Part 3

Tobacco, pp. 596-610.—Fermented and unfermented tobacco; Acid and basic constituents; Composition of ash; Composition of tobacco; Estimation of water; Estimation of nitric acid; Estimation of sulfuric and hydrochloric acids; Estimation of oxalic, malic and citric acids; Estimation of acetic acid; Estimation of pectic acid; Estimation of tannic acid; Estimation of starch and sugar; Estimation of ammonia; Estimation of nicotin; Polarization method of Popovici; Estimation of amid nitrogen; Fractional extraction; Burning qualities; Artificial smoker.

Fermented Beverages, pp. 610-641.— Description; Important constituents; Specific gravity; Determination of alcohol; Distilling apparatus; Specific gravity of the distillate; Hydrostatic plummet; Calculating results; Table giving percentage of alcohol by weight and volume; Determination of percentage of alcohol by means of vapor temperature; Improved ebullioscope; Indirect determination of extract; Determination of total acids; Determination in a vacuum; Estimation of water; Total acidity; Volatile acids; Tartaric acid; Tartaric, malic and succinic acids; Polarizing bodies in fermented beverages; Reducing sugars; Polarization of wines and beers; Application of analytical methods; Estimation of carbohydrates; Determination of glycerol; Coloring matters; Determination of ash; Determination of potash; Sulfurous acid; Salicylic acid; Detection of gum and dextrin; Determination of nitrogen; Substitutes for hops; Bouquet of fermented and distilled liquors; Authorities cited in Part Seventh; Index.

ILLUSTRATIONS TO VOLUME THIRD.

Page. Figure 1. Mill for grinding dry samples 7 ” 2. Comminutor for green samples 9 ” 3. Rasp for sugar beets 10 ” 4. Dreef grinding apparatus 11 ” 5. Water jacket drying oven 14 ” 6. Thermostat for Steam-Bath 15 ” 7. Spencer’s drying oven 17 ” 8. Electric vacuum drying oven 19 ” 9. Steam coil drying oven 21 ” 10. Carr’s vacuum drying oven 22 ” 10. (Bis.) vacuum oven open 23 ” 11. Apparatus for drying in a current of hydrogen 25 ” 12. Caldwell’s hydrogen drying apparatus 27 ” 13. Liebig’s ente 28 ” 14. Drying apparatus used at the Halle Station 29 ” 15. Wrampelmayer’s oven 30 ” 16. Ulsch drying oven 31 ” 17. Courtoune muffle 39 ” 18. Knorr’s extraction apparatus 45 ” 19. Extraction flask 46 ” 20. Extraction tube 46 ” 21. Extraction siphon tube 46 ” 22. Soxhlet extraction apparatus 48 ” 23. Compact condensing apparatus 49 ” 24. Improved compact extraction apparatus 51 ” 25. Knorr’s apparatus for recovering solvents 54 ” 26. Apparatus for recovering solvents from open dishes 55 ” 27. Common forms of pyknometers 63 ” 28. Bath for pyknometers 66 ” 29. Aereometers, pyknometers and hydrostatic balance 68 ” 30. Hydrostatic balance 69 ” 31. Course of rays of light in a nicol 77 ” 32. Theory of the nicol 78 ” 33. Laurent lamp 83 ” 34. Lamp for producing constant monochromatic flame 85 ” 35. Field of vision of a Laurent polariscope 86 ” 36. Laurent polariscope 88 ” 37. Tint polariscope 89 ” 38. Double compensating shadow polariscope 91 ” 39. Triple shadow polariscope 92 ” 40. Apparatus for producing a triple shadow 92 ” 41. Control observation tube 95 ” 42. Apparatus for the volumetric estimation of reducing sugars 131 ” 43. Apparatus for the electrolytic deposition of copper 151 ” 44. Apparatus for filtering copper suboxid 154 ” 45. Apparatus for reducing copper suboxid 154 ” 46. Distilling apparatus for pentoses 179 ” 47. Autoclave for starch analysis 199 ” 47. (Bis). Maercker’s hydrolyzing apparatus for starch 204 ” 48. Maranta starch × 350 } ” 49. Potato starch × 350 } ” 50. Ginger starch × 350 } ” 51. Sago starch × 350 } ” 52. Pea starch × 350 } ” 53. Bean starch × 350 } ” 54. Wheat starch × 350 } ” 55. Barley starch × 350 } to face 220 ” 56. Rye starch × 350 } ” 57. Oat starch × 350 } ” 58. Indian corn starch × 350 } ” 59. Rice starch × 350 } ” 60. Cassava starch × 150 } ” 61. Indian corn starch × 150 } ” 62. Laboratory cane mill 230 ” 63. Weighing pipette 231 ” 64. Gird’s gravimeter 233 ” 65. Machine for cutting canes 236 ” 66. Cane cutting mill 237 ” 67. Apparatus for pulping beets 243 ” 68. Apparatus for cold diffusion 245 ” 69. Sickel-Soxhlet extractor 247 ” 70. Scheibler’s extraction tube 248 ” 71. Battery for alcoholic digestion 250 ” 72. Rasp for sampling mother beets 251 ” 73. Hand press for beet analysis 251 ” 74. Perforating rasp 252 ” 75. Tube for continuous observation 253 ” 75. (Bis). Chandler and Rickett’s Polariscope 266 ” 76. Apparatus for polarimetric observations at low temperatures 267 ” 77. Construction of desiccating tube 268 ” 78. Apparatus for polarizing at high temperatures 269 ” 79. Oil press 312 ” 80. Apparatus for fractional distillation of petroleum ether 314 ” 81. Section showing construction of a funnel for hot filtration 316 ” 82. Balance and Westphal sinker 318 ” 83. Melting point tubes 322 ” 84. Apparatus for the determination of melting point 324 ” 85. Apparatus for determining crystallizing point 327 ” 86. Abbe’s refractometer 329 ” 87. Charging position of refractometer 330 ” 88. Prism of Pulfrich’s refractometer 331 ” 89. Pulfrich’s new refractometer 332 ” 90. Heating apparatus for Pulfrich’s refractometer 333 ” 91. Spectrometer attachment 333 ” 92. Oleorefractometer 335 ” 93. Section showing construction of oleorefractometer 335 ” 94. Butyrorefractometer 339 ” 95. Doolittle’s viscosimeter 343 ” 96. Lard crystals × 65 } ” 97. Refined lard crystals × 65 } to face 348 ” 98. Apparatus for determining rise of temperature with sulfuric acid 358 ” 99. Apparatus for determining heat of bromination 362 ” 100. Olein tube 374 ” 101. Apparatus for saponifying under pressure 380 ” 102. Apparatus for the distillation of volatile acids 388 ” 103. Apparatus for amid nitrogen 425 ” 104. Sachsse’s eudiometer 425 ” 105. Dialyzing apparatus 447 ” 106. Scovell’s milk sampling tube 470 ” 107. Lactoscope, lactometer, and creamometer 474 ” 108. Areometric fat apparatus 493 ” 109. Babcock’s butyrometer and acid measure 500 ” 110. Gerber’s butyrometers 502 ” 111. Gerber’s centrifugal 503 ” 112. Thermometer for butyrorefractometer 515 ” 113. Apparatus for determining carbon dioxid in koumiss 533 ” 114. Cuts of mutton 548 ” 115. Cuts of beef 548 ” 116. Cuts of pork 548 ” 117. Bath for artificial digestion 559 ” 118. Bag for collecting feces 563 ” 119. Fecal bag attachment 563 ” 120. Hempel and Atwater’s calorimeter 570 ” 121. Apparatus for acetic acid 603 ” 122. Apparatus for smoking 610 ” 123. Metal distilling apparatus 613 ” 124. Distilling apparatus 614 ” 125. Improved ebullioscope 623

VOLUME THIRD.

AGRICULTURAL PRODUCTS.

PART FIRST.

SAMPLING, DRYING, INCINERATION AND EXTRACTIONS.

=1. Introduction.=—The analyst may approach the examination of agricultural products from various directions. In the first place he may desire to know their proximate and ultimate constitution irrespective of their relations to the soil or to the food of man and beast. Secondly, his study of these products may have reference solely to the determination of the more valuable plant foods which they have extracted from the soil and air. Lastly, he may approach his task from a hygienic or economic standpoint for the purposes of determining the wholesomeness or the nutritive and economic values of the products of the field, orchard, or garden. In each case the object of the investigation will have a considerable influence on the method of the examination.

It will be the purpose of the present volume to discuss fully the principles of all the standard processes of analysis and the best practice thereof, to the end that the investigator or analyst, whatever may be the design of his work, may find satisfactory directions for prosecuting it. As in the previous volumes, it should be understood that these pages are written largely for the teacher and the analyst already skilled in the principles of analytical chemistry. Much is therefore left to the individual judgment and experience of the worker, to whom it is hoped a judicious choice of approved processes may be made possible.

=2. Scope Of the Work.=—Under the term agricultural products is included a large number of classes of bodies of most different constitution. In general they are the products of vegetable and animal metabolism. First of all come the vegetable products, fruits, grains and grasses. These may be presented in their natural state, as cereals, green fruits and fodders, or after a certain preparation, as starches, sugars and flours. They may also be met with in even more advanced stages of change, as cooked foods, alcohols and secondary organic acids, such as vinegar. In general, by the term agricultural products is meant not only the direct products of the farm, orchard and forest, but also the modified products thereof and the results of manufacture applied to the raw materials. Thus, not only the grain and straw of wheat are proper materials for agricultural analysis, but also flour and bran, bread and cakes made therefrom. In the case of maize and barley, the manufactured products may extend much further, for not only do we find starch and malt, but also alcohol and beer falling within the scope of our work. In respect of animal products, the agricultural analyst may be called on to investigate the subject of leather and tanning; to determine the composition of meat, milk and butter; to pass upon the character of lard, oleomargarine, and, in general, to determine as fully as possible the course of animal food in all its changes between the field, the packing house and the kitchen.

=3. Limitations of Work.=—It is evident from the preceding paragraph, that in order to keep the magnitude of this volume within the limits fixed for a single volume the text must be rigidly confined to the fundamental principles and practice of agricultural analysis. The interesting region of pharmacy and allied branches, in respect of plant analysis, can find no description here, and in those branches of technical chemistry, where the materials of elaboration are the products of the field only a superficial view can be given. The main purpose and motive of this volume must relate closely to the more purely agricultural processes.

=4. General Manipulations.=—There are certain analytical operations which are more or less of a general nature, that is, they are of general application without reference to the character of the material at hand. Among these may be mentioned the determination of moisture and of ash, and the estimation of matters soluble in ether, alcohol and other solvents. These processes will be first described. Preliminary to these analytical steps it is of the utmost importance that the material be properly prepared for examination. In general, this is accomplished by drying the samples until they can be ground or crushed to a fine powder, the attrition being continued until all the particles are made to pass a sieve of a given fineness. The best sieve for this purpose is one having circular apertures half a millimeter in diameter. Some products, both vegetable and animal, require to be reduced to as fine a state as possible without drying. In such instances, passing the product through a sieve is obviously impracticable. Special grinding and disintegrating machines are made for these purposes and they will be described further on.

There are some agricultural products which have to be prepared for examination in special ways and these methods will be given in connection with the processes for analyzing the bodies referred to. Nearly all the bodies, however, with which the analyst will be concerned, can be prepared for examination by the general methods about to be described.

=5. Preparation of the Sample.= (a) Vegetable Substances.—For all processes of analysis not executed on the fresh sample, substances of a vegetable nature should, if in a fresh state, be dried as rapidly as possible to prevent fermentative changes. It is often of interest to determine the percentage of moisture in the fresh sample. For this purpose a representative portion of the sample should be rapidly reduced to as fine a condition as possible. To accomplish this it should be passed through a shredding machine, or cut by scissors or a knife into fine pieces. A few grams of the shredded material are dried in a flat-bottomed dish at progressively increasing temperatures, beginning at about 60° and ending at from 100° to 110°. The latter temperature should be continued for only a short time. The principle of this process is based upon the fact that if the temperature be raised too high at first, some of the moisture in the interior cells of the vegetable substance can be occluded by the too rapid desiccation of the exterior layers which would take place at a high temperature. The special processes for determining moisture will be given in another place.

The rest of the sample should be partly dried at a lower temperature or air-dried. In the case of fodders and most cattle foods the samples come to the analyst in a naturally air-dried state. When grasses are harvested at a time near their maturity they are sun-dried in the meadows before placing in the stack or barn. Such sun-dried samples are already in a state fit for grinding. Green grasses and fodders should be dried in the sun, or in a bath at a low temperature from 50° to 60° until all danger of fermentative action is over, and then air- or sun-dried in the usual way.

Seeds and cereals usually reach the analyst in a condition suited to grinding without further preliminary preparation. Fruits and vegetables present greater difficulties. Containing larger quantities of water, and often considerable amounts of sugar, they are dried with greater difficulty. The principles which should guide all processes of drying are those already mentioned, viz., to secure a sufficient degree of desiccation to permit of fine grinding and at a temperature high enough to prevent fermentative action, and yet not sufficiently high to cause any marked changes in the constituents of the vegetable organism.

(b) Animal Substances.—The difficulties connected with the preliminary treatment of animal substances are far greater than those just mentioned. Such samples are composed of widely differing tissues, blood, bone, tendon, muscle and adipose matters, and all the complex components of the animal organism are to be considered. The whole animal may be presented for analysis, in which case the different parts composing it should be separated and weighed as exactly as possible. Where only definite parts are to be examined it is best to separate the muscle, bone, and fat as well as may be, before attempting to reduce the whole to a fine powder. The soft portions of the sample are to be ground as finely as possible in a meat or sausage cutter. The bones are crushed in some appropriate manner, and thus prepared for further examination. Where the flesh and softer portions are to be dried and finely ground, the presence of fat often renders the process almost impossible. In such cases the fat must be at least partially removed by petroleum or other solvent. In practically fat-free samples the material, after grinding in a meat cutter, can be partially dried at low temperatures from 60° to 75°, and afterwards ground in much the same manner as is practiced with vegetable substances.

As is the case with the preliminary treatment of vegetable matters, it is impossible to give any general directions of universal applicability. The tact and experience of the analyst in all these cases are better than any dicta of the books. In some instances, as will appear further on, definite directions for given substances can be given, but in all cases the general principles of procedure are on the lines already indicated.

=6. Preserving Samples.=—In most cases, as is indicated in the foregoing paragraphs, the sample may be dried before grinding to such a degree as to prevent danger from fermentation or decay. The fine-ground samples are usually preserved in glass-stoppered bottles, carefully marked or numbered. In some cases it is advisable to sterilize the bottles after stoppering, by subjecting them to a temperature of 100° for some time. In the case of cereals assurance should be had that the samples do not contain the eggs of any of the pests that often destroy these products. As a rule, samples should be kept for a time after the completion of the analytical work, and this is especially true in all cases where there is any prospect of dispute or litigation. In general it may be said, that samples should be destroyed only when they are spoiled, or when storage room is exhausted.

=7. Collecting Samples.=—When possible, the analyst should be his own collector. There is often as much danger from data obtained on non-representative samples as from imperfect manipulation. When personal supervision is not possible, the sample when received, should be accompanied by an intelligible description of the method of taking it, and of what it represents. In all cases the object of the examination must be kept steadily in view. Where comparisons are to be made the methods of collecting must be rigidly the same.

The processes of analysis, as conducted with agricultural products, are tedious and difficult. The absolutely definite conditions that attend the analysis of mineral substances, are mostly lacking. The simple determinations of carbon, hydrogen, nitrogen and sulfur, which are required in the usual processes of organic analysis, are simplicity itself when compared with the operations which have to be performed on agricultural products to determine their character and their value as food and raiment. We have to do here with matters on which the sustenance, health and prosperity of the human race are more intimately concerned than with any other of the sciences. This fact also emphasizes the necessity for care in collecting the materials on which the work is to be performed.

=8. Grinding Samples.=—In order to properly conduct the processes of agricultural analysis it is important to have the sample finely ground. This arises both from the fact that such a sample is apt to contain an average content of the various complex substances of which the material under examination is composed, and because the analytical processes can be conducted with greater success upon the finely divided matter. In mineral analysis it is customary to grind the sample to an impalpable powder in an agate mortar. With agricultural products, however, such a degree of fineness is difficult to attain, and moreover, is not necessary. There is a great difference of opinion among analysts respecting the degree of fineness desirable. In some cases we must be content with a sample which will pass a sieve with a millimeter mesh; in fact it may be found impossible, on account of the stickiness of the material, to sift it at all. In such cases a thorough trituration, so as to form a homogeneous mass will have to be accepted as sufficient. Where bodies can be reduced to a powder however, it is best to pass them through a sieve with circular perforations half a millimeter in diameter. A finer degree of subdivision than this is rarely necessary.

=9. The Grinding Apparatus.=—The simplest form of apparatus for reducing samples for analysis to a condition suited to passing a fine sieve is a mortar. Where only a few samples are to be prepared and in small quantities, it will not be necessary to provide anything further. After the sample is well disintegrated it is poured on the sieve and all that can pass is shaken or brushed through. The sieve is provided with a receptacle, into which it fits closely, to avoid loss of any particles which may be reduced to a dust. The top of the sieve, when shaken, may also be covered if there be any tendency to loss from dust. Any residue failing to pass the sieve is returned to the mortar and the process thus repeated until all the material has been secured in the receiver. The particles more difficult of pulverization are often different in structure from the more easily pulverized portions, and the sifted matter must always be carefully mixed before the subsample is taken for examination. Often the materials, or portions thereof, will contain particles tough and resistant to the pestle, but the operator must have patience and persistence, for it is highly necessary to accurate work that the whole sample be reduced to proper size.

Where many samples are to be prepared, or in large quantities, mills should take the place of mortars. For properly air-dried vegetable substances, some form of mill used in grinding drugs may be employed. Grinding surfaces of chilled corrugated steel are to be preferred. The essential features of such a mill are that it be made of the best material, properly tempered, and that the parts be easily separated for convenience in cleaning. The grinding surfaces must also be so constructed and adjusted as to secure the proper degree of fineness. In fig. 1 is shown a mill of rather simple construction, which has long been in satisfactory use in this laboratory. Small mills may be operated by hand power, but when they are to be used constantly steam power should be provided. In addition to the removal of nearly all the moisture by air-drying there are many oleaginous seeds which cannot be finely ground until their oil has been removed. For this purpose the grinding surfaces of the mill are opened so that the seeds are only coarsely broken in passing through. The fragments are then digested with light petroleum in a large flask, furnished with a reflux condenser. After digestion the fragments are again passed through the mill adjusted to break them into finer particles.

The alternate grinding and digestion are thus continued until the pulverization is complete. On a small specially prepared sample the total content of oil is separately determined.

Fresh animal tissues are best prepared for preliminary treatment by passing through a sausage mill. The partially homogeneous mass thus secured should be dried at a low temperature and reground as finely as possible. Where much fat is present it may be necessary to extract it as mentioned above, in the case of oleaginous seeds. In such cases both the moisture and fat in the original material should be determined on small specially prepared samples with as great accuracy as possible. Bones, hoofs, horns, hair and hides present special difficulties in preparation, which the analyst will have to overcome with such skill and ingenuity as he may possess.

The analyst will find many specially prepared animal foods already in a fairly homogeneous form, such as potted and canned meats, infant and invalid foods, and the like. Even with these substances, however, a preliminary grinding and mixing will be found of advantage before undertaking the analytical work. Many cases will arise which are apparently entirely without the classification given above. But even in such instances the analyst should not be without resources. Frequently some dry inert substance may be mixed with the material in definite quantities, whereby it is rendered more easily prepared. Perhaps no case will be presented where persistent and judicious efforts to secure a fairly homogeneous sample for analysis will be wholly unavailing.