlorid. If the salt has been reduced to a very fine powder, by stirring energetically for a minute, the hydrochloric acid will set free the perchloric acid and precipitate the sodium as chlorid, which in a few minutes settles, leaving a clear solution of the perchloric acid with the excess of hydrochloric acid. The clear supernatant liquid is then decanted upon a gooch, through which it may be rapidly drawn with the aid of suction, and the residue retreated with the strongest hydrochloric acid, settled, and again decanted, the salt being finally brought upon the filter where it is washed with a little strong hydrochloric acid. A large platinum cone will be found more convenient than the crucible, because of its greater capacity and filtering surface. When the filter will not hold all the sodium chlorid, the latter, after washing, may be removed by water or by mechanical means, with precautions not to disturb the felt, which is then ready for the remainder. Of course, if water is used, the felt had better be washed with a little strong hydrochloric acid before receiving another portion of the salt. This residue will be found to contain only an inconsiderable amount of perchlorate, when tested by first heating to expel the free acid and then treating the dry and powdered residue with ninety-seven per cent alcohol, which dissolves the perchlorate of sodium but has little soluble effect on the chlorid.

The filtrate, containing the perchloric acid with the excess of hydrochloric acid and the small per cent of sodium chlorid which is soluble in the latter, is then evaporated over the steam-bath till all hydrochloric acid is expelled and the heavy white fumes of perchloric acid appear, when it is ready for use in potassium determinations. Evidently the acid will not be chemically pure because the sodium chlorid is not absolutely insoluble in hydrochloric acid; but a portion tested with silver nitrate will prove that the sodium, together with any other bases which may have gone through the filter, has been completely converted into perchlorate, and unless the original chlorate contained some potassium or on evaporation the acid was exposed to the fumes of ammonia, the residue of the evaporation of a portion is easily and completely soluble in ninety-seven per cent alcohol and its presence is therefore unobjectionable. One cubic centimeter of the acid thus obtained gives on evaporation a residue of only 0.036 gram, which is completely soluble in ninety-seven per cent alcohol.

Caspari’s acid under similar treatment gave a residue in one case of 0.024 gram and in another 0.047 gram. If, however, a portion of pure acid be required, it may be obtained by distilling this product under diminished pressure and, as Caspari has shown, without great loss providing the heat is regulated according to the fumes in the distilling flask.

Some modification of the above treatment will be found necessary in case the sodium chlorate contains any potassium as an impurity, or if the latter has been introduced from the vessel in which the fusion was made. In these circumstances the hydrochloric acid would not suffice for the removal of potassium, since a trace might also go over with the sodium and thus on evaporation a residue insoluble in ninety-seven per cent alcohol be obtained. To avoid this difficulty, the mixture of sodium perchlorate and chlorid, after treating with hydrochloric acid for the reduction of the residual chlorate, being reduced to a fine powder, is well digested with ninety-seven per cent alcohol, which dissolves the sodium perchlorate but leaves the chlorid, as well as any potassium salt insoluble. By giving the alcohol time to become saturated, which was facilitated by stirring, it was found on filtering and evaporating that an average of about two-tenths of a gram of sodium perchlorate are obtained for every cubic centimeter of alcohol and that the product thus obtained is comparatively free of chlorids, until the perchlorate is nearly all removed, when more of the chlorid seems to dissolve. This treatment with alcohol is continued until on evaporation of a small portion of the latest filtrate, only a small residue is found. The alcoholic solution of the perchlorate is then distilled from a large flask until the perchlorate begins to crystallize, when the heat is removed and the contents quickly emptied into an evaporating dish, the same liquid being used to wash out the remaining portions of the salt. When the distillation is terminated at the point indicated, the distillate will contain most of the alcohol employed, but in a somewhat stronger solution, so that it requires only diluting to ninety-seven per cent to fit it for use in future preparations. The salt is then evaporated to dryness on the steam-bath and subsequently treated with strong hydrochloric acid for the separation of the perchloric acid.

One cubic centimeter of the acid prepared in this way, on evaporation gave a residue in one case of 0.0369 gram, and in another 0.0307 gram, completely soluble in ninety-seven per cent alcohol, which was then ignited and the chlorin determined by silver from which the equivalent of perchloric acid in the form of salts was calculated as 0.0305 gram. By neutralizing the acid with sodium carbonate, evaporating, igniting in an atmosphere of carbon dioxid till decomposition was complete, collecting the oxygen over caustic potash, allowing it to act on hydriodic acid by intervention of nitric oxid, according to a process soon to be published, titrating the iodin liberated, with standard arsenic and calculating the equivalent of perchloric acid, after subtracting the amount of acid found in the form of salts, the amount of free acid per cubic centimeter proved to be 0.9831 gram.

The whole process, even when the separation with alcohol is necessary, can not well require more than two days and during the greater part of that time the work proceeds without attention.

=273. Keeping Properties of Perchloric Acid.=—By most authorities it is asserted that perchloric acid is a very unstable body and is liable to decompose with explosive violence even when kept in the dark. It is probable that this tendency to spontaneous decomposition has been exaggerated. It is not even mentioned in Gmelin’s Handbook.

The most concentrated aqueous acid has a specific gravity of 1.65, is colorless, fumes slightly when exposed to the air, and boils at 200°. It has no odor, possesses an oily consistence and has a strong and agreeably acid taste. It reddens litmus without bleaching it and is slowly volatilized at 138° without decomposition. It is unaffected by exposure to the light, even the sun’s rays. It is not decomposed by hydrosulfuric, sulfurous, or hydrochloric acids, nor by alcohol. Paper saturated with the strong acid does not take fire spontaneously, but it deflagrates with red-hot charcoal.

The acid prepared by the method of Kreider has approximately the composition of the di-hydrate, HClO₄·2H₂O. Unless well evaporated, however, it is a little more dilute than is shown by the above formula. The di-hydrate is quite stable and the more dilute acid can be kept for an indefinite time. Kreider has kept the acid for six months and noticed no change whatever in its composition. Acid containing one gram of perchloric acid in a cubic centimeter has been kept three months with perfect safety. There is no reason why the strong aqueous acid should not be made a regular article of commerce by dealers in chemical supplies, under proper restrictions for storage and transportation.

The strong acid made in this laboratory by the Kreider method has not given the least indication of easy or spontaneous decomposition.

=274. The Analytical Process.=—The perchlorate process cannot be applied in the presence of sulfuric acid or dissolved sulfates. This acid, when present, is to be removed by the usual methods before applying the perchloric acid. Phosphoric acid may be present, but in this case a considerable excess of the reagent must be used. The process, as originally proposed by Caspari and carried out by Kreider, is as follows:

The substance, free from sulfuric acid, is evaporated for the expulsion of free hydrochloric acid, the residue stirred with twenty cubic centimeters of hot water and then treated with perchloric acid, in quantity not less than one and one-half times that required by the bases present, when it is evaporated, with frequent stirring, to a thick, sirup-like consistency, again dissolved in hot water and evaporated, with continued stirring, till all hydrochloric acid has been expelled and the fumes of perchloric acid appear. Further loss of perchloric acid is to be compensated for by addition of more. The cold mass is then well stirred with about twenty cubic centimeters of wash alcohol—ninety-seven per cent alcohol containing two-tenths per cent by weight of pure perchloric acid, with precautions against reducing the potassium perchlorate crystals to too fine a powder. After settling, the alcohol is decanted on the asbestos filter and the residue similarly treated with about the same amount of wash alcohol, settled, and again decanted. The residual salt is then deprived of alcohol by gently heating, dissolved in ten cubic centimeters of hot water and a little perchloric acid, when it is evaporated once more, with stirring, until fumes of perchloric acid rise. It is then washed with one cubic centimeter of wash alcohol, transferred to the asbestos, preferably by a policeman to avoid excessive use of alcohol, and covered finally with pure alcohol; the whole wash process requiring from about fifty to seventy cubic centimeters of alcohol. It is then dried at about 130° and weighed.

The substitution of a gooch for the truncated pipette employed by Caspari will be found advantageous; and asbestos capable of forming a close, compact felt should be selected, inasmuch as the perchlorate is in part unavoidably reduced, during the necessary stirring, to so fine a condition that it tends to run through the filter when under pressure. A special felt of an excellent quality of asbestos was prepared for the determinations given below and seemed to hold the finer particles of the perchlorate very satisfactorily.

A number of determinations made of potassium, unmixed with other bases or non-volatile acids, is recorded in the following table:

Potassium Potassium Error on Error on chlorid Volume of perchlorate potassium potassium Error on taken. filtrate. found. perchlorate. chlorid. potash.

Cubic Grams. centimeters. Grams. Grams. Grams. Grams. 0.1000 54 0.1851 0.0008— 0.0004— 0.0003— 0.1000 58 0.1854 0.0005— 0.0002— 0.0002— 0.1000 51 0.1859 0.0000 0.0000 0.0000 0.1000 50 0.1854 0.0005— 0.0002— 0.0002— 0.1000 48 0.1859 0.0000 0.0000 0.0000 0.1000 52 0.1854 0.0005— 0.0002— 0.0002—

Considerable difficulty, however, was experienced in obtaining satisfactory determinations of potassium associated with sulfuric and phosphoric acids. As Caspari has pointed out, the sulfuric acid must be removed by precipitation as barium sulfate before the treatment with perchloric acid is attempted, and unless the precipitation is made in a strongly acid solution, some potassium is carried down with the barium. Phosphoric acid need not be previously removed, but to secure a nearly complete separation of this acid from the potassium, a considerable excess of perchloric acid should be left upon the potassium perchlorate before it is treated with the alcohol. When these conditions are carefully complied with, fairly good results may justly be expected. Below is given a number of the results obtained:

(A) = Volume of filtrate. Cubic centimeters. (B) = Potassium perchlorate found. (C) = Error on potassium perchlorate. (D) = Error on potassium chlorid. (E) = Error on potassium potash.

Compounds taken. (A) (B) (C) (D) (E) Grams. Grams. Grams. Grams. Grams. Potassium chlorid = 0.10 Calcium carbonate = 0.13 50 0.1887 0.0027+ 0.0014+ 0.0005+ Magnesium sulfate = 0.13 82 0.1875 0.0016+ 0.0008+ 0.0005+ Ferric chlorid = 0.05 80 0.1861 0.0002+ 0.0001+ 0.0001+ Magnesium sulfate = 0.05 80 0.1843 0.0016- 0.0008- 0.0005- Manganese dioxid = 0.05 92 0.1839 0.0020- 0.0010- 0.0006- Sodium phosphate = 0.40 60 0.1854 0.0005- 0.0002- 0.0002-

In the last three experiments of the above table the amount of perchloric acid was about three times that required to unite with the bases present, and the phosphoric acid subsequently found with the potassium was hardly enough to appreciably affect the weight, although its absolute removal was found impossible.

That the magnesia does not produce any disturbing effect, as is supposed by the French chemists, Kreider has proved by the following test: One hundred and fifty milligrams of magnesium carbonate were treated with perchloric acid, evaporated till fumes of perchloric acid appeared, and cooled, when the magnesium perchlorate crystallized: But on treating it with about fifteen cubic centimeters of ninety-seven per cent alcohol containing two-tenths per cent of perchloric acid a perfectly clear solution was obtained. If, therefore, a sufficient excess of acid be used, no interference will be caused by the presence of magnesium.

While it is true, therefore, that the potassium perchlorate obtained may be contaminated with a trace of phosphoric acid, if the latter be present in large quantity, no fear of contamination with magnesia need be entertained if a sufficient quantity of the perchloric acid be used.

=275. Removal of the Sulfuric Acid.=—The practical objection to the removal of the sulfuric acid in the form of barium sulfate rests on the fact of the mechanical entanglement of some of the potash in the barium salt. Unless special precautions are taken, therefore, a considerable amount of the potash will be found with the barium sulfate.

Caspari has succeeded in reducing this amount to a minimum by the following procedure: The solution of barium chlorid is prepared by dissolving 127 grams of crystallized barium chlorid in water, adding 125 cubic centimeters of thirty-five per cent hydrochloric acid, and bringing the total volume up to one liter with water.

Five grams of the substance from which the sulfuric acid is to be removed are boiled with 150 cubic centimeters of water and twenty of strong hydrochloric acid. While the solution is still in ebullition it is treated, drop by drop with constant stirring, with the barium chlorid solution above mentioned, until a slight excess is added. This excess does not cause any inconvenience subsequently. After the precipitation is complete the boiling is continued for a few minutes, the mixture cooled and made up to a quarter of a liter with water. No account is taken of the volume of the barium sulfate formed since, even with the precautions mentioned, a little potassium is thrown down and the volume of the barium sulfate tends to correct this error. With a solution from which the sulfuric acid had been removed as above indicated, Caspari found a loss of only one milligram of potassium perchlorate in a precipitate weighing over 800 milligrams.

=276. Applicability of the Process.=—Experience has shown that sulfuric acid is the only substance which need be removed from ordinary fertilizers preparatory to the estimation of the potash by means of perchloric acid. The fact that this process can be used in the presence of phosphoric acid is a matter of great importance in the estimation of potash in fertilizers, inasmuch as these fertilizers nearly always contain that acid. The fact that the French chemists noticed that magnesia was a disturbing element in the process, as has been indicated in volume first, probably arose from its presence as sulfate. Neither Caspari nor Kreider has noticed any disturbance in the results which can be traced to the presence of magnesia as a base.

If ammonia be present, however, there is a tendency to the production of ammonium perchlorate which is somewhat insoluble in the alcohol wash used. Solutions therefore containing ammonia before treating by the perchlorate method for potash should be rendered alkaline by soda-lye and boiled. With the precautions above mentioned, the method promises to prove of great value in agricultural analysis, effecting both a saving of time and expense in potash determinations.

=277. Accuracy of the Process.=—The perchlorate was tried in conjunction with the platinum method on the two samples of potash fertilizer prepared and distributed by the official reporter on potash for 1893. One of the samples was of a fertilizer which had been compounded for the Florida trade and contained bone, dried blood, and potash, mostly in the form of sulfate. The other sample consisted of mixed potash salts, sulfate, chlorid, double salt, kainit, and about five per cent of the triple sulfate of calcium, potassium, and magnesium.

The results obtained by Wagner and Caspari on the two samples follow:

Sample No. 1. Sample No. 2. Per cent potash. Per cent potash. By the platinum method 13.25 37.98 By the perchlorate method 13.09 37.82

The perchlorate method on the whole appears to be quite as accurate as the platinum process, requires less manipulation and can be completed in a shorter time and at less expense for reagents.

AUTHORITIES CITED IN PART THIRD.

Connecticut Agricultural Experiment Station, Bulletin No. 97, p. 7.

Annual Report Connecticut Station, 1892, p. 32.

Colorado Agricultural Experiment Station, Bulletin No. 10.

Connecticut Agricultural Experiment Station, Bulletin No. 103, p. 9.

Annual Report, Massachusetts Agricultural Experiment Station, 1888, p. 202.

Vid. op. cit. 2, 1890, p. 110.

Traité de la Fabrication de Sucre, Horsin-Déon, p. 511.

Chemical Division, U. S. Department of Agriculture, Bulletin No. 37, p. 350.

Journal of the American Chemical Society, Vol. 17, p. 86.

Volume First, pp. 19, et seq.

Precht: Die Stassfurter Kalisalze.

Maercker: Die Kalidüngung, S. 1.

Vid. op. cit. supra, p. 3.

Vid. op. cit. 12, p. 5.

Vid. op. cit. 12, p. 7.

Volume First, pp. 378, et seq.

Chemical News, Vol. 44, pp. 77, 86, 97, and 129.

Chemical Division, U. S. Department of Agriculture, Bulletin No. 7, p. 38.

Vid. supra, Bulletin No. 43, p. 349.

Die Agricultur-Chemische Versuchs-Station, Halle a/S., S. 76.

Methoden van onderzock aan de Rijkslandbouw-proefstations, 1893, p. 7.

From the Official Swedish Methods. Translated for the Author by F. W. Woll.

Chemical Division, U. S. Department of Agriculture, Bulletin No. 35, p. 63.

Chemiker Zeitung, Band 18, S. 1320.

Journal of the American Chemical Society, Vol. 17, p. 85.

Chemical Division, U. S. Department of Agriculture, Bulletin No. 43, p. 26.

Vid. op. cit. 25, Vol. 17, p. 46.

Zeitschrift für angewandte Chemie, 1891, S. 281.

Zeitschrift für analytische Chemie, Band 32, S. 184.

Vid. op. cit. 25, Vol. 16, p. 364.

Vid. op. cit. 25, Vol. 17, p. 463.

Vid. op. et. loc. cit. supra.

Chemiker Zeitung, 1890, S. 1246.

Volume First, pp. 369, 375.

Annales de Chimie et de Physique {2}, Tome 46, p. 294.

Comptes rendus, Tome 73, p. 1296.

Zeitschrift für analytische Chemie, Band 14, S. 152.

Chemical News, Vol. 44, p. 316.

Rapport adressé par la Comité des Stations Agronomiques, 1887, p. 10.

Zeitschrift für angewandte Chemie, 1891, S. 691.

Vid. op. cit. supra, 1892, S. 233.

Vid. op. cit. 40, 1893, S. 68.

American Journal of Science, June, 1895, from advance proofs sent by author.

Watt’s Translation, Vol. 2, pp. 317-318.

Manuscript communication from Mr. Kreider.

Vid. op. et loc. cit. 43.

The residue showed phosphoric acid plainly when tested.

The residue showed phosphoric acid plainly when tested.

Only traces of phosphoric acid found in the residue.

Only traces of phosphoric acid found in the residue.

Only traces of phosphoric acid found in the residue.

Only traces of phosphoric acid found in the residue.

Zeitschrift für angewandte Chemie, 1893, S. 73.

Chemical Division, U. S. Department of Agriculture, Bulletin No. 38, p. 57.

PART FOURTH.

MISCELLANEOUS FERTILIZERS.

=278. Classification.=—Nitrogen, phosphoric acid, and potash are the most important of the plant foods both from a commercial and physiological point of view. They are the chief constituents of the most important fertilizers and manures, but are by no means the sole essential elements of plant nutrition. Lime, magnesia, soda, sulfur, chlorin, and many other elements are found constantly in plants and must be regarded as normal constituents thereof. It is the purpose here, however, to speak only of those substances which are used as fertilizers and which constantly or occasionally are subjected to chemical examination for determining their commercial or agronomic value. These bodies may be conveniently divided into two classes; viz., mineral and organic. Among those of mineral nature may be mentioned lime, gypsum, marls, wood-ashes, common salt, and ferrous sulfate; among those of organic nature may be included guano, hen manure, stall manure, composts, and muck.

=279. Forms of Lime.=—By the term lime is meant the product obtained by subjecting limestone or other lime carbonates to the action of heat until the carbon dioxid contained therein is expelled. The resulting lime, CaO, when exposed for some time to the air, or at once on the addition of water, is converted into the hydrate CaO₂H₂, known as slaked lime. On longer exposure to the air, the hydrate gradually absorbs carbon dioxid and becomes converted into carbonate. In whatever form, therefore, lime is applied to the soil, it is found in the end, as carbonate. A distinction should also be made between lime obtained from mineral substances and that got from organic products such as shells. Strictly speaking this is not a definite matter, inasmuch as limestones are sometimes but little more than aggregations of fossil shells. Practically, however, the distinction is made, and some farmers prefer shell lime to that of any other kind. Gas lime, that is lime which has been used for the purification of illuminating gas made from coal, is hardly to be considered in this connection, since it may contain very little even of the hydrate. In this case the lime has been converted largely into carbonate and sulfid.

=280. Application of Lime.=—For many reasons it is important that the lime be transported to the field before it has had time to be converted into hydrate. The transportation costs less in this state and it can be handled with far less inconvenience than when slaked. The lime should be placed in small piles and left thus, best covered with a little earth, until thoroughly slaked. It is then spread evenly over the surface. The quantity used per acre depends largely on the nature of the soil. Stiff clays and sour marsh lands require a larger dressing than loams or well aerated soils. From three to six thousand pounds per acre are the quantities usually employed. When the lime is once thoroughly incorporated in the soil it is rapidly converted into carbonate, but while in the caustic state it may act vigorously in promoting the decay of organic matter and may prove injurious in promoting the decomposition of ammonium salts with attendant loss of nitrogen.

=281. Action of Lime.=—The benefits arising from the application of lime to agricultural lands, although in many cases great, do not arise from any distinct fertilizing action of its own. Plants need lime for growth and need plenty of it, but as a rule any soil which is good enough to grow crops will contain enough lime to furnish that constituent of the crops for many years. Its action is both mechanical and chemical. By virtue of the latter property it renders available for plant food bodies already existing in the soil but existing in such shape as to be unavailable for plants. The supply of plant food available for the crops of one year is increased but this increase is at the expense of the following years. Lime is a stimulant. There is an European proverb that “lime enriches the father but beggars the son.” Nevertheless, a limestone country is usually a fertile one and soils containing plenty of lime naturally, are nearly always rich soils. It is said that the trees and plants which farmers pick out as indicative of rich land are nearly always those which prefer lime soils.

The mechanical action of lime on soils tends to lighten heavy clays and loams and to render firmer and more consistent the light and shifting sandy soils. When a lump of clay is stirred up in a bucket of rain water the water becomes muddy and remains that way for many days. If, however, to the bucket of muddy water a little lime water be added the suspended particles of clay begin to flocculate and soon the water is clear and the clay falls to the bottom, nor does it again make the water muddy for a long time when stirred up with it. The flocky character of the precipitate is tenaciously retained and it is necessary to knead the clay for some time to induce it to reassume its original heavy character. An action like this takes place when lime is added to heavy soils so that the soil becomes more porous and assumes a better tilth on plowing. With sandy soils an altogether different action takes place. In making mortar, as is well known, sand is stirred in with milk of lime and after being exposed to air for a while the mixture becomes hard and firm, the firmness increasing with age. This is due to the fact that when the mortar dries the lime begins to absorb carbon dioxid from the air and is converted into grains of carbonate which adhere strongly to neighboring sand grains and to each other so that the whole soon gets to be a solid mass. Something like this takes place in the soil and the sand grains are to some extent bound together. The increased firmness of the soil thus gained is often of considerable advantage.

Besides these actions, which are more or less mechanical, lime exerts a chemical action on many soil constituents. Feldspar and other common rocks contain potash, and this potash is in such a form as to be inaccessible to plants. These rocks exist in the shape of small particles in many soils and on them lime exerts a decomposing action, setting the potash free. Lime also hastens the decomposition of the nitrogenous organic matter and at the same time renders the soil more retentive of the products formed. The conversion of ammonia, resulting from the decomposition of such organic matter into nitrites and nitrates, is not easily accomplished without a proper amount of calcium carbonate. The microorganisms producing this change, which is known as nitrification, apparently require its presence for neutralizing the acid formed. In general, it may be said that the presence of lime hastens the putrefactive process. This is the reason it is so largely used in making composts.

It is difficult to say just what soils will be improved by liming and what will not, and it is a matter which must be settled by experiment in each case. As a rule heavy clays and loams are benefited, yet of two such soils, apparently identical, one may not be affected in any marked degree while the other may readily respond to treatment. Sandy soils are often improved but sometimes not. Sour, boggy lands, are usually improved by the addition of enough lime to neutralize their undue acidity. Marsh grasses and plants are more tolerant of acid in the soil than tame grasses are, so that in unlimed soil the former run out the latter. The application of lime alone to a very poor soil does not pay.

The particles of lime resting in the soil are partially dissolved by the next rainfall after application, or by the soil moisture, forming lime water, and the lime is distributed in this form through the soil to some extent. It all probably soon becomes converted into carbonate as ground air is usually quite rich in carbon dioxid. Indeed, for many soils, it is immaterial whether lime be applied as lime or as carbonate, granting, of course, that the latter be ground to a fine powder. Economy is in favor of the lime, however, not only because it needs no grinding, but because it is lighter than the corresponding amount of carbonate, making a saving in transportation. The difference is quite considerable, fifty-six pounds of lime being equivalent in effect to 100 pounds of carbonate. For these reasons as well as because it possesses some valuable properties not shared by the carbonate, it is possible that for most localities lime is to be preferred to any form of ground oyster shells, ground limestone, marble dust or the like.

One of these valuable properties not possessed by limestone, is said to be that of acting as a fungicide and insecticide. As a rule, fungi prefer acid reaction in the substances in which they grow, so that the strongly alkaline properties of lime may make a limed soil unsuitable for their growth.

=282. Analysis of Lime.=—Lime, which is prepared for use as a fertilizer, is rarely submitted to a chemical examination. It is easy to see, however, that such an examination is of some importance. If the real value of a sample be dependent on the content of lime, the actual quantity present as determined by analysis, must fix the value for agricultural purposes. The more important things to be determined are the quantities of lime, and of slaked lime, of undecomposed calcium carbonate, and of insoluble matter. It will be also of interest to determine the respective quantities of lime present as oxid, hydrate, and carbonate. If any question be raised in the case of slaked lime in respect of its origin, it can usually be answered by an examination of the unburned or unslaked residues. In perfectly slaked lime containing no débris, the analyst will be unable to discover whether it has been made from limestone, marble or shells. The lime used for agricultural purposes should be reasonably free of magnesia, and should not be air-slaked before transportation to the field. In dry air-slaking, a considerable quantity of carbonate may be formed.

=283. The Process.=—(1) Insoluble and Soluble Constituents.—A representative sample of the lime having been secured, it is reduced to a powder and passed through a half millimeter mesh sieve or ground to a fine powder in an agate mortar. Digest two grams of this sample with an excess of hydrochloric acid, for two hours with frequent stirring; filter, wash the residue with hot distilled water until chlorin is all removed, and dry to constant weight. The lime, magnesia, silica, and other constituents of the filtrate, are determined by the usual processes of mineral analysis.

(2) State of Combination of the Lime.—In a lime containing only small quantities of magnesia the lime carbonate may be determined by estimating the carbon dioxid by any one of the reliable processes in use. In every case sufficient acid must be employed to combine with all the bases present. Tartaric or hydrochloric acid may be used. From the volume or weight of the carbon dioxid obtained the quantity of calcium carbonate may be calculated. Since magnesium carbonate is more easily decomposed by heat than the corresponding calcium compound, any residual carbonate in a well-burned sample is probably lime. The total percentage of lime in the sample is to be determined in the usual way by precipitation as oxalate and weighing as carbonate or oxid. The lime existing as oxid can be determined by exposing a weighed sample in an atmosphere of aqueous vapor until all the lime is slaked. After drying at 100° the increase in weight is determined and the calcium oxid calculated from the formula, CaO + H₂O = CaO₂H₂.

If now the total lime be represented by a; the lime combined as carbonate by b; and that present as oxid by c; the quantity x existing as hydrate may be calculated from the equation

x = a - (b + c).

Example: Let the total lime be 88 per cent. CaO as carbonate, 2 “ “ CaO as oxid, 78 “ “

Then the CaO as hydrate = 88 - (2 + 78) = 8 per cent. The total lime as oxid and hydroxid may also be separated from that present as carbonate by solution in sugar. One gram of calcium oxid is completely soluble in 150 cubic centimeters of a ten per cent sucrose solution. Magnesia, iron and alumina do not interfere with the determinations.

=284. Gypsum or Land Plaster.=—This substance is highly prized as a top dressing for grass and for admixture with stall manure for the purpose of fixing ammonia. Its value in both cases depends upon its percentage of hydrated calcium sulfate. The quantity of gypsum mined in the United States in 1893 was a little over 250,000 tons. Of this amount only about 50,000 tons were used as fertilizer. In the same time there were imported into the United States, in round numbers, 170,000 tons. If the same proportionate part of this were used for fertilizing purposes, it may be said that the annual consumption of land plaster in the United States at the present time for agricultural uses is about 75,000 tons.

Gypsum, being a very soft mineral, is easily ground and should be in the state of a fine powder when used for fertilizing purposes. It is soluble in about 500 parts of rain water, so that when applied as a top dressing it is carried into the soil by rain. Its favorable action is both as a plant food and mechanically in modifying, in an advantageous way, the physical constituents of the soil. It is also valuable for composting and for use in stables by reason of its power of fixing ammonia by the formation of lime carbonate and ammonium sulfate:

(H₄N)₂CO₃ + CaSO₄ = (H₄N)₂SO₄ + CaCO₃.

=285. Analysis of Gypsum.=—For agricultural purposes it will be sufficient to determine the quantity of sulfuric acid, and to calculate therefrom the amount of calcium sulfate in the sample: Or the lime may be determined and the quantity of sulfate calculated therefrom.

(1) Insoluble Matter.—In the conduct of the work the sample of gypsum is rubbed to an impalpable powder in an agate mortar. The washed sample, about one gram, is dissolved in a large excess of dilute hydrochloric acid, the digestion being continued at near the boiling-point, with frequent stirring, for at least two hours. The solution is made alkaline, filtered, and the residue washed and dried to constant weight.

(2) Sulfuric Acid.—The washings and filtrate from the above determination are made up to a definite volume with water and divided into two equal parts. The sulfuric acid is estimated in one part by adding to it sodium carbonate until the acidity is nearly neutralized. The sulfuric acid is then thrown down at near boiling temperature by the gradual addition of barium chlorid solution. The barium sulfate formed is separated, washed, dried, and weighed in the usual manner.

(3) Iron and Alumina.—To the other half of the solution a little nitric acid is added and boiled to convert any ferrous into ferric iron. On the addition of ammonia the iron and alumina are separated as hydroxids, collected on a gooch, washed, dried, ignited, and weighed as oxids.

(4) In the filtrate the lime is thrown out as oxalate, and separated and weighed in the usual way as oxid. One part of CaO is equal to 2.4286 parts of CaSO₄.

(5) Moisture.—Dry about two grams of the sample to constant weight at 80°.

(6) Water of Crystallization.—Heat the residue from the above to 150°, until a constant weight is obtained. The loss represents water of crystallization.

(7) Carbonates.—Determine the quantity of carbon dioxid evolved by the usual process, and calculate the calcium carbonate.

=286. Solution in Sodium Carbonate.=—Gypsum is also easily decomposed by boiling with a solution of about ten times its weight of sodium carbonate. The calcium, by this operation, is converted into carbonate and can be collected on a gooch, washed, and estimated as usual, but in this case it will contain all the insoluble matters, from which the lime can be separated by solution in hydrochloric acid.

In the filtrate from the above separation the excess of sodium carbonate is removed by the addition of hydrochloric to slight acidity, and the sulfuric acid estimated as described in the preceding paragraph.

Pure gypsum has a composition represented by the following formula: CaSO₄·H₂O.

It contains:

Sulfur dioxid 46.51 per cent. Lime 32.56 “ “ Water 20.93 “ “

A commercial sample of ordinary gypsum should have about the following composition:

CaSO₄·H₂O 88.15 per cent. CaCO₃ 3.50 “ “ Fe₂O₃ and Al₂O₃ 1.50 “ “ Insoluble 2.80 “ “ Organic matter 0.50 “ “ Water and undetermined 3.55 “ “

=287. Common Salt.=—Common salt is highly esteemed in many quarters as a top dressing for lawns and meadows, and also for cultivated crops. Its action is chiefly of a mechanical and katalytic nature, since it does not form a very large percentage of the mineral food of plants. On account of its affinity for moisture it is also said to have some value as a condenser and carrier of water in times of drouth. On account of its great cheapness, selling often for less than ten dollars a ton, its use in moderate quantity entails no great expense. Its ability, however, to pay for its own use in the increased harvest is of a doubtful character when it is applied at a cost of more than a few dollars per acre. In the chemical examination of a sample of common salt which is to be used as a fertilizer, a complete analysis is rarely necessary. When desired it can be conducted according to the usual methods of mineral analysis. For practical purposes the moisture, insoluble matter, magnesia and chlorin should be determined and the quantity of sodium chlorid calculated from the latter number. Traces of iodin or bromin which may be present are of no consequence.

The moisture is determined by drying two grams of the well-mixed and finely-powdered sample to constant weight at 100°. The chlorin is obtained by precipitation of an aliquot part of a solution of the salt by set silver nitrate, using potassium chromate as indicator.

In the determination of insoluble matter it should not be forgotten that a little gypsum may be present, and this should be dissolved by rubbing to a finer powder and by repeated digestion in water. The magnesia and lime are separated and determined in the usual manner. If the quantity of gypsum present be sufficient to warrant it the sulfuric acid may be separated and weighed in the manner already described. Common salt when present in the soil in proportions greater than one-tenth per cent is injurious to vegetation.

=288. Green Vitriol.=—When iron is used as a fertilizer it is usually applied as ferrous sulfate. The value of iron in a soil is incontestable and by reason of the fact that fertile soils are always well aerated the iron present in the arable layer is found in the ferric state. When green vitriol is applied to the soil it undergoes gradual oxidation and appears finally in a more highly oxidized form. Iron acts directly on the plant in promoting the development of the chlorophyll cells, and is also found in almost all parts of the vegetable organism. A too great quantity of ferrous sulfate is destructive of plant growth in which respect it resembles common salt. It should therefore be applied with due regard to the dangers which might arise from an excessive quantity. It is not likely, however, that when applied in a finely powdered state at the rate of from two to four hundred pounds per acre it would ever prove poisonous to vegetation.

In the analysis of a sample of green vitriol it will be sufficient to determine the moisture, water of crystallization, iron, and sulfuric acid. The moisture may be ascertained by drying the finely powdered sample over sulfuric acid for a few hours. The water of crystallization is separated by exposing the sample to a temperature of 285° for two hours. The iron may be determined by oxidizing to the ferrous state by boiling with nitric acid and then precipitating with ammonia, and proceeding as directed for iron analysis. The sulfuric acid is separated as barium sulfate and determined as already directed.

=289. Stall Manures.=—There are no definite methods to be described for the analyses of that large class of valuable fertilizer produced in the stable and pen, and which collectively may be called stall manures. The methods of sampling have already been described, but only patience and tact will enable the collector to get a fair representation of the whole mass. These manures are a mixture of urine, excrement, waste fragments of fodder, and the bedding used for the animals. With them may also be included the night soil and waste from human habitations and the garbage from cities. All of these bodies contain valuable plant foods and the phosphoric acid, potash, and nitrogen therein are to be determined by the methods already given for these bodies when they occur in, or are mixed with, organic matter. In general, stall manures are found to have a higher manurial value than is indicated by the amount of phosphorus, potash, and nitrogen which they contain. Through them there is introduced into the soil large quantities of humus bodies whereby the physical state of the soil is profoundly modified and its adaptability to the growth of crops, as a rule increased. The addition of active nitrifying ferments in stall manure is also advantageous. Stall manures, however, may in many cases prove to be injurious to a crop, as for instance, when they are applied in a poorly decomposed state and in a season deficient in moisture.

It is essential therefore that the bedding of animals be in a finely divided state, whereby not only are the absorptive powers of the organic matter increased but also the conditions for their speedy decay favored. To avoid the loss of ammonia arising from decomposing urine it is advisable to compost the stall manure with gypsum or to sprinkle it from time to time with oil of vitriol.

In the analysis the moisture may be estimated by drying a weighed portion of the sample to constant weight at 100° or at a lower temperature in a vacuum. The potash and phosphoric acid are determined as usual, with previous careful incineration, and the nitrogen secured by the moist combustion process.

=290. Hen Manure.=—This fertilizing substance is a mixture of the excrement of the fowl yard with feathers, dust, and other débris. Measured by the standard applied to commercial fertilizers hen manure has a low value. As in the case of other farm manures, however, it produces effects quite out of proportion to the amount of ordinary plant foods which it contains. In a sample examined at the Connecticut station the percentages of fertilizing constituents were found to be the following:

Water 51.84 Organic and volatile matters 24.27 Ash 23.89

The organic matter contained 0.61 per cent of nitrogen as ammonia and the ash 0.97 per cent of phosphoric acid, and 0.59 per cent of potash, all calculated to the original weight of the sample. The percentage of water in this sample is undoubtedly higher than the average, so that it can hardly be taken to represent the true composition of this manure. The potash, phosphoric acid, and nitrogen are to be determined by some one of the standard methods already described, the two former after careful incineration.

=291. Guanos and Cave Deposits.=—The principal constituents of value in these deposits are nitrogen and phosphoric acid. The other organic matters are also of some value but have no commercial rating. The nitrogen may be present in all its forms; viz., organic, ammoniacal, amid, and nitric, and for this reason is well suited not only to supply nourishment to the plant in the earlier stages of its growth but also to cater to its later wants. In guano deposits in caves, due usually to the presence of bats, similar forms of fertilizers are found and the soluble constituents due to decay and nitrification are protected from the leaching to which they would be subjected in the open air.

In many localities in the United States these deposits are found, but the humidity of our climate has prevented the immense open deposits of guano that characterize some of the arid islands of the Pacific Ocean.

Many bat guanos examined in this laboratory have also been found to contain potash, in one case 1.78 per cent. It is suggested therefore that the analyst do not omit to examine each sample qualitatively for this substance and to determine its amount when indications point to its presence in weighable proportions. In the many samples of bat guano of American origin which have been analyzed in this laboratory in the last few years some very rich in plant food have been found. In one instance the total percentage of nitrogen present, was 10.11 per cent. In some cases the phosphoric acid is high but rarely in conjunction with a high content of nitrogen. In one instance where the total phosphoric acid reached 14.53 per cent, the content of nitrogen was 4.87 per cent.

In respect of the processes of analysis there are no especial directions to be given. The phosphoric acid, as given below, and the potash are to be determined by the usual methods, the total phosphoric acid and potash after the destruction of the organic matter.

In old cave deposits the processes of decay and nitrification seem to have long been completed and we have found very little power of inducing nitrification in culture solutions seeded from these samples.

=292. French Official Method for Total Phosphoric Acid in Guanos.=—To determine the phosphoric acid in guanos, the method officially adopted by the French agricultural chemists may be used.

Two grams of the sample are rubbed up in a porcelain crucible with a decigram of slaked lime to prevent the possible reduction of the phosphoric acid by the organic matter. The mixture is slightly moistened with a few drops of water, dried on a sand-bath, and afterwards heated to redness, best in a muffle, until organic matter is destroyed. The contents of the crucible are detached and placed in a flask of 200 cubic centimeters capacity. The crucible is well digested twice with some hydrochloric acid to dissolve any adhering fragments, and finally washed with hot water, the acid and water being added to the flask. The contents of the flask are boiled for fifteen minutes and then poured into a flat-bottomed dish, the flask well rinsed three or four times with small quantities of water, and the liquor and washings are evaporated to dryness to render the silica insoluble. The residue is taken up by a mixture of ten cubic centimeters each of hydrochloric acid and water, heated for a few minutes and filtered, and the dish well washed with successive small portions of water, but the total volume of the filtrate and washings should not exceed eighty cubic centimeters. In this filtrate the phosphoric acid may be determined by any one of the approved methods.

=293. Waste Leather.=—This material belongs probably to that class of nitrogenous substances which has already been considered in paragraph =149=. The chief manurial value of the waste is found in its nitrogenous content. The value of this for available plant food has been investigated by Lindsey. A complete resumé of the literature of the subject is also given by him.

The best way of identifying leather waste is by the process proposed by Dabney. It depends on the color produced in a solution of iron phosphate by the tannin compounds derived from the leather. The reagent is prepared by dissolving a freshly made precipitate of iron phosphate from ten grams of ferric chlorid in 400 cubic centimeters of an aqueous solution of forty grams of glacial phosphoric acid. A gentle heat promotes the solution of the phosphate.

In the case of a fertilizer supposed to contain leather, about one gram of the material is treated with thirty cubic centimeters of water and a few drops of sulfuric acid. The mixture is boiled and poured on a filter. To a portion of the filtrate some of the solution of iron phosphate is added, and the mixture made alkaline with ammonia. If leather be present in the sample, a purple or wine color will be developed. Lindsey could easily detect the leather when it was added in ten per cent quantities by the above method, and he regards this method as superior to the microscope which is unreliable in the case of finely ground material.

While leather, as such, decays slowly, and therefore is not at once available for the nourishment of plants it acquires greater utility after digestion in sulfuric acid. Artificial digestion experiments with leather previously treated with sulfuric acid show that, approximately, seventy per cent of the nitrogen pass into solution. Such a prepared leather has, therefore, a digestive coefficient in respect of nitrogen not much inferior to most organic bodies.

In comparative trials with sodium nitrate it was demonstrated that nitrogen in leather, previously dissolved in sulfuric acid, has a rank of about sixty when it is rated at one hundred in the soda salt.

For the estimation of the nitrogen in leather the moist combustion process is to be preferred.

=294. Analysis of Wood Ashes.=—The only kinds of ashes used extensively for manurial purposes are those derived from the burning of hard woods. The ash of soft woods, such as the pine, is too poor in plant foods to warrant its transportation to any great distance for manurial purposes. The methods of incineration of organic bodies for the purpose of obtaining and estimating their mineral contents will be fully discussed in the third volume of this work.

It is important in ash analysis to know whether there be enough of iron present to combine with all the phosphoric acid. For manurial purposes it will be found sufficient to determine the percentages of potash and phosphoric acid alone. For hygienic purposes it is advisable to examine the ash qualitatively and, if necessary, quantitatively for zinc, lead, copper, boric acid, and other bodies of a similar character which may be naturally present in the ash, or may have been added to the organic substance from which it was prepared for preservation or other purposes. The methods of making these special investigations will be discussed in the succeeding volume. At present will be given, however, not only the methods for detecting phosphoric acid and potash, but also for a complete analysis of an ash in so far as its usual constituents are concerned.

=295. Carbon, Sand, and Silica.=—The official agricultural chemists have recommended the following procedure for the determination of the unburned carbon, and the sand and silica.

Five grams of the ash are treated in a beaker, covered with a watch glass with fifty cubic centimeters of hydrochloric acid of 1.115 specific gravity, and digested on the water-bath until all effervescence has ceased. The cover is then removed and the liquid evaporated to complete dryness to render the silica insoluble. The residue is moistened with two or three cubic centimeters of hydrochloric acid and taken up with about fifty cubic centimeters of water, allowed to stand on the water-bath a few minutes, filtered, and thoroughly washed. The filtrate and washings are made up to a quarter of a liter for analysis. The residue is washed from the filter into a platinum dish and boiled about five minutes with twenty cubic centimeters of a saturated solution of pure sodium carbonate; afterwards a few drops of pure sodium hydroxid solution are added and the liquid allowed to settle, and it is then decanted through a tared gooch. The residue is boiled with sodium carbonate solution and decanted as before, a second and a third time, and finally brought upon the felt and thoroughly washed, first with hot water, then with a little dilute hydrochloric acid, and finally with hot water until free of chlorids. The residue in the gooch is dried at 110° to constant weight, giving the carbon and sand. It is then incinerated and the weight of the sand determined, the difference giving the carbon. It is advisable to examine the sand with a microscope to determine if it be pure. The alkaline filtrate and washings from the carbon and sand are acidified with hydrochloric, evaporated to dryness, and the silica separated and determined in the usual way.

Instead of determining soluble silica directly from the sodium carbonate solution, as above, another portion of the ash may be treated with hydrochloric acid and evaporated to dryness as before described, filtered on an ordinary filter, washed, burned, and weighed, giving the weight of silica plus sand, from which the weight of sand is deducted to obtain soluble silica. It is inadmissible to separate the soluble silica from the residue after it has been ignited.

Instead of limiting the quantity of hydrochloric acid used for moistening the dried residue, as suggested above by the official chemists, enough should be employed to fully saturate the mass. The weight of pure ash is obtained by subtracting from the weight of the sample taken the sum of the weights of carbon, sand, and carbon dioxid.

=296. Ferric Phosphate and the Alkaline Earths.=—The ferric phosphate, lime, magnesia, and manganese are determined in an aliquot part of the first hydrochloric acid solution and washings obtained above. Fifty or one hundred cubic centimeters may be used, corresponding to one or two grams of the original ash. The accurately measured quantity of the solution is carefully treated with ammonia until the precipitate formed on its addition becomes permanent on shaking. Ammonium acetate and acetic acid are then added until the mixture has assumed a strongly acid reaction. The separation of the ferric phosphate precipitate is promoted by gentle warming, and it is separated by filtration without unnecessary delay. If the precipitate be not large the sample contains no manganese and alumina in weighable quantities, and if the filtrate be not red the precipitate be washed with hot water containing a little ammonium nitrate. It is then ignited and weighed as Fe₂P₂O₈ and the quantity of ferric oxid computed therefrom. If, however, the precipitate be large it is well washed as above and then dissolved in as small a quantity as possible of hydrochloric acid, and the solution is again precipitated as above by the addition of ammonia, ammonium acetate, and acetic acid. The ferric phosphate obtained by the second precipitation is treated exactly as above described.

In case, however, any weighable quantities of manganese or alumina are present it will not do to weigh the precipitate of ferric phosphate directly even after a second precipitation. Also if the filtrate at first obtained have a red color the precipitate may contain basic ferric phosphate. In this latter case it should be ignited and weighed, then dissolved in hydrochloric acid and the ferric oxid estimated in the solution and from the difference the quantity of combined phosphoric acid calculated.

The separation of the iron from the phosphoric acid may be accomplished by adding tartaric acid to the hydrochloric acid solution of the iron phosphate above obtained and then ammonium chlorid and ammonia. The mixture is placed in a flask and ammonium sulfid added. The flask is closed, placed in a warm place, and allowed to stand until the supernatant liquid is clear and of a pure yellow color without a trace of green. The iron is separated by filtration, washed, dissolved, and estimated in the usual way.

If manganese and alumina be present the iron and manganese are separated from the phosphoric acid and alumina by the processes just given for the separation of iron from phosphoric acid. In the filtrate the alumina and phosphoric acid are separated as follows: The filtrate is evaporated in a platinum dish after the addition of an excess of pure sodium carbonate until no ammonia is set free by a further addition of the carbonate. Some nitric acid is then added and the evaporation continued to dryness. The residue is fused and after cooling softened with water, washed into a small beaker, some hydrochloric acid added, warmed, and filtered. Ammonia is next added until the reaction is alkaline. If no precipitate be produced no alumina is present. In this case more nitric acid is added, the solution again evaporated, and the phosphoric acid determined by the usual methods.

In case a precipitate is formed, showing the presence of alumina, nitric acid is added until the precipitate is dissolved, and then in slight excess and after evaporation the phosphoric acid separated by molybdic solution and determined as usual. From the filtrate the excess of molybdic acid is removed by hydrogen sulfid and the alumina determined in the filtrate: Or the alumina may be determined directly in the hydrochloric acid solution of the melt above obtained as aluminum phosphate by adding sodium phosphate, ammonia and acetic acid. The aluminum phosphate is separated by filtration and determined in the usual manner. The phosphoric acid is then determined in another aliquot part of the original filtrate from the first solution of the ash.

Since most ashes contain an excess of phosphoric acid above the quantity required to combine with the iron it is preferable to proceed on that basis as described in the next paragraph.

=297. Method Used in this Laboratory.=—The principle of the method rests on the assumption that all the phosphoric acid may be removed from the solution by the careful addition of iron chlorid. Any excess of iron is then removed by ammonium acetate and the manganese, lime, and magnesia, are separated in the filtrate. The percentage of iron is determined by reduction of the iron in another portion of the solution and titration with potassium permanganate. The process as conducted by McElroy, is as follows:

Moisture.—If the ash contain much carbon the water is best determined by drying in vacuo to avoid oxidation.

Sand, Silica, and Carbon.—Place a portion of the ash in a weighed platinum dish, weigh, and cover the sample with hydrochloric acid of 1.115 specific gravity. Evaporate to dryness on the water-bath, and then heat for fifteen minutes at 105° to 110° in an air-bath. Repeat the treatment with acid and drying: Finally cover with a third portion of acid and digest on the water-bath for an hour or two. Filter into a weighed gooch and wash the residue free of chlorids. The gooch is best weighed with the dish to avoid the necessity of transferring the silica which may adhere to the sides of the former. Dry at a few degrees above the boiling temperature of water and weigh. Where the ash contains much charcoal the drying is best done in a vacuum at 60° to 70°. The increase in weight found represents sand, silica, and carbon: Burn and reweigh. The loss is carbon.

Another portion of ash is treated as before except that it is filtered through a paper filter. The filtrate is united with that of the previous sample in a graduated flask. When the washing is completed the filter is placed in the dish, a weak solution of caustic soda added, and the mixture heated on the water-bath for some time. Decant while hot through a fresh filter and retreat the residue in the dish with another portion of alkali. Finally wash with hot water till the alkaline reaction disappears, then with weak hydrochloric acid, then with water until chlorids disappear. The washed mass on the filter is transferred to a platinum dish and ignited. The weight obtained represents sand.

Separation of Phosphoric Acid.—The united filtrates from the two determinations are placed in a graduated flask and made up to the mark. An aliquot portion of this solution representing half a gram of the original ash or any other convenient quantity is transferred to a beaker and a solution of ferric chlorid added until ammonia produces a brown precipitate in the mixture. Neutralize with ammonia and hydrochloric acid alternately until the liquid is as little acid as it can be and still remain clear. Add from ten to twenty cubic centimeters of a solution of sodium acetate (1:10) and bring to a boil. The liquid should be quite dilute. Filter and wash free of chlorids with boiling water containing some sodium acetate.

Manganese.—Make the filtrate faintly alkaline with ammonia and add ammonium sulfid. Any manganese sulfid which may form is separated by filtration, treated with dilute acetic acid and the resulting solution, which should be clear, heated to boiling, nearly neutralized with caustic soda, and mixed with bromin water. The resultant manganese dioxid is to be filtered into a gooch, ignited and weighed as Mn₃O₄.

Lime.—Reacidify the filtrate from the manganese sulfid with acetic acid, heat to boiling and add ammonium oxalate: Allow to stand over night, filter through a gooch and wash with water containing acetic acid. The calcium oxalate can be weighed as such, but it is preferable to dry thoroughly and then heat in a small bunsen flame until a change can be noted passing over the precipitate. If this is carefully done the residue will be calcium carbonate. In any case the result is to be checked by igniting over the blast lamp to constant weight and weighing the lime thus obtained.

Magnesia.—In the filtrate the magnesia can be determined by sodium phosphate in the usual manner. In very accurate work the calcium oxalate obtained as directed above can be dissolved and reprecipitated, and the magnesia in the filtrate added to that in the first filtrate.

Iron.—For iron another aliquot portion of the original solution is taken, acidified with sulfuric evaporated to drive off hydrochloric acid, rediluted and passed through the Jones reductor described in paragraph =112=. The filtrate is titrated with potassium permanganate solution in the usual manner.

Alkalies.—For the alkalies another aliquot portion is taken and precipitated while hot, with barium chlorid and barium hydrate, filtered, and ammonia and ammonium carbonate added to remove the excess of barium salt. Refilter, evaporate to dryness in a platinum dish, and ignite gently to expel all ammonia salts, repeat this operation after taking up with water and finally heat to constant weight. The weight obtained represents a mixture of potassium and sodium chlorids, with usually carbon derived from impurities in the ammonia. A little magnesia is often present. The potassium is estimated by means of platinum solution, and the potassium chlorid found deducted from the total weight gives the sodium chlorid. The carbon is usually unweighable, though it often looks as if present in considerable quantity. It may be estimated, however, by dissolving the mixed chlorids in weak hydrochloric acid and filtering through a gooch before making the potassium estimation. The estimation of the magnesia remaining with the mixed chlorids may be effected by evaporating the alcoholic solution remaining after the precipitation of the potassium to dryness, redissolving in water, placing the solution in a flask provided with gas tubulures, introducing hydrogen, and placing in the sunlight. The platinum is soon reduced, leaving the liquid colorless. Heating facilitates the reaction. Displace the hydrogen by a current of carbon dioxid, filter, concentrate the solution and precipitate the magnesia by sodium phosphate in the usual manner.

Phosphoric Acid.—It is best to determine the phosphoric acid directly in an aliquot part of the first filtrate from the hydrochloric acid solution of the ash obtained as described under the determinations of sand, silica and carbon. When there is not enough of the material for this, the precipitate of ferric phosphate may be dissolved and the phosphoric acid determined after separation with ammonium molybdate.

Sulfuric Acid.—Fifty cubic centimeters of the original hydrochloric acid filtrate, obtained as described under the determinations of sand, silica and carbon, are heated to boiling, and the sulfuric acid thrown out by the gradual addition of barium chlorid. During the precipitation the mixture is kept at the boiling temperature, but taken from the lamp and the precipitate allowed to settle from time to time until it is seen that an additional drop of the reagent causes no further precipitate. The barium sulfate is collected, dried, and weighed in the usual manner.

Chlorin.—Dissolve from one to five grams of the ash in nitric acid in very slight excess, or in water. If the solution be made in nitric acid the excess must be neutralized if the chlorin be determined volumetrically; and if the solution be in water, nitric acid must be added if the determination be gravimetric.

The volumetric determination is accomplished in the usual manner with a standard silver nitrate solution, using potassium chromate as indicator. The gravimetric determination is effected by precipitation with silver nitrate, collecting, washing, and drying at 150° the silver chlorid obtained.

Carbon Dioxid.—The carbon dioxid is most conveniently estimated in from one to five grams of the ash, according to its richness in carbonates, by the apparatus described in volume first, or some similar device.

=298. Official Method for Determinations of the Alkalies.=—Evaporate the filtrate and washings from the sulfuric acid determination, paragraph =297=, in a porcelain dish to dryness, redissolve in about fifty cubic centimeters of water and add milk of lime, or barium hydroxid solution, which must be perfectly free from alkalies, until no further precipitation is produced, and it is evident there is an excess of calcium hydroxid or barium hydroxid present; boil for two or three minutes, filter hot, and wash thoroughly with boiling water, precipitate the lime and baryta from the filtrate with ammonia and ammonium carbonate, filter, evaporate the filtrate to dryness in a porcelain dish, and drive off the ammonia salts by heat below redness. When cold, redissolve in fifteen or twenty cubic centimeters of water, precipitate again with a few drops of ammonia and ammonium carbonate solution, let stand a few minutes on the water-bath and filter into a tared platinum dish and evaporate to dryness, expel the ammonia salts by heating to just perceptible dull redness, weigh the potassium and sodium chlorids obtained and determine the potassium chlorid with platinic chlorid as usual.

The potassium may also be determined by the perchlorate method, or the total chlorin be determined volumetrically, and the relative percentages of potassium and sodium chlorids calculated by the usual formula: Or multiply the weight of chlorin in the mixture by 2.1035, deduct from the product the total weight of the chlorids and multiply the remainder by 3.6358. The product expresses the weight of the sodium chlorid contained in the mixed salts. The indirect method is only applicable when there are considerable quantities of alkalies present and where they exist in approximately molecular proportions. It is therefore a process rarely to be recommended in ash analysis.

=299. Statement of Results.=—The bases which are found present in the ashes of wood and other vegetable tissues exist without doubt before incineration, chiefly in combination with inorganic acids. Even the phosphorus and sulfur which after ignition appear as phosphates and sulfates, have previous thereto existed in an organic form to a large extent. The silica itself is profoundly modified in the organism of the growing plant and doubtless does not exist there in the purely mineral form in which it is found in the ash. During the progress of incineration, with proper precautions, all the phosphorus and sulfur are oxidized and appear as phosphoric and sulfuric acids. The silica is reduced to a mineral state, and if a high heat be employed silicates are formed. The organic salts of lime, magnesia and other bases at a low temperature are converted into carbonates, and if a higher temperature be used, may appear as oxids. The organic compounds of alkalies will be found in the ash as carbonates. It would be useless, therefore, to try to state the results of ash analysis in forms of combination similar to those existing in the original vegetable tissues. It is not certain even that we can in all cases judge of the form of combination in which the different constituents exist in the ash itself. It is therefore to be preferred in a statement of ash analysis to give the bases in the form of oxids, and the sulfur and phosphorus in the form of anhydrids, and the chlorin in its elementary state. In this case an equivalent amount of oxygen to the chlorin found must be subtracted from the total. If an attempt be made to combine the acid and basic elements the chlorin should first be united with sodium, and any excess thereof with potassium, and the amount of base so combined calculated to oxid and deducted from the total of such base or bases present. The carbonic acid present should be combined first with alkalies after the chlorin has been supplied. The phosphoric acid should be combined first with the iron and afterwards with lime or magnesia. In all cases the percentages should be based upon the ash, after the carbon and sand have been deducted, or it is also convenient at times to throw out of the results the carbon dioxid and to calculate the other constituents to the ash free of that substance. In determining the quantities of mineral matters removed from soil by crops, the ash should be determined with great care, freed of carbon and sand, and the calculations made on the percentage thus secured. In all statements of percentages of the essential constituents of ash, as regards fertilizing materials, it should be specified whether the percentage is calculated on a crude ash, the pure ash, that is free of carbon and sand, or upon a basis excluding the carbon dioxid. For the purpose of fertilizer control, the analyst and dealer will be satisfied, as a rule, with the determination of the percentages of phosphoric acid and potash alone. To the other constituents of an ash is not assigned any commercial value.

AUTHORITIES CITED IN PART FOURTH.

Compiled for author by Mr. K. P. McElroy.

Volume First, pp. 356 et seq.

Volume First, pp. 337 and 390.

Volume Second, p. 81.

Day: Mineral Resources of the United States, 1893, p. 713.

Frankland: Agricultural Analysis, p. 240.

Volume Second, p. 9.

Annual Report Connecticut Agricultural Experiment Station, 1888,