Chapter I: Preface: To Volume Third (1)

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 }
” 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.

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.

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.

=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.

DRYING ORGANIC BODIES.

=12. Volatile Bodies.=—In agricultural analysis it becomes necessary to determine the percentage of bodies present in any given sample which is volatile at any fixed temperature. The temperature reached by boiling water is the one which is usually selected. It is true that this temperature varies with the altitude and within somewhat narrow limits at the same altitude, due to variations in barometric pressure. As the air pressure to which any given body is subjected, however, is a factor in the determination of its volatile contents, it will be seen that within the altitudes at which chemical laboratories are found, the variations in volatile content will not be important. This arises from the fact that while water boils at a lower temperature, as the height above the sea level increases, the corresponding diminished air pressure permits a more ready escape of volatile matter. As a consequence, a body dried to constant weight at sea level, where the temperature of boiling water is 100°, will show the same percentage of volatile matter as if dried at an altitude where water boils at 99°. When, therefore, it is desirable to determine the volatile matter in a sample approximately at 100°, it is better to direct that it be done in a space surrounded by steam at the natural pressure rather than at exactly 100°, a temperature somewhat difficult to constantly maintain. However, where it is directed or desired to dry to constant weight exactly at 100°, it can be accomplished by means of an air-bath or by a water-jacketed-bath under pressure, or to which enough solid matter is added to raise the boiling-point to 100°. It is not often, however, that it is worth while to make any special efforts to secure a temperature of 100°. When bodies are to be dried at temperatures above 100°, such as 105°, 110°, and so on, an air-bath is the most convenient means of securing the desired end. The different kinds of apparatus to be employed will be described in succeeding paragraphs.

=13. Drying at the Temperature of Boiling Water.=—The best apparatus for this process is so constructed as to have an interior space entirely surrounded with boiling water or steam, with the exception of the door by which entrance is gained thereto. The metal parts of the apparatus are constructed of copper, and to keep a constant level of water and avoid the danger of evaporating all the liquid, it is advisable to have a reflux condenser attached to the apparatus. It is also well to secure entrance to the interior drying oven, not only by the door, but also by small circular openings, which serve both to hold a thermometer and to permit of the aspiration of a slow stream of dry air through the apparatus during the progress of desiccation. The gaseous bodies formed by the volatilization of the water and other matters are thus carried out of the drying box and the process thereby accelerated. The bath should be heated by a burner so arranged as to distribute the flame as evenly as possible over the base. A single lamp, while it will boil the water in the center, will not keep it at the boiling-point on the sides. The temperature of the interior of the bath will not therefore reach 100°. The interior of the oven should be coated with a non-detachable carbon paint to promote the radiation of the heat from its walls, as well as to protect the parts from oxidation where acid fumes are produced during desiccation. Instead of a reflux condenser a constant water level may be maintained in the bath by means of a mariotte bottle or other similar device.

When a bath of this kind is arranged for use with a partial vacuum, it should be made cylindrical in shape, with conical ends, as shown in fig. 5, in order to bear well the pressure to which it is subjected. Among the many forms of steam-baths offered, the analyst will have but little difficulty in selecting one suited to his work. To avoid radiation the exterior of the apparatus should be covered with a non-conducting material.

=14. Drying In a Closed Water Oven.=—When it is desired to keep the temperature of a drying oven exactly at 100° instead of at the heat of boiling water, a closed water oven with a thermostat is to be employed. The oven should be so constructed as to secure a free circulation of the water about the inner space. Since as a rule the water between the walls of the apparatus will be subjected to a slight pressure, these walls should be made strong, or the cylindrical form of apparatus should be used. The thermostat used by the Halle Station is shown in Fig. 6.[4] A =⋃= shaped tube, with a bulb on one arm and a lateral smaller tube sealed on the other, is partly filled with mercury and connected by rubber tubes on the right with the gas supply, and on the left with the burner. The end carrying the bulb is connected directly by a rubber and metal tube with the water space of the oven. This device is provided with a valve which is left open until the temperature of the drying space reaches about 95°. The tube conducting the gas is held in the long arm of the =⋃= by means of a cork through which it passes air-tight and yet is loose enough to permit of its being moved. Its lower end is provided with a long ▲ shaped slit. When the valve leading to the water space is closed and the water reaches the boiling point, the pressure of the vapor depresses the mercury in the bulb arm of the =⋃= and raises it in the other. As the mercury rises it closes the wider opening of the ▲ shaped slit, thus diminishing the flow of gas to the burner. By moving the gas entry tube up or down a position is easily found in which the temperature of the drying space, as shown by the thermometer, is kept accurately and constantly at 100°.

In a bath arranged in this way a steam condenser is not necessary. Since, however, in laboratories which are not at a higher altitude than 1,000 feet the boiling-point of water is nearly 100°, it does not seem necessary to go to so much trouble to secure the exact temperature named. There could be no practical difference in the percentage of moisture determined at 100°, and at the boiling-point of water at a temperature not more than 1° lower.

=15. Drying in an Air-Bath.=—In drying a substance in a medium of hot air surrounded by steam, as has been described, the process is, in reality, one of drying in air. The apparatus usually meant by the term air-bath, however, has its drying space heated directly by a lamp, or indirectly by a stratum of hot air occupying the place of steam in the oven already described. The simplest form of the apparatus is a metal box, usually copper, heated from below by a lamp. In the jacketed forms the currents of hot air produced directly or indirectly by the lamp are conducted around the inner drying oven, thus securing a more even temperature. The bodies to be dried are held on perforated metal or asbestos shelves in appropriate dishes, and the temperature to which they are subjected is determined by a thermometer, the bulb of which is brought as near as possible to the contents of the dish. One advantage of the air-bath is in being able to secure almost any desired temperature from that of the room to one of 150° or even higher. Its chief disadvantage lies in the difficulty of securing and maintaining an even temperature throughout all parts of the apparatus. Radiation from the sides of the drying oven should be prevented by a covering of asbestos or other non-combustible and non-conducting substance. The burner employed should be a broad one and give as even a distribution of the heat as possible over the bottom of the apparatus.

=16. Spencer’s Air-Drying Oven.=—In order to secure an even distribution of the heat in the desiccating space of the oven, Spencer has devised an apparatus, shown in the figure, in which the temperature is maintained evenly throughout the apparatus by means of a fan.[5] The oven has a double bottom, the space between the two bottoms being filled with air. The sides are also double, the space between being filled with plaster. The fan is driven by a toy engine connected with the compressed air service or other convenient method. Thermometers placed in different parts of the apparatus, while in use, show a rigidly even heat at all points so long as the fan is kept in motion. The actual temperature desired can be controlled by a gas regulator. This form of apparatus is well suited to drying a large number of samples at once. Portions of liquids and viscous masses may also be dried by enclosing them in bulbs and connecting with a vacuum.