Part 45

The nearest brix degree corresponding to this specific gravity (=58=) is 19. The total weight of the solution is equal to 100 × 1.079, viz., 107.9 grams. Since the solution contains nineteen per cent of solid matter as determined by the hydrostatic balance, the total weight of solid matter therein is 107.9 × 19 ÷ 100 = 20.5 grams. The total per cent. of solid matter in the original sample is therefore 20.5 ÷ 25 × 100 = 82 and the specific gravity corresponding thereto (page 74) is 1.42934.

The specific gravity of a massecuite may also be determined in pyknometers especially constructed for this purpose.

=230. Determination Of Water.=—The accurate determination of water in sirups and massecuites is a matter of considerable difficulty. The principles of conducting the process (=26=), applicable also to the determination of water in honeys and other viscous liquids, are as follows: In all cases where invert sugar is present the drying should be conducted at a temperature not exceeding 75° or 80°. In dense molasses and massecuites a weighed quantity should be dissolved and made up to a definite volume and an aliquot portion taken for the determination. In order to secure complete desiccation at a low temperature, the drying should be accomplished in partial vacuum (pages 22, 23). The process of desiccation should be conducted in shallow, flat-bottom dishes which may be conveniently and cheaply made of aluminum and the process is hastened by filling the dish previously with thoroughly dried fragments of pumice stone. When the sample does not contain any invert sugar the desiccation can be safely accomplished at the temperature of boiling water. Drying should be continued in all cases until practically constant weight is obtained.

=231. Determination Of Ash.=—Ash is an important constituent of the sirups, molasses, and massecuites from canes and exists in very much larger quantities in the same products from beets. The ash may be determined directly by careful incineration, but it is customary to add a few drops of sulfuric acid, sufficient to combine with all the bases present and be in slight excess. The presence of sulfuric acid is of some advantage in the beginning of the carbonization and renders the process somewhat easier of accomplishment. When sulfuric acid is used, the weight of ash obtained must be diminished by one-tenth to allow for the increased weight obtained by the conversion of the carbonates into sulfates. In general, the principles and methods described on pages 36-40 are to be employed.

=232. Determination of Reducing Sugars in Sirups, Molasses, and Massecuites.=—The quantity of reducing sugars in the products derived from the sugar beet, as a rule, is insignificant. In the products from sugar cane there are large quantities of reducing matters which, in general, are determined by any of the standard methods already given. It has been shown by the author that the juices of healthy sugar canes contain a small quantity of invert sugar, but this statement has been contradicted by Bloufret. It is certain, however, that the reducing bodies derived from the products of manufacture of sugar cane and sorghum deport themselves in a manner somewhat different from pure invert sugar. In the absence of definite information in respect of the constitution of these bodies, the methods applicable to dextrose and invert sugar may be applied.

Since the paragraphs relating to these processes were printed some important improvements in the preparation of the alkaline copper solutions have been made. The copper carbonate solution, as has already been said, is peculiarly suited to the determination of reducing sugars in the presence of sucrose and the modified forms of this solution, and the methods of employing them with invert sugar, dextrose, levulose, and maltose, are described below.

=233. Estimation of Minute Quantities of Invert Sugar in Mixtures.=—The method of Hiller and Meissl, paragraph =142=, may be used for the estimation of small quantities of invert sugar in mixtures. A modified form of Soldaini’s reagent is, however, to be preferred for this purpose. Ost has proposed and tested a copper carbonate solution for the purpose mentioned which gives reliable results. The solution has the following composition:

One liter contains 3.6 grams crystallized copper sulfate. 250.0 ” potassium carbonate. 100.0 ” hydrogen potassium sulfate.

This reagent undergoes no change when kept for a long while, especially in large vessels. Even in smaller vessels it can be kept for a year or more without undergoing any change.

The method of analysis is the same as that described in paragraph =128=, with the exception that the boiling is continued for only five minutes instead of ten, and the quantities of the copper and sugar solutions used are doubled, being 100 and fifty cubic centimeters respectively. In no case must the solution used contain more than thirty-eight milligrams of invert sugar. The quantity of sucrose in the mixture is obtained by polarization (=94=). Ost has also recalculated the reduction values of the common sugars for the strong copper carbonate solution, and the numbers obtained are slightly different from those given on page 142.

For different percentages of invert sugar in mixtures of sucrose, the quantities of invert sugar are calculated from the number of milligrams of copper obtained by the following table:

(A) = Milligrams of copper obtained. (B) = Pure invert sugar. (C) = Invert sugar. (D) = Sucrose.

MILLIGRAMS OF INVERT SUGAR IN MIXTURES OF 5(C) 2(C) 1.5(C) 1.0(C) 0.8 (C) 0.6(C) 0.5(C) (A) (B) 95(D) 98(D) 98.5(D) 99.0(D) 99.2 (D) 99.4(D) 99.5(D) 88 37.9 37.1 36.0 35.4 34.7 34.2 33.9 33.6 85 36.3 35.5 34.5 34.0 33.4 32.9 32.5 32.2 80 33.9 33.0 33.2 31.7 31.2 30.7 30.2 29.9 75 31.6 30.7 30.0 29.5 29.0 28.5 28.1 27.7 70 29.4 28.5 27.8 27.4 26.8 26.4 25.9 25.6 65 27.3 26.3 25.7 25.3 24.7 24.3 23.8 23.5 60 25.2 24.2 23.6 23.2 22.6 22.2 21.8 21.5 55 23.1 22.1 21.6 21.2 20.6 20.2 19.8 19.6 50 21.2 20.1 19.6 19.2 18.6 18.3 17.9 17.7 45 19.3 18.2 17.6 17.2 16.7 16.3 16.0 15.8 40 17.3 16.3 15.7 15.3 14.8 14.5 14.2 14.0 35 15.4 14.5 13.8 13.4 13.0 12.7 12.5 12.3 30 13.5 12.6 12.0 11.6 11.2 11.0 10.8 10.6 25 11.5 10.8 10.3 10.0 9.5 9.3 9.1 9.0 20 9.6 9.1 8.6 8.3 7.9 7.7 7.5 7.3 15 7.7 7.3 6.9 6.7 6.3 6.1 5.8 5.6 10 5.8 5.4 5.1 5.0 4.7 4.5 4.2 3.9

MILLIGRAMS OF INVERT SUGAR IN MIXTURES OF 0.4(C) 0.3(C) 0.2(C) 0.1(C) 0.05(C) 0.02(C) (A) 99.6(D) 99.7(D) 99.8(D) 99.9(D) 99.95(D) 99.98(D) 88 33.3 85 32.0 31.8 80 29.7 29.5 75 27.4 27.2 70 25.3 25.0 65 23.2 22.8 60 21.2 20.8 20.4 55 19.3 18.9 18.5 50 17.4 17.0 16.7 45 15.6 15.3 14.9 40 13.8 13.5 13.2 35 12.1 11.9 11.5 10.3 30 10.4 10.2 9.9 8.8 25 8.8 8.6 8.2 7.3 20 7.1 6.9 6.6 5.8 4.9 15 5.4 5.2 5.0 4.4 3.7 2.0 10 3.8 3.5 3.4 3.0 2.5 1.7

=234. Soldaini’s Method Adapted to Gravimetric Work.=—By reason of their better keeping qualities and because of their less energetic action on non-reducing sugars, copper carbonate solutions are to be preferred to the alkaline copper tartrate solutions for gravimetric determinations of reducing sugars in cane juices and sugar house products, provided the difficulties which attend the manipulation can be removed. Ost has succeeded in securing perfectly satisfactory results with copper carbonate solution by slightly varying the composition thereof and continuing the boiling, for the reduction of the copper, ten minutes. The copper solution is made as follows:

17.5 grams crystallized copper sulfate. 250.0 ” potassium carbonate. 100.0 ” ” bicarbonate.

The above ingredients are dissolved in water and the volume of the solution completed to one liter. The object of the potassium bicarbonate is to secure in the solution an excess of carbon dioxid and thus prevent the deposition of basic copper carbonate on keeping. The manipulation is conducted as follows:

One hundred cubic centimeters of the copper solution are mixed with half that quantity of the sugar solution in a large erlenmeyer, which is placed upon a wire gauze, heated quickly to boiling and kept in ebullition just ten minutes. The sugar solution should contain not less than eighty nor more than 150 milligrams of the reducing sugar, and the quantity of the solution representing this should be diluted to fifty cubic centimeters before mixing with the copper solution. After boiling, the contents of the erlenmeyer are quickly cooled and filtered with suction through an asbestos filter and the whole of the copper suboxid washed into the filter tube. This precipitated suboxid is washed once with a little potassium carbonate solution then with hot water and finally with alcohol, well dried, heated to redness, and the copper oxid obtained reduced to metallic copper in an atmosphere of hydrogen entirely free of arsenic. From the weight of metallic copper obtained the quantity of sugar which has been oxidized is calculated from the tables below.

It is evident that the process given above may be varied so as to conform to the practice observed in this laboratory of cooling the boiling solution sufficiently at once by adding to it an equal volume of recently boiled, cold water, collecting the precipitated copper suboxid in a gooch, and, after washing it, securing solution in nitric acid and the precipitation of the copper by electrolysis.

TABLE SHOWING MILLIGRAMS DEXTROSE, LEVULOSE AND INVERT SUGAR OXIDIZED, CORRESPONDING TO MILLIGRAMS OF COPPER REDUCED.

Copper. Dextrose. Levulose. Invert.

435 152.3 145.9 147.5 430 149.8 143.4 145.3 425 147.3 140.9 143.1 420 144.8 138.4 140.8 415 142.3 135.9 138.5 410 139.8 133.5 136.2 405 137.3 131.1 133.9 400 134.9 128.7 131.6 395 132.5 126.4 129.3 390 130.1 124.1 127.0 385 127.8 121.8 124.8 380 125.5 119.5 122.6 375 123.3 117.2 120.4 370 121.1 115.0 118.2 365 119.0 112.8 116.0 360 116.9 110.6 113.9 355 114.8 108.5 111.8 350 112.8 106.4 109.8 345 110.8 104.3 107.8 340 108.8 102.3 105.8 335 106.8 100.3 103.8 330 104.9 98.4 101.8 325 103.0 96.5 99.9 320 101.1 94.6 98.0 315 99.2 92.8 96.2 310 97.4 91.0 94.4 305 95.6 89.2 92.6 300 93.8 87.5 90.9 295 92.0 85.8 89.2 290 90.2 84.1 87.5 285 88.4 82.4 85.8 280 86.7 80.8 84.1 275 85.0 79.2 82.4 270 83.3 77.6 80.7 265 81.5 76.1 79.1 260 79.8 74.6 77.5 255 78.1 73.1 75.9 250 76.5 71.6 74.3 245 74.9 70.1 72.7 240 73.3 68.6 71.1 235 71.7 67.2 69.5 230 70.1 65.7 68.0 225 68.5 64.3 66.5 220 66.9 62.8 65.0 215 65.3 61.4 63.5 210 63.8 59.9 62.0 205 62.2 58.5 60.5 200 60.7 57.0 59.0 195 59.1 55.6 57.5 190 57.6 54.1 56.0 185 56.0 52.7 54.5 180 54.5 51.2 53.1 175 53.0 49.8 51.6 170 51.5 48.4 50.2 165 50.0 46.9 48.7 160 48.5 45.5 47.3 155 47.0 44.1 45.8 150 45.5 42.7 44.4 145 44.0 41.3 42.9 140 42.5 39.9 41.5 135 41.0 38.5 40.1 130 39.6 37.1 38.6 125 38.1 35.7 37.2 120 36.7 34.3 35.8 115 35.2 32.9 34.3 110 33.7 31.6 32.9 105 32.2 30.3 31.4 100 30.7 29.0 30.0 95 29.2 27.7 28.5 90 27.8 26.4 27.1 85 26.3 25.1 25.6 80 24.8 23.8 24.2 75 23.3 21.5 22.8 70 21.8 20.2 21.4

CORRESPONDING TABLE FOR MALTOSE.

Milligrams Milligrams Milligrams maltose maltose copper anhydrid hydrate obtained. oxidized. oxidized.

435 263.7 277.6 430 259.3 273.0 425 255.0 268.4 420 250.9 264.1 415 247.0 260.0 410 243.2 256.0 405 339.4 252.0 400 235.6 248.0 395 231.9 244.1 390 228.2 240.2 385 224.6 236.4 380 221.1 232.7 375 217.7 229.1 370 214.4 225.6 365 211.1 222.2 360 207.9 218.8 355 204.7 215.4 350 201.5 212.1 345 198.3 208.7 340 195.2 205.4 335 192.0 202.1 330 188.8 198.8 325 185.7 195.4 320 182.5 192.1 315 179.4 188.8 310 176.3 185.6 305 173.3 182.4 300 170.3 179.2 295 167.3 176.1 290 164.4 173.0 285 161.4 169.9 280 158.5 166.8 275 155.5 163.7 270 152.6 160.7 265 149.7 157.6 260 146.8 154.6 255 143.9 151.5 250 141.1 148.5 245 138.2 145.5 240 135.4 142.5 235 132.5 139.5 230 129.7 136.5 225 126.8 133.5 220 124.0 130.6 215 121.2 127.6 210 118.4 124.7 205 115.7 121.8 200 112.9 118.9 195 110.2 116.0 190 107.4 113.1 185 104.7 110.2 180 101.9 107.3 175 99.2 104.4 170 96.4 101.5 165 93.7 98.6 160 90.9 95.7 155 88.2 92.8 150 85.4 89.9 145 82.6 87.0 140 79.9 84.1 135 77.1 81.2 130 74.4 78.3 125 71.6 75.4 120 68.9 72.5 115 66.1 69.6 110 63.4 66.7 105 60.6 63.8 100 57.9 60.9 95 55.1 58.0 90 52.3 55.1 85 49.6 52.2 80 46.8 59.3 75 44.1 56.4 70 41.4 53.5

=235. Weighing the Copper as Oxid.=—In the usual methods of the determination of reducing bodies, the percentage is calculated either volumetrically from the quantity of the sugar solution required to decolorize a given volume of the alkaline copper solution, or the reduced copper suboxid is brought into a metallic state by heating in an atmosphere of hydrogen or by electrolytic deposition. A quicker method of procedure is found in completing the oxidation of the cupric oxid by heating to low redness in a current of air. For this determination the precipitation of the cuprous oxid and its filtration are made in the usual manner. The cuprous oxid is collected in a filtering tube, made by drawing out to proper dimensions a piece of combustion tube, and has a length of about twelve centimeters in all. The unchanged part of the tube is about eight centimeters in length and twelve millimeters in diameter. It is filled by first putting in a plug of glass wool and covering this with an asbestos felt on top of which another plug of glass wool is placed. After the cuprous oxid is collected in the tube it is washed with boiling water, alcohol and ether. The rubber tube connecting it with the suction is of sufficient length to permit the tube being taken in one hand and brought into a horizontal position over a bunsen. The tube is gradually heated, rotating it meanwhile, until any residual moisture, alcohol or ether, is driven off from the filtering material. The layer of glass wool holding the cuprous oxid is gradually brought into the flame and as the oxidation begins the material will be seen to glow. The heating is continued for some time after the glowing has ceased, in all for three or four minutes, the tube and the copper oxid which it contains being brought to a low redness. The current of air passing over the red-hot material in this time oxidizes it completely. The filtering tube, before use, must be ignited and weighed in exactly the same manner as described above. The heat is so applied as not to endanger the rubber tube attached to one end of the filtering tube nor to burn the fingers of the operator as he turns the tube during the heating. After complete oxidation the tube is cooled in a desiccator and weighed, the increase of weight giving the copper oxid. For the atomic weights, 63.3 copper and 15.96 oxygen, one gram of copper oxid is equivalent to 0.79864 gram of copper, and for the weights 63.17 copper and 15.96 oxygen, one gram of copper oxid equals 0.79831 gram of copper. From the amount of metallic copper calculated by one of these factors, the reducing sugar is determined by the tables already given.

=236. Estimation of Dry Substance, Polarization and Apparent Purity for Factory Control.=—For technical purposes the methods of determining the above factors, proposed by Weisberg and applicable to concentrated sirups, massecuites, and molasses, may be used. Five times the half normal quantity of the material, viz., 65.12 grams, are placed in a quarter liter flask, dissolved in water and the flask filled to the mark. In the well shaken mixture, which is allowed to stand long enough to be free of air, the degree brix is estimated by an accurate spindle. For example, in the case of molasses, let the number obtained be 18.8.

Fifty cubic centimeters of the solution are poured into a 100 cubic centimeter flask, the proper quantity of lead subacetate added, the flask filled to the mark with water, its contents filtered, and the filtrate polarized in a 200 millimeter tube. Let the number obtained on polarization be 22°.1. This number may be used in two ways. If it be multiplied by two the polarization of the original sample is obtained; in this case, viz., 44°.2. In the second place, if 44.2 be multiplied by 0.26048 and this product divided by the specific gravity corresponding to 18°.8. viz., 1.078, the quotient 10.68 is secured representing the polarization or per cent of sugar contained in the solution of which the degree brix was 18.8°. From the numbers 18.8 and 10.68 the apparent purity of the solution, 56.8, is calculated, viz., 10.68 × 100 ÷ by 18.8. The original product as calculated above gives a polarization of 44.2 and this number multiplied by 100 and divided by 56.8 gives 77.8, or the apparent percentage of dry matter. The original sample of molasses, therefore, had the following composition: