PRINCIPLES AND PRACTICE
OF
AGRICULTURAL ANALYSIS.
A MANUAL FOR THE EXAMINATION OF SOILS,
FERTILIZERS, AND AGRICULTURAL PRODUCTS.
FOR THE USE OF ANALYSTS, TEACHERS, AND
STUDENTS OF AGRICULTURAL CHEMISTRY.
VOLUME III.
AGRICULTURAL PRODUCTS.
BY HARVEY W. WILEY,
Chemist of the U. S. Department of Agriculture..
EASTON, PA.
Chemical Publishing Co.
1897.
COPYRIGHT, 1897,
By Harvey W. Wiley.
PREFACE TO VOLUME THIRD.
The concluding volume of the Principles and Practice of Agricultural Analysis has been written in harmony with the plan adopted at the commencement of the first volume. In it an effort has been made to place the analyst or student en rapport with all the best methods of studying the composition of agricultural products. During the progress of the work the author has frequently been asked why some special method in each case has not been designated as the proper one to be used. To do this would be a radical departure from the fundamental idea of the work; viz., to rely on the good judgment and experience of the chemist. It is not likely that the author’s judgment in such matters is better than that of the analyst using the book, and, except for beginning students pursuing a course of laboratory instruction, a biased judgment is little better than none at all. For student’s work in the laboratory or classroom it is probable that a volume of selected methods based on the present work may be prepared later on, but this possible future need has not been allowed to change the purpose of the author as expressed in the preface of the second volume “to present to the busy worker a broad view of a great subject.” For the courtesy and patience of the publishers, for the uniformly commendatory notices of the reviewers of volumes one and two, and for the personal encouraging expressions of his professional brethren the author is sincerely grateful. He finds in this cordial reception of his book a grateful compensation for long years of labor. The plates of the first edition of the three volumes have been destroyed in order to insure a re-writing of the second edition when it shall be demanded, in order to keep it abreast of the rapid progress in the field of agricultural chemical analysis.
Washington, D. C.,
Beginning of January, 1897.
TABLE OF CONTENTS OF
VOLUME THIRD.
PART FIRST.
SAMPLING, DRYING, INCINERATION
AND EXTRACTIONS.
Introduction, [pp. 1-3].—Methods of study; Scope of the work; Limitations of work; General manipulations.
Methods of Sampling, [pp. 3-13].—Vegetable substances; Animal substances; Preserving samples; Collecting samples; Grinding samples; Grinding apparatus.
Drying Organic Bodies, [pp. 13-36].—Volatile bodies; Drying ovens; Air baths; Drying in vacuum; Electric drying ovens; Steam coil apparatus; Drying in hydrogen; Drying in tubes; Drying viscous liquids; General principles of drying.
Incineration, [pp. 36-40].—Principles of incineration; Products of combustion; Purpose and conduct of incineration; German ash method; Courtonne’s muffle.
Extraction of Organic Bodies, [pp. 40-57].—Object of extraction; Solvents; Methods of extraction; Extraction by digestion; Extraction by percolation; Apparatus for extraction; Knorr’s extraction apparatus; Soxhlet’s extraction apparatus; Compact extraction apparatus; Recovery of solvents; Authorities cited in Part First.
PART SECOND.
SUGARS AND STARCHES.
Introduction, [pp. 58-62].—Carbohydrates; Nomenclature; Preparation of pure sugar; Classification of methods of analysis.
Analysis by Density of Solution, [pp. 63-72].—Principles of the method; Pyknometers; Calculating volume of pyknometers; Hydrostatic balance; Areometric method; Correction for temperature; Brix hydrometer; Comparison of brix and baumé degrees; Errors due to impurities.
Estimation of Sugars with Polarized Light, [pp. 74-120].—Optical properties of sugars; Polarized light; Nicol prism; Polariscope; Kinds of polariscopes; Character of light; Description of polarizing instruments: Laurent polariscope; Polariscope lamps; Soleil-Ventzke polariscope; Half Shadow polariscope; Triple field polariscope; Setting the polariscope; Control observation tube; Quartz plates; Correcting quartz plates; Application of quartz plates; Sugar flasks; Preparing sugar solutions for polarization; Alumina cream; Errors due to lead solutions; Double polarization; Mercuric compounds; Bone-black; Inversion of sugar; Clerget’s method; Influence of strength of solution; Calculation of results; Method of Lindet; Use of invertase; Activity of invertase; Inversion by yeast; Determination of sucrose; Determination of raffinose; Specific rotatory power; Calculating specific rotatory power; Variations in specific rotatory power; Gyrodynatic data; Birotation.
Chemical Methods of Estimating Sugar, [pp. 120-149].—General principles; Classification of methods; Reduction of mercuric salts; Sachsse’s solution; Volumetric copper methods; Action of copper solution on dextrose; Fehling’s solution; List of copper solutions; Volumetric laboratory method; Filtering tubes; Correction of errors; Permanganate process; Modified permanganate method; Specific gravity of cuprous oxid; Soldaini’s process; Relation of reducing sugar to quantity of suboxid; Factors for different sugars; Pavy’s process; Peska’s process; Method of Allein and Gaud; Method of Gerrard; Sidersky’s modification; Titration of excess of copper.
Gravimetric Copper Methods, [pp. 149-170].—General principles; Laboratory copper method; Halle method; Allihn’s method; Meissl’s method; Determination of invert sugar; Estimation of milk sugar; Determination of maltose; Preparation of levulose; Estimation of levulose.
Miscellaneous Methods of Sugar Analysis, [pp. 171-196]; Phenylhydrazin; Molecular weights of carbohydrates; Birotation; Estimation of pentosans; Determination of furfurol; Method of Tollens; Method of Stone; Method of Chalmot; Method of Krug; Precipitation with pyrogalol; Precipitation with phloroglucin; Fermentation methods; Estimating alcohol; Estimating carbon dioxid; Precipitation with earthy bases; Barium saccharate; Strontium saccharate; Calcium saccharate; Qualitive tests; Optical tests; Cobaltous nitrate test; The Dextrose group; Tests for levulose; Tests for galactose; Tests for invert sugar; Compounds with phenylhydrazin; Detection of sugars by means of furfurol; Bacterial action on sugars.
Determination of Starch, [pp. 196-226].—Constitution of starch; Separation of starch; Methods of separation; Separation with diastase; Separation in an autoclave; Principles of analysis; Estimation of water; Estimation of ash; Estimation of nitrogen; Hydrolysis with acids; Factors for calculation; Polarization of starch; Solution at high pressure; Method of Hibbard; Precipitation with barium hydroxid; Disturbing bodies in starch determinations; Colorimetric estimation of starch; Fixation of iodin; Identification of starches; Vogel’s table; Muter’s table; Blyth’s classification; Preparation of starches for the microscope; Mounting in canada balsam; Description of typical starches; Authorities cited in Part Second.
PART THIRD.
SEPARATION AND DETERMINATION
OF CARBOHYDRATES IN CRUDE OR
MANUFACTURED AGRICULTURAL PRODUCTS.
Sugars in Vegetable Juices, [pp. 227-253].—Introduction; Sugar in the sap of trees; Sugar in sugar canes; Weighing pipettes; Gravimeter; Reducing sugars in juices; Preservation of juices; Direct estimation of sugar; Cutting or shredding canes; Methods of analysis; Drying and extracting; Examination of bagasse; Fiber in canes; Sugar beets; Estimation of sugar in sugar beets; Machines for pulping beets; Instantaneous diffusion; Pellet’s process; Alcohol digestion; Extraction with alcohol; Determination of sugar in mother beets; Determination of sugars without weighing; Continuous observation tube.
Analysis of Sirups and Massecuites, [pp. 254-264].—Specific gravity; Determination of water; Determination of ash; Determination of reducing sugars; Estimation of minute quantities of invert sugar; Soldaini’s gravimetric method; Weighing the copper as oxid; Analyses for factory control.
Separation of Carbohydrates in Mixtures, [pp. 264-292].—Occurrence of sugars; Optical methods; Optical neutrality of invert sugar; Separation of sucrose and invert sugar; Separation of sucrose and raffinose; Determination of levulose; Formula for calculating levulose; Separation of sucrose from dextrose; Estimation of lactose in milk; Error due to volume of precipitate; Separation of sucrose, levulose and dextrose; Sieben’s method; Wiechmann’s method; Copper carbonate method; Winter’s process; Separation with lead oxid; Analysis of commercial glucose and grape sugar; Fermentation method; Oxidation method; Removal of dextrose by copper acetate; Separation of dextrin with alcohol.
Carbohydrates in Milk, [pp. 293-298].—Copper tartrate method; The official method; The copper cyanid process; Separation of sugars in evaporated milks; Method of Bigelow and McElroy.
Separation and Determination of Starch and Fiber, [pp. 298-306].—Occurrence; Separation of starch; Dry amyliferous bodies; Indirect method of determining water; Removal of oils and sugars; Preparation of diastase; Estimation of starch in potatoes; Constitution of cellulose; Fiber in cellulose; Official method; Separation of cellulose: Solubility of cellulose; Qualitive reactions for cellulose; Rare carbohydrates; Authorities cited in Part Third.
PART FOURTH.
FATS AND OILS.
General Principles, [pp. 309-316].—Nomenclature; Composition; Principal glycerids; Presses for extraction; Solvents; Freeing extracts of petroleum; Freeing fats of moisture; Sampling and drying for analysis; Estimation of water.
Physical Properties of Fats and Oils, [pp. 317-350].—Specific gravity; Balance for determining specific gravity; Expression of specific gravity; Coefficient of expansion of oils; Densities of common fats and oils; Melting point; Determination in capillary tube; Determination by spheroidal state; Solidifying point; Temperature of crystallization; Refractive power; Refractive index; Abbe’s refractometer; Pulfrich’s refractometer; Refractive indices of common oils; Oleorefractometer; Butyrorefractometer; Range of application of the butyrorefractometer; Viscosity; Torsion viscosimeter; Microscopic appearance; Preparation of fat crystals; Observation of fat crystals with polarized light; Spectroscopic examination of oils; Critical temperature; Polarization; Turbidity temperature.
Chemical Properties of Fats and Oils, [pp. 351-406].—Solubility in alcohol; Coloration produced by oxidants; Nitric acid coloration; Phosphomolybdic acid coloration; Picric acid coloration; Silver nitrate coloration; Stannic bromid coloration; Auric chlorid coloration; Thermal reactions; Heat of sulfuric saponification; Maumené’s process; Method of Richmond; Relative maumené figure; Heat of bromination; Method of Hehner and Mitchell; Author’s method; Haloid addition numbers; Hübl number; Character of chemical reaction; Solution in carbon tetrachlorid; Estimation of the iodin number; Use of iodin monochlorid; Preservation of the hübl reagent; Bromin addition number; Method of Hehner; Halogen absorption by fat acids; Saponification; Saponification in an open dish; Saponification under pressure; Saponification in the cold; Saponification value; Saponification equivalent; Acetyl value; Determination of volatile fat acids; Removal of the alcohol; Determination of soluble and insoluble fat acids; Formulas for calculation; Determination of free fat acids; Identification of oils and fats; Nature of fat acids; Separation of glycerids; Separation with lime; Separation with lead salts; Separation of arachidic acid; Detection of peanut oil; Bechi’s test; Milliau’s test; Detection of sesamé oil; Sulfur chlorid reaction; Detection of cholesterin and phytosterin; Absorption of oxygen; Elaidin reactions; Authorities cited in Part Fourth.
PART FIFTH.
SEPARATION AND ESTIMATION OF BODIES
CONTAINING NITROGEN.
Introduction and Definitions, [pp. 410-418].—Nature of nitrogenous bodies; Classification of proteids; Albuminoids; Other forms of nitrogen; Occurrence of nitrates.
Qualitive Tests for Nitrogenous Bodies, [pp. 418-422].—Nitric acid; Amid nitrogen; Ammoniacal nitrogen; Proteid nitrogen; Qualitive tests for albumni; Qualitive tests for peptones and albuminates; Action of polarized light on albumins; Alkaloidal nitrogen.
Estimation of Nitrogenous Bodies in Agricultural Products, [pp. 423-432].—Total nitrogen; Ammoniacal nitrogen; Amid nitrogen; Sachsse’s method; Preparation of asparagin; Estimation of asparagin and glutamin; Cholin and betain; Lecithin; Factors for calculating results; Estimation of alkaloidal nitrogen.
Separation of Proteid Bodies in Vegetable Products, [pp. 432-448].—Preliminary treatment; Character of proteids; Separation of gluten; Extraction with water; Action of water on composition of proteids; Extraction with dilute salt solution; Separation of bodies soluble in water; Separation of the globulins; Proteids soluble in dilute alcohol; Solvent action of acids and alkalies; Method of extraction; Methods of drying separated proteids; Determination of ash; Determination of carbon and hydrogen; Estimation of nitrogen; Determination of sulfur; Dialysis.
Separation and Estimation of Nitrogenous Bodies in Animal Products, [pp. 448-462].—Preparation of sample; Extraction of muscular tissues; Composition of meat extracts; Analysis of meat extracts; Use of phosphotungstic acid; Separation of albumoses and peptones; Estimation of gelatin; Estimation of nitrogen in flesh bases; Treatment of residue insoluble in alcohol; Pancreas peptone; Albumose peptone; Authorities cited in Part Fifth.
PART SIXTH.
DAIRY PRODUCTS.
Milk, [pp. 464-512].—Composition of milk; Alterability of milk; Effects of boiling on milk; Micro-organisms of milk; Sampling milk; Scovell’s milk sampler; Preserving milk for analysis; Freezing point; Electric conductivity; Viscosity; Acidity and alkalinity; Determination of acidity; Opacity; Creamometry; Specific gravity; Lactometry; Quévenne lactometer; Lactometer of the New York Board of Health; Density of sour milk; Density of milk serum; Total solids; Formulas for calculating total solids; Determination of ash; Estimation of fat; Fat globules; Number of fat globules; Counting globules; Classification of methods of analysis; Dry extraction methods; Official methods; Variations of extraction methods; Gypsum method; Estimation of fat in malted milk; Comparison of fat methods; Wet extraction methods; Solution in acid; Solution in alkali; Method of Short; Method of Thörner; Liebermann’s method; Densimetric methods; Areometric methods; Lactobutyrometer; Volumetric methods of fat analysis; Method of Patrick; The lactocrite; Modification of Lindström; Babcock’s method; Method of Leffmann and Beam; Method of Gerber; Proteid bodies in milk; Estimation of total proteid matter; Copper sulfate as a reagent; Precipitation by ammonium sulfate; Precipitation by tannic acid; Separation of casein from albumin; Estimation of casein; Factors for calculation; Separation of casein; Separation of casein with carbon dioxid; Separation of albumin; Separation of globulin; Precipitants of milk proteids; Precipitation by dialysis; Carbohydrates in milk; Dextrinoid body in milk; Amyloid bodies in milk.
Butter, [pp. 512-523].—General principles of analysis; Appearance of melted butter; Microscopic examination; Refractive power; Estimation of water, fat, casein, ash and salt; Volatile and soluble acids; Relative proportion of glycerids; Saponification value; Reichert number; Reichert-Meissl method; Elimination of sulfurous acid; Errors due to poor glass; Molecular weight of butter; Substitutes for and adulterants of butter; Butter colors.
Cheese and Koumiss, [pp. 524-536].—Composition of cheese; Manufacture of cheese; Official methods of analysis; Process of Mueller; Separation of fat from cheese; Filled cheese; Separation of nitrogenous bodies; Preparation of koumiss; Determination of carbon dioxid; Acidity; Estimation of alcohol; Proteids in koumiss; Separation by porous porcelain; Separation by precipitation with alum; Separation with mercury salts; Determination of water and ash; Composition of koumiss; Authorities cited in Part Sixth.
PART SEVENTH.
MISCELLANEOUS AGRICULTURAL PRODUCTS.
Cereals and Cereal Foods, [pp. 541-545].— Classification; General methods of analysis; Composition and analysis of bread; Determination of alum in bread; Chemical changes produced by baking.
Fodders, Grasses, and Ensilage, [pp. 545-547].—General principles of analysis; Organic acids in ensilage; Changes due to fermentation; Alcohol in ensilage; Comparative values of dry fodder and ensilage.
Flesh Products, [pp. 547-555].—Names of meats; Sampling; General methods of analysis; Examination of nitrogenous bodies; Fractional analysis of meats; Starch in meats; Detection of horse flesh.
Methods of Digestion, [pp. 555-564].—Artificial digestion; Amylolytic ferments; Aliphalytic ferments; Proteolytic ferments; Pepsin and pancreatin; Digestion in pancreas extract; Artificial digestion of cheese; Natural digestion; Digestibility of pentosans.
Preserved Meats, [pp. 565-566].—Methods of examination; Estimation of fat; Meat preservatives.
Determination of Nutritive Values, [pp. 566-576].—Nutritive value of foods; Comparative value of food constituents; Nutritive ratio; Calorimetric analysis of foods; Combustion in oxygen; Bomb calorimeter; Manipulation and calculation; Computing the calories of combustion; Calorimetric equivalents; Distinction between butter and oleomargarin.
Fruits, Melons and Vegetables, [pp. 577-582].— Preparation of samples; Separation of carbohydrates; Examination of the fresh matter; Examination of fruit and vegetable juices; Separation of pectin; Determination of free acid; Composition of fruits; Composition of ash of fruits; Dried fruits; Zinc in evaporated fruits; Composition of melons.
Tea and Coffee, [pp. 582-588].—Special points in analysis; Estimation of caffein; Iodin method; Spencer’s method; Separation of chlorophyll; Determination of proteid nitrogen; Carbohydrates of coffee; Estimation of galactan; Revised factors for pentosans; Use of roentgen rays.
Tannins and Allied Bodies, [pp. 588-596].— Occurrence and composition; Detection and estimation; Precipitation with metallic salts; The gelatin method; The hide powder method; Permanganate gelatin method; Permanganate hide powder method; Preparation of infusion.
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 | to face | 220 |
| ” | 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 | ||
| ” | 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 | to face | 348 |
| ” | 97. | [Refined lard crystals] | × 65 | ||
| ” | 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.
Figure 1. Mill for Grinding Dry Samples.
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.
Figure 2. Comminutor for Green Samples.
In the case of green vegetable matters which require to be reduced rapidly to a fine state of subdivision in order to secure even a fairly good sample some special provision must be made. This is the case with stalks of maize and sugar cane, root crops, such as potatoes and beets, and green fodders, such as clover and grasses. The chopping of these bodies into fine fodders by hand is slow and often impracticable. The particles rapidly lose moisture and it is important to secure them promptly as in the preparation of beet pulp for polarization. For general use we have found the apparatus shown in [fig. 2] quite satisfactory in this laboratory. It consists of a series of staggered circular saws carried on an axis and geared to be driven at a high velocity, in the case mentioned, 1,400 revolutions per minute. The green material is fed against the revolving saws by the toothed gear-work shown, and is thus reduced to a very fine pulp, which is received in the box below. Stalks of maize, green fodders, sugar canes, beets and other fresh vegetable matters are by this process reduced to a fine homogeneous pulp, suited for sampling and for analytical operations. Such pulped material can also be spread in a fine layer and dried rapidly at a low temperature, thus avoiding danger of fermentative changes when it is desired to secure the materials in a dry condition or to preserve them for future examination. Samples of sorghum cane, thus pulped and dried, have been preserved for many years with their sugar content unchanged.
Figure 3. Rasp for Sugar Beets.
Such a machine is also useful in preparing vegetable matter for the separation of its juices in presses. Samples of sugar cane, sugar beets, apples and other bodies of like nature can thus be prepared to secure their juices for chemical examination. Such an apparatus we have found is fully as useful and indispensable in an agricultural laboratory as a drug mill for air-dried materials.
It is often desirable in the preparation of roots for sugar analysis to secure them in a completely disintegrated state, that is with the cellular tissues practically all broken. Such a pulped material can be treated with water and the sugar juices it contains thus at once distributed to all parts of the liquid mass. The operation is known as instantaneous diffusion. The pulp of the vegetable matter is thus introduced into the measuring flask along with the juices and the content of sugar can be easily determined. Several forms of apparatus have been devised for this purpose, one of which is shown in [fig. 3]. This process, originally devised by Pellet, has come into quite general use in the determination of the sugar content of beets.[1] It is observed that it can be applied to other tubers, such as the turnip, potato, artichoke, etc. It is desirable, therefore, that an agricultural laboratory be equipped with at least three kinds of grinding machines; viz., first, the common drug mill used for grinding seeds, air-dried fodders, and the like; second, a pulping machine like the system of staggered saws above described for the purpose of reducing green vegetable matter to a fine state of subdivision, or one like the pellet rasp for tubers; third, a mill for general use such as is employed for making sausages from soft animal tissues.
Figure 4. Dreef Grinding Apparatus.
10. Grinding Apparatus at Halle Station.—The machine used at the Halle station for grinding samples for analysis is shown in [Fig. 4].[2] It is so adjusted as to have both the upper and lower grinding surfaces in motion. The power is transmitted through the pulley D, which is fixed to an axis carrying also the inner grinding attachment B. Through C₂, C₃, C₄, and C₁, the reverse motion is transmitted to the outer grinder A. By means of the lever E the two grinding surfaces can be separated when the mill is to be cleaned. The dree mill above described is especially useful for grinding malt, dry brewers’ grains, cereals for starch determinations and similar dry bodies. It is not suited to grinding oily seeds and moist samples. These, according to the Halle methods, are rubbed up in a mortar until of a size suited to analysis, and samples such as moist residues, wet cereals, mashes, beet cuttings, silage, etc., are dried before grinding. If it be desired to avoid the loss of acids which may have been formed during fermentation, about ten grams of magnesia should be thoroughly incorporated with each kilogram of the material before drying.
11. Preliminary Treatment of Fish.—The method used by Atwater in preparing fish for analysis is given below.[3] The same process may also be found applicable in the preparation of other animal tissues. The specimens, when received at the laboratory, are at once weighed. The flesh is then separated from the refuse and both are weighed. There is always a slight loss in the separation, due to evaporation and to slimy and fatty matters and small fragments of the tissues which adhere to the hands and the utensils employed in preparing the sample. Perfect separation of the flesh from the other parts of the fish is difficult, but the loss resulting from imperfect separation is small. The skin of the fish, although it has considerable nutritive value, should be separated with the other refuse.
The partial drying of the flesh for securing samples for analytical work is accomplished by chopping it as finely as possible and subjecting from fifty to one hundred grams of it for a day to a temperature of 96° in an atmosphere of hydrogen. After cooling and allowing to stand in the open air for twelve hours, the sample is again weighed, and then ground to a fine powder and made to pass a sieve with a half millimeter mesh. If the samples be very fat they cannot be ground to pass so fine a sieve. In such a case a coarser sieve may be used or the sample reduced to as fine and homogeneous a state as possible, and bottled without sifting.
The reason for drying in hydrogen is to prevent oxidation of the fats. As will be seen further on, however, such bodies can be quickly and accurately dried at low temperatures in a vacuum, and thus all danger of oxidation be avoided. In fact, the preliminary drying of all animal and vegetable tissues, where oxidation is to be feared, can be safely accomplished in a partial vacuum by methods to be described in another place. In order to be able to calculate the data of the analysis to the original fresh state of the substance, a portion of the fresh material should have its water quantitively determined as accurately as possible.