mm "N'VERSITY OF B.C. LIBRAR 3 9424 00126 2523 P*OC£SSING-CK£ U.B.C. LIBRARY 9n HMjWffWffBfB Shi Ctbraru 3.n ttuvh vi Mum hi a ■ »•>. ^H P ■ Digitized by the Internet Archive in 2010 with funding from University of British Columbia Library http://www.archive.org/details/dairychemistryprOOrich DAIRY CHEMISTEY. WORKS PUBLISHED BY CHARLES GRIFFIN & CO. FOODS : Their Composition and Analysis. By A. Wykteb Blyth, M.R.C.S., F.C.3., Barrister-at-Law, Public Analyst for the County of Devon, and Medical Officer of Health for St. Marylebone. With Elaborate Tables, Folding Utho-Plate, and Photographic Frontispiece. Fourth Edition, Revised and En- larged. 21s. " An admirable mgest of the most recent state of knowledge. . . . Interesting even to lay readers." — Chemical News. A GRICULTURAL CHEMISTRY AND ANALYSIS: A Practical Handbook for the Use of Agricultural Students. By J. M. H. Mlnro, D.Sc, Professor of Chemistry, Downton College of Agriculture. (Griffin' I '/'<-,■!,, lological Manual*.) [In preparation. Now ReAJ>Y. In large 8vo. Handsome Cloth, with Plate and Numerous Illustrations. 21s. BR;EWI1TG: THE PRINCIPLES AND PRACTICE OF. A TEXT-BOOK FOR THE USE OF STUDENTS AND PRACTICAL MEN. By WALTER J. SYKES, M.J)., D.P.H., F.I.C., Editor of the Analyst. "We consider it one of the most couplet?: in CONTENTS and novel in arrange- ment that has yet been published."— .Brewers' Journal. \<>w ready, Vol. I., Complete in itself. 15s. TECHNICAL MYCOLOGY: THE UTILIZATION OF MICRO-ORGANISMS IN THE ARTS AND MANUFACTURES. A Practical Handbook for Bacteriologists, Analysts, and others. By Prof. FKAXZ, LAFAR, of Vienna. Translated by CHAS. SALTER. In two vols., large 8vo, with Plate and Illustrations. " The chapters teem with interesting matter from beginning to end. . . . The plan is admirable, the classification simple, the style good, and the tendency of the whole volume is to convey sure information to the readi ■ FIXED OILSTTATS, BUTTERS, AND WAXES : Their Prepara- tion and Properties, and the Manufacture therefrom Of Candles, Soaps, and other Products. By C. R. Alder Wright, D.Sc, F.R.S., Late Lecturer on Chemistry, St. Mary's Hospital Medical School. In large 8vo, handsome cloth, with 144 Illustrations. 28s. "Br. Wrights work will be found ABSOLUTELY inmsi-kn.-ahle by every Ch mist. ISSHe with information valuable alike to the Analyst and the Technical Chemist."— The Anal >i si. FOOD SUPPLY. l'-v I.'ui.eki I'.ki • i .. Agricultural Superintendent to the Royal Dublin Society. With Appendix on FRES1 B.VED FOODS. By «'. a. Mil' iim.i.. B.A.. K.I. •'. With many Engravings from Photographs illustrating the Chief Breeds of Cattle, Sheep, PigB, Poultry, &c. Cloth, 4s. Ba. "A Practical Handbook, bj one of the ablest, best known, and most experienced agricultural writers oi the present day. North British Agriculturist. PRACTICAL SANITATION. A Handbook for Sanitary Inspectors and others interested in sanitation. Bj Qkobsi Bud, M.D., D.P.H., Medical Officer, Staffordshire County Council, with Appendix on sanitary Law, bj h Mam.kv. ma.. Mi;., D.P.H., Medical Officer ot \\,-t Bromwich. Fifth Edition, Thorough!) Revised and Enlarged, (loth, 6s. "Abounds in pi HedicalJoumal. CHEMISTRY FOR ENGINEERS AND MANUFACTURERS. Bj Bzbtkam Blount, i . i i .. F.C.8. and A. G. Bloxah, F.I.C.. P.C.8. w Ith Illus- trations. In two »ol i old Separately. Vol, i The Chemistry of i kneering. Building; and Metallurgy, 10s. 6d. vol. II. The Chemistry of the Manufacture ii ■ 9D0CSKDSD beyond all expectation, and havi produced a worl which should givi hi i powkj tothi Engineer and Manufacturer. Th i LOKDOS CB i'i l in l IN A t n . I I I- IMIII; STREET, STRAND, W.( DAIRY CHEMISTRY: Fore Milk and Shippings L29 In I lifferenl Churns, 126 Colostrum, .... 129 CONTENTS. ix PAGR PAGE Change of, to Normal Milk , 131 Detection, 140 Limits and Standards, 132 Boric Acid and Borax, 140 Society of Public Analysts Salicylic Acid, . 141 Standard, 132 i Fluorides, . 141 Triple Standard, . 133 Formaldehyde, 142 Variations of Fat in Milk on Preservation of Samples, 144 Standing, 133 Action of Heat, 145 Court of Queen's Bench De Condensed Milk, . 146 cision, 135 Composition of Sweetenec [ Practical Allowance, 135 Milk, . 146 Appeal to the Cow, . 136 Unsweetened, . 147 Adulterations, . 136 Dilution, 148 Added Water, 136 Food Value, . 148 Cane-Sugar, &c., . 137 Milk Powders, 149 Glycerine, 137 Sterilised Milk, . 149 Starch, .... 137 Analytical Characters, 150 Brains and Mammary Tissue , 13S Detection of, in New Milk , 152 Fat Abstracted, . 138 Action of Cold, 154 Preservatives, . 139 Composition, 154 Objections, . 139 Of Melted Frozen Milk, 156 Advantages, . , . 140 CHAPTER IV.— The Chem [Cal Control of the Dairy. Duties of the Dairy Chemist, 158 Clotted Cream Samples and Sampling, 159 Cheese, and Butter, 1 80 Testing, 161 Failures and their Probable Sample cans, 162 Causes, 180 Analysis of Samples, 163 Modifications, . 180 Testing, .... 164 Gerber's Acido - butyro Determination of Specific metric Method, 180 Gravity, 164 Gaertner and Hugershoff's Lactometers, 164 Tester, . 181 Use of, . 165 Excelsior Gearing, . 182 Estimation of Total Solids, 167 Rapid Gearing, 183 Weighing, 169 The Lister Machine, . 184 Stokes' Rapid Method, 170 Apparatus, &c, 184 Estimation of Fat, 170 Chemicals, . 185 Babcock Method, 170 Modes of Operation, . 185 Measuring, 171 Milk, Skim Milk, Whey, New Milk, . 172 and Buttermilk, . 185 Cream, . 172 Reading the Fatty Layer, 1 86 Separated Milk, 173 Cream, . 187 Acid, 173 Sour Milk, . 188 Cleaning Test Bottles, 173 Clotted Cream, Buttei * Working and Oiling, 173 Cheese, &c, . 1S8 Revolving Disc, . 173 Cleaning Bottles, . 188 Leffmann-Beani Method, 174 Butyrometer with two Beimling Machine, . 174 openings, . 188 Apparatus, 175 Cream, . 189 Chemicals, . 177 Butter, . 189 The Process, . . 177 Cheese, . 189 Testing Milk, &c, . 177 Calculation of Result 5, 189 Cream, . . 178 Water Estimation in Sour Milk, . 179 Butter, &c, . 1S9 CONTENTS. Stokes' Modification, Soxhlet's Areonietric Pro- cess, Control of Milk during Delivery, Solution of Analytical Problems, Low Specific Gravity, . High „ . . Sweet Taste, " Poor" Milk, Unusual Taste and Smell, Sour Milk, .... Thick Milk, .... Sediment, .... Skim Milk, .... l'Af.E 191 192 195 197 197 199 200 200 201 203 204 204 205 Distinction from Separated Milk, . Rising of Fat Globules, Composition, Control of Separators, Separator Slime, . Separators, . Cream, Composition, Ash, . Density, Clotted Cream, Thickness of Cream, Artificial Thickening of Cream 205 2U5 209 209 ■21o 211 214 214 216 217 219 221 224 CHAPTER V. — Biological and Sanitary Matters. Micro-organisms and the De- Analytical Figures, . 232 composition of Milk, 225 Total Solids, 232 Classification, 225 Loss on Ignition, 232 Action on Milk, . 225 Chlorine, .... 232 Lactic Fermentation, 226 Free and Albuminoid Am- Butyric ,, 227 monia, 232 Alcoholic ,, 227 Nitric Acid, 234 Curdling Organisms, . 227 Nitrites, .... 234 Curdling and Peptonising Oxygen Absorbed from Per- Organisms, 227 manganate, 236 Chromogenic Organisms, . 228 Phosphates, 235 Moulds 229 Interpretation of Results, 236 Pathogenic Organisms, 229 Bacteriological Examinations, . 237 Convejance of Disease Preparation of Nutrient Media , 237 through Milk, . 229 Procedure, .... 238 Conveyance of Disease Interpretation of Results, through Contaminated Summary of Sanitary Precau- -Milk,. 230 tions, .... 239 Water Supply, 230 Products formed from Milk by Inspection of Source, . 231 < Irganisms, 240 Chemical Analysis, 231 Koumiss, .... 241 Taking of Samples, . 231 Kejihir, .... 243 Colour and Smell, 231 Mazoum, .... 244 CHAPTER VI. -Hitter. Definition, .... 24"> "it ion, .... 2l."> Variations in Percentages ol Water, .... 247 Action of Salt, . . . 2»^ TIhoi \ ot i Ihurning, . . :'v.i Temperature of < Ihurning, . 251 Preservatives, . . . . 261 Proximate Analysis of Butter, Water, .... Solids not Fat and Salt. F.it find A I r ervatives, Interpretation of Result s, 261 26 1 263 263 26 » 26 » 266 CONTENTS. XI PAGE PAGE Analysis of Butter Fat, . 257 Gravimetric Method of Preparation for Analysis, 257 Hehner, . 276 Recapitulation of Properties, 257 Thermometric Method, . 276 Estimation of Volatile Fatty Heat Evolved by Hydrolysis , 277 Acids, .... 25S Manmene Test, . 277 Reichert Process, 258 Thompson and Ballan - Kreis' Modification, 262 tyne's Modification 277 Theory of Reichert 's Pro- Richmond Modification, 278 cess, 263 Physical Examination of Butte r Estimation of Saponification Fat, .... . 279 Equivalent, . 266 with Polarised Light, . 279 Kcettstorfer's Method, 266 Density, . 281 Estimation of Soluble and In- Expansion, 281 soluble Fatty Acids, 268 Mode of Expressing Result s, 382 Hehner and Angell Method ,268 Determination, . 283 Modification by American Molecular Specific Volumes, 285 Association of Agri- Refractive Index, 285 cultural Chemists, . 269 Oleo-refractometer, . 285 Johnstone, 271 Butyro-refractometer, 287 Blunt, .... 271 Viscosity, 290 Morse and Burton, 271 Behaviour of Butter on Melt Specific Colour Tests for ing, 290 Adulterants, . 272 Melting point of Fat, . 291 Baudouin's, 272 Detection of Adulteration, 291 Becchi's, .... 272 Margarine, . 292 Wellmann's, 272 Influence of Keeping on the Behaviour of Butter Fat with Analytical Properties, 292 Solvents, 273 Buttermilk, 296 Critical Temperature of Definition, . 296 Solution, 273 Composition, 296 Valenta's Method, 273 Variations of Fat, 296 Iodine and Bromine Absorp- Ash, .... 296 tion, .... 274 Chemical Control of Churning Von Hiibl's Method, . 274 Operations, 297 Bromine Absorp CHA tion, 276 PTER VII — Ot her Milk Products. Cheese, 298 Analysis, .... 309 Action of Rennet, 298 Richmond's Method, . 309 Composition of Curd and Whey, 298 Water, Fat, Ash, 309 Rennet, .... 300 Proteids and Products o I Preparation, 300 Ripening, . 310 Properties, 300 Stutzer's Method, 311 Testing, . 301 Ash, Mineral Matter, 311 Classification, 301 Water, 311 Soft Cheeses, 301 Fat, .... 311 Hard , , 302 Nitrogen Proteids and Pro Composition, 302 ducts of Ripening, 311 Cream Cheeses, 303 Duclaux's Method, 315 Soft „ . 303 Water, Fat, Extracts, 315 Hard ,, . . 304 Ash, Salt, . 315 Skim Milk ,, . . 305 Proteids and Products o E Proteids in Cheese, . 305 Ripening, . 315 Detailed Composition, 306 Volatile Acids, . 316 Heavy Metals in Cheese, . 308 Devarda's Method, 317 Ripening, 308 Adulterations, 317 Nil CONTENTS. PA'iR PAGE Other Products from Milk, 318 •Tunkets, . 320 Commercial Milk-Sugar, 318 Proteid Compounds, . 320 Preparation, 318 Milk Wine, . . 320 Examination, . 318 Milk ( locoa, . . 320 Detection of Adulteration, 319 CHAPTER VIII. -The Milk of Mammals Other than the Cow. Classification, .... 321 Milk of Gamoose, 328 Composition of Animal Fat, 321 Composition, .•;•_>* Sugar, ..... 322 Fat, . 329 Proteids, ..... 322 Casein, 329 Composition of Milk, 322 Albumin, . 329 Human Milk, .... 323 Sugar, 330 Appearance,. 323 Ewe, 331 Properties, .... 323 Goat, 332 Composition, 323 Mare, 333 Variation with Lactation, . 324 Ass, .... 334 Probahle Mean Composition, 325 Milk as a Food and Medicine, . 334 Variation of Constituents, . 325 Heat of Combustion of Con- Composition Before and After stituents, . 335 Suckling, 325 Food Value, . 336 Comparison with Cow's Milk, 326 As Food for Infants, 336 Buffalo, 327 Artificial Human . Vlil'k, ! 336 Composition, 327 Peptonised Milk, . 337 Fat, 328 Diabetic Milk, . 337 APPENDIX A. — Experimental Evidence that the Fat Cream is Solid at Low Temperatures, APPENDIX B. IN 338-341 Standardisation and Calibration of Apparati 9, 342-346 I. Weights, ....... 342 II. Burettes, ....... 344 III. Pipettes, ....... 345 IV. Flasks, . . . . . . .840 V. Leffmann-Beam or Gerber Bottles, .... 846 VI. Lactometers, ....... 346 VII. Thermometers, ...... 846 347 856 . 3*9 APPENDIX C— Usefi-i. Tables, ... LIST OF ILLUSTRATIONS. FIG. PAGE 1. Milk Scale, ...... ei 2. Diagrammatic View of Air-bath, 72 3. Stokes' Tube, ...... 99 4. Thermo-lactometer, . 165 5. Soxhlet's Lactometer, • 165 6. Glass Jar, ....... 166 7. Lister- Babcock Milk Tester, . 171 8. Beimling's Separator, . 174 9. Automatic Burette, . 176 10. Neck of Bottle, ...... 178 11. Gaertner and Hugershoff's Milk Tester, 182 12. Milk Tester (steam driven), 1S2 13. The Lister Machine, .... 184 14. Neck of Bottle, ..... 1S6 15. Lister-Stokes Machine, .... 191 16. Soxhlet's Apparatus for Examination of Milk, . 193 17. Alexandra Separator, .... facing 212 18. Burmeister and Wain Separator, 212 19. Alpha Separator, ..... 213 20. Oleo-refractometer, .... 2S6 21. Butyro-refractometer, .... 288 22. Curves of Specific Volume, 340 LIST OF TABLES. ii. in. IV. v. VI. VII. VIII. IX. X. XI. XII. XIII Composition of Mucoid Proteid. Change of Rotation of o-Milk-sugar in Solutioi Composition of Casein, . ,, Pepto-caseoses, . ,, Trypto-caseoses, ,, Hydrolo-caseoses, ,, Chymo-caseoses, Ash of Milk, Salts of Milk, . Fat of Milk, Properties of Milk Fat [Richmond), {Pi™), • Density of Milk Fat, Specific Gravities and Volumes of Fat, Solubility of Calcium Butyrate, . Properties of the Acids of Series C„H2„+iCOOH, Comparison of the Four Typical Fatty Acids, . Specific Gravity of Water, Variation of Specific Gravity of Milk on Dilution, Specific Gravity and Volume of Milk, . Expansion of Milk, .... For Correcting Specific Gravity of Separated Milk to 60 For Calculating the Amount of Milk-sugar from the Quantities of Copper Reduced, Comparison of Percentage of Fat by Dry and Wet Ether, ...... Comparison of Percentage of Fat by Bell and Adams Methods, Comparison of Percentage of Fat by Ritthausen and Adams' Methods, . Composition of Milk after Filtration through Paper, Estimation of Milk Solids by Densimetric Method, For Calculating Percentages of Proteids in Milk, Acidity of Milk on Standing, ,, ,, to Litmus and Phenolphthalein, Alcohol Tables (Hehner), Average Composition of Milk, . Limits for Milk, . 3 10 26 29 30 30 30 32 33 35 37 37 38 39 44 46 49 51 57 64 66 F., 67 LIST OF TABLES. rABLE XIV. XV. XVI. XVII. XVIII. XIX. XX. XXI. XXII. XXIII. XXIV. XXV. XXVI. XXVII. XXVIII. XXIX. XXX. XXXI. XXXII. XXXIII. XXXIV. XXXV. XXXVI. Percentage of Ash in Milk, Analyses of Abnormal Milks, Percentage of Solids not Fat in Mixed Milk, Composition of Milk of Different Breeds of Cattle (Fat), Analysis of Samples Highest and Lowest in Fat, Composition of Milk of Different Breeds of Cattle (Solids not Fat), .... Variations in Solids not Fat in Milk of the same Cow Solids in Milk of Cows of Different Breeds ( Vitth), Composition of Milk of Different Breeds of Cattle, Solids in Milk of Cows of Different Breeds (Bell), Variations of Fat in Different Churns, . Mean Monthly Averages of Milk, Daily Variations, .... Composition of Morning and Evening Milk, Variations on Partial Milking, . Variations of Fat with Solids not Fat, . Composition of Viscous and Non- Viscous Secretions before Parturition, .... Composition of Ash of Colostrum, Average Composition of Colostrum, Change of Colostrum after Parturition, Change of Colostrum to Normal Milk, . Composition of Colostrum, Variations in Composition of Milk on Standing (Lar Churns), ..... Variations in Composition of Milk on Standing (Small Churns), ..... Variations in Composition of Milk on Standing (Pan) Composition of Sweetened Milk, ,, Unsweetened Milk, Dilution of Condensed Milk, Composition of Milk Powders, . Composition of Sterilised Milk (Six Hours), ,, ,, (Twenty-four Eours), ,, New Milk, Percentage <>f Albumin in Milk al Various Temperatures, Comparative Analyses of Mixed Fresh and Sterilised Milks, .... WWII. Composition of the Solid and Liquid Portions o Milk, .... XXXVIII. Composition of Frozen Milk (Comparative), XXXIX. „ ,, (Vieth), . \l.. ,, ., (as Retailed), Strengl h of 8ulphurio Acid, XLL For Estimating Fal in Cream, , Frozen PAGE 121 122 122 123 123 124 I2fi 12.5 125 126 126 127 127 128 128 129 129 130 130 131 131 131 134 134 135 147 147 148 149 151 151 151 154 154 1 58 l.'.ti 156 157 177 179 LIST OF TABLES. XV11 TABLE XLII. For Calculating Fat in Cream, . Calculation of Fat in Separated Milk, . Composition of Separated Milk, ,, Separator Slime. , , Ash of Separator Slime, XLIII. Composition of Cream, . >> »» • • • ., Ash of Cream, . XLIV. Calculation of Fat in Cream, Density of Cream at Different Temperatures, Composition of Froth of Cream, XLV. „ Clotted Cream, . XL VI. Ratio of Fat to Total Solids in Cream, . Relation between Fat and Viscosity in Cream, Results obtained with Various Separators, Average Results of Water Analysis, Composition of Mare's Milk Koumiss, . ,, Cow's Milk Koumiss, . ,, American Koumiss, ,, Kephir, . ,, ,, Grains, . ,, ,, Powder, ,, Mazoum, Composition of Butter, . XLVII XLVIII XLIX L LI LII ,, Butters, . Variations of Water in Butter, . ,, ,, ,, (Faber), ,, ,, Butters on Keeping, Temperature of Churning, Characteristics of Butter, . Results with Reichert Process, . ,, Reichert-Meissl Process, . ,, Reichert- Wollny Process, Distillation of Volatile Acids of Butter (Two Variations of Critical Temperature with Fatty Acids, Maumene Figures with Acids of Different Strengths, Heat Equivalent of Apparatus, . Expansion of Butter and Margarine, Density of Butter Fat, . ,, Oils and Fats, Muter's Relation of Refractive Index to Reichert Figures, .... Values of Butyro-refractometer Degrees, Tables) Insoluble 241 PACE 187 207 209 210 211 215 216 217 21. 8 219 219 219 220 222 224 236 241 -243 243 243 244 244 244 245 246 246 247 247 248 251 256 259 260 262 265 273 27- 279 282 284 2s 4 2S7 2.88 LIST OF TABLES. Variations of Butyro-refractometer Degrees with Temperature, ..... 289 Variations of Insoluble Fatty Acids on Keeping Butter, 293 Properties of Old Butter Fat (A lien and Moor), . 294 (Clayton), . . 294 LIII. The Reichert-Wollny Figures of Butters (Besana), . 295 „ „ (Vieth), . 295 Composition of Butter Milk from Sweet Cream, . 296 ,, ,, Ripened Cream, . 296 ,, Ash of Buttermilk, . . 296 ,, Curd and Whey, . . . 298 Whey, ..... 299 ,, Curd and Whey separated by Acidifi- cation, .... 299 Sour Milk Whey, . . .300 Action of Rennet at Different Temperatures, . . 300 LIV. Cream Cheeses, ...... 303 LV. Soft Cheeses, ...... 303 LVI. Hard Cheeses, ...... 304 LV1I. Skim Milk Cheeses, ..... 305 Roquefort Cheese, ..... 305 LVIII. Detailed Composition of Cheeses, . . 306,307 ,, ,, Roquefort Cheese, . . 308 LIX. Analyses of Cheese (Stutzer), .... 314 ,, ,, (Dwinux), . . - . 316 ,, ,, (Devarda), .... 317 Limits of Commercial Milk-Sugar, . . . 319 LX. Analyses of Sugars, ..... 320 Composition of Milk Cocoa, .... 320 LXI. Size of Fat Globules in Mammalian Milk, . . 321 LXII. Properties of Mammalian Fats, .... 322 LXIII. Composition of Mammalian Milk, . . . 323 LXIV. Mean Composition of Human Milk, . ■ . 324 LXV. Variations in Composition of Human Milk during Lactation, ...... 324 Probable Mean Composition of Human Milk. . . 326 Variation of Constituents of Human Milk, . . 325 Composition Before and After Suckling, . . 325 ,, ,, ,, Maxima and Minima), . 826 Composition of Milk agreeing Well and Badly, . 826 Ash of Human Milk. . . . 327 the Milk of the Buffalo, . . 328 ., ,, Qamoose, . . 328 ,, the Fit ol '•it Be Milk, . . :;•_".» the Sugar of Qamoose Milk, . . 880 LIST OF TABLES. XIX TABLE PAGE LXVI. Composition of Ewe's Milk, . . . .331 LXVII. „ „ .... 332 Correction of Specific Gravity of Ewe's Milk for Temperature, ..... 332 LXVIII. Composition of Goat's Milk, .... 332 LXIX. „ Mare's Milk, .... 333 ,, Ass's Milk, .... 334 ,, Constituents of Milk, . . . 334 Heats of Combustion, ..... 335 Composition of Peptonised Milk, . . . 337 „ Diabetic Milk, .... 337 Expansion of Cream, ..... 33S ,, Separated Milk, . . . .338 Specific Volumes of Separated Milk, . . . 339 Expansion of Fat of Cream, .... 339 Butter Fat, . . . .341 LXX. Values of Weights, ..... 343 LXXI. Calibration of Burette, ..... 345 LXXII. Boiling Point of Water under Different Pressures, . 347 LXXIII. For the Correction of Specific Gravity of Milk, Op. p. 348 LXXIV. For the Calculation of Total Solids from Fat and Specific Gravity, .... Op. p. 348 LXXV. For the Calculation of Total Solids from Fat and Specific Gravity, .... Op. p. 348 LXX VI. For the Calculation of Total Solids from Fat and Specific Gravity, ..... 34S LXXVII. For the Calculation of Total Solids from Fat and Specific Gravity, ..... 350 LXXVIII. For the Calculation of Total Solids of Skim Milk, . 352 LXXIX Soxhlet's Areometric Method, . . . Op. p. 352 LXXX. For the Conversion of Thermometric Scales, . . 352 LXXXI. Weights and Measures, ..... 354 LXXXII. For the Conversion of Barn Gallons into Imperial Gallons, ...... 355 LXXXIII. Weights of Dairy Products, . . . .356 LXXXIV. For the Calculation of the Weight of Butter in Pounds obtained on Churning Cream, . . Op. p. 356 DAIRY CHEMISTRY. CHAPTER I. INTRODUCTORY THE CONSTITUENTS OF MILK. Contents. — General Composition — Fat — Sugar — Albuminoids — Salts — Colour — Reaction — Milk-Sugar — Glucose — Products derived from Milk-Sugar — The Albuminoids of Milk — Products of Hydrolysis — General Action of Hydrolysis — Mineral Constituents — Other Con- stituents of Milk— The Gases of Milk— The Fat of Milk— Products of Hydrolysis — Fatty Acids — Other Compounds — Rancidity. General Composition. — Milk is the normal secretion of the mammary glands of a mammal ; the milk of all mammals has a similar composition, consisting of fat, sugar, albuminoids, mineral constituents, and small quantities of other compounds. The milk of the cow has been studied in greater detail than that of any other animal on account of the extended use of this animal's milk and the products derived from it as human food ; the greater portion of this work will, therefore, be devoted to the consideration of the chemical properties of cow's milk, and the expressions "milk," "butter," Arc., must be taken as applying to the products derived from the cow, unless described to the contrary. Much, however, that is stated with regard to the cow may be taken as applying equally to the milk of other animals ; but our knowledge of the chemical composition of the milk of any animal, except the cow, is very incomplete. Studies, more or less incomplete, have been made of the milk yielded by woman, the goat, the ass, the mare, the gamoose, and the sheep, and analyses, few in number, have been made of the milk of other mammals, both terrestrial and marine. It is probable that there exist wider differences than are yet recognised between the milk yielded by different animals. Fat. — The fat in milk is of peculiar and complex composition; it differs from all other fats in that it contains compound gly- cerides partly built up of fatty acids of low molecular weight. It exists in milk in the form of small globules. Many have thought that a true membrane surrounds each globule, and Bechamp considers this view as proved by the behaviour of milk when treated with ether. He finds that milk is capable of 1 1 INTRODUCTORY — THE CONSTITUENTS OF MILK. dissolving a very large quantity of ether, much more than would he dissolved in the aqueous portion of the milk, and he explains this by the theory that the ether is dissolved by the fat contained in the membranes. His theory assumes that the ether has passed into the membrane by the process known as "endosmose," and that the endosmose is stopped only when the pressure exerted by the distended membrane is equal to the osmotic pressure ; the presence of fat to small amount in the excess of ether which separates is explained as partly due to a process of exosmose of the fat within the membrane concurrently with the endosmose, and partly to the bursting of a number of the globules. The opponents of his theory urge that the amount of fat in the excess of ether which separates, if this be great, is too large to be explained by assuming exosmose, or the bursting of the globules, which should not take place to a greater degree with a large excess of ether than with a small. Storch has i-ecently put forward the view that no real mem- brane exists round the fat globules, but that a gelatinous "mucoid" membrane (slim-membran, in Danish) surrounds them; this consists, according to him, of a combination of G parts of a " mucoid " proteid with 94 parts of water (membran-slim). He bases his view — (1) On the fact of the existence of this mucoid substance in cream and butter, and therefore presumably in milk ; he proves its existence, and, in fact, isolates it, by washing cream with water and separating the layer of globules till milk-sugar, casein, an aldehydrol. Modifications. — Milk-sugar exists in several modifications which are distinguished from each other chiefly by their beha- viour towards polarised light. MODIFICATIONS OF MILK-SUOAR. \) The best known modification is the hydrated a-milk-sugar, usually known as crystallised milk-sugar ; this is the form in which it crystallises from water. The a-moditication exhibits multi-rotation — i.e., when dissolved in water it has a much higher specific rotation than that which it attains after a lapse of time. The author has found that when dissolved in water it causes a lowering of the temperature of the solution by about | a degree C. By shaking up the finely powdered sugar with water, a solution is obtained containing about 7-5 grammes per 100 c.c. at 15° C, the quantity dissolved inereasuig roughly about T gramme per 100 c.c. for each degree above 15° C. No thermal change was detected in this solution by a thermometer reading to "01° 0., but the temperature rose steadily till it attained that of the surrounding atmosphere, which was kept constant ; the rate of rise was identical with that of a previously prepared solution of milk-sugar of the same strength, which had been cooled to the same temperature. Brown and Pickering have, however, shown that a slight thermal change takes place with change of rotatory power ( + 0-19 calorie per gramme). No change in density or molecular weight indicated by freezing point determination was observed on keeping solutions of milk- sugar, though the specific rotation varied very widely. It is usually stated that a freshly prepared solution of o-milk sugar contains 14'55 per cent, at 10° 0. ; while by long standing in contact with milk-sugar, or by boiling, a saturated solution containing 21-64 per cent, can be obtained. The author is unable to confirm the figure for the freshly prepared solution. 15 '5° The density of well formed crvstals is 1*545 at z, bad 15-o crystals — i.e., those which are strained, have, however, a lower density. The hydrated a-modification is practically insoluble in alcohol, ether (in ether saturated with water it dissolves to the extent of "00075 gramme per 100 c.c), chloroform, benzene, and other organic solvents. It is slightly, but distinctly, soluble in amyl alcohol on boiling, but is probably dehydrated. It is unaffected by heating to 100" C, but the water of hydra- tion is given off at 130° C. ; at 170° a change takes place with formation of lacto-caramel, and it melts at 2135° C. When dissolved in water the specific rotatory power remains constant for a short period, 3 minutes at 20° C., 6 minutes at 15° C, and 15 minutes at 10° 0. ; the rotation then gradually falls. The following series of observations (Table I.) will show the nature of the chancre in rotation : — 10 INTRODUCTORY — THK CONSTITUENTS OF MILK TABLE I. — Change of Rotation of cc-Milk-Sugar in Solution. Time T. Observed Rotation, RT calculated Rotation. Difference. 2-2 iniii. 12-73° \ + 02 2*7 „ 12*78 - -03 3*2 „ 12-68° 1 12-75° + -07 42 „ 12-83° - -08 4-7 „ 12-7.T + -02 6-0 „ 12-73° J + -02 110 „ 12-48° 12-49° + -oi 1625 ,, 12-23° 12-23° 23 0 ,, 1 1 -83° 11-91° +"•08 32 5 „ 11-53° 11-51° - 02 430 ,, 1 1 -23 11-11° - 12 54 5 „ 10-73 10-72 - -01 360-0 „ sn:; 8-03° 24 hrs. 1-95J = Re- 7-95° The solution used was examined in a 198-4 mm. tube using the sodium light; two determinations gave 7-090 and 707- per cent, of anhydrous milk-sugar, and, as the solution had a density of 1*0265 at 17° (the temperature of observation), it contained 7-651 grammes of hydrated milk-sugar per 100 cc. It is seen that the rotation is approximately constant for the first 6 minutes, and averages 12-75°, which corresponds to [a]ij = 83-99°. After 24 hours the rotation is constant at 7*95°, which corresponds to [a]D = 52-37°. The figures given in the "calculated" column are deduced by the formula — log (RT - R»>) = -68124 - -00491 (T - 6). The fact that the fall in rotation is expressed by a logarithmic curve shows that the rate of change is proportional to the amount of unchanged substance in solution ; this is Harcourt's law of simple chemical change. The ratio between the initial rotation and the final rotation, 83*99 which may be called the bi-rotation ratio, is ■ = 1-604. 02*37 The mean of several determinations has led to the value for [a]r, of tin- hydrated a-modification 84*0°, and the bi-rotation ratio 1-6 ; these are the figures given by S.hinoeger, who. how- ever, assigned to them an approximate value only. The small amount of t henna! change during change "t" rotal ion and absence '>t' change in density and freezing point show, with a considerable degree of probability, thai the change manifested by alteration in rotation is intramolecular. It is probably MODIFICATIONS OF MILK-SUGAR. 11 caused by the migration of the water of hydration from one carbon atom to another. The anhydrous modification of the a-modification is obtained by heating the hydrated modification to 130° C. It is hygro- scopic and dissolves in water with evolution of heat; the solu- bility is much greater than that of the hydrated modification. The optical properties are stated by Schmoeger to be the same as those of the hydrated modification. The /3-modifi.cation is the one to which all others are con- verted on dissolving in water. Schmoeger gives the specific rotatory power [a]D as 52-53° at 20° C, diminishing -075° for each degi-ee C. above this and increasing for lower temperatures. The author can absolutely confirm these numbers. It has never been prepared pure in the solid state, though considerable evidence of its existence, both in the hydrated and anhydrous modifications, has been obtained by the author. By the addition of alcohol or, better, ether to a very highly supersaturated hot solution of milk-sugar, it sets to a solid mass, which may be dried in vacuo, and does not then lose weight at 100° C, but which contains, however, a certain amount — 2 to 4 per cent. — of water of hydration which is lost at 130° C. There is no appreciable change in rotation on dissolving this product in water and taking readings at intervals ; as some of the read- ings obtained have been above, and some below, that ultimately obtained, it is probable that the very slight differences noticed were due to errors of observation. By precipitating less strong solutions of milk sugar by alcohol, products can be obtained which contain very nearly, if not quite, the same percentage of water as the hydi-ated a-modification, but which have a much smaller, but not constant, bi-rotation ratio. These also give a constant rotation for a few minutes on dissolving in water and behave as mixtures of the a and f3 hydrated modifications. They have a less density than the a-modification, but it is not certain whether this may not be due to the very imperfect crystallisation which takes place, the products appearing nearly amorphous. By evaporating aqueous solutions of milk-sugar on the water bath, an anhydrous sugar can be obtained, which has a very slight bi-rotation ratio, which is not constant. As this varies from 1-09 to l-02, such sugar probably consists of the anhydrous /S-modification, mixed with a small amount of the a-modification. A specimen having a bi-rotation ratio of l-03 had a density of 15 "5° 1"585 at , g ,0 and dissolved in water with a slight evolution of 15-5 ° heat. There is some evidence that the hydrated /S-modification dis- solves in water with a greater absorption of heat than the a-modification, as the mixtures obtained by precipitation with 12 INTRODUCTORY — THE CONSTITUENTS OF MILK. alcohol cause a greater lowering of temperature than the a-modification. The solubility appears to be greater. There exists also a /-modification, which is obtained in the anhydrous form by the rapid evaporation of aqueous solutions in metallic vessels. Schmoeger states that it has a bi-rotation ratio of-r — , which Tanret confirms. I'D By the addition of ammonia, the change which the a- and y- modifications slowly undergo on solution in water becomes almost instantaneous. By raising the temperature, the rate of change is increased and is practically instantaneous on boiling. Constitution. — The author proposes the following formula? to explain the existence of the three modifications : — Taking the constitution given above — OCH2 CH2OH . 4(CHOH)CH OCH3(CHOH)COH, °f 0 we see that the end groups are represented — C — C^ as an aldehyde. H Now, an aldehydrol is a combination of this with water. It OH does not appear probable that the group — C OH is present in an H aldehydrol, but the molecule 0Ho appeal's to combine as a radicle of small valency, which may be conveniently represented thus (oil?) 7 .o © The aldehydrol is represented thus — C — C v-rf^ k " OH OH Taking the form — C— C— OH as an unstable modification of I I H H OH, 0 / \ this, it is Been that this might form the group — C— C— OH which is a hydrated anhydride. jj jj OH OH The group — C=C — H could equally well be formed. ASYMMETRIC CARBON. 13 Of these three formula? the aldehydrol and aldehyde represent the /3 hydrated and anhydrous modifications respectively. The anhydride formation probably can be assigned to the a-modifi- cations, as the anhydrous a-modification has the properties of an anhydride — e.g., it is hygroscopic. The ethylenic configuration would be left for the y-modification ; the hydrated form of this modification would probably be formed with great difficulty, if it exists at all ; the evidence of the existence of a hydrated 7-modi- fication is very weak. In the ethylenic formula the carbon atom next the end would be either non-asymmetric or opposite to that in the aldehyde ; when this passes to the aldehyde formation, it becomes asym- metric, containing the groups H and OH opposed to each other; The anhydride formula contains this carbon atom as an asym- metric one with the groups H and O (oHoj opposed. Calling the combined effect on rotatory power of the other asymmetric carbon atoms x, and the effect of the opposed groups H and OH a, the effect of the groups H and O f oh2J may be taken as greater than a, say a + b. We have, then, the total effect of the asymmetric carbon atoms as x + a + b in the a-modification, x + a in the /3-modification, and x or (x — c) in the y-modification. It is evident that the rotatory power of the /3-modification is intermediate between the other two. Asymmetric Carbon. — An asymmetric carbon atom is one which is combined with four different radicles thus — a— C— (3 or d—C—y. 7 P It is probable that the atoms do not lie in the same plane, but are symmetrically grouped round the carbon atom as at the four corners of a regular tetrahedron thus — 14 INTRODUCTORY — THE CONSTITUENTS OF MILK. If we take up a regular tetrahedron and hold it by the corners a and 3, we see that there are two possible arrangements ; in one, y is towards us ; in the other, 6. It is found that compounds containing an asymmetric carbon atom exist in two modifications closely resembling each other, but differing in their effect on polarised light ; both affect the ray to the same extent, but in opposite directions. If we take a regular tetrahedron, and weight the corners, and spin it round the centre, we find that as long as two of the corners are weighted equally we can always find such a position that those two corners follow the same path when the system is in equilibrium ; if all the four corners are weighted unequally, it is impossible to find a position in which two corners follow the same path. Looking at right angles to the axis of rotation we may repre- sent the paths as straight lines ; thus, for a non-asymmetric system, the sequence of appearance of the corners at any point will be a, y, ft, 6 or a, 6, 3, y, and the apparent path of the sequence will be denoted by the dotted lines, which are the same whichever sequence is adopted or whether y and 6 are transposed. With an asymmetric system we have . The sequence a, y} ft, b moves apparently in one direction. By transposing a and ft, the paths of the corners are ' .1 a. ) 6 The sequence a. y, ft, 6 moves apparently in the opposite direction to that previous to transposition. The nature of polarised light and the effect of molecules thereon is not fully elucidated, but the above illustration is given to demonstrate how a right- and Left-handed effect may be produced from what is probably the besl representation of an asymmetric carbon atom. If we have more than one asymmetric carbon atom in a molecule, each will produce its combined effect. A molecule CHEMICAL PROPERTIES OF MILK-SUGAR. 15 containing two asymmetric oarbon atoms may exist in three modifications ; one, in which both atoms show a right-handed effect ; a second, in which both show a left-handed effect ; a third, in which one shows a right-handed and one a left-handed effect. It is convenient to suppose that the effect is produced on the centre of the molecule, thus — 7— C— /3 > the compound .... | .... would have, supposing y — C — /S > I s f$ to be the greater radicle, an effect produced in the directions of the arrows, and the effects of the two asymmetric atoms on the centre would be opposite. We may represent the three modifications thus — I as the right-handed, ^ $ q y while the left-handed I would be y — C— /3 — > % % and the one in which the effects of the two atoms tended to neutralise each other would be that given above. The solubility of milk-sugar in water is small compared with the solubilities of other carbohydrates; owing to the tendency of milk-sugar to form supersaturated solutions it is difficult to determine its exact solubility, but the mother liquors from which crystals have deposited usually contain about 21 per cent. The a-modification crystallises in wedge-shaped forms which often have the face at the end of the wedge greatly prolonged. The 7 -modification crystallises in needles. The taste of the a-modification is not sweet, and from its comparative insolubility it appears to be gritty. In solution the /3-modification has a sweet taste of about a quarter the sweetness of cane-sugar. As already stated, on heating to 170° C. it turns brown, and lacto-caramel is formed ; a similar change takes place by heating an aqueous solution to 100° C. for some houi's; the presence of small amounts of alkali greatly increase the browning of the solution. The rotatory power is greatly diminished. Chemical Properties. — Milk-sugar, in common with other aldoses and ketoses, reduces alkaline solutions of copper, silver, and mercury, forming cuprous oxide, and metallic silver and mercury respectively. On this fact the well-known Fehling's test for sugar is based. The amount of reduction is constant for fixed amounts of milk-sugar under the same conditions, and is nearly proportional to the amount of milk-sugar. Each sugar 16 INTRODUCTORY THE CONSTITUENTS OF MILK. shows a definite amount of reduction in the same way, and a valuable method for distinguishing them is thus available. The difference between reduction by various sugars is not due to any difference in the reaction with the metallic salt, but depends on their relative stability towards alkalies. On warming with dilute nitric acid (sp. gr. T2) an energetic action takes place, mucic acid, together with saccharic, oxalic, and other acids being formed ; the mucic acid, which can be separated by its relative insolubility, amounts to about 35 per cent, of the weight of the milk-sugar. This is due to the galactose portion of the milk-sugar. Strong nitric acid (sp. gr. 1*5) mixed with sulphuric acid, to absorb the water formed in the reaction, gives rise to the formation of tri- and penta- nitrates ; both these compounds have explosive properties. The penta-nitrate is a constituent of certain high explosives. On heating with an excess of precipitated copper oxide gummy acids are formed, such as galactinic and pecto-galactinic acids, compounds which are also formed from galactose. By oxidation with bromine lacto-bionic acid is formed, in which the COH group is converted into COOH. Potassium permanganate in acid solution oxidises it to carbonic acid, but the reaction is not complete, not more than 80 per cent, of the theoretical quantity of carbon dioxide being obtained. By heating with phenylhydrazine acetate two compounds are formed \ one of these — phenyl-lactosazone — is sparingly soluble in cohl water, but readily in hot, from which it separates on cooling in yellow needles melting at 197° C. with decomposition. It is also soluble in alcohol and ether; the latter solvent extracts it from aqueous solution. The second compound is an anhydride of phenyl-lactosazone, and is almost insoluble in hot water ; but can be crystallised from hot dilute alcohol in yellow needles which melt at 218°. Milk-sugar is distinguished from other sugars by its osazone forming an anhydride. By treating with strong cold hydrochloric acid the phenyl- hydrazine groups are removed, and lactosone is formed. The relation between these compounds is shown by the following formula; : — Sugar. Osazone. Osone. H i = 0 H— C-OH C ii o c=n— x; 1 II II HC = N-N7 V,ll. The osone is readily r ■> converted into the OMZO&6 by treat ni'-iit with phenylhydrazine acetate. GLUCOSE AND GALACTOSE. 17 By reduction with sodium amalgam a mixture of mannitol and dulcitol, hexahydric alcohols of the formula C,.H14On, with lactic acid and methyl, iso-propyl and hexyl alcohols is formed. On heating with acetic anhydride and sodium acetate an oct- acetyl-lactose is formed. This crystallises in stout prisms from a mixture of alcohol and chloroform, and has an ill-defined melting point about 90° C. Its solution in chloroform is optically inactive, or very slightly hevo-rotatory. Milk-sugar dissolves lime, baryta, lead, copper, and mercuric oxides, and probably forms compounds with them. No com- pound with sodium chloride is known. Ammoniacal lead acetate precipitates milk-sugar from an aqueous solution. It is not fermentable by ordinary yeast, and is unacted on by invertase, diastase, rennet, pepsin, and trypsin. There exists, however, an enzyme, which has been called lactase, which is found in fresh kephir grains, which hydrolyses it to glucose and galactose. The enzvme does not appear to be present in dried kephir grains, but is probably found in other sub- stances. The action of acids generally is to convert it into glucose and galactose. Some organic acids, such as citric, are, however, without action on milk-sugar. Preparation. — Milk-sugar is prepared on a large scale by evaporating whey in vacuo, after neutralisation of any acid with lime and clarification with alum or other means, and allowing it to crystallise. The product is purified by re-solution, treatment with animal charcoal and re-crystallisation. In countries where alcohol used in manufacturing purposes is free from duty the sugar is precipitated from solution by this means instead of being crystallised from water. On a small scale, it is best to precipitate the proteids from milk or whey by as small a quantity of acid mercuric nitrate (p. 78) as possible. The clear filtrate is neutralised with dilute caustic soda solution till a very faint tinge is given with phenolphthalein ; it is filtered from the prec:pitate thus produced, which consists of mercury salts. Sulphuretted hydrogen is passed through the clear solution to remove the mercuric oxide dissolved by the sugar, and, after filtra- tion from mercuric sulphide, the sulphuretted hydrogen is expelled by boiling. On evaporating the solution, milk-sugar crystallises out ; crystallisation may be hastened by vigorously stirring the concentrated solution while it is being rapidly cooled. GlllCOSe and Galactose. — These are two isomeric sugars of the monose type. Both are aldoses or aldehydrols, and have been obtained in three modifications. 18 INTRODUCTORY THE CONSTITUENTS OF MILK. Their constitution is given by E. Fischer as Glucose, Galactose. COH COH I I H— C— OH H— C— OH I I OH— C— H OH— C— H I I H— C— OH OH— C— H I I H— C— OH H— C— OH I I CH2 OH CH2 OH Wohl and List have confirmed the constitution of galactose. They are thus isomeric sugars differing only in the third asymmetric carbon atom from the aldehyde group. It is not known whether these sugars on dissolving them in water give a constant rotation for a short time as in the case of milk-sugar. Their specific rotatory powers [a]D are Glucose. Galactose. /3-modification, . 52-7° 80-3° a-modification, . 105° 120° Bi-rotation ratio, 2 1-5 Both sugars give, on treatment with phenylhydrazine acetate, nearly insoluble osazones. These are converted into osones by treatment with strong cold hydrochloric acid. Products derived from Milk-Sugar. —The most important of these products is formed by the action of certain micro- organisms on milk-sugar during the so-called lactic fermentation. By their action the milk-sugar is split up into lactic or oxy- propionic acid almost quantitatively, a certain portion, however, being converted into other products, of which carbon dioxide is the most important. The micro-organisms which produce lactic acid are acted on inimically by acids, so that not much more than 1 per cent, of lactic acid is formed, unless the solution is kept neutralised by chalk or other means. H Its formula as usually given is CH3— C— COOH, so that it con- I OH tains an asymmetric carbon atom ; it is not, however, optically active, though the isomeric sarcolactic acid possesses this pro- perty. It appears to be a racemoid compound intermediate between sarcolactic acid and the dextrolactic acid discovered by Purdie. It has a remarkable tendency to form compounds which contain less water. i tn evaporating aqueous solutions of lactic acid, dehydrolactio acid is formed, 0aH10O6, which, by further evaporation (espe- cially at a high temperature), gives lactide, C(;HS(),. PRODUCTS DERIVED FROM MILK-SUGAR. 19 Lactic acid acts as a monobasic acid ; while dehydrolactic acid behaves as a monobasic acid, monohydric alcohol and an ethereal salt at the same time ; lactide is a neutral substance. Sarcolactic acid gives the same lactide, which, on boiling with water, is converted into the inactive modification. To explain the fact that lactic acid is inactive and easily forms anhydrides, the author proposes to assign the following formula? to H Lactic acid, . . . CH3— C— 0— COOH I H H I CH3— C— 0— C OH Dehydrolactic acid, q CH8— C COOH H H H CH3— C— O— C = 0 Lactide, .... * CH3— C C = 0 or I \ / L J \/ CH3— C— 0— C = 0 0 H H I Sarcolactic acid, . CH3 — C — COOH I OH The so-called syrupy lactic acid is a mixture of lactic and dehydrolactic acids with probably a little lactide. Wislicenus has shown that by direct titration with alkali lactic, and dehydro- lactic acids are estimated, while by further boiling with excess of alkali one molecule of lactic acid is produced for each molecule of dehydrolactic acid, and two for each molecule of lactide. Dehydrolactic acid has not been obtained pure, but appears to be amorphous and nearly insoluble in water. Lactide can be prepared by subliming syrupy lactic acid at 150° in a current of dry air. It is insoluble in water, but can be crystallised from alcohol in colourless rhombic plates melting at 124-5° 0. It boils at 255° C. Syrupy lactic acid is said to have a specific gravity of 1 *2485. Lactic acid is not appreciably volatile in dilute solution, but * The second formula is probably the more correct, as Henry has found its vapour density to agree with the formula C6H804. The first formula is introduced to show its derivation from sarcolactic acid. 20 INTRODUCTORY THE CONSTITUENTS OF MILK. passes over with water to a slight extent as the solution becomes concentrated. Lactic acid is soluble in and miscible in all proportions with water, alcohol, ether, and glycerol. It is insoluble in petroleum ether. Fats also dissolve it. It is probable that the lactic acid present in milk is, partially at all events, dissolved in the fat. As milk almost immediately after milking contains organisms which produce lactic acid, it may be considered as a normal constituent of milk ; indeed Bechamn has held that it is produced from milk by organisms (micro-zymes) derived from the udder itself. That this view is erroneous is shown by the fact that Lister, Pohl, Warington, and others have succeeded in preserving milk, drawn direct into sterilised vessels, for a considerable length of time without the development of acidity. Lactic acid probably exists in milk, not in the free state, but as a salt, at all events until the acidity is sufficient to curdle the milk on boiling. The Albuminoids Of Milk — Properties. — Our present knowledge of the albuminoids of milk is far from complete, though much work has been done on the subject. This is due to the fact that it is extremely difficult to obtain these com- pounds in anything like a state of purity. The method of crystallisation, which is so largely depended on in the case of other bodies, being unavailable, and as albuminoids are altered in their essential properties by very many reagents, the choice of methods of purification is limited. The difficulty is still further increased by the peculiar behaviour of casein in retaining calcium salts, if once it has been brought into contact with them, as is the case in milk. The albuminoids of milk have been pre- pared in as pure a state as possible by the general method of precipitating them by some reagent, dissolving them, repreeipi- tating as many times as may be thought necessary, and, tinally, by eliminating such impurities as may have been introduced during the process. As there is no means of knowing when all the impurities have been eliminated, it is possible that we are yet unacquainted with the albuminoids of milk in a state of purity. This should not be forgotten during the study of the milk albuminoids. The milk albuminoids are bodies of complex composition con- taining carbon, oxygen, nitrogen, hydrogen, phosphorus, and sulphur. The way in which these elements are combined is not known, but some light is thrown on the constitution of albumi- noids by the production of amido-acids (leucine or amido-caproic acid, for instance) by the action of acids or other substances (•:/.. certain enzymes) as a far ad vanced decomposition product ; the xantho-protein reaction — the production of a yellow colour by evaporating with nitric acid and treatment with ammonia — is characteristic of leucine, and the fact of albuminoids giving HYDROLYSIS OF ALBUMINOIDS. 21 this reaction is further evidence of their being derivatives of this body. The action of alkalies on albuminoids is to produce, amongst other substances, oxalic acid and ammonia. The mole- cule of albuminoids is very complex, as is evident by their being indiffusible bodies. By the action of acids and certain enzymes, e.y., peptase (pepsin), they are resolved into simpler bodies which become more and more diffusible as the decomposition advances. During the simplification just mentioned evidence is afforded of the splitting off of portions by the fact that some of the decom- position products are free from sulphur. Hydrolysis of Albuminoids. — Albuminoids are easily hydro- lysed by the action of heat, acids, and various enzymes. The products, which are called " albumoses " and " peptones," are numerous and cannot be separated with certainty from each other. They are classed as follows : — Proto-albumoses : precipitated from solution by saturation with sodium chloride. Deutero-albumoses (I.) : precipitated from the sodium chloride saturated solution by acetic acid. Deutero-albumoses (II.) : precipitated by saturation with ammonium sulphate. Peptones; unprecipitated by saturation with ammonium sul- phate or sodium chloride with or without the addition of acetic acid. Dys-peptones (Dys-albumoses) are bodies produced by the action of enzymes ; they are insoluble. The, products of hydrolysis obtained by different means are not identical ; thus the albumoses produced by pepsin and trypsin have not the same composition. To distinguish between the products of hydrolysis the author proposes a nomenclature which shall indicate the means by which the product has been obtained. If an enzyme is the hydrolytic agent, it is proposed to use a prefix indicating the enzyme ; for pepsin (peptase), trypsin (tryptase), and rennet (chymase) the author uses the prefixes, "pepto-,'' " trypto-," and "chymo-" respectively. For acid hydrolysis, the prefix "hydrolo-" seems most convenient. As an example, the; products obtained from casein would be called as follows : — Hydrolysing Products of Hydrolysis. Agent. Acids, . . Proto-hydrolo-caseose, Deutero-hydrolo-caseose, and Hydrolo-caseone. Pepsin, . . Proto-pepto-caseose, Deutero-pepto-caseose. Pepto-caseone and Dys-pepto-caseose. Rennet,. . Proto-chymo-caseose, Deutero-chymo-caseose. Chymo-caseone (?) and Dys-chymo-caseose. The prefix "hetero-" is often used instead of "hydrolo," 22 INTRODUCTORY — THE CONSTITUENTS OF MILK. "auti-" for " pepto," and "amphi-" for " trypto-." The author, however, believes that the above nomenclature is more con- venient and expressive. It is extremely probable that there exists more than one proto-albumose and, similarly, several deutero-albumoses. The hydrolysis of albuminoids can be carried beyond the stage of peptones ; tyrosine, leucine, and other ainido-compounds are formed. During hydrolysis, the hydrolysts are not destroyed, or are destroyed with extreme slowness, and appear to be able to act on a relatively enormous quantity of the hydrolyte. The time taken to produce a given change on a given quantity of hydro- lyte is inversely proportional to the quantity of hydrolyst. Each hydrolyst has a certain optimum temperature at which it acts most rapidly, the action being diminished at both higher and lower temperatures. Certain substances — e.g., acids — affect the rate of hydrolysis ; their influence, however, follows laws which are not fully known. This may be perhaps due to the hydro- lysing effects of the acid combined with those of other hydrolysts taking a course influenced by both of them. Views of Different Authorities. — The number of albumi- noids present in milk (of the cow) has been variously stated at from one to eight by different observers. The most recent work has tended to reduce the number to not more than four, the larger number described having been obtained by faulty methods of separating these bodies or by the action of some reagent used on the albuminoid. Many of the products described are now known to be mixtures of one or more of the albuminoids with various impurities, or decomposition products obtained during the separation of the albuminoids one from another. The theories of leading observers are briefly given as follows: — Duclaux maintains that there is only one albuminoid in milk, which exists in two forms — the coagulable and noncoagulable ; he gives to this albuminoid the name of casein. The first modi- fication is not in a state of solution, and can be separated by filtration through a porous jar ; it is combined with the phos- phates of the alkaline earths, and this causes it to differ in its properties from the other modification, which is in a state of true solution and passes through the porous jar. Were this view correct, the coagulable modification should gradually lose its distinctive properties as it is purified from phosphates; and, on the other hand, the non-coagulable modification should be capable of being converted into the other by associating it with phosphates ; neither alternative has as yet been found possible, and, as two albuminoids having distinct properties can be separ ated from milk, Duclaox's view is hardly tenable. Sammarsten describes two albuminoids] our. casein, corre- sponding to Duclaux's coagulable casein : the other, lact- VIEWS OF DIFFERENT AUTHORITIES. 23 albumin, corresponding to Duclaux's non-coagulable casein. He shows that lact-albumin has the properties of a true albumin, approaching very closely to serum-albumin, but differing from it in certain physical constants, which entitles it to rank as a distinct body. Sebelein has shown that there exist in milk traces of a globulin, in addition to the casein and albumin of Hammarsten. Halliburton describes the albuminoids of milk as caseinogen and lacto-albumin ; there is no essential difference between the casein of Hammarsten and the caseinogen of Halliburton, except a difference of name. He reserves the name casein for the curd produced by the action of rennet.* Hewlett, a pupil of Halliburton, has confirmed Sebelein's statement as to the existence of globulin in milk, though he has shown that Sebelein's globulin was probably contaminated with small amounts of casein. Musso and Menozzi have claimed the presence in milk of a body midway between casein and albumin ; this is probably the globulin of Sebelein in an impure state, as their description is in fair accordance with a statement of the properties of the latter. Radenhausen and Danilewsky have described many albu- minoids in milk. Hammarsten and — later — Chittenden and Painter have shown that their view that casein is a mixture of two compounds is untenable, while the various lacto-protein * The author dissents strongly from Halliburton's nomenclature " caseinogen" and " casein " for the following reasons : — 1. Casein is derived from the Latin caseum, and the termination oyen from the Greek root yev. 2. y £i> means "to beget." In the words hydrogen, oxygen, chromogen, &c, this meaning is preserved, and they mean that hydrogen, oxygen, and chromogen are essential constituents which, with others, make water, acids, and colour respectively. In fibrinogen and caseinogen this meaning is not preserved ; the termination means that these bodies are substances which are split up into fibrin and casein with other substances. 3. The action of rennet does not appear to differ materially from that of other proteolytic enzymes. Thus, the action of pepsin on casein is strictly analogous ; pepsin, as it only acts in acid solution, cannot act on a solution of casein, but splits it up into soluble caseoses and the insoluble dys- casein-peptone (dys-pepto-caseose). It appears from recent researches that the insolubility of dys-pepto-caseose is due to its combination with calcium salts (chiefly phosphate). Rennet, which acts in neutral solution, splits up casein into soluble chymo-caseoses and an insoluble dys-chymo-caseose (curd) ; this likewise owes its insolubility to a combination with calcium salts (preferably phosphate). If calcium salts be completely removed, no insoluble dys-caseose is produced in either case. 4. The name "casein" has probably been given by Halliburton to the dys-caseose on account of its being used largely in cheese. It is not, how- ever, essential for cheese. The casein precipitated by acids can also be made into good cheese. 5. " Casein " has priority over " caseinogen," for the albuminoid of milk, and, except by Halliburton and his school, is universally accepted. 2-4 INTRODUCTORY — THE CONSTITUENTS OF MILK. bodies have been shown to be the result of their method of separating casein and albumin. Wynter Blyth has described a body called galactin in milk ; this is essentially lacto-protein, perhaps contaminated with some organic salts, and has no real existence in milk, being portions of the casein and albumin which had escaped separation, together with products of their decomposition during the process used for their removal. Bechamp supposes that the albuminoids of milk number three — casein, albumin, and a body having the properties of an enzyme, which he calls galacto zymase ; this enzyme he finds liquefies starch paste, evidently not its normal function in milk ; his results have not been confirmed. He also supposes the casein and albumin to exist in milk in combination with bases (soda, lime, or potash). Biel has described syntonin as a normal constituent of milk, but the existence of this must be considered doubtful at present. Palm has stated that albumoses are found in milk ; this is probably not wholly correct ; it is possible that traces of albu- moses are formed during the decomposition to which milk is prone, but no other observer has identified more than traces, while Palm gives 1*5 per cent, as occurring in milk. True peptone has been proved to be absent. Storch's researches have been referred to (p. 2). Babcock has found very small amounts of nuclein, and the same observer has with Russell separated a proteolytic enzyme. From the above list of the various albuminoids described as existing in milk we may select the four of whose existence we have the strongest evidence ; these are casein, lact-albumin, lacto-globulin, and Storch's mucoid ; the last two, however, are only found in traces in milk, and, practically, the albuminoids may be reduced to the former two. Of the other albuminoids described, the syntonin of Biel and the galacto-zyrnase of Bechamp must be considered to have a doubtful existence, though there is some probability of their being present. The other compounds described are hypothetical. The main reactions that distinguish the four albuminoids of milk are as follows: — Casein is precipitated by saturating the solution with sodium chloride, magnesium sulphate, and ammo- nium sulphate; globulin is soluble in a saturated solution of sodium chloride, but is precipitated by magnesium ami ammo- nium sulphates; albumin is soluble in saturated solutions of sodium chloride and magnesium sulphate, but is precipitated by saturation with ammonium sulphate, while Storch's mucoid is not in solution; albumin is, however, precipitated from a satu- rated solution of magnesium sulphate by acidifying Blightly, and is redissolved by neutralisation of the solution. Casein and globulin are precipitated by the addition of acid, while albumin CASEIN. 25 (and globulin, if much salt is present) is not so precipitated. Casein has the remai-kable property of being acted on by chymase, the enzyme of rennet, with the formation of an insoluble product ; albumin is coagulated by the action of heat, the raising of the solution to about 70° C. being sufficient to precipitate a great portion. Casein (and globulin 1) are removed from solution by filtration through a porous cell, while albumin remains dissolved. Properties common to the three albuminoids are solubility in alkalies, insolubility of their copper, mercury, and other salts, insolubility in alcohol ; all are precipitated by tannin and phospho-tungstic acid. Casein. — This albuminoid, when pure, is a white amorphous body without taste or smell ; it is practically insoluble in water, dissolving in this menstruum to the extent of about 0-1 per cent.; it is quite insoluble in alcohol and ether. Very dilute acids seem to diminish the solubility ; but it is soluble in stronger acids, becoming, however, changed ; a solution of casein in acetic acid has been used as glue; it is completely soluble in caustic alkaline solutions even when very dilute; the solutions of the carbonates, bi-carbonates, and phosphates ot the alkalies also dissolve it, and from these solutions, as well as those of the alkalies, it is pre- cipitated unchanged by the addition of sufficient acid to neutralise the alkali. It has the property of forming an opalescent solution when it is dissolved in the least possible excess of sodium phosphate, and the addition of small quantities of calcium chloride is made ; it gives then a solution having the appearance of milk. It is highly probable that milk contains casein in this form. Casein has a peculiar affinity for calcium salts, especially the phosphate. It is extremely difficult to free it from this body, the purest preparations that have been pre- pared having always been contaminated with small amounts of this compound. Casein yields a comparatively small amount of sulphide if boiled with an alkali, and contains less of this element than either glohulin or albumin ; it also differs from these compounds by containing phosphorus ; on analysis, like other albuminoids, it does not yield very concordant results ; the most probable composition is as follows : — Per cent. Per cent. Carbon, . . 53 13 Sulphur, 0-77 Hydrogen, 7-06 Phosphorus, . 0 86 Nitrogen, . 15-78 Oxygen, . . 22-40 The formula and constitution of casein are not known. The composition of casein is variously stated by different authorities. The following are the most reliable results : — 26 INTRODUCTORY — THE CONSTITUENTS OF MILK. Authority. Hammarsten. Chittenden. Stohmann. Lehmann. Rittbanaen. Per cent. Per cent. Per cent. Per cent. Per cent. C 52-96 53-30 5408 5400 54-22 H 7-05 7-07 7 09 7*04 717 N 15 65 15-91 15 57 15-60 15-49 S ■72 •82 '77 '77 •91 P ■85 •87 •85 0 22-78 22 03 21-70 The author has calculated the two following formulae as possible for casein ; the first agrees with the results of Hammar- sten, and Chittenden and Painter, while the second represents the figures obtained by Stohmann, Lehmann, and Ritthausen :— I. II. C1;2Ho74N44SP055. Ci;oH.26sN42SP05l. Per cent. Per cent. c 52 96 54 04 H 7-03 7 10 N 15-81 15 56 S •82 •84 P •80 •82 0 22-32 21 -60 Hammarsten and Chittenden purified their casein by solution in alkali and re precipitation several times ; Ritthausen worked on the copper salt; and Lehmann used what he designated "genuine" casein, which was separated from milk by the use of a porous plate. Lehmann found that in "genuine" casein L45 to 1*75 parts of lime were combined with 100 parts of casein; one molecule CaO to one molecule C^^H.^N^SPO^ requires a proportion I '49. Slildner has also shown that two lime compounds exist containing 1-55 and 2'39 per cent. CaO, respectively, which correspond with CaO and 2CaO to one molecule of casein. It is noticed that the sulphur is lower than that calculated from either of the above formula?. By treating casein with alkalies a portion of the sulphur is removed as sulphide. It is possible that in the purification of the casein by solution in dilute alkali and precipitation by acids that a small amount of decomposition sets in. When dissolved in dilute alkali it baa a leevo-rotary action on polarised light, the rotatory power [«L being, according to Roppe Sevier, about 69° to the left ; Bechamp skives it as 100°. It is completely precipitated from milk by copper sulphate ; if the LACTALBUMIN. 27 solution be neutral, a definite compound containing about 1 per cent, of copper is obtained ; basic compounds are probably obtained if the solution be alkaline. Mercury salts precipitate casein completely, even in acid solution ; it is also precipitated by meta-phosphoric acid. Bechamp maintains that casein is a weak dibasic acid, forming acid and neutral alkaline salts, an observation which Soldner confirms. Casein has probably a- higher molecular weight than the other albuminoids existing in milk. Preparation of Casein. — Casein is prepared from milk by diluting to about five times its volume, and adding sufficient acetic acid to give 0*1 per cent, of the acid in the solution ; the casein is precipitated, carrying down with it the fat ; the pre- cipitate is well washed by decantation some ten times, collected on a cloth filter, washed on the filter, and then dried, as far as possible, by pressure. This precipitate is dissolved in the least possible excess of ammonia, the solution allowed to stand for some time (to allow the fat to rise), then syphoned off and filtered, and the filtrate precipitated, as before, by acetic acid : the precipitate washed and redissolved in ammonia ; and this treatment repeated three or four times. The casein is now rubbed up in a mortar with 80 per cent, alcohol, and the alcohol poured off; the treatment with alcohol is repeated several times, using, finally, absolute alcohol ; it is then treated two or three times with ether in the same manner, and then extracted for some hours in a Soxhlet extractor to remove the fat, and the ether evaporated off at as low a temperature as possible. This casein may, if a very pure product is required, be redissolved, reprecipitated, and the treatment with alcohol and ether repeated; the casein is finally dried at 100° to 105° C, and is then a white amorphous powder ; if casein containing water is dried it forms horny masses. Lactalbumin. — This albuminoid has the property character- istic of albumins of being coagulated by raising the temperature of its solution to 70° C. ; the precipitation is never complete, since as much as 12 per cent, may be left in solution, according to Sebelein. Lactalbumin, like other albumins, is not precipitated by saturating its solution with magnesium sulphate ; on the addition of acetic acid to the solution a precipitate of albumin is obtained, and this is redissolved on neutralisation of the acid. It is, like other albumins, precipitated by sodium sulphate added to satur- ation, and also by ammonium sulphate. It is also precipitated by tannin, phospho-tungstic acid, and other general reagents. The salts of albumin with copper, mercury, and lead are insol- uble. Alcohol precipitates it and the precipitated albumin is soluble in water. It has a specific rotatory power [«]D of — 67 "O8 (Bccliamp). 28 INTRODUCTORY THE CONSTITUENTS OF MILK. Lactalbumin has the following composition, according to Sebelein : — Per cent. Per cent. Carbon, . . . 52-19 Sulphur, . . 1 73 Bydrogen, . . 7"18 Oxygen, . . 23-13 Nitrogen, . . 1.377 It differs from casein by containing no phosphorus and about twice as much sulphur. When boiled with an alkaline solution of lead acetate it gives a very strong sulphur reaction. There appears to be no difference in composition between soluble and coagulated albumin. Preparation of Lactalbumin. — Milk is saturated with magnesium sulphate and filtered. To the clear filtrate is added as much acetic acid as will give J per cent, of acetic acid ; lact- albumin is precipitated, and is filtered off. The precipitate, with the filter, is stirred up with water, and the acid neutral- ised; the lactalbumin dissolves. The solution is filtered, and reprecipitated by saturating with magnesium sulphate and adding j per cent, of acetic acid ; this is repeated three or four times; the solution of lactalbumin is then dialysed to remove salts. The solution is precipitated by alcohol, the precipitate washed with alcohol and ether and, finally, dried at a low tem- perature. Lactalbumin, prepared in this way, is a white powder without taste, and completely soluble in water Lacto- Globulin. — This albuminoid is coagulated by heat and precipitated by neutral sulphates, tannin, , Calcium citrate, Ca3(CcH507)2, . Lime combined with proteids, . Per cent. 10-62 916 12-77 9 22 5 47 3 71 4-05 7-42 8 90 23-55 513 LOO '00 The mineral salts, as stated above, would amount to *90 per cent., as against -75 per cent, of ash obtained. According to Soldner 36 to 56 per cent, of the phosphoric acid and 53 to 72 per cent, of the lime are not in solution, but are in the colloidal form. The amount of insoluble ash — i.n., ash insoluble in hot water — amounts to about 52 per cent, of the milk ; and the soluble ash to -23 per cent. The soluble ash consists mainly of the chlorides of the alkalies, with a little carbonateand a mere trace of phosphates. The insoluble ash is mainly composed of double phosphates of the formula CaKP04, the lime being partially replaced by magnesia and the potash by soda ; double carbonates of the formula CaNa.-,(COa)., also exist in traces ; these compounds are insoluble in water, and this accounts for the fact that the insoluble ash is always higher than the sum of the calcium and magnesium phosphates. An ash of this composition is only formed when the milk is homogeneous ; if it is curdled, by natural souring or by the addition of acids, the precipitated lumps do not contain sufficient alkali metals to form these compounds, and much calcium and magnesium phosphates are formed ; on dissolving in water, soluble alkaline phosphates go into solution, and calcium and magnesium phosphates, together with varying proportions of double phosphates, are left insoluble. Curdled milk gives the same total proportion of ash as fresh milk, but the soluble ash is higher and the insoluble ash lower. 3 34 INTRODUCTORY — THE CONSTITUENTS OF MILK. Other Constituents Of Milk. — Besides the constituents mentioned, minute traces of silica, iodine, fluorine, acetates, and thio-cyanates have been described. None of the salts of milk require a detailed description. They, together with the acids and bases composing them, are described in any elementary book on chemistry. Among the other substances present in traces in milk the following have been described : — Urea, hypoxanthine and other nitrogenous basic substances, a colouring-matter, odorous sub- stances and alcohol (described by Bechamp, but certainly not ordinarily present). Bechamp has described a starch-liquefying enzyme as present in milk ; and Babcock and Russell have adduced evidence show- ing the presence of a proteolytic enzyme. The Gases Of Milk. — It is extremely probable that the gases of milk are derived from the air by absorption during and after milking. Oxygen, nitrogen (probably argon), and carbon dioxide are present in fresh milk. As the milk is kept the amount of oxygen decreases and that of the carbon dioxide increases ; this is probably due to aerobic micro-oi-ganisms, which absorb the oxygen and give out carbon dioxide. The gases of milk may also include products of decomposition; thus in decomposed milk, volatile sulphur compounds of evil odour are present. If such, as is probably the case in dirty surroundings, were present during milking they would be absorbed to some extent by the milk. The gases have no practical importance. Milk is sometimes charged with carbon dioxide under high pressure to form an effervescing drink. In this case, and in koumiss and kephir, products of fermentation of milk, the carbon dioxide is an important constituent. The Fat of Milk. Constitution. — The fat in milk is found in the shape of small globules varying in size, according to Besana, Fleischmann and other authorities, from -01 mm. to 0016 mm. in diameter. There is some probability that the total weight of globules of any size is eo,ual to the total weight of globules of any other size. The fat consists of a mixture of glycerides — i.e., ethereal salts of glycerol. It appears most probable that there are three acid radicles in combination with each glycerol residue, thus — ''.ill.-, { ( 'isH.iaOj ( (> si !,:,<), which reprpsents glyceryl butyro-oleo-stearate. This view has been formed from the following tacts: — (1) Were the fat a SAPONIFICATION. 35 mixture of glyceryl ti-ibutyrate with other glycerides, it would be possible to dissolve out the glycei-yl tributyrate by means of alcohol, leaving nearly the whole of the other glycerides behind. This is not the case. The portion soluble in alcohol contains a notable quantity of the higher glycerides. (2) If glyceryl tributyrate existed as such in milk fat it should be possible to distil it off under reduced pressure, but this cannot be done. We know nothing of the way in which the fatty acids are combined with glycerol ; it is convenient, however, to state the composition as if each glyceride existed separately. Composition. — The average composition of the fat of milk appears to be, from the mean results obtained by different observers, as follows : — Butyrin, 3-85 per cent, yielding 3'43 °/0 Fatty acids and 1 '17 °/0 Glycerol. Caproin, 3 -60 „ ,, 3 '25 „ „ "86 Caprylin, -55 ,, ,, '51 ,, „ "10 Caprin, 19 ,, ,, 1-77 „ ,, "31 Laurin, 7*4 ,, ,, 6'94 „ ,, 1-07 Myristin, 20-2 ,, ,, 1914 „ ,, 253 Palmitin, 25 "7 ,, ,, 24 "48 „ ,, 2-91 Stearin, 1-8 „ ,, 172 „ ,, "19 Olein, &c, 35-0 ,, ,, 33-60 ,, „ 339 Total, 100-00 Insoluble, 87 '65 Total, 12*53 Total, 94-84 In this table, butyric, caproic, and caprylic acids have been classed as soluble in water, and the others insoluble ; this is not, strictly speaking, correct, as capric and, probably, lauric acids are also slightly soluble ; on the other hand, caprylic acid pos- sesses so slight a solubility in water that it probably is not wholly dissolved. The figure 87 65 per cent, is, however, a near approximation to the mean found for the insoluble fatty acids. The figure for the total amount of glycerol 12-53 also agrees with that found. Besides the constituents enumerated above, there also exist in the fat of milk traces of cholesterol (which doubtless replaces a portion of the glycerol), lecithin, a colouring-matter, and pos- sibly, also a hydrocarbon. Saponification. — On boiling with a solution of caustic alkali, the fat undergoes hydrolysis, thus — R, + 3NaOH = C3H5(OH)3 + NaR + NaR, + NaR„ R, R and Ry/ representing radicles of the fatty acids. If the hydrolysis be carried out in presence of alcohol a 36 INTRODUCTORY — THE CONSTITUENTS OF MILK. portion of the caustic alkali is converted into an alkali ethoxide (alcoholate) thus — NaOH + C2H5OH = C2H3ONa + H20. This acts in a slightly different manner to the hydroxide, though the ultimate products of hydrolysis are identical. The actions are probably as follows : — ( R (i.) 3NaOC2H5 + C3H, \ R. = C3H5(ONa)3-f-C.,H5R + C2H5R, + CHSR„. (ii.) C8H5(ONa)s + 30H2 = C3H3(OH)3 + 3NaOH. (iii.) 3NaOH + CgH,R + C2H5R, + C2H5R„ = 3C2H5OH + NaR + NaR, + NaR,,. In the first stage, sodium ethoxide and fat form sodium glyceroxide and ethyl salts (esters). In the second, the glyceroxide is decomposed by the water present into glycerol and sodium hydroxide; while, in the third, the esters are hydrolysed by the hydroxide into alcohol and sodium salts of the fatty acids (soaps). The action between the sodium hydroxide and the alcohol is never complete, and it is probable that the formation of esters is only partial ; evidence of the formation of ethyl butyrate can be obtained by warming a little of the fat with alcoholic soda, when the characteristic pine-apple odour of ethyl butyrate is at once developed. By carefully avoiding any excess of alkali and distilling the ethyl butyrate as soon as possible, Wanklyn and Fox have succeeded in obtaining about 3 per cent, of volatile acid (probably chiefly butyric) in the form of ester. It is probable that the equation (ii.) may not represent the way in which sodium glyceroxide acts on the substances present ; a portion may follow this equation — (iv.) C3H5(ONa)3 + 3C2H5OH = C3H5(OH)3 + 3C8H5ONa, The glyceroxide may act on alcohol forming ethoxide, instead of on water forming hydroxide. Allen and Homfray have shown that by the action of a very small quantity of caustic soda on acetin (glyceryl tri-acetate), a very large proportion of ethyl acetate is formed, many mole- cules <>f ethyl acetate being produced by each molecule of sodium ethoxide; this can only be explained by the action shown in equation (iv.). Duffy has shown that ethyl and amy] steaiate may be pro- duced from glyceryl Stearate and sodium ethoxide and amoxide respectively. The action of sodium ethoxide on milk fat has a practical bearing on butter analysis, owing to the volatility of ethyl butyrate, which, unless precautions are taken, is liable to cause loss of butyric acid on saponification. PROPERTIES OF MILK FAT. 37 From their sodium salts the acids may be set at liberty by the addition of a mineral acid. Properties. — Milk fat is insoluble in water, but dissolves about -2 per cent, of this substance. It is not volatile, though when heated to 100° C. a loss of weight is noticed owing to the dissolved water being volatilised. On further heating at this temperature, in a current of hydrogen, no change is noticed ; but if oxygen be allowed access a gradual increase of weight, due to oxidation, is found ; if the heating be prolonged, say for a week, the weight again decreases, and profound changes, the nature of which has not been elucidated, take place. Solid and Liquid Portions. — The fat of milk being an undoubted mixture has no sharply denned melting point. If rapidly cooled to a low tempei'ature it becomes solid, and melts on warming at from 29-5° to 33° C. By slow cooling it does not solidify as a whole, but behaves as a solution of fat of a high melting point in fat of a low melting point. The author obtained the following figures (Table II.) by allowing a sample to cool down gradually to about 25° C, and separating the liquid portion from the deposited solid : — TABLE II. — Properties of Milk Fat (Richmond). 1 Original Fat. Liquid Fat at 25° C. Solid Fat. Sp. gr. at 15'5°, Reichert-Wollny, . Iodine absorption, . Reichert-Wollny, . •922 26-1 c.c. 31-6 c.c. 37*5 Original Fat. Liquid Fat at 17° C. 39-0 c.c. 41-3 c.c. 199 c.c. 27 6 Liquid Fat at 0°C. 45-0 c.c. Pizzi has also recorded the following experiments (Table III.):- TABLE III. — Properties of Milk Fat (Pizzi). Original Liquid at 26-2° Liquid Liquid at 21-2° at 17-0" Liquid at 12-4° Liquid | Liquid atll-Ci at 6-5° Solid at 26"2° Sp. gr. at 26-2°, •908 •912 •916 923 •927 Melting point, Solidifying ,. 36° 25° ... ::: 44° 35° c.c. c.c. c.c. c.c. c.c. c.c. c.c. c.c. Reichert- 1 Wollny, . J 26 96 28-05 29-81 3157 30 36 32-34 3410 19-91 Iodine absorp- \ tion, . . / 32-96 34-50 38-80 40-75 42-75 52-25 58-50 25-38 3* INTRODUCTORY — THE CONSTITUENTS OF MILK. Solid Fat deposited from Liquid at 26-2° by cooling to 21-2°. Solid Fat deposited from Liquid at 21-2° by cooling to 17-0°. Solid Fat deposited from Liquid at 17-0" by cooling to 12-4°. Solid Fat deposited from Liquid at 12-4' by cooling to 11 -O". Solid Fat deposited from Liquid at 11 -0* by cooling to 6-5°. Melting point, Solidifying ,, Reichert- 1 Wollny, j Iodine absorp- ) tion, . . \ 43-5° 21° 20-13 c.c. 28 13 31° 16-5° 27-59 c.c. 38-70 18° 13° 29-70 c.c. 41-25 17° 14° 29-37 c.c. 45-50 10 5° 8 -.3° 31 02 c.c. 50*55 The above figures all show that the liquid fat is somewhat richer in both volatile and unsaturated acids than the original fat, while the solid portion is correspondingly poorer in these constituents. There is, however, no sharp separation. The density of the fat of milk is as follows : — Temperature. Mean. Limits. Authorities. 15" 15° 37-8 37 -N 39-5 39-5° 100° ,. . . 15^ (,n alil8S) •9307 (solid) ■9118 (liquid) •9113 ( „ ) •8667 ( ,, ) •9094— -9140 •9104— -9117 •8650— -8685 Fleischmann. / Bell, Allen, \ Muter, &c. Author. Numerous. The last figure is not a true density, as it is not corrected for the expansion of glass between 15*5° and 100° ; it has been assumed that the volume of the glass instrument used to deter- mine the density is the same at 100° as at 15-5°. The error has no practical importance when the figures thus obtained for different samples are compared, as they are all subject to the s;ime correction. From the average specific gravities given above the author has calculated the true specific gravities and specific volumes ; these are — PROPERTIKS OF MILK FAT. 39 Temperature. Specific Gravity. Specific Volume. Calculation. 15° 4° •9300 1 -0753 1 0844 37-8° 4° •9057 1-1041 11041 39-5° 4° •9045 11056 11056 100° 4° •8637 1-1578 11578 The figures calculated are based on the assumption that the expansion is regular between 15° and 100°, and that it averages •000863 for each degree Centigrade ; on this assumption the specific volume of liquid fat at 15° is higher, and the specific gravity is lower than that of the solid. 15-5° The specific gravity of liquid fat at 15-5' (calculated) is -922. It is interesting to note that the specific gravity of the liquid fat obtained by the author (above) had a specific gravity of "922. The specific gravities of the liquid fats obtained by Pizzi appear to have been taken at the temperatures at which the fat was separated, and on calculating to 15° have values from -921 to -925. On the whole the evidence available appears to show that the specific gravity of solid fat is greater than that of liquid fat at the same temperature. In connection with this, it may be mentioned that E. W. T. Jones has shown that the specific gravity of other fats is greater when partially solidified at 37-8° than when liquid at this tem- perature. The index of refraction of the fat of milk averages 1-4506 at 35°, and the limits observed have been 1-4550 to 1-4586. Stohmann has determined the heat of combustion of butter fat as 9-231 small calories per gramme, while Atwater found from 9-320 to 9362 calories in three samples of butter, which appear from the analytical results of Schweinitz and Emery to have been of doubtful purity. The fat of milk is soluble in all hydrocarbons which are liquid at the ordinary temperature, in their halogen derivatives, in ether, carbon bisulphide, nitro- benzene, and acetone. It is slightly soluble in alcohol and to a considerable extent in amyl alcohol when cold, but in all proportions when hot. Glycerol, when hot, dissolves it to a very small extent. It appears to mix in all proportions with esters. Fatty acids have a limited solvent effect, those of higher molecular weight dissolving more than 40 INTRODUCTORY — THE CONSTITUENTS OF MILK. the lower homologues. Phenol also dissolves it to some extent. On cooling a strong solution of the fat in any solvent, the portion deposited has not the same composition as the original lat, but is of the same nature as the solid portion obtained by slow cool- ing of the melted fat. The molecular weight of the fat has been determined by Garelli and Carcano by Kaoult's cryoscopic method in benzene solution to be from 696 to 716. That calculated from the amount of alkali necessary for saponification is 720 to 740. Products of Hydrolysis. Glycerol. — This is the simplest tri-hydric alcohol and has CH2OH the constitution — CHOH . It was discovered by Scheele in CH2OH 1779 in olive oil, and was first recognised in butter in 1784. The anhydrous product is a thick syrupy liquid, which can be obtained in crystals by cooling to a low temperature ; the melting point of the solid glycerol is given as 17°C. by Henniger and 20° 0. by Nitsche. It boils at 290° C. under the ordinary pressure, but undergoes slight decomposition; it can be readily distilled without change under reduced pressure. It is not volatile with steam. An aqueous solution containing less than 75 per cent, glycerol can be boiled without loss ; but from solu- tions containing more than 75 per cent, glycerol it is somewhat volatile (llelmer). Anhydrous glycerol volatilises slowly at 100°C. When heated above 150° C. it is inflammable. 15-5° The density at . „ „,, is 1 2675 ; the refractive index at the same temperature is T47 18. When heated to its boiling point, especially if not pure, various products, of which acrolein (C.,H(0) is the most important, an given off. I >i- and tri-glyceric alcohols arc also formed. By the action of acid oxidising agents e.g.t chromic acid and potassium permanganate in acid solution it is wholly converted into carbon dioxide and water. Alkaline permanganate converts it quantitatively into oxalic acid. I * y the action of bromine in the cold glycerose is formed, which is an aldehyde ; by further oxidation with bromine a» a high temperature, or by boiling with CHjOH I dilute nitric acid, glyceric acid n is produced. conn PRODUCTS OF HYDROLYSIS — GLYCEROL. 41 COOH Tartronic acid CHOH is, under certain conditions, also COOH produced together with glycolic, glyoxylic, «oxalic, and formic acids. Glyceric acid appears to have a constitution similar to lactic acid (q.v.), from which it differs only by containing the group CH,2(OH) in place of CHg. It forms a lactone and a dehydro- derivative, and contains an asymmetric carbon atom. By the action of fuming nitric acid (mixed with sulphuric acid to preserve its strength) glyceryl tri-nitrate (nitro-glycerine), usually mixed with small quantities of di- and mono-nitrates, is formed. This is a heavy explosive liquid of specific gravity 1*6 and of limited solubility in water. It has been proposed to estimate glycerol as " nitro-glycerine." This compound is best known as a powerful explosive. With strong sulphuric and phosphoric acids glyceryl mono- hydrogen sulphate and mono-glyceryl di-hydrogen phosphate are produced. These have the composition — S02(OH)OC8Ha(OH), and PO(OH)2OC3H5(OH)2 respectively. When glycerol is heated with alkalies above 250° C. a variety of products are formed ; among these are formic, acetic, acrylic, and lactic acids. The oxygen of the air seems to play an impor- tant part in these changes, as all the products contain more oxygen and less hydrogen. No change takes place below 250°, especially in the absence of air. Several glyceroxides are known — i.e., bodies in which the hydrogen of the hydroxyl groups is replaced by metals. By heating lead oxide with glycerol, lead glyceroxide is formed. Glycerol also dissolves lead oxide. By treating glycerol with sodium dissolved in alcohol a crys- talline deposit of the composition (XHLNaOg, CoH0O is formed, which, when heated at 100° in a current of hydrogen, loses alcohol. It is a white amorphous powder, very hygroscopic and immediately decomposed by water. Calcium, strontium, and barium hydroxides are freely soluble in glycerol, and form glyceroxides, which may be dissolved in water ; the aqueous solutions do not give precipitates with carbonic anhydride. By the action of hydrochloric and hydrobromic acids, mono- and dichlor-hydrin and mono- and dibrom-hydrin are produced. There are two possible mono-chlor- and mono-brom-hydrins : thus — CH2C1 CH2(OH) CHOH and CHC1 CH2(OH) CH2(OH) 4J INTRODUCTORY — THE CONSTITUENTS OK MILK. and similarly two di-hydrins : thus — CH,C1 CHjCl CH(OH) and CHC1 CH2C1 CH,(OH) Both compounds arc simultaneously produced. By the action of alkalies on both the dichlor-hydrins, epichlor- CH2C1 hydrin CHxn is produced. CH2 A mono-iod-hydrin also appears to be produced by the action of hydriodic acid. The penta-chloride and penta-bromide of phosphorus produce trichlor- and tribrom-hydrins, which are the a-trichlor- and a-tribrom-derivatives of propane. Phosphorus tri-iodide or concentrated hydriodic acid produce a mixture of allyl and iso-propyl iodides witli propylene. By the action of dehydrating agents acrolein, acrylic aldehyde, C3H40 is formed. Glycerol is very soluble in water and alcohol, but insoluble in ether and chloroform. Cholesterol, C2l)H4.iOH, is a mono-hydric alcohol, con- taining one unsaturated bond. This is shown by its combina- tion Avith two atoms of bromine to form dibrom-cholesterol, C'.10H4.,Br.,OH. It has a melting point of 144° to 146° C, and may be sublimed unchanged. It is laevo-rotatory, having an [«]D — 36"6 (Dragendorff) or -31 6 (Lindenmeyer). It is easily soluble in hot alcohol, crystallising out on cooling in characteristic plates ; occasionally from alcohol and more often from etlier it is obtained in needles. Oholesteryl acetate, melting point 92°, is obtained by the action of acetic anhydride on cholesterol. The benzoate is obtained by heating cholesterol with benzoic acid under pressure, and melts at 150° to 151° C. The most characteristic reaction is the following, due to Sal- kowski : — About 10 milligrammes of cholesterol are dissolved in 2 c.c. of chloroform, and the solution shaken with an equal measure of strong sulphuric acid in a corked test tube. The chloroform layer becomes blood-red, passing to cherry-red and purple, the last colour being permanent for several days. The sulphuric acid acquires a well-marked green fluorescence. If the test tube be not corked, or if the chloroform solution be poured into a basin, the colour changes to blue, green, and, finally, yellow, probably due to moisture. On addition of water the solution becomes paler, then blue, and. finally, nearly colourless, while showing a fine green fluorescence. By cautiously heating cholesterol with a drop of strong nitric acid and adding ammonia before the product bas cooled com pletely, a yellowish red coloration is produced. FATTY A CI PS. 43- If a mixture of 3 measures of concentrated hydrochloric acid and 1 of a solution of ferric chloride be evaporated with a little cholesterol, a reddish-violet coloration changing to blue is pro- duced. By substituting sulphuric acid for hydrochloric acidT a carmine colour is produced, passing gradually to violet, which is changed to scarlet on treatment with ammonia. Fatty Acids. Acids Of the Series, CmH.,,l + 1COOH.— As far as is known, only the normal acids of this series, in which n is an odd number, occur in the fat of milk. Butyric Acid, CH,CH2CH2COOH.— Grunzweig has proved that the butyric acid of the fat of milk is normal. This acid is a liquid with a characteristic smell, which is specially developed in dilute solution ; the anhydrous acid has a sharp acid smell, the characteristic smell being hardly perceptible. The acid solidifies at — 19° C. The solidified acid melts at - 2° to + 2° C. according to Linnemann, and at - 4*5° to - 2° C. according to Zander. The boiling point is variously stated according to different authorities. Thus — Linnemann gives . . . . . . 162-3° C. Lieben and Rossi, . . . . . 163 2° Kahlbanm, 161 -5° Bmhl, 161 5°- 162-5° Zander, 162-3° The author finds i6r5°-162-5° ■20° The density is given as -9587 at -p,- by Bruhl, -9746 at 0° by Zander, and -9886 at 0° by Linnemann. It is very difficult to prepare the anhydrous acid by distillation alone, the last traces ol water being retained with great obstin- acy ; dehydrating agents remove this water, and the acid is somewhat hygroscopic. It is soluble in all proportions in watei', but is separated as an oily layer on saturating the solution with calcium chloride. It is extracted from aqueous solution by ether. From dilute solutions it distils twice as fast as water — i.e., the vapour arising from a dilute solution contains double the proportion of butyric acid contained in the solution. Its solu- bility in the mixture of higher fatty acids of milk fat is very small. By the action of strong chromic acid at the boiling point it is oxidised to a mixture of carbon dioxide and water, but dilute solutions are unaffected. Alkaline permanganate oxidises it to carbon dioxide ; Johnstone states that oxalic acid is formed from 44 INTRODUCTORY — THE CONSTITUENTS OK MILK. butyric acid by the. action of alkaline permanganate, but other observers are unanimous in denying this. The salts of butyric acid are all soluble in water. When ignited they leave a residue of the carbonate of the metal (except the silver and mercury salts, which leave metallic silver and no residue, respectively;. The calcium salt has the following solubility : — I Linusic acid 204° More soluble in hot water than sativic acid. In- soluble in ether. Other Compounds.— Lecithin, C44H9q09PN, exists in small quantities in butter fat ; on saponification it gives glyceryl phosphoric acid, fatty acids and choline; it contains 3-84 per cent, of phosphorus and gives 8"8 per cent, of P.205 on oxidation. The quantity does not exceed *5 per cent, of the fat. There is also a colouring-matter of unknown composition and an odori- ferous principle. Rancidity— Products of Decomposition.— But little is known of the real nature of the changes which take place when butter becomes rancid. The following statement will give an idea of the probable nature of the changes : — The first action seems to be hydrolysis of the fat, splitting it up into fatty acids and glycerol ; the latter, perhaps, is not liberated as such, but is oxidised, yielding aldehydes and acids soluble in water, but not so volatile as the soluble acids o butter ; the volatile acids are liberated, and the smell of these can be detected in rancid butter. The odoriferous principle is destroyed. The unsaturated fatty acids are oxidised to form hydroxv acids, which are perhaps slightly soluble in water, but 4 50 INTRODUCTORY — THE CONSTITUENTS OF MILK not volatile ; the total capacity for combining with bromine is reduced by this cause. It is probable that the fatty acids of the series, CHH2u+1COOH, are but slightly affected. The effect of rancidity is — (1) To diminish the glycerol produced on saponification. (2) To increase the soluble acids. (3) To increase slightly the volatile acids. (4) To decrease the insoluble acids. (5) To increase the total molecular proportion of acids. (6) To greatly increase the free acids. (7) To diminish the unsaturated acids by (8) The formation of hydroxy acids. If the change takes place in the presence of water, some of the products are soluble therein ; hence the fat separated from the water will not have the same characters as fat which has become rancid alone. If freely exposed to the air, some of the products may be volatile. THE SPECIFIC GRAVITY OF MILK. 51 CHAPTER II. ANALYSIS OF MILK. Contexts. — Specific Gravity of Milk — Estimation of Total Solids — of Ash — of Citric Acid — of Milk-Sugar — of Cane-Sugar — of Starch — of Fat and Cream — of Proteids — of Total Acidity — Analysis of Milk Products. The Specific Gravity Of Milk — Modes of Expression- Specific gravity is the weight of a unit of volume. The unit of volume is a cubic centimetre, the unit of weight one gramme, and the specific gravity of any substance is the weight of one cubic centimetre in grammes. As one cubic centimetre of water at 4° 0. weighs one gramme, the specific gravity of water at 4°C. is exactly 1 ; at temperatures higher and lower than 4°C. water expands, and therefore has a specific gravity less than 1. Table VI. gives the specific gravity of water at different tem- peratures : — TABLE VI. — Specific Gravity of Water. Temperature. Specific Gravity. Temperature. Specific Gravity. 0° c. •99988 40° •99237 4° 1-00000 50° •98817 10° •99975 60° •98343 15 -55° (60° F.) •99910 70° •97794 20° •99826 80° •97193 30° •99575 90° •96561 37-78° ( 100° F.) •99313 100° •95865 As at 4° C. one cubic centimetre of water weighs one gramme, a practical method of ascertaining the specific gravity at this temperature is to take the weight of any volume of the liquid and to compare it with the weight of an equal bulk of water. To ascertain the specific gravity at any other temperature — say, for example, 30° C. — the weight of any volume of liquid is ascer- tained and compared with the weight of water at that tempera- ture divided by the specific gravity at that temperature — in the case taken -99575. 52 ANALYSIS OF MILK. The following formula may be used for determining specific gravity : — H wt. of a known vol. of liquid x sp. gr. of water at same temp. wt. of same volume of water at same temperature. In practice it is customary to assume that water at 15*55° C. (60° F.) has the specific gravity I. Thus, to ascertain the specific gravity at 15-55° C. (60° F.) it is customary to weigh a known volume of liquid, and to compare it with the weight of an equal volume of water at that temperature. All specific gravities in this volume are stated in this way unless otherwise mentioned. In order to avoid confusion the symbol 15*o 5° specific gravity at -- _0 is often used to express this mode of 1 D'OO expression. This means that the weight of a volume of liquid at lo'oo0 is compared with the weight of an equal volume of water at 15'55°. 15-55° 20° . Similarly, the expression specific gravity at — -; — or — is used to express the true specific gravities at 15*55° and 20° respectively. It is occasionallv convenient to compare the weight of a Liquid at some other temperature with the weight of water at the same temperature ; thus the specific gravity of fats is taken sometimes 100° . at 100° C, and the expression specific gravity at ^ is used to express the value obtained by dividing the weight of a volume of fat at 100° C. bv the weight of an equal volume of water at 100° C. If we ascertain the weight of water held by a certain vessel at a definite temperature, we can ascertain the specific gravity of any liquid by tilling it with the liquid at the same temperature ami weighing it. If we fill the vessel with the liquid at any other temperature, the volume contained will not be the same as that of the water, owing to the expansion of the vessel itself altering the capacity. Nevertheless, specific gravity is frequently ascertained on the assumption that the vessel does nol alter in capacity by change of temperature. As the vessel is usually made of glass, this mode of expression of specific gravity may be 20 termed the "apparent specific gravity in glass at — ._,' (or whatever the temperature may be). As a matter of fact, specific gravities of milk arc usually determined as "apparent specific gravities in glasa at .. .. DETERMINATION OF SPECIFIC GRAVITY. 53 Determination of Spe3ific Gravity. — There are two methods of determining specific gravity, which is, as above stated, the weight of unit volume, or, expressed as an equation — W We may either determine the weight of a known volume, or the volume of a known weight. Both methods are used in practice, the first in two ways : — (1) A vessel of known volume is filled with the liquid and its weight taken. (2) A plummet of known volume is immersed completely in the liquid, and the loss of weight due to the displacement of an equal volume of liquid noted. The second method is applied (3) by immersing a float of known weight, and noting the volume immersed ; the volume immersed will be equal to a volume of the liquid of weight equal to that of the float. Determinations of specific gravity by method (1) are made by specific gravity bottles and Sprengel tubes, by method (2) by a Westphal balance, and by method (3) by hydrometers, of which lactometers are special forms of limited range suited for milk. For exact determinations of the specific gravity of milk, a Sprengel tube presents many advantages. It is a U-shaped tube with narrow capillary ends bent outwards at right angles, one being rather smaller than the other; the wider of the two has a fine line etched round it, to which the liquid in the tube may be adjusted, the U and the other capillary being completelv filled. The weight of the dry and empty tube is first ascertained, the tube is then filled with pure distilled water, and immersed in water at exactly lb'550 C. (60° F.) ; when it is seen that no further expansion or contraction takes place, the water should be adjusted to the line on the wider capillary by the cautious appli- cation of a piece of blotting paper to the end of the narrow capillary ; the tube is then wiped dry and weighed. The differ- ence in the two weights gives the weight of the water contained in it. The tube is then filled with milk and immersed in water at 15-55° C. (60° F.), and the milk similarly adjusted to the line; the weight of milk divided by the weight of water gives the 15*55° specific gravity of the milk at ' '„ „ . 1 ° ! 15-55 A specific gravity bottle is used in a similar manner; the liquid, after inserting the stopper and immersing the bottle in water at 15-55°, is adjusted to the line by drawing out the excess with a very fine tube. A Sprengel tube of 10 to 20 c.c. capacity is the most suit- 54 ANALYSIS OF MILK. able size ; it is a disadvantage to use a larger one, as the time taken for the milk to assume the temperature of the sur- rounding water is so much increased that there is danger of a portion of the cream separating. The advantages of a Sprengel tube over a specific gravity bottle are : — (1) Greater surface for a given volume ; and therefore the temperature is adjusted quicker. (2) There is no stopper to fit ; consequently, no error can be due to difference of position owing to inaccuracy of fit. The Westphal balance consists of a balance of the " steel-yard " type, carrying a glass plummet at one end ; it is so adjusted that the pointer is at zero when the plummet hangs in air, and is provided with a weight, which, when hooked on to the end, causes the pointer to be at zero when the plummet is immersed in water at 15'55° C. The beam is divided into ten parts, each indicated by a notch, and riders weighing the same, y1^, jfo, and joVo °f tne weignt are provided. To take the specific gravity, the plummet is immersed in milk at 15"55°, and riders are placed on the notches of the beam till the pointer is at zero. If the T\j rider is on notch 3, the specific gravity is 1'03 ; if, in addition, the y^g rider has to be placed on notch 2, the specific gravity is 1-032 ; and if, in addition, the yAfl rider has to be placed on notch 4 the specific gravity is 1-0324. If a rider is already on a notch, and it is desired to place another thereon, it may be hung on the turned up end of the rider already in position. A rule may be given as follows :■ — Count 1 for the weight hung on the end, the first place of decimals from the notch on which the \ rider is hung, the second place from the notch on which the ,',, rider is hung, the third place from the yi^ rider, and the fourth place from the -j—^ rider. This method has the advantage of being somewhat more rapid than the use of the Sprengel tube, but is not quite so accurate, as the adjustment of riders and balance cannot practically be performed with very great accuracy. hi dairy work the lactometer is generally used. From a strictly scientific point of view, there are many objections to lactometers, but their practical convenience is so great that they are instruments of extreme value. The faults of lactometers are : — (1) They do not indicate true specific gravities, but the inverse of this specific volumes; consequently, the scale is not divided into equal parts. The divergence from equality is, however, so small in a lactometer, which has only a limited range, as to render it practically admissible to t real the smaller divisions as equal. (2) The exaci point at which the level of the liquid cuts the stem of the lactometer cannol be ascertained, as, owing to VARIATION IN MILK. 55 surface energy, the liquid is attracted to a higher level round the stem of the lactometer than the surface of the liquid ; more- over, the height to which the liquid is attracted varies with the nature of the liquid. As milk has always the same composition within narrow limits, there is no practical difference in the height to which it is attracted round the stem ; the eye soon becomes trained in making the proper allowance for this. (3) Lactometers are only correct at the temperature at which they are graduated ; at other temperatures their volume varies ; no inconvenience on this account is felt in practice, as this is allowed for in the tables given for correcting the specific gravity to a temperature of 15-55° C. (60° F.). Practical instructions for the use of lactometers will be given later under the " Testing of Milk." "Variation in Milk. — The specific gravity of the milk of individual cows varies from 1-0135 to 1-0397; when the mixed milk of a herd is tested it rarely falls outside the limits of 1 -030 and 1-034. The average specific gravity of milk is 1-0322. The specific gravity is dependent on two causes — the amount of solids not fat, which, being dissolved in water, raises the specific gravity ; and the fat, which, being lighter than water, lowers it. By removing the fat (with a small proportion of other constituents) as cream the specific gravity of the milk is raised. By the addition of water the specific gravity is lowered. The specific gravity has been — and is — largely used as a test for the addition of water to milk; for the detection of large amounts of water to milk it has some value. That it is a test of the roughest kind is shown by the following facts : — (1) The variations in specific gravity are from 1-0135 to 1-0397 — i.e., nearly twice its bulk of water could be added to milk of the highest specific gravity to reduce it to the lowest. These, of course, are exceptional cases, and the specific gravity of the mixed milk of a herd is nearly always between 1-030 and 1-034. At least 10 per cent, of water could be added to milk of 1 -034 specific gravity before it would be suspected by this test. (2) A milk of 1032 specific gravity, if the cream is all removed, would give a product of about 1-036 specific gravity ; and an addition of rather more than 10 per cent, of water would bring the specific gravity back to 1-032. (3) If to milk ot 1-032 specific gravity sufficient cream be added to raise the percentage of fat 4 per cent., the specific gravity will be found to be about 1-028. The same result would be arrived at were the milk allowed to stand, and the upper portion removed. As an absolute test the specific gravity is liable to be greatly misleading ; as a preliminary test it is of the greatest import- ance, and should never be neglected. 56 ANALYSIS OF MILK. As stated above, the specific gravity is raised by the solids not fat, and lowered by the fat. This fact is not only true qualitatively, but also, as the following demonstration will show, quantitatively. By our definition that specific gravity (S) is the weight (W) of the unit of volume (V), we get the equation — W s = v (1) Lit us suppose we have a mixture (having the specific gravity S) of two substances, A and B, of differing specific gravities S and SB. Let us suppose that the respective weights are A and B, and let A + B = 100. Then by (1) Volume of A= ' , volume of B= --, and volume of mixture = '"" Then 100= A B_ A 100-A s s. Sn s, s„ 100 _A(SB-SA) 100 S S.S- s„ 111(1 W)=\rB' A SB a vHJOS^, Now in the same way S = SA + BS( As both SA and SB arc constants, we may write inns,. S=SA+BS KB } andS = SB- + AS KA J KB and KA being constants. . . (2) Now, as A ■- 11 = 100, A is the percentage by weight of this substance j and us 100 xS expresses the total number of grammes in 100 e.c. of the mixture, As [g the number of grammes of < his sul stance in 1 00 c.c. Prom il |iiations above given we can deduce the law that "if two substances of differing Bpecific gravity be mixed, the specific gravity of the mixture will be equal to the specific gravity VARIATION IN MILK. 57 of one of the substances plus the number of grammes of the other per 100 c.c. of the mixture multiplied by a constant factor." Regarding milk as a mixture of fat and a solution of solids not fat in water, we can say that the specific gravity of a milk is equal to the specific gravity of the solution of solids not fat plus the number of grammes of fat per 100 c.c. multiplied by a constant. In the solution of solids not fat we have in 100 c.c. of it x grammes of solids not fat ; let us assume that their density is y. Then x grammes will occupy a volume . T^et the specific gravity of the solution be S. The 100 c.c. weigh 100 S grammes, and the water in this weighs 100 S - x grammes; it also measures 100 c.c. Now, as the specific gravity of water is 1, 100 S - x = 100 - — 100 S = 100 + x y S = 1 +x 100 y- (3) 3/-1 Now, ^rr— is a constant, provided that y remains constant. 100 y r J Putting the equation into words we find " that the specific gravity of a solution of solids not fat is equal to 1 plus the number of grammes of solids not fat in 100 c.c. multiplied by a constant." It is known, however, that the specific gravity of substances in solution is not quite constant, but varies slightly with dilution. The following figures will show that in milk the law just enumerated holds good within the limits of experimental error. A poor skim milk was diluted with water, and the total solids and specific gravity at 15-55° estimated : — Total Solids per Cent. Specific Gravity. Constant. 9-280 8-758 8-318 7-777 7-456 6-455 1 -03544 1 03343 1-03170 1-0295(1 1 -02829 1 (12439 •003688 •003693 •003694 •003684 •003690 •003688 From the laws expressed by equations (2) and (3) we see that the specific gravity of an aqueous liquid containing a substance in solution or in admixture can be expressed equally as a direct 5£ ANALYSIS OF MILK. multiple of the number of grammes per 100 c.e. ; for if we suppose that the substance A is water, SA will equal 1, and equation (2) can then be written — s l i i;s Kn. which is practically equation (3). Formulae for Calculations. — In oi-der to deduce a formula expressing the relation between specific gravity and percentage by weight of fat and solids not fat, let us call the specific gravity (for convenience) 1 + S, the percentage by weight of fat F, and of solids not fat "N. Then the number of grammes of fat per 100 c.c. will be F x (1 + S) and of solids not fat N x (1 + S). The weight of the water in 100 c.c. is then 100 x (1 +S) - N x (1 +S) - F X (1 +8) grammes ; and its volume 100 x (1 + S) - N x (1 + S) - F x (1 + 8) c.c. The volume of fat and solids not fat in 100 c.c. is therefore 100 - (100 x (1 + S) - - N x (1 + S) - F x (1 + S)) e.c. which equals N x (1 + S) + F x (1 + 8) - 100 S .... (4) Let us assume that the specific gravity of fat is / and of solids not fat n. F x (1 + S) Then the volume of fat in 100 c.c. is — -~ — and of solids not rat ; therefore n X (i + S) + Fx(l+S)-1008 = Fx(1/S) + Nx(1+S) or 8 tfx(l + B) X (,+S)+Fx(l+S)-F*(1 I or ion s X (l | S) ( " - ' j + F x (1 + S)^ j ' ). Now, as a and /' are constant, we may write for ( j, a ; and for (' . V U. Then the equation stands 1,MI 8 M , ., I g a N + 6 I It is usual, however, to estimate total Bolids (T) and fat in an analysis. T X F, and, therefore, X T V. FORMULAE FOR CALCULATIONS. .r)9 The equation (5) may be written 1 + s = " ( - F) + ;' E l°0 S m ,1 I v ia\ or ... " I + '' - '<) * (6) 1 +s In expressing the specific gravity of milk it is usual to do so in lactometer degrees, which are the specific gravity multiplied by 1000 minus 1000. Thus if the specific gravity be 1-032, the lactometer degrees are 1-032 x 1000- 1000 = 32. Let us express lactometer degrees by the symbol G. Then G = 1000 S, and, substituting this in (6), we get / =-^H= 10a T+ 10 {!> - a) F. 1 + S The specific gravity was expressed as 1 + S for ease in calcu- lation ; it is better, however, to substitute the symbol D in the formula, which then stands as ~ = 10a T + 10 (6 - a) F 1 (; tl or T = ,,. x - 10a H4*)' 0> As, by the definition above, a = — and b =' — — , we could n J calculate a formula, did we know the specific gravities of solids not fat and fat, but we do not know both of these. Fleischmann has determined the specific gravity of the fat of milk to be 15° C. •9307 at -, but it is impossible to determine the specific lo \j, gravity of solids not fat in solution. Moreover, Fleischmann's determination of the specific gravity was made on fat in the solid state, and it is possible that in milk it may have a different specific gravity. By transforming equation (7) into the form 1 G /b - a\ F -(^r) 10a TD \ a ) T and making a large number of determinations of — > T, and F in different milks, we can form each pair of results into simul- taneous equations and solve them. In this way we can get a large number of values for a and b, and, from the mean of these, we can calculate the specific gravities of fat and solids not fat respectively. This method is not wholly free from objection, as, unless there is a considerable difference between the figures actually determined, the figures from which a and b are calcu- 60 ANALYSIS OF MILK. lated are so small as to be greatly affected by experimental error ; while, if the difference be large (as in the case of analyses of cream and skim milk), it is found that the experimental error is also increased. For this reason, and also for the reason that the specific gravity of fat and solids not fat are themselves liable to slight variations, it is necessary to deduce the formula from a great many determinations, which means much labour in calculal ing. In or ler to ascertain the specific gravities of fat and solids not fat in milk, the author has calculated their value from over 200 analyses made by the ii)osh exact methods at his command, and finds the following figures : — Specific gravity of fat, ..... "93 ,, ,, solids not fat, . . . 1*616 It is seen that the author's figui*e, calculated from actual analyses, agrees wdth Fleisc'nnann's determination of the specific gravity of fat. As the specific gravity of milk does not vary much, it will not G make an appreciable error if, instead of ^ , the expression I nnh be used ; this form of calculation is much easier. The idea of deducing a relation between specific gravity, fat, and total solids appears to have arisen with Behrend and Morgen, who published a table. Shortly afterwards Clauznitzer and Mayer, and Hehner published formula', but as they were founded on inaccurate data, they are now abandoned. Fleischmann and Morgen next published a formula in which the specific gravity of fat was assumed to be "94 ; this was corrected by Fleischmann after his determination of the specific gravity of fat as "1)3. His formula is T = -2665 ^ L-2F. Hehner and the author deduced the formula T = -254 G + 1-164 F.* This is in the less scientifically correct, bu1 more convenient form : as it was found that milk differing appreciably in specific gravity from L-0322 did not give results which agreed well with He formula, various approximations have been made to this. The author has calculated a formula which ui\,^ practically the same results, but is more scientifically correct, and which i "t require the application of approximations. This is T= ■•_•<;•_' | " i liT l". I thi original papei a slighl correction For skim milks was included in the formula : tlii^ baa now been abandoned. MILK SCALE. Gl As the previous foi'mula? were deduced from analyses to which objection could be taken, the author has deduced a new formula from the results of analyses made as exactly as possible. 1 2 F. T = -2G2o-^ This has been found to be expressed by the G 6 simpler formula T = —. + r- F + -14 within very small limits if the specific gravity lies between 1-020 and 1-036. The formula T = — + - F also approximates 4 o ri closely to that of Hehner and the author. Other formulae have been devised by J. K. Brown, Babcock, and others. Of the above formula?, that of Fleischmann agrees best with the results when Soxhlet's method of fat estimation is used ; that of Hehner and the author when the Society of Public Analysts' methods are employed; while if the methods mentioned later as most exact in the author's opinion be employed, the author's formula gives the most satisfactory results. The fat calculated from the specific gravity and total solids almost invariably agrees within •2 per cent, with the determination made by the appropriate method. Milk Scale — In order to save calculation the author has devised a slide rule, known as the "milk scale" (Fig. 1), from which the percentage of fat can be read off directly from the specific gravity and percentage of total solids. On one side a scale is placed indi- cating total solids, 1 per cent, of total solids being represented by 1 inch ; on the other side the fat is shown by a scale of 1 -164 (li inches) to 1 per cent. ; the slide carries the specific gravity scale, 1° being equal to •254 inch. The line indicating the specific gravity found is placed against the total solids estimated ; an arrow then gives the fat as calculated by the formula T = -254Ci + 1164F. :■- Fig. 1. Milk Scale. 62 ANALYSIS OF MILK. A scale is also made to express the formula T = -25G + 1-2F+ -14. In this case the total solids scale is 1 inch to 1 per cent., the fat scale 1 -2 inches to 1 per cent , and the specific gravity -25 (^ inch) to 1°. The arrow is placed -14 inch lower than in the case of the other scale. To facilitate reading, Cassal and Gerrans propose to add two sliding pointers, one on the total solids scale, and one on the specific gravity slide, which are first placed against the part of the scales corresponding to total solids and specific gravity found respectively, and the two pointers are then adjusted. This arrangement prevents the possibility of error in adjusting the slide. The author has also employed a runner made out of a piece of brass bent round the milk scale, in which two holes are cut, leaving a narrow bar between them ; this bar partially covers both the total solid and specific gravity scales, and has a fine line drawn upon it at right angles to the scales. By adjusting this line to the total solids, and the specific gravity to the line, the object sought by Cassal and Gerrans is attained. The idea of the runner is due to Lieutenant Mannheim of the French Artillery, who, in 1851, devised it for a logarithmic slide rule. The scales are divided into tenths, hundredths being estimated by the eye ; a decimal scale, or, better, a vernier, as suggested by Sykes, can be applied to the runner, rendering it easier to read the second place of decimals. This, however, is not neces- sary, the error due to unavoidable circumstances being greater than the error of computation of the hundredths. Tables are given from which the fat calculated from different percentages of total solids and specific gravities can be read off. By our definitions n-\ . . /- 1 a = - and h - .—, n J and from the values given above in the formula mentioned, a and b can be calculated. Thus, taking the formula T - '2625 + 1 '2 F, 2625 .! and 1-2 = l> a a b or 30-5 24 0 23 4 320 31 0 24-5 23 9 32-5 315 25-0 24-4 33 0 319 25 5 24-9 33-5 32 4 26 0 25-4 34 0 32-9 26 5 25-8 34 5 334 27-0 263 35 0 33 8 27'5 26-8 35 '5 34 3 36 0 34 7 Mode of Averaging Specific Gravities. — It is not, there- fore, correct in averaging milk analyses, where specific gravities and percentages by weight are expressed, to obtain the average specific gravity by adding the specific gravities together and dividing by the total number, but specific gravities must be first calculated to specific volumes, and these averaged, and the average specific gravity deduced from the average specific volume. Thus, to average the following analyses : — Specific gravity, 1 ■( »22 L-036 Total s,.ii, is, 20-0 LO-O The average total solids is = = 15 ; but the average .„ . . 1-022 + 1-036 . ... . . 1 specific gravity is not ^ =1-029, but >9785 + .9653 1 •9719 = 10289. The error is, however, small if the Bpecific gravities do DOl differ greatly, and may very frequently be neglected. On the other hand, it", instead of averaging percentages of total solids by weight, we average the number of grammes per 100 c.c, we obtain correcl results by averaging the specific gravities. MODE OF AVERAGING SPECIFIC GRAVITIES. 65 The following rules may be stated : — (1) If equal volumes of different milks be mixed, the specific gravity of the mixture will be the mean of the specific gravities of the milks (2) If equal weights of different milks be mixed, the specific volume of the mixture will be the mean of the specific volumes of the milks. Instead of taking the solids not fat as one substance, we may consider its constituents — lactose, proteids, and mineral matter — separately. Calling the percentage of fat F, lactose L, proteids P, and mineral matter A, we may write g=106F + 10cL + 10dP + lOeA. by the same reasoning employed in deducing formula (5). The author has deduced from the mean of many analyses the formula g = - -761 F + 4 L + 2-5714 P + 7*5715 A. From these factors the following specific gravities are deduced, as previously shown : — Specific gravity of fat, -93 ,, ,, lactose,. ..... 1*666 ,, ,, proteids, ..... 1*346 ,, ,, mineral matter, . . . . 4 12 Using these specific gi-avities, together with Vieth's estimate of the proportions of lactose, proteids, and mineral matter — 13 : 9 : 2 — we can calculate what the specific gravity of solids not fat should be. As Vieth's proportions are by weight, we must transform specific gravities into specific volumes. Specific volume of lactose = 1-666 ~ •6 " ,, proteids = 1 1-346 ~ •743 )> ,, mineral matter 1 1 4-12 ~ •243 V Then specific gravity of S.n.F. = 13 x -6 + 9 x -743 + 2x .^T^l^* 24 which is in approximate agreement with that given above, 1*616 — i.e., within 1 per cent. It is a useful check on an analysis to calculate the specific gravity from the percentage of milk-sugar, proteids, fat, and 5 66 ANALYSIS OF MILK. mineral matter ; this should agree within small limits with that found. The Alteration of Specific Gravity by Change of Tem- perature.— Milk, like most other substances, alters in specific gravity by change of temperature. Though it contains a large amount of water, it does not share the anomaly which this substance possesses of attaining its maximum specific gravity at 4° C. (39° F.). Tt decreases in specific gravity when heated from its freezing point - -55° C. (31° F.). The following figures (Table VIII.) show the average apparent expansion of milk in glass : — TABLE VIII.— Expansion of Milk. Temperature in •F. Volume. Temperature in °F. Volume. 31 1-00000 60 1-00229 35 1-00016 65 1-00298 40 1-00041 70 1-00372 45 1-00074 75 1-00451 50 1-00114 80 1 00549 55 1-00164 The expansion is greater with rich milk than with poor milk ; the above figures referring to milk having a specific gravity of T032 and containing 3-8 per cent. fat. Table LXXIII. in Appendix C affords a means of correcting to 60° F. the specific gravity of milk when taken by a lactometer at any temperature from 33° F. to 85° F. The table gives specific gravities from 1-020 (20 degrees) to 1*036 (36 degrees) and is applicable to whole milk only. The portion from 45° F. to 75° F. is, with a few alterations, due to Vieth ; this has been repeatedly checked by the author, and in a few places slightly changed in accordance with the results obtained. The other portion has been calculated by the author. The table is used by looking up the degrees of specific gravity found (or the nearest whole degree) in a horizontal line, and tin- temperature in a vertical line; the figure at the intersection of the two lines is the specific gravity corrected to 60° F. The specific gravity of separated milk may be corrected to 00 " K. by the following table. Asthc expansion is practically uniform for the variations in quality met with, the table is given in a simpler form. THE RISE OF SPECIFIC GRAVITY OF MILK ON STANDING. 67 TABLE IX. — For Correcting Specific Gravity of Separated Milk to 60° F. Temp. Take off. Temp. Add on. Temp. Add on. "F. °F. •I. 50 11 60 •o 70 1-4 51 1-0 61 •1 71 16 52 •9 62 •3 72 1-8 53 •8 63 •4 73 1-9 54 •7 64 ■5 74 2-0 55 •5 65 •6 75 2 2 56 4 66 •8 76 2 3 57 •3 67 9 77 2 4 58 •2 6S 1-1 78 26 59 1 69 1-2 79 2-7 The author lias devised a scale for correcting the specific gravity of milk to 60° F. It is usually engraved on the " milk-scale," and is used by adjusting the specific gravity found (on the slide) to the arrow at 60° F. The corrected specific gravity is found opposite the temperature at which the determination was made. The corrected specific gravities obtained by the " milk-scale " agree generally within -1 of those taken from the table. At very low temperatures, however, there is sometimes a larger difference. The Rise of Specific Gravity of Milk on Standing.— Milk drawn from the udder contains a large number of air bubbles, and its specific gravity cannot be taken ; after the expiration of an hour or so these have disappeared, and a specific gravity determination is possible. It was first observed by Recknagel that the specific gravity taken after the expiration of one hour was lower than the specific gravity subsequently obtained. He found the rise in specific gravity to be regular, more rapid at low temperatures than high ones, and to amount on the average to "001. He attributed the change to an alteration in the volume of the casein. Vieth completely confirmed Recknagel's observation, and found the average rise to be '0013; Bourcart also observed the phenomenon. The author has studied Recknagel's phenomenon (as this ehange in specific gravity has been called). In about 70 per cent, of his experiments the rise in specific gravity has been observed, varying from -0015 to '0003, and averaging "0006, while in 30 per cent, of the observations no rise in specific gravity was indicated. The experiences of Babcock and Farrington agree with that of the author. The author's experiments have confirmed the statement of 68 ANALYSIS OF MILK. Recknagel, that the rise is more rapid when the temperature is low than when high ; the same ultimate specific gravity is attained whatever the temperature. Recknagel's phenomenon appears to he unconnected with the milk-sugar ; it is possibly enzyniic, as in one experiment the author found that the addition of a trace of salicylic acid delayed the rise, though, as the milk had to be well shaken to dissolve the salicylic acid, too much reliance cannot be placed on this result. It is possible that Recknagel's explanation is the correct one, and that an intra-molecular change takes place in the casein. An analogous change, manifested in a different manner, is known to take place in the fibrin of the blood. It is, how- ever, difficult to reconcile the idea that it is enzymic, with the fact that the rise is more rapid at low than high temperatures. The author's experiments on the change of density of cream by heating (Appendix A.) have rendered it probable that Reck- nagel's phenomenon is due largely to tlie increase of density of the fat on solidification. Contrary to the author's former conjecture, there seem to be no particular periods of the year in which Recknagel's pheno- menon is observed or not. Samples have been found at all seasons which show a marked change in specific gravity, while others examined almost simultaneously have shown no change. It must be mentioned that Recknagel's phenomenon has been denied by some. Smetham attributes the change in specific gravity solely to the presence of air bubbles. The weight of evidence is, however, greatly against this view ; it is incon- ceivable that air bubbles generated by milking a cow should be persistent for twelve hours, while if they are formed in the milk by other means, say by running through a separator, they dis- appear in one hour. The final specific gravity is always taken as the true specific gravity of milk, and the term is so used in this volume. The Estimation of Total Solids.— The total solids of milk are estimated by evaporating the water and weighing the residue. "Wanklyn's Method. — Wanklyn proposed to limit the time of drying to three hours at the temperature of boiling water ; lie weighed 5 grammes in a platinum basin, kept it for three hours rui a briskly boiling water-bath, and, after cooling in a desiccator, weighed the residue. This method has now entirely fallen into disuse, as the residue thus obtained still contained a quantity of water, wliieh could be driven off by further evaporation. Method of Society of Public Analysts. — A very obvious modifical ion of t bis is to conl inu8 * be drying on n water bal li or in an oven al 100" C. till the weighl is constant, This method has been adopted by the Society of Public Analysts. It is not, however, possible to attain absolute constancy, as a decomposition babcock's method. 69 due to heating takes place, and the weight continually slightly diminishes on further heating ; for this reason the weight is usually considered constant when less than 1 milligramme per hour is lost on further drying. The method yives very good results, and duplicates agree closely ; but it is doubtful whether the results represent accurately the true total solids of the milk. First, an absolutely constant weight is not attained ; and, next, the residue is markedly brown, indicating decom- position ; the point taken as constancy is really a point where it may be assumed that the bulk of the water is driven off, and comparatively little decomposition has taken place. The author has found by taking smaller quantities of milk — about 1 gramme — and spreading this over a large surface during evaporation, that a nearly white residue is obtained, and constancy of weight can be attained. It appears probable that the decomposition to which the browning is due takes place during the heating of the milk before evaporation is concluded. In support of this view it may be noted that Cazeneuve and Haddon have observed that formic acid is produced by heating milk to the temperature of boiling water, and Johnstone has found that formic acid added to milk had an enormous influence on the results. The results obtained by the estimation of total solids by the evaporation of 1 gramme spread over a large surface, from which the water was very quickly driven off, were always slightly higher than when 5 grammes were used, when evaporation was very much slower. In order to secure rapid evaporation, the milk has been spread over a large surface by the use of sea sand and other granular substances. Vieth has found that evaporation on sand gives practically the same results as direct evaporation in a basin. Babcock's Method. — Babcock has used asbestos as a medium for spreading the milk over. The method as adopted by the Association of Official Agricultural Analysts (of America) is described on p. 100. The author has found Babcock's method most satisfactory, and finds it convenient to operate as follows: — Place about 3 grammes of fine asbestos fibres in a small platinum basin, and ignite strongly (preferably in a muffle) ; after weigh- ing, add about 5 grammes of milk, and again weigh as quickly as possible to the nearest milligramme. Place the basin for an hour or two on a water bath, and dry in a water-oven till constant in weight. The residue thus obtained shows no signs of browning, and a constant weight, which shows no appreciable change on | pro- longed drying, can be obtained. The "total solids" by this method are somewhat hygroscopic, and care must be exercised in weighing. 70 ANALYSIS OF MILK. Macfarlane's Method. — Macfarlane uses " clirysotile " or Canadian asbestos for this purpose ; this substance cannot be ignited, being a hydrated mineral, and for some reason, which is at present obscure, does not seem to be so satisfactory as the Italian asbestos. The residue obtained by drying on " chryso- tile " is very distinctly bi'own, and the results are much lower than those given by other methods. Adams' Method. — Adams uses a paper coil, which is tirst dried at 100° C and weighed, for the estimation of total solids. The results thus obtained are frequently low. Duclaux has proposed the use of sponge, and Ganntner of wood fibre ; but these substances have never come into general use. Drying, — The author has found that by evaporation in vacuo over sulphuric acid good results are obtained if the milk be spread on blotting paper or on asbestos ; the result is slightly higher than when the drying is performed at 100° C. In order to shorten the time of drying, Gerber and Raden- hausen experimented with acetic acid and alcohol. They found that by coagulating the casein with these substances a skin no longer formed on heating, and the time of evaporation was materially shortened. For this reason the use of acetic acid, or alcohol, or a mixture of the two, has been largely adopted for the estimation of total solids. A much greater browning of the total solids takes place, and constant results are quite impossible of attainment when acetic acid or alcohol is used ; by a some- what close adherence to arbitrary conditions as to time of drying very fair results may, however, be obtained in this way in a short time, but the method cannot be recommended where accuracy is of importance. If the smell be not objected to, it is better to use butyric acid in place of acetic. It may sometimes be of importance to estimate the water driven off, instead of deducing it from the difference between the percentage of total solids and 100. To accomplish this, about 4 grammes of asbestos should be placed in a U-tube, and, after drying by passing a current of dry air, this should be weighed. About 5 grammes of milk should be weighed in, and the U-tube suspended in a beaker of water. This is connected with another weighed U-tube filled with pumice moistened with strong sulphuric acid, and provided with a bulb in which the bulk of the water can condense. A current of air (or preferably, hydrogen) dried by .sulphuric acid should be passed through the tubes, and the water in the beaker boiled. After about three hours heating, t he sulphuric acid tube should be removed, and, after cooling, weighed. The increase of weight of the sulphuric acid tube will rive the weight of the water in the milk taken. It is not advisable to dry the total solids at temperatures DRYING APPARATUS. 71 exceeding 100° C, as the decomposition of the residue by heat is increased at higher temperatures. Drying Apparatus.— For the drying of total solids the following conditions may be laid down for the drying ap- paratus : — (1) The temperature must not exceed 100° C. (212° P.). (2) The moisture must be removed as soon as it is converted into vapour. The usual form of water-oven used consists of a water-jacketed metal box with a door to it ; very little provision is made for the removal of the moisture, as no current of air is allowed to circulate through the whole of the interior. Various forms of air-baths, with a regulator for maintaining a constant temperature of 100° C. (212° F.), have been proposed; of these, the best are those of Griffin and Adams. These do not give quite satisfactory results for milk analysis, because the temperature for which they are regulated is the temperature of the air in the bath, while the basins in which the milk is dried are heated to a somewhat higher temperature by conduction. The following figures were obtained with a Griffin's air-bath ; a porcelain capsule filled with mercury was placed on various shelves in the bath, and the temperature of the mercury noted. The air had a constant temperature of 100° C. : — Temperature on bottom, ...... 136° ,, on cork on bottom, .... 102° ,, on shelf, ...... 104° ,, in upper part, 96° Constancy of temperature cannot be depended upon in an air- bath : it is, therefore, preferable to use a water-oven. The author has devised a water-oven for milk analysis, which has given highly satisfactory results. It consists of a jacketed copper box, opening only at the top, and closed with a movable lid ; on the lid is a chimney about 1 foot high. The bottom portion of the jacket contains four 8-foot coils of thin copper tubing, which coinrmmicate with the exterior by four holes at the side of the bath, and with the interior by four holes, one in each corner. The jacket is closed, except for one opening, in which a condenser is placed. About 1 inch from the bottom a sheet of copper is fixed, in which is a round hole of diameter equal to half the width of the interior. The jacket is tilled with distilled water, which is heated either by a steam coil or a gas flame ; perforated copper shelves are used to support the basins, &c, containing the substances to be dried. The heating is chiefly done by conduction from the sides of the bath through the shelves ; a current of hot air, approach- ing in temperature to that of boiling water, is always passing through the bath, and rapidly removes the vapour. The condenser is supplied with cold water, and prevents loss ANALYSIS OF MILK. of water. It conduces greatly to the efficiency of the bath to use distilled water, as no scale is produced on the coils and sides of the oven. To prevent loss of heat the oven may be lagged with felt, asbestos, or kieselguhr. The most efficient condenser has been found to be a spiral coil of tubing (preferably copper), which fits rather closely into a tube. The cold water enters at the top, and passes by a straight portion of the tubing to the lowest coil, whence it circulates upwards, and finds an exit at the top. A diagrammatic figure of the bath will assist comprehension of the details (Fig. 2). Fig. 2. — Diagrammatic View of Air kit h. A very convenient water-bath for milk analysis is that devised by Vieth ; the chief advantage of this lies in the lid, which, instead of merely having holes made in it in which the basins lit. has a copper ring fastened into each. This enables ESTIMATION OP ASH. 73 the basins to be taken off without contact between the fingers and the hot lid. This bath may be heated by a steam coil or a gas flame, and is conveniently supplied with water by a constant level apparatus. If dry steam is available it is very convenient to use steam coils to heat the bath, and to condense the steam after it has passed the coils. The condensed steam can be used as distilled water, and is usually pure enough for all purposes. It is liable, however, to contain traces of copper, if this metal is employed in the construction of the coils, condenser, ut carbon is dissolved. The whole is transferred to a 100 c.c. flask, the bulk not being allowed to get above 50 to 60 c.c, and half a gramme of dry calcium chloride added. To this mixture a few drops of phenol-phthalein solution arc added, (hen a 1<> per cent, solution of caustic soda, till a permanent pink colour is perceptible, and, finally, 25 c.c. of lime water. In this way all the phosphoric acid is precipitated as calcium phosphate. The mixture is made up to 100 c.c, mixed, and filtered through a dry filter. To 50 c.c. of the* filtrate (=50 c.c. milk) normal sulphuric acid is added till the pink colour is gone, then a few drops of methyl orange, and the addition of acid continued until the yellow is just N changed to pink. - caustic soda solution is added till the liquid assumes a yellow tinge, excess of* soda being avoided. At this stage all acids likely to be present exist as salts neutral to ESTIMATION OF MILK-SUGAR — BY ALCOHOL. I I phenol-phthalein, except boric acid and a little carbonic acid, which last is expelled by a few minutes boiling. The solution is cooled, a little more phenol-phthalein added, and as much glycerin as will give at least 30 per cent, of that substance in N the final solution, and titrated with — caustic soda till a perma- 5 nent pink colour is produced. Each c.c. of — caustic soda solu- tion is equal to "0124 gramme crystallised boric acid or -0070 gramme boric anhydride. Phosphoric acid can be separated from boric acid by precipi- tation as calcium phosphate, if not more than *2 per cent, of crystallised boric acid be present. As excessive heating is apt to drive off boric acid, it is neces- sary to carry the charring so far only as will give a colourless solution. Estimation of Citric Acid in Milk.— The proteids are precipitated by acid mercuric nitrate (p. 78) and a measured volume of the clear filtrate exactly neutralised with dilute caustic soda solution, using phenol-phthalein as indicator. A white precipitate of mercury and calcium phosphate and citrate is thrown down, collected on a filter and washed with water ; it is removed from the filter, suspended in water, and a little dilute hydrochloric acid added ; sulphuretted hydrogen is passed through to precipitate the mercury as mercuric sulphide. After filtration, the solution is boiled to remove sulphuretted hydrogen, a little calcium chloride added, and cooled. It is then carefully neutralised, phenol-phthalein being used as indicator; the preci- pitate of calcium phosphate is filtered off, and the solution boiled and concentrated to a small bulk ; the calcium citrate is thus precipitated. This should be washed with boiling water, collected on a small filter and ignited. To the ignited residue an excess of standard hydrochloric acid is added and the excess titrated back with standard alkali, methyl orange being the best indicator. N Each cubic centimetre of hydrochloric acid used represents •006-1 gramme of citric acid. The result must be corrected for the volume of the fat and proteids thrown down as directed under milk-sugar. Estimation Of Milk-Sugar.— Milk-sugar is generally esti- mated indirectly, as it is not possible to isolate it quantitatively from milk in a state of purity. The following method may, however, be used to obtain an approximate determination of the milk-sugar : — By Alcohol. — To 10 c.c. of milk add 20 c.c. of 90 per cent, alcohol, well mix and filter; of the filtrate take 10 or 15 c.c, evaporate to dryness on a water-bath and dry at 100°O. (212°F.) 76 ANALYSIS OF MILK. till the weight is constant. Ignite the residue and weigh the ash. The weight of the residue less the weight of the ash will give the weight of the milk-sugar. The volume of the aqueous portion must be calculated ; on mixing alcohol and water a con- traction takes place ; this with the quantities given is *4 c.c. ; the volume occupied by the proteids is on the average 25 c.c. ; the volume of the fat is obtained by multiplying the percentage by weight by "111. The percentage of milk-sugar is obtained by the following formula : — ,. 30 -(-65 + -111 *)«,.... 1 M = x (R -A) x 10 x — where .;■ = number of c.c. taken for estimation of residue. I) = specific gravity of milk. Y = percentage of fat in milk. R = weight of residue. A = ,, ash. M = percentage of milk -sugar. This method has a tendency to yield too high results. By the Polariscope. — The quickest method of milk-sugar estimation is by the polariscope ; before the milk can be polar- ised it is necessary to completely remove the fat and albuminoids, which interfere either by making the solution too opaque for reading or by polarising to the left. Wiley's Method. — The investigations of Wiley have shown that mercury compounds are the most efficient for this purpose, of which "acid mercuric nitrate" is the most convenient This is prepared as follows : — Mercury is dissolved in twice its weight of nitric acid of speci6c gravity 1 "42, and, after solution, an equal bulk of water is added. Basic lead acetate has also been used to remove fat and proteids, but Wiley has proved that the results are not accurate, owing to the incomplete removal of proteids. Still more inaccurate is the use of acetic acid, followed by boiling, which has been recently recommended by Mlyth. Wiley-Ewell Method. — Wiley and Ewell give the following method as the best for estimating milk-sugar by the polariscope : — They used a Schmidt & Qsensch polarimeter, with which 200 millimetres of a solution of 32'91 grammes of milk-sugar in 100 c.c. read l"" divisions of the scale. They take 65*82 grammes of milk, add 10 <■.<•. of acid mercuric nitrate solution (in this case the solution of mercury in nitric acid is diluted with 5 volumes of water), and dilute to 100 c.c. A similar quantity of milk is taken, 10 c.c. of acid mercuric nitrate added and diluted to 200 >■■'•. Each of these solutions La well mixed, filtered, and rised in a 1("» mm. tube. Calling the reading <>f* the solution obtained from 100 c.c. x, WILEY-EWELL METHOD. 79 and that obtained from 200 c.c. y, the true percentage of milk- x y sugar is — r. 8 Ux - y) The double dilution does away with any correction for the volume of the precipitated fat and proteids. The rationale of the process lies in the fact, that while the percentage of milk- sugar and the volume of the precipitate are constant, the total volume varies. Let m be the percentage of milk-sugar, and v the volume of precipitate ; then x = 4m x ,„ (1) 100 -v and y = 2m x (2) 8m2 x 200 -v 100 x 200 Now xy _ ( 100 -K) (200-t;) 1^T^) =~ a{ Am* 10° -2mx 20° ^ \4mXlW^ -mX200^"J 8m2 x 100 x 200 ~4(4m x (200 -v) x 100 -2m x (100 -v) x 200) 8m2 x 100 x 200 4(4m x 100 x 200 - 2m x 100 x 200 - 4m x lOOu + 2m x 200y) 8m2 8m The volume may be calculated thus : — From (1) we see that 100-, imxJ°° x ir>rk 4m x 100 or v = 100 ioo -fr1? y x 100 = 100- x-y _ 10Qj;-200y x-y which may be similarly deduced from (2). This method not only allows of an accurate estimation of milk-sugar to be made in milk without correction of any kind, but enables the volume of the precipitate of fat and proteids to be calculated. The author, in conjunction with Boseley, has shown that the experimental error of Wiley and Ewell's method is, however, very appreciable ; and, though correct in principle, it is not so accurate in practice as originally claimed. 80 ANALYSIS OF MILK. The greatest delicacy of Wiley and Ewell's method — i.e , the point at which the influence of unavoidable errors in reading is least — is obtained when the volume of water added to the more dilute solution is equal to the volume of the milk taken, less that of the fat and precipitated proteids. Vieth Method. — Vieth, when using the small Mitscherlich half-shadow polaiiscope made by Schmidt and Eisenach, prefers to add the stronger mercuric nitrate solution, described above, direct to the milk, and to polarise the resulting filtrate. He finds the volume of precipitated proteids from 100 c.c. of milk to amount on the average to 3 c.c, and, consequently, adds 3 c.c. of acid mercuric nitrate solution to allow for this. The method is carried out as follows : — Measure 50 c.c. of milk into a small flask, add 1*5 c.c. of acid mercuric nitrate, and well mix by shaking violently ; pour the mixture on to a filter, and fill a polarimeter tube with the filtrate; polarise, and correct the reading for that obtained in a blank reading — i.e., by reading a tube filled with water. As the [a] of milk-sugar is 52-5°, the reading, if in angular degrees, can be converted into percentages of milk-sugar by the following formula — 100 x 100 m= 525 x/Xn Where m = number of grammes of milk-sugar per 100 c.c. of solution polarised. / = length of tube in millimetres. r = reading in angular degrees. If a tube of 198-4 millimetres be used (these tubes are sup- plied with the instrument used by Vieth), the formula becomes If the length of the tube be 200 millimetres, the formula is The resulting figure representing milk-sugar in the solution polarised must be submitted to correction. The volume of the liquid from which the fat and proteids have been precipitated is the volume of the milk flu* thai of the mercuric nitrate minus that of the proteid precipitate and fat. As the volume of the mercuric nitrate was purposely made equal to thai of the proteids, both of I bese may be negleoted, one compensating for the other. Taking the volume of the milk as loo cc, the volume of fal in thia will be the percentage by weighl of fat multiplied by the specific gravity of the milk, divided by the specific gravity of the fat. RICHMOND-BOSELEY METHOD. 81 The milk sugar may be either calculated as hydrated or anhydrous sugar ; it is usual to calculate it in milk analysis as anhydrous sugar. The following formula expresses the percentage of anhydrous milk-sugar in the milk : — , , "O"^ 1 „ '" = 1-042 * -100— *dX'9"' m1 = percentage of anhydrous milk-sugar by weight, r = reading, F = percentage of fat by weight, d = specific gravity of milk. For the expression — --- it is usually exact enough to employ the expression F x 1*11. As an example let us suppose that r = 5*5° F = 4-l d = 1 -032 5*5 1 ml = , - .- x '9545 x - ^ x 95 = 4-58 per cent. 1 '042 1 '0.5- Vieth states that when cream is analysed by this method, it is necessary to dilute with an equal bulk of water, the results being of course doubled. Richmond-Boseley Method. — The author, in conjunction with Boseley, has shown that the calculation necessary in Vieth's method can be eliminated by adding to 100 c.c. of milk (a) A quantity of water in c.c. equal to ^ degree of specific gravity. (b) „ „ „ „ the fat x 1-11. (c) ,, ,, ,, to reduce scale readings to percentages of milk-sugar. (d) 3 c.c. of acid mercuric nitrate. The percentage of milk-sugar can be read off' directly in scale readings. The values of c are : — For polariscopes reading angular degrees — With 198-4 mm. tube, 10-0 c.c. „ 200 „ 1085 „ ,, 500 ,, 10-85 ,, (divide readings by 2-5). For the Laurent sugar scale (100°= 21-67 angular degrees) — With 200 mm. tube, 2-33 c.c. (divide readings by 5). „ 400 „ 2-33 „ ( „ „ 10). „ 500 „ 2-33 „ ( „ „ 12-5) For the Ventzke scale (100°= 34-G4 angular degrees) — With 200 mm. tube, 6'65 c.c. (divide readings by 3). „ 400 ,, 6-G5 ,, ( ., „ 6). „ 500 „ 6-65 „ ( „ „ 7-5). 82 ANALYSIS OF MILK. Deniges' Method. — Deniges objects to the use of mercuric nitrate because it necessitates the use of a glass polarimeter tube, brass being attacked by the solution, and prefers the use «>f meta-phosphoric acid to precipitate the proteids. His method is as follows: — Prepare sodium meta-phosphate by carefully heating sodium-ammonium-hydrogen phosphate (microcosmic salt) in a platinum dish, till it is completely fused and no longer evolves gas. Pour on a cool plate, break up, and preserve in a stoppered bottle. Prepare a 5 per cent, aqueous solution by boiling 5*7 grammes of the finely powdered salt with 50 c c. of water for five minutes, at the expiration of which time solution should be complete. Add immediately 50 c.c. of cold water, cool under a jet of water, and make up to 100 c.c. Twelve per cent, of the meta-phosphate is converted into ortho-phosphate by the boiling, and this is allowed for by taking 5'7 grammes instead of 5 grammes. Add 25 c.c. of this freshly prepared solution to 10 c.c. of milk, then 60 c.c. of water, and 3 c.c. of acetic acid ; make up to 100 c.c. and filter ; after rejecting the first few drops, fill a polarisation tube with the filtrate. A 500 mm. tube is to be used, if possible, in preference to one of less length. It is hardly necessary to make any correction for the volume of the precipitate on account of the great dilution. As only 10 c.c. of milk are taken and diluted to 100 c.c, a very good polariscope must be used if accuracy is required. Unless glass polarisation tubes are un- obtainable, the use of mercuric nitrate is preferable; an advantage of employing mercuric nitrate is that citric acid can be estimated in the same solution. Fehling's Solution Method. — Another method, which is largely employed for the estimation of milk-sugar, depends on the oxidation of the sugar by alkaline cupric solution, and the consequent reduction of the copper to the state of cuprous oxide. The alkaline cupric solution cannot be applied direct to milk, as the proteids are somewhat attacked by the alkaline solution. The solution usually employed is Fehling's cupric tartrate solution, which is prepared by dissolving 34*639 grammes of pure, crystallised copper sulphate in water, and diluting to 500 c.c; 173 grammes of pure sodium-potassium tartrate (Rochelle salt), and 51 to 55 grammes of sodium hydroxide of good quality are also dissolved in water and made up to 500 c.c. Equal parts of these solutions are mixed (preferably al the time of making the test) to form Fehling's solution. It is convenient to use a 50 per cent, solution of caustic soda solution, which has been filtered clear through asbestos, for making the alkaline tartrate solution* The percentage ol Bodium hydroxide is esti- mated in this b\ titration, and suofa a quantity is weighed out ill give 51 grammes. Most of the impurities in ordinary o'sullivan's method. 83 caustic soda are insoluble in a 50 per cent, solution, so that this affords a ready means of purification. Before estimating the milk-sugar in milk, the fat and proteids must be removed; this maybe accomplished by the following methods : — (i) By diluting 10 c.c. of milk to about 100 c.c, adding I'O c.c. of 10 percent, acetic acid solution and boiling; after cooling, the whole is made up to 100 c.c. (Citric acid may be substituted for acetic acid.) (2) Add to 25 c.c. of milk about 200 c.c. of water and 10 c.c. of copper sulphate solution, as above ; carefully neutralise with dilute caustic alkali solution, and make up to 250 c.c. This solution contains a small amount of copper. (3) Carefully neutralise 10 c.c. of the filtrate from the milk which has been treated with acid mercuric nitrate with caustic alkali till exactly neutral to phenolphthalein, filter, and pass sulphuretted hydrogen through the nitrate ; filter, to separate the precipitated mercuric sulphides, and boil the filtrate to expel sulphuretted hydrogen. Make up to 100 c.c. (The mercury may be precipitated by ph sphoric acid ; add a small quantity of phosphoric acid or a soluble phosphate to the filtrate from mercuric nitrate ; exactly neutralise, filter and wash the pre- cipitate, and make up to 100 c.c ) (4) Deniges' method, as above described. Each of the methods of separating the fat and proteids gives a solution, of which 50 c.c. contains the milk-sugar in 5 c.c. of milk, which, in a normal milk, contains about ^ gramme of milk-sugar. The following modes of manipulation are among those in use: — (1) 0 'Sullivan's Method. — Measure 50 c.c. of the filtrate into a beaker, and place this in a briskly-boiling water bath ; dilute a mixture of 30 c.c. of the copper solution, and 30 c.c. of the alkaline tartrate solution, with about twice its volume of water, and boil over a flame. When the milk-sugar solution has attained the temperature of the water-bath, pour into it the Folding's solution, and keep on the water-bath for 13 to 15 minutes. Filter through a small filter, or, preferably, through a Cooch crucible, leaving the cuprous oxide as much as possible in the beaker ; immediately the last drops of solution have been poured on the filter, pour boiling tveU-boiled water on the preci- pitate, and wash several times by decantation. Finally, transfer the precipitate to the filter, and wash well with boiling water. If a filter is used, transfer it to a small crucible, and ignite over a very small flame till the filter is thoroughly charred, and then gradually increase the flame till the highest available tempera- ture is obtained. It is better to use a porcelain crucible than a platinum one, because platinum is permeable to reducing gases from the flame, and complete oxidation cannot be obtained. If 84 ANALYSIS OF MILK. a Gooch crucible is used it should be ignited in a muffle, and the cuprous oxide thus converted into cupric oxide. The weight of the cupric oxide multiplied by -6024 will give the weight of hydrated milk-sugar. If a filter is used, the weight of the ash must, of course, be deducted ; this should be obtained by igniting filters of the same kind, which have been treated in exactly the same manner as in the estimation of milk-sugar, using the same quantity of Fehling's solution, but omitting the milk-sugar. This is necessary, because the filter takes up mineral matter from the Fehling's solution. If this precaution is taken, filtra- tion through paper is satisfactory. The author finds it far more satisfactory, instead of employing an arbitrary factor, which is not of absolute exactitude, to weigh out a quantity of pure milk-sugar, approximating as nearly as possible to that contained in the solution to be tested, and to estimate the copper oxide obtained by treating it side by side with the actual estimation. The extra trouble is nominal, and the slight variations in the factor, due to dilution, &c,, are thereby compensated. (2) Wein's Method. — The same quantities of solutions are used, but the Fehling's solution, instead of being diluted with water, is mixed directly with the milk-sugar solution, placed over a naked flame, and raised as rapidly as possible to boiling; boiling is continued for exactly four minutes. The solution is filtered through a tube about 1 cm. wide, constricted at the end, and plugged with asbestos. This tube is weighed, after having been gently ignited, and the filtration is hastened by means of a water pump ; a small funnel is used to pour the solution into the tube. The precipitate of cuprous oxide is washed with boil- ing well-boiled water, and transferred to the tube When the precipitate is well washed, the tube is sucked as dry as possible by the pump. It is then detached from the filter pump, and connected with a hydrogen apparatus, being clamped in a hori- zontal position. A gentle current of hydrogen is passed through, and the tube cautiously heated by a small name till all the cuprous oxide is reduced to metallic copper, and the tube is dry ; it is allowed to cool while the -hydrogen is passed slowly through, and weighed. The increase of weight gives the amount of copper reduced. Table X. should be used to calculate the amount of hydrated milk-sugar from the copper. The table IS used as follows: — Look up in the table the weight of copper /expressed in milligrammes) nearest to the weight obtained, and calculate from this, by a proportion sum, the corresponding weight of milk-sugar. Thus, it the weight of copper is 334*1 milligrammes, take the Weight of milk-SUgar corresponding to 335 milligrammes. . 261*6 .-. 3841 =2616 ■ 'l^'i 2609. VOLUMETRIC METHOD. 85 By taking a weight of milk-sugar as nearly as possible equal to that in the solution, and estimating the copper reduced by this, the calculation can be made in a similar manner from this. The cuprous oxide may be reduced in a Gooch crucible by placing it in a muffle, and passing in a current of hydrogen. TABLE X. — For Calculating the Amount of Milk-Sugar from the Quantities of Copper Reduced. This table is due to Wein. Copper. Milk-Sugar. 1 | Copper. | Milk-Sugar. Copper. Milk-Sugar. 120 86-4 215 158 2 310 •232-2 125 90-1 220 1619 315 236-1 130 93 8 225 165 7 320 240-0 135 97-6 230 169-4 325 243-9 140 1013 235 173-1 330 247 7 145 105-1 240 176-9 335 251-6 150 108-8 245 180-8 340 255-7 155 112-6 250 184-8 345 259-8 160 116-4 255 188-7 350 263-9 165 120 2 260 192-5 355 268-0 170 123 9 265 196 4 360 272-1 175 127-8 270 200-3 365 276-2 180 131-6 275 204-3 370 280-5 185 135 4 280 208-3 375 284-8 190 139 3 285 212-3 380 289 1 195 143 1 290 216-3 385 293-4 200 146-9 295 220 3 390 297-7 205 150-7 300 224-4 395 302-0 210 154-5 305 228-3 400 306-3 Volumetric Method. — Instead of weighing the copper reduced, the determination may be made volumetrically. The estimation is carried out as follows : — Place the solution obtained by removing the proteids by Methods 1, 3, or 4 (given above) in a burette graduated to ■£$ c.c. Place in a small flask 10 c.c. of Fehling's solution accurately measured (or 5 c.c. of each of the copper and alkaline tartrate solutions), diluted with 30 c.c. of water, and bring this to the boil by means of a small flame. Run in the sugar solution, adding 2 c.c. at a time, and boiling between each addition. When the blue colour of the liquid has nearly disappeared the sugar solution should be added in smaller amounts, but the titration should not be unduly pro- longed. The end of the reaction is reached when, on removing the flame, and allowing the cuprous oxide to settle, the super- natant liquid appears colourless or faintly yellow when viewed against a white surface. To make sure that the copper is all reduced a few drops of the liquid may be filtered through a small filter into acetic acid, and potassium ferrocyanide added. 86 ANALYSIS OF MILK. If copper be still present, a brown coloration will be observed. It is advisable to repeat the titration, using -2 c.c. less of the milk-sugar solution, which may be all added at once, and the boiling continued for four minutes ; a small excess of copper should be present, and this is reduced by small additions of the sugar solution. Should no copper be present, the experiment must be repeated, using a still smaller amount of liquid. Ten c.c. of Fehling's solution is reduced by -0676 gramme of hydrated milk-sugar; this quantity is, therefore, contained in the volume of sugar solution used for titration. For example, 10260 grammes of milk were, after removal ot proteids, made up to 100 c.c. Ten c.c. of Fehling's solution required 13-0 and 13d c.c. of this in two experiments, mean 13-05 c.c; therefore, l.'i-Oo c.c. contain 'OGTo gramme milk-sugar. and 100 c.c. contain "518 ,, 10-260 grammes milk contain -518 ,, = 5-05 per cent, hydrated milk-sugar. = 4 '80 per cent, anhydrous milk-sugar. It is advisable to titrate a solution of pure milk-sugar con- taining about -5 gramme per 100 c.c. to obtain the exact value of 10 c.c. of Fehling's solution. Pavy's Solution Method. — Pavy's ammoniacal cupric solu- tion may be substituted for Fehling's solution. This is prepared by mixing 120 c.c. of Fehling's solution, 400 c.c. of 12 per cent, caustic soda solution, and 300 c.c. of strong ammonia (specific gravity -880), and diluting the whole to a litre. One hundred c.c. of this solution are placed in a small Hask, which is closed by an india-rubber stopper with two holes ; through one passes the nozzle of a Mohr's burette, and through the other a bent tube, which dips into a Hask containing cold water to absorb the ammonia given off. Hydrogen or coal gas may be passed through the flask containing the Pavy solution. The solution is brought to boiling, and the sugar solution run in gradually, till the blue colour of the liquid is destroyed, the boiling being maintained the whole time, and the sugar solution run i t i slowly towards the end. As the reaction takes place somewhat slowly, boiling musl be continued for a few minutes before it can be finally decided that the blue colour is permanent. It is necessary to repeat the titration, adding a little less of the solution, as with Fehling's solution. This may be advan- tageously added all at once, and the boiling continued for five minutes. If the boiling be unduly prolonged, the ammonia may be boiled oil', ami cuprous oxide will then begin to deposit ; in order to avoid this, Shenstone places a tapped funnel in the cork, by meanfl of which an addition of strong ammonia can be made if necessary. ESTIMATION OF CANE SUGAR IN MILK. 87 Stokes and Bodmer strongly recommend this method, and state that the reducing power of milk-sugar is 52 per cent, of that of glucose- — i.e., 100 c.c. of Pavy solution = "0961 gramme of milk-sugar. It is advisable to standardise the Pavy's solution on a solution of pure milk-sugar containing -5 gramme per 100 c.c. Hehner has shown that by varying the proportion of salts in solution, such as alkaline tartrates and carbonates, the accuracy of the results is affected ; by standardising the solution at the time of using with a solution of pure milk-sugar, the results are, however, reliable enough for estimating the milk-sugar in milk. Allen has modified the procedure by placing a layer of petro- leum over the Pavy solution, and dispensing with the cork. This enables an ordinary burette, or even pipette, to be used. Estimation of Cane Sugar in Milk.— Cane sugar is some- times added as an adulterant of milk, but the determination is more often required in the case of condensed milks. An approximate estimation may be made by estimating the sugar by precipitation with alcohol, and the milk-sugar by Fehling or Pavy solution ; the difference between the two will not be far from the cane sugar. Muter Method. — Muter estimates as follows: 10 grammes of milk are evaporated to dryness on 4 grammes of hydrated calcium sulphate with frequent stirring, so that nothing sticks to the basin. The dry residue is powdered, placed in a dried filter, and extracted with ether in a Soxhlet apparatus. The residue, together with the filter, is transferred to a beaker, 20 c.c. of hot (not boiling) water added, and the whole well stirred ; 30 c.c. of rectified spirit (60° overproof, sp. gr. '820) are then added, and the mixture allowed to cool, stirring occa- sionally. When cool it is thrown on a filter and washed with proof spirit till the filtrate measures 120 c.c. 60 c.c. are evapor- ated in a dish on the water-bath and the residue weighed; the residue is then ignited and the ash weighed, the weight of the residue less that of the ash being the total sugar. In the other 60 c.c, the milk-sugar is estimated by Fehling's or Pavy's solu- tion ; the difference between this and the total sugar is cane sugar. A deduction shoidd be made from this of '5 per cent, when the difference is '5 or under, -2 „ ,, ,, -5 to 1-0, •1 ,, ,, ,, 1-0 to 1-5, and none per cent, if the difference exceeds 2*0. This method is stated to give fair results with percentages of cane sugar exceeding a half per cent. The cane sugar may also be estimated by determining the total polarisation of the sample as directed for milk-sugar, and by estimating the milk-sugar gravimetrically or volumetrically by Pavy's or Fehling's solution. The difference between the 88 ANALYSIS OF MILK. percentage of anhydrous milk-sugar found by reduction of copper and that deduced from the polarisation divided by 1*217 will give the percentage of cane sugar. This method yields excellent results with mixtures of fresh milk and cane sugar, and with many samples of sweetened condensed milks, but is apt to lead to figures below the truth, if the milk has been much heated, owing to the reduction in the rotatory power of milk-sugar under these conditions. Stokes-Bodmer Method. — Stokes and Bodmer prefer to esti- mate the milk-sugar by titration with Pavy's solution (Feh ling's solution can be substituted for this), to invert the cane sugar by boiling with 2 per cent, of citric acid for ten minutes, and then to estimate the combined milk-sugar and resulting mixture of glucose and fructose by titration ; the difference between the two figures will be due to the products of hydrolysis of cane sugar. In this case it is advisable to standardise the solution on a mixture of milk-sugar and inverted cane sugar in about the same proportions as found in the milk. The determinations may also be made gravimetrically. By Invertase. — The best method of estimating cane sugar depends on the hydrolysis of cane sugar by invertase, the enzyme of yeast. This is carried out as follows : — Estimate the rotation due to milk and cane sugar by polarisation of the solu- tion obtained by precipitation with mercuric nitrate (100 c.c. of milk should be taken). 25 c.c. of the solution are placed in a flask, a drop or two of phenol-phthalein added, and dilute caustic soda solution run in till neutral. This solution is filtered into a 50 c.c. flask, and the precipitate washed with water till the filtrate and washings measure about -15 c.c. -05 gramme of invertase, or 1 gramme of yeast, is added, together with a drop of acetic acid and a few drops of toluene, and the whole made up to 50 c.c. The flask is corked and allowed to remain at about 55° (131° F.) for five hours. A little alumina cream is added and the whole made up to 55 c.c, Altered, and polarised ; the temperature at which the solution is polarised should be noted. The reading should be multiplied by — = 2*2 j the reading due to cane sugar is found by the formula iimi (i; i:;) s — 142-66 ., R = rotation due to sucrose. K, = ., before inversion. I!„ = ., after inversion corrected by multiplying by 2*2. 1 = temperature in degrees Centigrade. Tin- percentage of cane sugar is calculated from the rotation deduced from this formula by the method given for milk-sugar, DETECTION AND ESTIMATION OF STARCH IN MILK. 89 bearing in mind that the [a]D of cane sugar is 66*5° instead of 52'5°, and that it does not require to be converted into anhydrous sugar. Other Methods. — An approximation to the percentage of cane sugar can be obtained by determining the total polarisation, and deducing the milk-sugar by multiplying the ash by 6*5. This method serves for controlling the preparation of condensed milk, but is of course of only approximate accuracy. Another method, which gives fair approximate results, is to calculate the solids not lat (a) from the specific gravity and per- centage of fat, (b) from the percentage of ash by multiplying by 12. The cane sugar will be represented by a — b. Cotton's Method of Detecting Cane Sugar. — Cotton gives the following test for cane sugar in milk : — 10 c.c. of the milk are mixed with *5 gramme of powdered ammonium molybdate and 10 c.c. of dilute hydrochloric acid (1 : 10). In a second tube 10 c.c. of milk of known purity, or 10 c.c. of a 6 per cent, solu- tion of lactose, are similarly treated. The two tubes are placed in the water-bath and the temperature gi'adually raised. At about 80° C. the milk, if adulterated with saccharose, assumes an intense blue colour, whilst the genuine milk, or solution of lactose, remains practically unaltered. On boiling, these also turn blue, but to a less extent than the adulterated milk. This test will detect •! per cent, of cane sugar, but if this substance be added to milk, larger quantities are almost inva- riably added. Detection and Estimation of Starch in Milk.— Starch is occasionally added to milk as an adulterant, and can be detected by the blue colour given by iodine; the iodine test is best applied to the whey, as the proteids of milk somewhat interfere. Starch cannot be estimated with any great exactitude, as it becomes partly converted into other bodies in milk, either by means of an enzyme or by micro-organisms. To estimate it, the milk should be raised to boiling and cooled; the milk-sugar should be estimated by one of the gravimetric methods given above, preferably by that of Wein. 20 c.c. of milk should be diluted to about 95 c.c, 3 c.c. of 10 per cent, acetic acid added, and the whole warmed to about 80° C, cooled and made up to 100 c.c. 50 c.c. of the filtrate should be carefully neutralised, and warmed to 65° C. (150° F.) ; 2 c.c. of a diastase solution (containing the diastase from 2 grammes of malt) should be added, and the solution kept at 65° C. for two hours. At the expiration of that time it should be raised to boiling and evapor- ated on the Avater-bath to less than 25 c.c. ; a little alumina cream should be added, if the solution be not clear, and the total made up to 25 c.c. This should be filtered and polarised. The VO ANALYSIS OF MILK. copper reduced by 10 c.c. of this solution should be estimated by Wein's method. The results should be calculated as follows : — Multiply the polarisation by 2b; the result will be the polarisation due to milk-sugar, maltose, and dextrin ; calculate, from this and the determination of milk-sugar, the polarisation due to maltose and dextrin. Calculate the copper reduced from the 10 c.c. of diluted filtrate = 4 c.c. of milk by the table on p. So, and subtract from this the milk-sugar present in this as calculated from the first estimation ; the difference multiplied by 1*2 will represent maltose. The polarisation due to maltose can be calculated, using the value 137° for the [a]u, and the difference will be due to dextrin. From this the percentage of dextrin can be calcu- lated, using the value for [a]u of 200°. The percentage of dextrin plus that of the maltose divided by 1*056 will give that of the starch. An approximate estimation may be made by subtracting from the solids not fat the ash multiplied by 12. The estimation of starch is unsatisfactory, even if no other foreign sugar be present ; if other sugars have also been added, it is nearly impossible to estimate them. The Estimation Of Fat.— More attention has perhaps been paid to the estimation of fat in milk than of any other consti- tuent. The methods are very numerous, and may conveniently be divided into three classes : — (1) Gravimetric methods, in which the fat is separated from the milk by a suitable solvent, and weighed after evaporation of the solvent. (2) Volumetric methods, in which the fat is separated from the milk by suitable means, and its volume measured. (?) i Indirect methods, in which the amount of fat is deduced from the determination of some physical property. Of these methods the gravimetric methods are undoubtedly the most accurate, though they are all to a certain extent tedious and not capable of use by unskilled persons. The solvent chiefly used for extracting the fat is ether, which Lb convenienl on account of the low boiling point and heat of volatilisation, its great solvent power for fat, and its comparative greal miscibility with water, which renders it unnecessary bo have the milk solids in a state of absolute dryness. Petroleum ether, chloroform, carl Lisulphide, benzene, carbon tetrachloride, and amy] alcohol have also been used, but, though they give the same results, are n t jo convenient. (1) Gravimetric Methods. The leading gravimetric methods are discussed in the folio* pages ; on the whole the Adams method is the best, though I GRAVIMETRIC METHODS. 91 due to Storch, Werner-Schmidt, and Bell are little, if at all, inferior in accuracy. The Adams Method. — Dr. M. A. Adams, Public Analyst for Kent, was led to devise this method from his observation that when milk was dropped on blotting-paper, it spread out to a much greater extent than was possible in a basin, flask, or even on a flat surface of glass ; he was of opinion that extraction of fat by ether would be much more complete. As originally designed, the method was as follows : — Strips of white blotting-paper, " mill 428," 2^- inches wide by 22 inches long, were coiled up loosely and held by having a brass ring slipped over them. These were dried at 100° C. to constant weight, the weighings being performed in a weighing bottle to prevent absorption of moisture from the atmosphere. 5 c.c. of milk was pipetted out into a small beaker and the weight noted ; one of the coils was dropped in and the milk absorbed as com- pletely as possible by the blotting-paper. When absorption was complete, the coil was carefully removed and stood, dry end downwards, on a glass plate, the beaker being again weighed and the quantity of milk taken up by the coil found from the difference of the two weights. The coil was transferred to a drying oven at 100° C, and left therein till it ceased to lose weight. The original method was thus available for the deter- mination of total solids as well as of fat. The dry coil was placed in a Soxhlet extractor, and the fat separated from the solids not fat by ether. The total extract, after evaporation of the ether and drying at 100° C, was regarded as fat. Allen and Chattaway modified this method by rolling up a piece of string with the coil, so that the layers of paper were kept from touching each other ; they also wrapped a piece of filter paper around it, in order that no milk might escape when a weighed quantity was poured thereon. Thompson also modified it by hanging up a strip by one end and running the milk on to it from a pipette, afterwards noting the weight of milk delivered by the pipette. He preferred to use filter paper instead of the blotting-paper recommended by Adams. Vieth, immediately after the publication of the method, sub- jected it to an exhaustive test, and criticised it somewhat severely. He showed that blotting-paper contained matter soluble in ether, and that, as Adams had ignored this, the fat estimations made by Adams were too high ; he also showed that the substance in filter paper soluble in ether was extracted with comparative slowness by this solvent. Faber later showed the same thing. Notwithstanding these criticisms, the Milk Committee ap- pointed by the Society of Public Analysts recommended its adoption by their members ; it was indeed recommended that the papers should be previously extracted, but nothing was said 92 ANALYSIS OF MILK. of the difficulty of completely removing the matter soluble in ether, it being implied that twelve siphonings were sufficient to effect this. The recommendation of the Milk Committee was adopted at a General Meeting of the Society, and it thus became a quasi-official method. The use of this method for determining total solids was abandoned. Notwithstanding the recommendation of the Milk Committee that the coils should be extracted previously to use, it became the general practice to omit this, and to use unextracted coils, making a deduction, from the weight of total extract, of the weight of the extract obtained from a coil when extracted alone for the same length of time. The author showed that this last modification was not free from error ; the matter soluble in ether was found chiefly to consist of a calcium salt of resinous acids, which was only of limited solubility in ether; the acids themselves were much more soluble, and when these were liberated by acids — even the small amount of acid found in milk — a greater extract was obtained in a given time. As the time usually allowed for extraction (1| hours) was not sufficient to remove the whole of the soluble matter from the blotting-paper — as much as ten hours being necessary — it followed that the matter extracted by ether from the coil was greater when a milk (containing small amounts of acid) was placed on a coil than when the coil was extracted alone. The difference was represented by the amount of resinous acids equivalent to the acidity of the milk, and was naturally not constant. He found that alcohol completely extracted the coils — a fact also noted almost simultaneously by Soxhlet — but preferred the use of alcohol containing 10 per cent, of acetic acid. Ether containing acetic acid was also efficacious. As the result of Soxhlet's researches, Schleicher and Schiill placed a " fat-free " paper on the market, and this is very generally employed. W a Her and Liebermann objected to the use of ether as a solvent for fat, on the ground that other substances contained in milk were soluble in this menstruum. The author has found, however, that, provided the coil is well dried previous to extraction, chloroform, benzene, and petroleum ether give the same results as anhydrous ether; ordinary ether, which contains small amounts of water and alcohol, gives, however, slight I v higher results, especially if the coils are allowed merely to air- dry. The error introduced by the use of ordinary ether is small, and is very frequently neglected. Schleicher and Schiill's "fat-free" paper gives a small ether extract consisting chiefly <>!' loose fibres ; this does not. as a rule, exceed 2 milligrammes, a Weighl which may in many cases be neglected as within the limits of experimental error. GRAVIMETRIC METHODS. 93 Attempts have been made to substitute other substances for the blotting-paper; Abraham, indeed, before Adams published his method, had used "Parker's fibre liut.:' Wiley, and also Johnstone, tried asbestos paper, but the results were not satis- factory. The action of the blotting-paper appears to be slightly different from that supposed by Adams. Undoubtedly he was correct in supposing that the milk was spread out over a large surface ; the author's experiments showed that when milk was filtered through blotting-paper the filtrate contained the solids not fat, but only a small amount of fat. This view was found by Yieth not to be entirely correct ; he found that a portion of the casein was also removed from the milk by blotting-paper. When milk is spread on blotting-paper the portion which soaks in consists of the whole of the water, milk-sugar, and salts, and a considerable proportion of the proteids, together with a small amount of fat ; the bulk of the fat, together with a proportion of the casein, is left on the surface, and is very easily extracted by the ether. The following mode of procedure is considered most correct by the author : — . Hang up a convenient number of strips of Schleicher and Schull's "fat-free" paper (or blotting-paper, from which the ether-soluble matter has been extracted by acid-alcohol or other means) from clamps (letter-clips are very serviceable). Pain on, from a pipette, 5 c.c. of each of the samples to be tested in a slow stream, so as to spread the milk well over the paper ; the strip should be held by its free end, so as to be nearly horizontal. The weight of the milk delivered by the pipette should be noted, care being taken that it is delivered into the weighing vessel at the same rate and in the same manner as it was run on to the paper. The papers are allowed to hang up till apparently dry ; flies must not be permitted to settle on the surface of the paper, as they consume portions of the fat. When the strips are dry enough to handle they should be rolled up in loose coils of a diameter such that they will easily go into the Soxhlet extractors (f to 1 inch), and these should be fastened either by a brass ring, a piece of cotton, or a small pin. A number, or other mark serving to identify the sample, should be placed on each, and a blank coil — i.e., one containing no milk — should also be rolled up. The coils should be dried at 100° C. for about an hour. A sufficient number of wide-necked flasks should be carefully cleaned, and allowed to stand for fifteen minutes inside the balance case. The lightest of these should be placed on the right-hand pan of the balance as a tare, and the others successively weighed against it, the weights required to produce equality being noted. The coils should be placed in the Soxhlet extractors, the flasks 94 ANALYSIS OF MILK. fitted, and a measured volume of dry ether, sufficient to fill the extractor well above the upper portion of the siphon, poured into each. The blank coil should be placed in a Soxhlet extractor, and extracted into the "tare." The Soxhlet ex- tractors are connected to upright condensers, and the ether made to boil by partially immersing the flasks in water at 50° to C0° C. Extraction should be continued for tive hours. The ether should be distilled off, and the flasks placed, side downwards, in a drying oven at 100° C. for about twenty minutes, being rotated, and air being blown in every five minutes to remove the vapour of ether. This time is sufficient to dry them if dry ether has been used. After cooling for fifteen minutes the flasks should be weighed, the "tare" being again placed on the right-hand pan of the balance, and the percentage of fat calculated from the increase of weight. The "tare" is used to correct for the small quantity of " extract " obtained from the paper, and to neutralise the effect of any change of weight of the flasks due to handling. The connection between the flasks and the extractors and between the extractors and condensers may be made by corks, provided they have been well extracted by ether. The tare and the drying of the coils may be omitted, and ordinary ether used in place of dry ether without greatly affecting the results. Dry ether is prepared by washing the commercial preparation with water, shaking the washed ether with calcium chloride, and, after allowing it to stand over calcium chloride for a day or two, distilling. Either sufficiently pure for most purposes may be obtained by distilling (from a water-bath not exceeding 40° C. in tempera- ture) the commercial product from a flask to which Glynsky's bulbs are fitted. The first fractions boiling below 34-3° 0. and the last boiling above 34 -8° C. should be rejected. The following figures show the amount of difference that may be expected between the two modes of procedure : — Percentage of Fat. Dry ether, &c, . .4*49 1-59 Ordinary el her, dec, 1-58 l -i;i Difference, . . . 09 02 •111 .« 3 09 3-42 3-05 4 21 •28 •jus 313 3-45 3-0fi 4-:u ■09 •07 hi •03 ■IS Tin- average difference is tunnel to be "06. The Bell Method (often called the Somerset House Method).— Dr. Jame Bell, when Principal of the [nland Revenue Laboratory at Somersel Bouse, on being appointed GRAVIMETRIC METHODS. 95 referee under the "Sale of Food and Drugs Act" devised this method for the estimation of fat and solids not fat in milk. His directions for the analysis of fresh milk (slightly abridged) are as follows : — 10 grammes of milk are weighed in a platinum capsule, 3 inches in diameter and 1 inch in depth, containing a glass stirrer. The capsule is placed on a water bath and its contents evaporated almost to dryness, the milk being well stirred during evaporation. The residue should be neither too moist nor too dry, as either condi- tion tends to prevent the complete extraction of the fat. When the proper point has been reached, the mass is treated repeatedly Avith ether, the stirrer being each time used to pulverise the solid matter which, in order to ensure that no portion escapes the action of the solvent, should assume a fine state of division. The ether is used warm for the last three treatments. After each washing the ethereal solution of the fat is carefully poured through a small filter. To remove the last traces of fat from the filter, the upper part is cut off, divided into small pieces, which are placed in the remaining portion of the filter in tlie funnel, and washed with a little ether. The filtrates are received into a tared beaker, from which the ether is gently evaporated, and the fatty residue finally dried in a water-oven till the weight is constant. The capsule containing the non-fatty residue is dried at 100° C. until a constant weight is arrived at. Though the directions are not very explicit the author has found no difficulty in working the method. Twelve portions of 25 c.c. each of ether are sufficient to completely extract the fat. A wide-mouthed flask may be conveniently substituted for the beaker directed to be used, and the ether may be distilled off after each two treatments, the distilled ether being used again. Though requiring a good deal of attention, the method is fairly rapid, two hours being sufficient for the estimation of fat. When the ether is poured upon the pasty residue, it becomes solid in a very short time, and can be easily pounded to a tine powder. This appears to be due to two causes — the coagulation of the casein, and the crystallisation of the milk-sugar ; as is pointed out in the chapter on Milk-Sugar (p. 11), the crystals have the composition of a mixture of hydrated and anhydrous milk-sugar in indefinite proportions, and, as hydrated milk-sugar does not lose its water of hydration at 100" C, it follows that the solids not fat obtained by this method contain a proportion of the milk-sugar in this modification. It follows, therefore, that the estimation of solids not fat is not very accurate, hence this method should not be employed if an exact determination of solids not fat be desired. The determination of fat has proved in the author's hands to be accurate, as is shown by the following 96 ANALYSIS OF MILK. figures of determinations of fat by the Bell and Adams methods respectively : — Fat. Bell, 42s 461 -19 2-69 3'13 3-45 3-00 803 4-16 ,, Adams. 4 29 4.39 -30 2'61 31)9 342 3H6 S21 421 This method is also applied to sour milk ; the portion taken for analysis should be first neutralised with decinormal sodium hydroxide solution (Bell does not say what indicator is to be used, but the author prefers delicate litmus paper*), and the evaporation should be carried rather further than in the case of fresh milk, Bell directing that the residue attain the condition of a firm paste. The analysis is otherwise conducted as directed for fresh milk. For each cubic centimetre of decinormal soda added, a deduction from the weight of the solids not fat should be made for the increase of weight due to the soda added. Contrary to Bell's statement the author has found that, if the milk be very sour, it is impossible to properly powder the residue, and in these cases the fat has a tendency to be lower than that found in the fresh milk. If the milk be not very sour a powdery residue can be obtained, and the fat estimated in the fresh milk and that determined in the sour milk show a satis- factory agreement. This is in accord with the view expressed above as to the cause of the solidification of the residue on the addition of ether ; if a considerable portion of the milk-sugar has been changed to lactic acid, which is converted into sodium lactate /a salt not easily crystallising) on the addition of soda, the crystallisation cannot take place. It is directed to dry the solids not fat to constant weight : this in the author's hands has proved impossible. An attempt was made to dry to such an extent that less than 1 milligramme per hour should be lost ; this may be interpreted in more than one sense, either that in the space of one hour less than 1 milli- gramme should be lost, or that in the space of (say) three hours less than 3 milligrammes should be lost. Such a trifling differ- ence of procedure led, however, to a difference of more than 1 per cent, in the weight of solids not fat. It is evident that to obtain anything like comparable results, a very rigid mode of procedure must be laid down ; as this has nut been done outside the Government Laboratory, the author can only consider Bell's method for the estimation of the solids not fat of sour milk valueless and unreliable. Tho Storch Method. — The essential point of this method consists in drying the milk on pumice (or other medium) and extracting with ether after finely grinding in a mortar. \ originally designed by Storch, 1(* grammes of milk were dried ;it 100* C. on about an equal weighl of pumice in pieces * The indicator used ie > matter "t some importance, as the results differ a liit it phenol phthalein be substituted tm litmu THE GRAVIMETRIC METHODS. 97 about the size of a small pea ; the pumice was ground in a mortar to a very fine powder, which was then transferred to a conical tube, and ether allowed to percolate through it till no more fat was extracted, the ether being received in a tared flask. The pumice was removed and reground, and percolation again con- tinued ; and this treatment was repeated till no more fat was extracted. The method was somewhat tedious, though very exact. In order to avoid the troublesome grinding of a hard substance like pumice and to economise time, the author prefers to use kieselguhr in place of pumice ; the method is performed as follows : — About 3 or 4 grammes of ignited kieselguhr or fossil meal are placed in a porcelain basin, a cavity being made in the centre, and 10 grammes of milk allowed to flow in, care being taken that none is permitted to fall on the sides of the basin. The kieselguhr is dried on a gently-boiling water bath, being stirred occasionally as drying proceeds ; after about an hour's drying the kieselguhr can be powdered in the basin with a small pestle. The powder is transferred to a wide test tube, with a hole at the bottom, containing a half-inch plug of cotton wool, which has previously been well extracted with ether; both basin and pestle should be scraped, and the basin should be rinsed two or three times with kieselguhr, the pestle being used to grind up the rinsings with any portions adhering to the sides. The rinsings are added to the tube, and a circular piece of filter paper, of such size as to fit the tube, placed over the kieselguhr. The tube is placed in a Soxhlet extractor and extracted with ether for three hours; care must be taken that the top of the tube is well above the top of the siphon and that the ether is not distilled at such a rate that it fills and overflows the upper portion of the tube. After three hours' extraction the tube is removed from the extractor, the kieselguhr emptied out into the basin, and, after allowing the ether to evaporate, again powdered, and re-extracted for another three hours ; the quantity obtained in the second extraction is very small. The ether is then evaporated and the fat dried at 100°C. in a tared flask ; after weighing, the fat should be dissolved in a little ether, when any kieselguhr which may have run through will be detected ; this should not be the case, if the plug of cotton wool was properly packed. Schleicher and SchulPs thimbles may be used instead of the glass tube. Other media, such as kaoliD, plaster of Paris, Ac, may be sub- stituted for pumice or kieselguhr, and, as long as the essential point of the method, fine grinding, is adhered to, the results are independent of the medium. Kieselguhr is, however, the most convenient. 7 98 ANALYSIS OF MILK. The Soxhlet Gravimetric Method. — This method was long considered the best for the estimation of fat in milk. It was worked as follows : — About 20 grammes of plaster of Paris were placed in a porcelain basin, a cavity being made in the centre of the heap, and 10 grammes of milk carefully poured upon it. The basin was placed on a gently-boiling water-bath, and when the plaster began to set, it was stirred with a glass rod ; this prevented the formation of hard lumps and enabled the plaster to be completely removed from the basin. When quite dry, the plaster was roughly crushed to a coarse powder, and placed in a "cartridge," made by rolling a strip of filter paper round a ruler and folding the ends, and extracted in a Soxhlet extractor* for two hours ; no further extract was obtained by longer extraction. The author found that by applying Storch's principle of fine grinding, that appreciably higher results could be obtained, and Vieth showed that, by placing only 5 grammes of milk on 20 grammes of plaster instead of 10 grammes, an increased extract was also furnished. These observations prove that Soxhlet's method did not furnish accurate results. This is due to the fact that the plaster, in setting, encloses portions of the milk solids, and the fat is thereby protected from the action of the ether ; when fine grinding is resorted to, the ether is enabled to penetrate the whole mass, and the last traces of fat are dissolved ; in this case, the method is essentially that of Storch. When less milk is used, it is spread over a greater surface, and setting does not take place so readily. This method is now very rarely used, having been supplanted by the Adams and Werner-Schmid methods. The Werner-Schmid Method. — This method differs from most others, in that the milk is not reduced to a solid state by evaporation previous to the extraction of the fat by ether. In order to render the casein, which hinders the extraction of the fat from milk, soluble, Werner-Schmid heated the milk with an equal bulk of hydrochloric acid till the fat floated in a nearly clear layer at the top, shook the resulting solution with ether, and drew oil' an aliquot portion of the ethereal layer. Stokes has devoted much attention to this method and has studied the effect of slight modifications. Werner-Schmid's directions are: — Take a test tube of about 50 c.c capacity, graduated in tenths of ;i c.c, and introduce 1 0 c.c. of milk ; add 10 c.c. of hydrochloric acid, boil, with shaking, until the liquid turns dark-brown, and cool by placing the tube •The Soxhlel extractor was really devised by Szombathy; it was described by Soxhlel in tl>" paper in which the above method was given, and due credil waa given by loin to 1 1 1 « ■ inventor. The apparatus is. however, dwaya known bj Soxhlet's name. THE GRAVIMETRIC METHODS. 99 in cold water ; add 30 c.c. of ether, shake round and let stand ; then measure the volume of the ethereal solution, draw off 10 c.c. with a pipette, evaporate the ether, and dry the fat at 100° C. Stokes prefers not to boil, but to plunge the test tube contain- ing the mixture of milk and acid in boiling water for five or ten minutes. He recommends the use of washed ether. T. E. Hill has also examined the method, and considers that the milk should be weighed, not measured. Hill notices that a fluffy-looking stratum is formed beneath the ether, and, following Stokes, adds three-fourths of this to the bulk of the ethereal layer for calculating purposes. He also points out that Werner-Schmid's method is not applicable to the determination of fat in milk to which cane sugar has been added, a conclusion confirmed later by Dyer and Roberts, who showed that by boiling cane sugar with hydrochloric acid a substance soluble in ether was formed. Stokes later introduced a new form of tube, in which the middle portion is narrowed for greater accuracy of measurement of the ethereal layer (Fig. 3). Allen proposed to draw off as much ether as possible, to add a further supply, to draw that off as completely as could be done, and to continue washing in this way till . all the fat was separated from the aqueous layer. Stokes' Molinari and Stokes have both described forms of Tube. apparatus in which the ethereal solution can be com- pletely removed from the aqueous layer without the necessity for pipetting it off These apparatus offer no special advantage and are not used. The author prefers to dilute the milk with an equal bulk of water before heating with hydrochloric acid, as there is then no tendency for the formation of a fluffy-looking layer at the point of junction. He finds that it is necessary to wait for ten minutes at least after the ether has apparently separated from the aqueous layer, in order to allow the fine globules of water to settle out of the ether. Analysts who have used this method are generally agreed that it gives results practically identical with that of Adams; it is a question whether the drawing off of an aliquot portion of the ether is to be preferred to the extraction of the whole of the fat. In the first case, there is a tendency to be slightly low, owing to the fact that the ether, which dissolves in the aqueous portion, retains a minute proportion of fat ; in the other, the tendency is to be somewhat high, as the water which dissolves in the ether dissolves a small amount of substances other than fat ; in either case, however, the error introduced is very small and may usually be neglected. 100 ANALYSIS OF MILK. This method is eminently adapted for the estimation of fat in sour milk. A weighed portion of the well-mixed milk should be placed in a graduated tube, and diluted with an equal bulk of water; a quantity of hydrochloric acid, slightly greater than the total volume of the diluted milk, should be added, and the whole boiled till clear. After cooling, ether should be added, the tube shaken, and the ether allowed to settle for ten minutes, .before taking out the stopper of the tube, it is an advantage to cool the upper portion of the tube to as low a temperature as possible, so that any ether which may have collected round the stopper may be drawn inwards. An aliquot portion of the ether should be drawn off, and evaporated and the fat weighed. Owing to the presence of lactic acid in sour milk, which is soluble in ether, and gives a non-volatile lactone on heating, the results have a tendency to be slightly high. For this reason also, the whole of the fat should not be extracted by repeated shaking with ether, as a greater amount of lactic acid is thereby extracted ; the ethereal layer may be, however, washed with water to remove this. This method has the advantage of being more rapid than the Adams process, though it requires rather more personal atten- tion ; it is not, however, quite so accurate, but can nevertheless be recommended for ordinary work. Smetham has devised an extractor on a similar principle to Soxhlet's for extracting liquids with ether ; the fat may be removed in this apparatus after boiling with hydrochloric acid. Babcock's Asbestos Method. — Babcock has used asbestos as a medium for evaporation of the milk previous to extraction with ether. Otiginally it was contained in a glass tube and dried in a current of air, but he has modified it by the use of a perforated metal cylinder. The following is the method as adopted by the Association <>t' Official Agricultural Chemists (of America) : — Provide a hollow cylinder of perforated sheet metal, 60 mm. long and 20 mm. in diameter, closed 5 mm. from one end by a disc of the same mat. rial. The perforations should be about 0-7 mm. in diameter and about 07 mm. apart. Fill loosely with 1*5 to 25 grammes of freshly-ignited woolly asbestos, free from fine and brittle material ; cool in a desiccator and weigh. Introduce a weighed quantity of milk (3 to 5 grammes) and dry at 100° C. to constant weight f" C. and weigh. The fat may also be determined by difference, drying the extracted cylinders at LOO 0. This method has been studied by the Association and has been found to give the same results as the Adams method. It has the ad\ antage that fat, solids not fat . and total solids are directly estimated. THE GRAVIMETRIC METHODS. 101 Macfarlane has described a method essentially the same, but uses chrysotile or Canadian asbestos for the purpose ; this being a hydrated mineral cannot be ignited. He uses a cup-shaped glass tube with a hole at the bottom, and operates with 10 grammes of milk. The author finds that this method gives practically identical results for fat with the Adams method, but the solids not fat and total solids are low. It is used to a considerable extent in Canada for official work. The Kitthausen Method. — If milk is diluted with water, a solution of copper sulphate added, and the acid neutralised, the whole of the proteids are precipitated as copper salts ; these carry down with them the whole of the fat. After washing, to remove milk-sugar, &c, and drying, the fat may be extracted with ether ; or a little strong alcohol may be poured on the pre- cipitate to remove water, after which ether will extract the fat ; the ethereal and alcoholic solutions are evaporated together and the fat weighed. The fat may be similarly extracted from the casein precipitated by the addition of acetic acid to the diluted milk. The results agree well with the Adams method, except in the case of very highly skimmed milks, when there is a tendency to be low. This method has the advantage that the fat can be determined on the same portion of milk used for the estimation of proteids and milk-sugar. The following comparative figures will show the results which may be expected : — Fat by Ritthausen, . . 4-93 2-87 1-38 4-00 0-04 Fat by Adams, . 4-97 2-89 1-43 3-99 017 This method is also suitable for the estimation of fat in condensed milks. Other Methods of Gravimetric Fat Determination. — The other methods for the estimation of fat in milk are very numerous ; a few of those which have been proposed may be brie fly noticed. Wanklyn's method consists in extracting the fat from the solids of milk dried per se. The totality of the fat is never obtained, as, owing to the hard, horny character of the residue, a considerable proportion of the fat is protected from the ether. This method attained considerable notoriety, owing to its semi- official adoption by the Society of Public Analysts more than twenty years ago, but has now fallen into almost complete dis- use. It has been modified by stirring the residue during evaporation so as to obtain a more granular residue, and by evaporating in a conical flask so as to expose a large surface to 102 ANALYSIS OF MILK. the ether, but the results, even with these modifications, have been unsatisfactory. Hoppe-Seyler and, later, Liebermann have proposed to shake the milk with potash (to dissolve the casein), and then to extract with ether, but the separation of the ether is so slow as to render this method impracticable. Morse, Piggott, and Burton add the milk to anhydrous copper sulphate, which combines with the water, giving a dry residue at once ; they then extract with petroleum ether. Baynes proposes to dry the milk on powdered glass, a method essentially the same as that of Storch. Sand has also been largely used in Germany; but as it is very difficult to grind this up, its use is not to be recommended. Marpmann has proposed the use of cotton-wool, Ganntter of wood-fibre, and Duclaux of sponge ; the principle of these methods is the same as that of Adams. Fernandez-Krug and Hampe mix a measured volume of milk with a finely-divided mineral substance — usually 5 c.c. of milk with 11 grammes of washed and dried kaolin — and add 5 grammes of finely-powdered anhydrous sodium sulphate. The sodium sulphate absorbs the water contained in the milk, and, after well stirring, the residue is quite dry ; this is transferred to a flask holding 100 c.c. and 25 c.c. of ether added; after shaking for five minutes, an aliquot portion is withdrawn by a pipette, over the point of which a piece of cotton wool is wrapped, and the fat estimated by evaporation and weighing. Froidevaux precipitates the casein and fat with a solution containing 35 grammes of calcium phosphate and 6 c.c. acetic acid per litre; 90 c.c. of this solution are mixed with 10 c.c. of milk, and the fat determined as in the Ritthausen process. (2) Volumetric Methods. These, being suitable for use in the rapid testing of milk, will be more conveniently considered in the chapter on "The Testing of Milk." (3) Indirect Methods. Estimation of Cream. — One of the earliest and simplest methods of estimating the fat in milk is to allow the milk to stand, and to measure the volume of cream thrown up. For this purpose a creamometer or cylindrical vessel, the upper portion of which is divided into spaces, each representing the ,,',,- th part of the total volume up to the highest line, is employed. It is filled up to the mark, and allowed to stand at rest for some time — six, eight, twelve, or twenty-four hours — and the volume of cream measured. A good milk should throw up alx>ut 10 per cent, of its cream in eight hours. INDIRECT METHODS. 103 The method is of very slight value for a determination of the fat in milk, as comparatively slight variations in the conditions make enormous variations in the volume of cream. Thus, the author has found that a milk — freshly drawn and not cooled — containing 5-3 per cent, of fat threw up 25 per cent, of cream in six hours, while another milk with the same percentage of fat, which had been raised to the boiling point and cooled, only threw up 2 per cent, of cream in the same time. These, of coui'se, are extreme instances, and it is found in a majority of cases that the percentage of cream thrown up in six to eight hours divided by 3 will give an approximation to the percentage of fat. It has been proposed to modify this method by raising the cream by centrifugal force, and apparatus have been made to fit on to the spindle of cream separators ; though more concordant results are thus obtained, these methods have not the accuracy of many of the volumetric methods, by which they have been superseded as practical methods. Faber has, however, shown that very accurate results may be obtained by measuring the volume of cream thrown up from skim milk, after whirling in the lactocrite for one hour, and dividing by 3. It has been proposed to deduce the percentage of fat in milk from the opacity of the sample. Various forms of "lactoscope " have been proposed which measure either the thickness of the layer of milk which obscures a given light, or the amount of light passing through a given layer of milk. The accuracy of the lactoscope is approximate only, and the instrument is now rarely used. The calculation of the fat from the specific gravity and total solids has already been described. The author has tried an expansion method, which depends on the difference of the expansion by heat of fat and milk serum — that of the former being about three times that of the latter. Densimetric Method of Pat Estimation. — By placing about 200 c.c. on a pleated filter and collecting such portions as run through in the first quarter of an hour, the milk serum — i.e., a solution of the solids not fat in water — may be separated without much change in composition. A series of experiments by the author showed that the solids not fat in the filtered milk were, after correcting for the volume of the fat removed, on the average •12 per cent, lower than in the unfiltered milk. Vieth gives the following experiment : — 200 c.c. of milk were filtered ; after one hour 50 c.c. of milk had run through ; after four and a half hours more, 26 c.c. were collected ; and 108 c.c. were poured out from the filtrate. The results of analyses of these four milks were — 104 ANALYSIS OF MILK. Original Milk. First Filtrate. Second Filtrate. Left on Filter. Total solids, Pat,. Solids not fat, . Proteids, . Per cent. 13-42 4 43 8-99 3-66 Per cent. 914 9-08 3-68 Per cent. Per cent. 8-14 i 3-95 •03 4 80 811 915 2 43 3-89 For every 100 parts of water there were present Solids not fat, . Proteids, . 10 38 4-23 9 99 | 4-05 8-83 1 10 63 2-65 4-52 The differences as compared with the original milk were Solids not fat, . Proteids, . -•39 -1-55 +'25 -■18 -1-58 +"29 This experiment shows that a portion of the proteids is removed with the fat, and corroborates the author's conclusion that when the portion run through in the first fifteen minutes is taken, there is only a slight loss of solids not fat. The author has found that if the specific gravity of the filtered milk less 1 be divided by -004, and the difference between the specific gravities of the milk before and after filtration be divided by "0008, the figures so obtained very fairly represent the solids not fat and fat respectively. The following figures (Table XI.) will show the agreement that mny be expected : — TABLE XT. — Estimation of Milk Solids by Densimktric Method. Specific Gravity. Solids not Fat. Fat. Before Filtration. After Filtration. UittVrences. Found. Calc. I'nlltlll. Calc. IVr .t. Per ct. Per ct. Per ct. L-0308 1 -0340 •0032 8-63 8-60 :::n 40 1-031 s 1-0348 • 1-8 1-6 3 0 2-f weighing the casein, the nitrogen in the precipitate may be estimated by Kjeldahl's method, and multiplied by 6*38. In this C&se it is not necessary to dry the casein, but the preci- pitate with the filter may be dropped into a digestion flask, the acid added, and the method performed as directed for total nitrogen. ESTIMATION OF CASEIN AND ALBUMIN. 109 Maissen and Musso have proposed the use of rennet for pre- cipitation of the casein, but this is not accurate. As casein is not entirely insoluble in water, especially in the presence of acid, the results have a tendency to be low, espe- cially if the nitrogen be estimated. On the other hand, it is difficult to wash the casein absolutely free from other milk solids (1 calcium citrate); hence the weight of the "casein" obtained by precipitation is thus raised. In practice, the two errors have a tendency to compensate one another. Albumin is estimated by boiling the filtrate from the casein ; the filtrate is raised just to boiling over a small flame, and digested on the water-bath for fifteen minutes ; the albumin separates in a pulverulent form. It is collected on a tared filter or, preferably, in a Gooch crucible, and dried at 100° C. ; the nitrogen may be estimated by the Kjeldahl method, and multiplied by 6-38. The albumin is precipitated practically in a state of purity, and no correction for the ash need be made, but, owing to the precipitation not being complete, the results are slightly low ; if the casein has not been completely preci- pitated, a portion may be found with the albumin. A small quantity of so-called "lacto-protein " remains in solu- tion after precipitation of the casein and albumin; this chiefly consists of the unprecipitated portions of casein and albumin. It may be estimated by precipitation as copper salt by Ritthausen's method, as described above; by precipitation by tannin and estimation of the nitrogen in the precipitate by Kjeldahl's method ; or by evaporation of the solution and estimation of the nitrogen. Segelein's method, though more tedious, is preferable to the above ; to 10 grammes of milk, 20 c.c. of a saturated solution of magnesium sulphate are added. Solid magnesium sulphate in the form of powder is then added in small quantities at a time till no more is dissolved. The solution is allowed to stand for twelve hours and filtered ; it is washed four or five times with a saturated solution of magnesium sulphate, an operation which takes some time. The filter and its contents are dropped into a Kjeldahl digestion flask, 30 c.c. of sulphuric acid added, and the nitrogen estimated, as previously described ; an increased volume of soda solution to neutralise the 30 c.c. of acid used must be employed. The nitrogen multiplied by 6 -38 will give the weight of casein. The magnesium sulphate must be free from sodium sulphate, commercial "Epsom salts" often containing this impurity. If distinct acidity be developed in the milk, this should be neutral- ised previous to the addition of magnesium sulphate. The albumin is separated by diluting the filtrate and preci- pitating by the addition of tannin, or phosphotungstic acid ; the precipitate is collected on a filter, and the nitrogen therein 110 ANALYSIS OF MILK. estimated by Kjeldahl's method. The albumin may be less exactly estimated by boiling the nitrate after dilution and addi- tion of a small quantity of acetic acid ; it is collected on a tared filter and weighed as such. In order to avoid the tedious washing with a saturated solu- tion of magnesium sulphate, Leffmann and Beam take a larger quantity of milk (say 20 grammes), dilute with twice its bulk of saturated magnesium sulphate solution, add powdered magnesium sulphate till saturated, and make up to a definite volume with saturated magnesium sulphate solution in a graduated cylinder. The solution is allowed to stand and the lower clear portion is removed by a pipette ; this is filtered and an aliquot portion taken ; the albumin is estimated in this, as directed above. The casein is determined by subtracting the albumin nitro- gen from the total nitrogen and multiplying the difference by 6-38. Sodium chloride, to which a little calcium chloride has been added, can be substituted for magnesium sulphate ; the preci- pitate is less easy to treat, owing to the formation of hydrogen chloride on heating the precipitate with sulphuric acid. Duclaux has devised an ingenious method, which can be applied to the determination of casein and albumin. A quantity of milk is placed in a beaker, and a porous cell (the opening of which is closed by a cork, through which a tube passes) is immersed in it. The tube is connected to a water-pump and a vacuum maintained in the porous cell ; the serum, containing in solution the milk-sugar, albumin and salts, filters through the porous cell, while the casein and fat together with a portion of the salts remain behind. A Berkefeld filter may be substituted for the porous cell. Filtration is hastened if the outside of the filter be rubbed from time to time with a rubber-tipped rod, which removes the closely adherent casein layer. The author has attempted to remove the casein by the addition of 2 c.c. of glacial acetic acid, and 1 c.c. of " alumina cream " to 100 c.c. warmed to 40° C. ; the serum is filtered through a filter, the filtrate being poured back till it becomes clear, or through a Gooch crucible Densimetric Methods. — The specific gravity of the serum obtained by either method may be determined and the casein deduced from the difference in specific gravity between the milk and the serum. The serum may be polarised and the albumin deduced from the difference between the reading obtained and that due to the milk-sugar. The solids, milk-sugar, and ash may be estimated in the serum, and the total solids and fat in the milk ; from these data the casein and albumin can be deduced. The calculations in Duclaux's method are somewhat compli- 1 : — ESTIMATION OF CASEIN AND ALBUMIN. Ill Let S??i be the specific gravity of the milk. Tm ,, total solids of the milk in grammes per 100 c.c. Fm ,, fat of the milk in grammes per 100 c.c. Am ,, ash of the milk in grammes per 100 c.c. Ss ,, specific gravity of the serum. Ts ,, total solids of the serum in grammes per 100 c.c. As ,, ash of the serum in grammes per 100 c.c. Ms ,, milk-sugar of the serum in grammes per 100 c.c. Then 100 Sm - Tm is the weight of the water in 100 c.c. of milk, and 100 Ss - Ts the weight of water in 100 c.c. of serum. For 100 grammes of water there are Tm x 100 100 Sara - Tm ° Fm x 100 100 Sm - Tm Am x 100 100 Sm - Tm Ts x 100 100 Ss - Ts As x 100 100 Ss - Ts grammes of total solids, fat, ash, serum solids, and serum ash. The casein is equal to Tm x 100 A.s x 100 / Fm x 100 Am x 100 Ts x 100 100ti?n-Tm 100 Ss - Ts \100Sm-Tm 100 Sm - Tm 100 Ss LOO \ -Ts) This is expressed as grammes in 100 grammes of water, and must be multiplied by — — to obtain grammes per 100 c.c. of milk, or by lOOSm-Tm . _. . zt^tf, to obtain percentages. 100 Sm If total solids, fat, &c. , are estimated as percentages by weight, the Tm x 100 A . 1.*..,. j. *m Tm x 100 Ts x 100 . expressions m _ Tm must be substituted for mSm.Tm> W^Ts for Ts x 100 , — -— — , and so on. lOOSs-Ts To obtain the albumin: — Let the symbols be as before, then for 100 grammes of water there are Ts x 100 , .., grammes ot serum solids. 100 Ss - Ts As x 100 loo Ss - Ts M* x 100 100 Ss - Ts ash. milk-sugar. The albumin is equal to Ts x 100 / As x 100 Ms x 100 \ . „ , 1- = = 1 grms. in 100 grms. ot water. lOOSs - Ts \ 100 Ss - Ts 100 Ss - Ts ) ° 112 ANALYSIS OF MILK. To obtain grammes per 100 c.c. of milk, this must be multiplied by 100 Sot - Tm . . .100 Sm - T/,/ — — , and to obtain percentage bj -— . 1W 100 hm If the milk-sugar be expressed as grammes per 100 c.c. of the milk (Mm), ., . Urn x 100 M.s x 100 the expression .,„, = — „ must be substituted for ,„„ ,, =- 100 >S>» - Tm 100 S* - T« If it be desired to deduce the amount of casein from the difference of specific gravity between the milk and the serum obtained by the author's method, the following formula must be used : — Let Stw be the specific gravity of the milk, and Ss ,, specific gravity of the serum, ¥m the fat in grammes per 100 c.c, A?h ,, ash of the milk in grammes per 100 c.c, As ., ash of the serum in grammes per 100 c.c, the casein is equal to .„ 1000 Sm - 1000 + Fm x -757 , . . , „ „ lrtM, a 11MM1 100 x — [Am - As) v. 7-5 - 1000 S« + 1000 100 - tm grammes per 100 c.c. This involves the assumptions that the volume of the pre- cipitated casein is equal to the volume of 2 c.c. of acetic acid + 1 c.c. of alumina cream, and that the specific gravity is unchanged by this dilution ; the assumptions are nearly correct. For expression (Am - As) x 7 "5 the figure l'O maybe used without much error. Polarimetric Methods. — If the albumin is to be deduced from the polarisation of the serum, it is best to calculate the reading to percentage of milk-sugar, as directed under the estimation of milk-sugar. The difference between the appan nt percentage of milk-sugar thus found, and the true percentage multiplied by the factor -74, will give the percentage of albumin. The factor is obtained by dividing the specific rotatory power of milk-sugar by that of albumin. As albumin polarises to the left, and milk-sugar to the right, the apparent percentage of milk-sugar deduced from polarisation of the serum will be less than the true percentage. The polarisation method suffers from the disadvantage that the serum is apt to be somewhat dark in colour, and the readings are consequently not very sharp ; still, if an estimation be required in a short time, it is u fairly good method. Estimation of Casein. Lohmann's Method. — Lehmann has devised a method for the estimation of casein in milk by means of unglazed porcelain plates; the plate is vetted with water, and 5 grammes of milk diluted with 6 grammes of water placed in the centre, After about an hour ami a hall the serum is separated, and the casein, together with the tat. is removed with a spatula ; the last traces of casein are removed by setting the plate in water. The fat is removed by extraction with DETERMINATION OF TOTAL ACIDITY. 113 ether, the casein being ground up to extract the last traces ; the casein is dried at 100° C. on a weighed filter, and weighed ; from the weight is deducted the weight of the ash left on incineration. The results are said to be very accurate. The casein is obtained in the state in which it exists in the milk. Schlossman's Method. — Schlossman proposes to estimate casein by warming 10 c.c. of milk mixed with 3 to 5 parts of water to 40°, and adding 1 c.c. of a concentrated solution of alum. Should the flocculent precipitate not subside rapidly an additional 0-5 c.c. of alum solution may be added, since a slight excess (up to 1 c.c.) does not affect the results. The precipitate is allowed to stand for some minutes, and is then filtered. After having been washed with water and dried, the filter and its contents are extracted with ether in a Soxhlet extractor (an estimation of fat being thereby obtained) ; the nitrogen deter- mined by Kjeldahl's method, and multiplied by 6*38, gives the weight of the casein. Richmond's Method. — The albumin in milk, which has been raised to the boiling point, behaves with all methods as casein. An approximate estimation of real casein in milk, which has been heated, can be made as follows : — Twenty-five grammes of milk are evaporated to dryness, ignited, and the phosphoric acid estimated in the ash, as directed on p. 74. Twenty-five c.c. of the filtrate, produced by adding 3 c.c. of ;icid mercuric nitrate to 100 c.c. of milk, are taken, made alkaline, and, without removing the precipitate, evaporated down, and ignited : the phosphoric acid is estimated in the ash. The casein is calculated from the following formula : — Let Pi=P205 obtained from 25 grammes of milk, P2 = P205 obtained from 2.5 c.c. of filtrate, F = percentage of fat, and S = the specific gravity. T, /t, r> 100- 1-11F\ onr>0 Then case n= ( P! - P2 x — 5 I x 20o 2. The coagulated albumin is deduced by subtracting this figure from the apparent percentage of casein estimated by one of the methods previously described. Determination of Total Acidity— Lactic Acid.— One hundred c.c. are placed in a beaker ; a little phenolphthalein (5 c.c. of a -1 per cent, solution) is added, and the milk titrated N with 1 alkali till a faint pink colour is obtained. Storch uses a solution of lime (lime-water), containing solid lime, in place of standard soda solutions, as it remains constant in composition, and is almost exactly twentieth normal. The strength of the solution remains constant, as if anv of the lime 8 114 ANALYSIS OF MILK. is removed by carbon dioxide, more is dissolved ; its strength is but little affected by ordinary variations of temperature. It is to be recommended for dairy use, as no precaution, except to have an excess of lime in the bottle, is necessary. N Generally speaking, about 20 c.c. of -_) alkali is required ; N each cubic centimetre of ^ alkali is called 1° of acidity, hence a milk requiring 20 c.c. will have 20° of acidity. It is a frequent practice to calculate the acidity as lactic acid; this practice is, however, to be deprecated, as freshly-drawn milk has a very distinct acidity, though lactic acid is in all probability absent. The acidity of milk to phenol phthalein is clue partly to the mono- and di-basic phosphates, and partly to the dissolved carbonic acid. The following figures by Smetham and Ashworth are in- structive : — Milk direct from cow, ,, ,, (after boiling), Mixed milk from vat (at once), ,, ,, (after 12 hours), 267 1 2 2 is \) 21 T I. n. ' Original milk at once, 16-7° 18-9° Milk after 12 hours, .... 20- )° 20 „ . ... 21 1° 28 „ . 22 2' ,, 2 days, .... 77 -s 217 3 ., 107-8° 97-8° 6 „ . . . . 127 80 7 „ . . . . 107-8° 16 ,, 120-0° ... The gradual rise of acidity, on keeping, is well marked ; this is, of course, due to the production of lactic and carbonic acids. It is interesting to note the diminution of acidity in milk on boiling; this is probably due partly to the deposition of calcium salts having an acid reaction, and partly to the expulsion of carbonic acid. Instead of n s i i i lj phenolpht halein, delicate neutral litmus paper may be employed; milk is practically neutral to this. The acidity can be titrated with fair accuracy, though the end point of the titration is not well marked. There is more justifi- cation for calculating the acidity to litmus as lactic acid, as both the salts of milk and carbonic acid are not appreciably acid to litmus paper. THE ANALYSIS OF MILK PRODUCTS. 115 The following figures obtained by the author on sour milks will show the enormous difference in the two results ; the figures have in both cases been calculated to lactic acid: — I. II. III. IV. V. .eidity (to phenolphthalein), ,, (to litmus paper), 1-24 ■65 1-89 114 1-82 1-28 1 -52 •86 1 -32 ■56 There is no good method for the quantitative determination of lactic acid ; the results of the titration with litmus give approximate results. An approximation nearer the truth may . N . be made by distilling some of the milk into a little » alkali, N titrating back the alkali with - acid, using litmus paper as indicator, and subtracting the volatile acidity from the total acidity ; the non-volatile acidity is taken as lactic acid. An estimation of lactic acid is rarely, if ever, required in practice, the determination of the total acidity serving for almost all purposes. The Analysis of Milk Products.— For the analysis of milk products, the methods described above can generally be used. The following notes will show where it is advisable to depart from them or employ modifications. Cream. — The methods given above may be employed in the analysis of cream. The following method of determining total solids, fat (by difference), solids not fat, and ash is convenient. 4 to 5 grammes are weighed in a wide platinum basin, which is placed in a water-oven, till the water has apparently evapor- ated and the solids not fat stick to the bottom of the basin ; when this occurs — after about an hour's drying — the basin is inclined so that the fat runs down to the side away from the solids not fat. Under these conditions drying is completed in about five hours. After weighing the total solids, the basin is replaced in the water-oven for a few minutes to melt the fat ; 25 c.c. of amyl alcohol are poured on, the basin again placed in the water-oven for ten minutes, and the amyl alcohol solution of fat carefully decanted while still hot ; with care, none of the solids not fat passes away with the amyl alcohol. This process is repeated eight times more, the basin being allowed to stand all night between the fourth and fifth treatments. After the last treat- ment, the amyl alcohol is drained off as far as possible, and the basin and its contents dried for three hours in the water-oven. The residue is weighed as solids not fat. This is now burnt over a low flame, and the residue weighed as ash. Ether or chloroform may be substituted for amyl alcohol, but the latter is cheaper and less volatile. For the determination of milk-sugar by polarisation, the 116 ANALYSIS OF MILK. cream should be diluted with water ; 50 grammes may be made up to 100 c.c, and 1 c.c. of acid mercuric nitrate added. If total nitrogen is determined, the cream should be evapor- ated in a wide-mouthed flask, and the bulk of the fat extracted, as, otherwise, great charring of the fat takes place (if the cream be treated by the Kjeldahl method), and much carbon, difficult to dissolve, is prcduced. Skim Milk. — The methods of milk analysis may be applied ; the fat is rather more difficult of extraction. If Ritthausen's method be used for proteid determination, it is not necessary to extract the fat, but to dry and weigh the copper precipitate, and afterwards to subtract the percentage of fat found from the per- centage of proteids plus fat. Condensed Milk. — About 30 to 35 grammes of the well- mixed milk should be weighed into a 100 c.c. flask, diluted with 50 to 60 c.c. of water, and the solution raised to the boiling point ; this is cooled, made up to 100 c.c, and the total weight taken. The diluted solution is analysed as a milk. The fat is rather more difficult to extract than from ordinary milk, and longer extraction should be given ; if cane sugar is present, the Werner-Schmid process must not be used for the estimation of the fat, as cane sugar yields a substance soluble in ether. TVhen soluble albumin is estimated, a fresh portion which has not been boiled is employed. Decomposed Milk — ['reparation of Sample. — The whole contents of the bottle are turned out into a heaker and whisked for a minute or two with a brush made of fine wire ; the inside of the bottle is scraped with a wire all over, some of the milk is poured back, and the contents shaken ; this is now emptied into the beaker and again whisked. Portions of about 5 grammes are weighed out for total solids and ash, fat, and total nitrogen. Estimation of Acidity. — Twenty grammes of milk (if this quan- tity can be spared) are placed in a beaker, and titrated with ' caustic soda solution, using delicate litmus paper as indicator. To the portion weighed out for total solids, which should be N in a wide flat-bottomed basin, a quantity of -r— soda solution, calculated from the determination of tin' acidity, should be added. The basin is placed on the water-bath and evaporated to dryness; when apparently dry, it is placed in the watermen for two hours, weighed, then replaced, and re-weighed alter one hour's interval ; thi.^ is repeated till the loSS is less than I milli- gramme. Prom the final weight of total solids a ipiant it v equal \ to the number of c.c, of soda added ■ '0022 is subtracted, and the remainder represents the total solids. FERMENTED MILK. 117 The residue in the basin is ignited, and the residue weighed ; N from the weight a quantity equal to the number of c.c. of soda added x -0053 is subtracted ; the remainder represents the ash. The fat is best estimated by the Werner-Schmid method ; an aliquot portion of the ether should be measured off and eva- porated, as, if an attempt be made to extract the whole of the fat, a considerable proportion of lactic acid will be extracted ; if, however, an aliquot portion of the ether be taken, the amount of lactic acid dissolved does not seriously affect the results. Fat may be estimated with about equal accuracy by one of the Leffmann-Beam methods ; a portion of the milk, as nearly equal to that normally employed as possible, is weighed into a bottle, and the fat read off in the usual manner ; the reading should be corrected by multiplying by 15-25 (if 15 c.c. be used) or 1 1 -22 (if 11 c.c. be used), and dividing by the weight taken. The other estimations are made as for milk. Fermented Milk — Kephir and Koumiss. — Estimation of Alcohol. — 100 grammes of milk are weighed into a flask, and about 50 c.c. are carefully distilled, and received into another flask ; the distillate is mixed with a little baryta water, to render the solution alkaline, and again distilled ; about 30 c.c. are collected and weighed. The density of the second distillate is carefully taken, and the percentage of alcohol in the distillate is deduced from Table XIII. (due to Hehner). The percentage of alcohol in the milk is found by multiplying the weight of the distillate by its percentage of alcohol, and dividing by the weight of the milk taken. To the residue in the flask from which the milk was distilled, 25 c.c. of water are added, mid 25 c.c. distilled off; this treatment is repeated several times until the last 25 c.c. are approximately neutral. The mixed distillates are added to the portion which had previously been made alkaline with baryta, and the solution titrated with baryta water (or sulphuric acid) till neutral to phenolphthalein. The liquid is filtered, and evaporated to dry- ness, and the residue, consisting of the barium salts of volatile acids, weighed ; a little sulphuric acid is added and the basin ignited ; the weight of the barium sulphate, multiplied by "5803, is subtracted from the total weight ; the remainder represents the weight of the volatile acids ; this, multiplied by 116-75 and divided by the weight of the barium sulphate, will give their equivalent. Estimation of Proteids. — The proteids precipitated by the acid developed in the milk are filtered off, and either weighed, or the nitrogen is determined in them ; the filtrate is boiled, and the precipitate weighed as albumin ; in the filtrate from this, 118 ANALYSIS OF MILK. TABLE XIII.— Alcohol Tables (Hehner). Specific Gravity at Off K. 60° F. Alcohol per cent. l»j Weight. Specific 1 Gravity at 60° F. 60° F. Alcohol per cent, by Weight. 1 „ Specific Gravity at e - i Alcohol per cent, by Weight ■9999 •05 •9969 1 75 •9939 3 47 8 •11 8 T81 8 353 7 ■16 7 1-87 i :;•.-,!( (i •21 6 1-94 0 3 ().-) 5 ■26 5 2 -Oft 5 3 71 4 ■32 4 2-06 4 3-76 3 •37 3 211 3 3-82 2 ■42 2 2 17 ■> 3'88 1 •47 1 2 22 1 3-94 0 ■53 0 2-28 0 4-00 •9989 ■58 ■99-39 2 33 •9929 4-06 8 •63 8 2-39 8 4- 12 7 •68 7 2 44 / 4-19 6 ■74 6 2 50 6 4-2.-> 5 •7!. 5 256 5 4 31 4 •84 4 261 4 4 37 3 •89 3 2 07 3 4-44 2 •95 2 2-72 2 4 -.Hi 1 100 1 2-7s 1 4-.-.II 0 L-06 0 283 0 4 02 ■9979 112 •9949 2-89 •9919 4 69 8 119 8 2 94 8 4 7.-» 7 1 -25 7 3 00 / 1 S| 6 1-31 6 3 06 0 4-N7 5 1 -37 5 3-12 5 4-94 4 1-44 4 3-18 4 5-00 3 1 -.-.() 3 3-24 3 5-06 2 1 -.-,ii 2 3 29 2 5 12 1 1 -62 1 3-35 1 5-19 0 1-69 it 3-41 0 5-25 albumoses are estimated by precipitation with tannin or phos- photungstic acid, and determining the nitrogen in the preci- pitate. The total acidity to litmus paper may be calculated as lactic acid; from this an amount equivalent 10 the volatile acids is subtracted. Carbonic acid can only be estimated if the koumiss or kephir was in a corked bottle. The worm of a champagne tap is care- fully turned off to Leave a perfectly smooth stem : the tap is also carefully re-ground to make sure that it fits. A drying and absorbing apparatus is fitted up, consisting of in ;i U-tube containing pumice and Bulphuric acid, (/>) a U-tuhc containing Boda lime immersed in a Weaker of cold water, (c) a U-tube tilled half with soda lime and half with Calcium chloride. These are connected in the order named, and the end of (a) is BUTTKRMILK. 119 connected by a short piece of indiarubber tubing to the cham- pagne tap. (6) and (c) are weighed, and the tap (closed) carefully forced through the cork of the bottle ; the tap is slightly opened and the carbon dioxide allowed to slowly escape ; when the escape of gas becomes slack the bottle may be slightly warmed, by placing it in warm water, and shaken to promote further escape. When no more gas comes off the tap is disconnected, a soda lime tube substituted, and a current of air drawn through the apparatus. (6) and (c) are dried, cooled and again weighed ; the increase represents the amount of carbon dioxide which has escaped from the bottle. The total contents of the bottle are now weighed and the percentage calculated. There still remains a little carbon dioxide dissolved ; this can N be best estimated by titrating a weighed amount with -r-r barvta water, using phenolphthalein as indicator ; the difference between the acidity thus estimated and that estimated as previously described under Decomposed milk, Mall represent, without great N error, the carbon dioxide (1 c.c. — alkali = '0022 gramme CO.,). This should be added to the amount estimated by absorption. Buttermilk and whey are analysed by the methods given for milk ; the total proteids of whey cannot be determined by Ititthausen's method, and the total nitrosren must be estimated. 120 NORMAL MILK. CHAPTER III. NORMAL MILK I ITS ADULTERATIONS AND ALTERATIONS, AND THEIR DETECTIONS. Contents. — Chemical Composition of Milk — Colostrum — Limits and Standards of Milk — Adulterations of Milk — Preservatives — The Action of Heat on Milk — Condensed Milk — Sterilised Milk — The Action of Cold on Milk. The Chemical Composition of Milk— Average compo- sition.— The milk of the cow has, on the average, the following composition (deduced from about 200,000 analyses made in the Laboratory of the Aylesbury Dairy Company, Limited) : — Per cent. Per cent Water, . . 87-10 Casein, . 300 Fat, . 3 90 Albumin, . . 40 Milk-sugar, 4*75 Ash, . 75 It is essentially an aqueous solution of milk-sugar, albumin, and certain salts, holding in suspension globules of fat and, in a state of semi-solution, casein, together with mineral matter. Small quantities of other substances are also found, which have been referred to (Chap. I.). When evaporated, a residue is left, which is known as the solids of milk ; these are empirically divided into fat and solids not fat. It was first pointed out by "Wanklyn that the solids not fat in milk show comparatively small variations. Though this rule is by no means absolute, it is to a great extent borne out in practice, especially in dealing with the mixed milk of several cows. Limits and Variations. — The following arc the maximum and minimum percentages which have conic under the author's notice; the highest fat is recorded by Bannister, the highest and lowest solids not fat and the lowest fat were observed in the Aylesbury Dairy Company's Laboratory: — Maximum, M minium. I'.-lt. Solids DOt K:it. I'it cent. Per cent, 12-52 1060 104 4!)0 ABNORMAL MILK. 121 Vieth gives the average proportion between milk-sugar, pro- teids and ash in milk as 13:9:2. The author has found that this ratio is marvellously exact, the average being Milk-sugar, 52*8 % as against 542 calculated from Vieth'a ratio. Proteids, 37 "S ,, 37 5 „ Ash, 8-3 ,, 8-3 Table XIV. will give the percentage of ash (calculated on the solids not fat) found in milks containing the percentages of solids not fat named. TABLE XIV. — Percentage of Ash in Milk. Percentage of Ash on the Solids not Fat. Solids not Fat. No. of Samples. Limits. Average. 10-5 1 8-1 97 1 8*1 96 1 8-1 9 5 1 8-4 9 4 2 8-1 to 8-5 8-3 9 3 2 8-0 „ 8-6 8-3 9 2 12 8-0 „ 8-6 8-3 91 33 7'9 ,, 9-1 8-3 9 0 43 7-9 ,, 8-8 8 25 8-9 53 7-9 „ 8-7 8-3 8-8 36 8-0 ,, 8-9 8 25 8-7 15 7-9 „ 8-0 8 3 8-6 11 8-0 „ 8-6 8-3 8-5 8 8-1 ,, 8-7 8-4 8-4 10 83 „ 9-5 8-6 8-3 5 8-5 ,, 8-9 8-7 8-2 7 8 6 ,, 9-1 8-9 8-1 7 8-8 „ 9-4 9 0 8-0 4 8-8 „ 10-0 9-2 7-7 1 911 253 S-3 All the above samples were undoubtedly genuine. Abnormal Milk. — Samples which differ greatly from the mean percentage of solids not fat almost invariably show a pro- portion of milk-sugar, proteids, or ash very markedly varying from the average. The following analyses (Table XV.) of abnormal milks will show this : — 122 NORMAL MILK. TABLE XV. — Analyses of Abnormal Milks. No. Water. Fat. Sugar. Proteids. Ash. Total. Solids not Fat. Analyst. Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. 1 89-00 4-90 1-91 3-35 •86 100-02 610 Vieth. 2 8o 20 7-80 3-13 3-32 •76 100-21 6-60 3 85-3 it -4 '78 4-9 4 833 lOo •76 6-2 5 8614 3-62 4-66 4-58 ■82 99-82 10-24 6 7 314 2-79 2-59 3-77 •88 •94 ... 6-04 Bodmer. L< >\ve. •")• 10 8 87-24 4-32 419 3-47 •78 100-00 8-44 Lloyd. There appears to be good evidence of authentication in the case of all these samples ; the table could easily be extended, but the author has chosen those milks which show a very marked departure from the average. Solids not Pat. — From the observations at his disposal, which exceed a million, the author has calculated (Table XVI.) the probable number of samples of the mixed milk of a herd of cows which will be found between the percentages named per 100,000 examined. TABLE XVI. — Percentage of Solids not Fat in Mixed Milk. Percentage of Solids not Fat. Number of Samples. 8-4 to 8-5 8-3 .. 8-4 8-2 ,. 8-3 s-l ,, 8-2 8-0 ,, 8-1 Below 8*0 1892 •_'4J 27 22 s 2 Composition of Milk of Different Breeds of Cattle. — Tables XVII. and XVIII. give the number of samples which are Sound to fall between tie- percentages named of fat ami solids not fat respectively for the milk of single cows Different breeds are kept separate. COMPOSITION OF MILK. 123 Tables XVII. to XX. are chiefly compiled from analyses by Vieth. TABLE XVII. — Composition of Milk of Different Breeds of Cattle (Fat). Percentage of Fat. Dairy Shorthorn. Pedigree Shorthorn. Kerry. Jersey. Red Polled. Other Breeds. Total. Above 10 1 2 3 8 to 10 1U 6 11 1 28 7 ,, 8 11 3 17 36 4 71 6 „ 7 76 8 111 113 6 21 335 5 „ 6 382 91 408 136 41 45 1103 4 „ .5 1313 594 659 89 70 70 2795 3-5 ,, 4 625 362 182 14 31 43 1257 3-0 „ 3-5 309 173 84 3 26 34 629 2-9 28 15 (5 6 4 59 2-8 25 15 7 1 5 53 2-7 21 8 7 2 3 41 2-6 16 10 2 2 1 31 2 5 5 5 1 11 24 8 5 1 1 1 16 2 3 5 1 2 8 2 2 2 1 3 21 5 1 7 2 0 2 1 3 19 2 1 3 1-8 I 1 17 1 1-6 1 i i 1-5 14 i 1-3 1 i 12 10 1 i Tbe analysis of the samples showing the highest and lowest fat was Total solids, .... . 20-97 11-55 Fat, 12-52 1-04 Ash, •73 •85 Solids not fat, 8-23 10 51 Authority, .... Bannister. Authoi 124 NORMAL MILK. TABLE XVIII. — Composition of Milk of Different Breeds of Cattle (Solids not Fat). Percentage of Solids not Fat. Dairy Shorthorn. Pedigree Shorthorn. Kerry. Jersey. Red Polled. Other Breeds. Total. Above 10 21 6 15 2 7 51 9-5 to 10 112 37 88 91 16 47 391 9-0 „ 9o 972 390 744 200 69 114 2489 8-5 „ 9-0 1491 734 594 91 76 59 3045 8-4 108 70 23 2 6 6 215 8-3 62 30 22 2 7 2 125 8-2 36 9 6 2 1 54 si 12 9 3 1 1 26 8-0 15 7 3 25 7 9 10 2 2 1 1 16 7-8 5 1 6 7"7 3 2 2 7 7 6 2 1 1 ... 4 / ••) o ... 2 7-3 1 1 71 1 1 6 6 1 1 6 2 1 1 6-1 1 1 4!) 1 1 The samples yielding below 7 per cent, of solids not fat were all obtained from one cow. The following are analyses on different dates of her milk : — TABLE XIX. — Variations in Solids not Fat in Milk FROM THE SAMK Cow. S§ S3 a ■ x> - - . 70 en .'i- 4 C5 ^2 *£ 7 8-87 North Devon, 13-11 3-43 9-68 Dutch 12-40 3-75 8 65 Ayrshire, 13-46 4 24 9*22 Shorthorn, 12-78 3-92 8-86 It is difficult to give the probable percentages of fat that may be expected to be found, as the amount of fat in a milk is not only dependent on that yielded by the cow, but is influenced by the fact that, owing to its not being in solution, it varies accord- ing to the conditions under which the milk is kept. Variations of Fat in Different Churns. — When the mixed milk of a herd of cows has been examined, the fat has not been found to fall below 2-98 per cent.; when the milk is divided into portions, as is the case when it has to be transported by railway, considerable variations in fat are sometimes noticed. As examples, the following analyses may be quoted : — Series I. Series 11. Specin; gravity, 1 0345 1 -0.341 1 1-0320 1 0325 1 0320 1 0310 p. ct. p. ct. p. ct p. ct. p. ct. ]). ct. Total solids, J 1 -28 1 1 (ifi 14-16 1 1 -22 12-42 13-42 Fat, . 210 2-50 5-10 2-60 3-70 4 -SO Solids not fat, . 9-10 '.lie. 906 S-(J2 8-72 8-62 Seasonal and Monthly Variations. — Distinct variations according to season are found; these will be shown by Table XXIII., which gives the mean monthly averages of milk for the past sixteen years. The year, roughly speaking, can be divided into four periods : (1) November, December, and January ; the milk is rich, both in fat and solids not fat. (2) February, March, and April ; the solids not fat do not show appreciable diminution, but the fat becomes less in quality. (3) .May, .1 une, July, and August ; the fat is low. though I here is a tendency to rise at the end df the period. In July and A.UgUSl the solids not fat arc below the average. (\) September and October; an improvement in quality both in fat and solids not. fat is noticed. These periods correspond approximately to the seasons ; winter DAILY VARIATIONS. 127 milk is of very good quality, while summer milk is the poorest ; the spring and autumn are transition periods. The quality varies in an inverse ratio to the quantity yielded. In the analyses below (Table XXIII.) the specific gravity has always been determined by a lactometer ; the total solids were estimated from 1881 to February 1894, since when, fat deter- minations have been made. The total solids or the fat have been calculated by the formula devised by Hehner and the author. TABLE XXIII. — Mean Monthly Averages of Milk. Month. Specific Gravity. Total Solids. Fat. Solids not Fat. Per cent. Per cent. Per cent. January, 1 -0322 12-88 4 02 S-86 February, . 1 -0322 12-78 3-93 8-85 March, " . 1 0322 1271 3-88 8-83 April, 1 -0322 12-66 3-84 8-82 May, . 1 0323 12-66 3-82 S-S4 June, . 1 -0322 12 -.59 3-79 SS0 July, . . . 1-0317 12-66 3-93 8-73 August, 1 0316 12 73 4-02 8-71 September, 1-0319 12-92 4-12 8-80 October, 1 -03-22 13-13 4-21 8-92 November, . 1 0322 13-19 -1-30 8-89 December, . 1-0322 13-04 416 8-88 Daily Variations. — It has been found that the percentage of fat varies slightly according to the day of the week, as is shown by the following figures : — Day, Per cent. Fat, Mon. 3-70 Tues. 3-78 Wed. 3-75 Thurs. 3 75 Fri. 3-7.5 Sat. 3-73 Sun. 3-74 It is seen that Monday's milk is the lowest in fat ; this is probably due partly to a disturbance in the quality arising from the interval between milking on Sunday night and Monday morning not being identical with the usual interval, and partly to the influence of the Sunday holiday on the milkers, rendering them rather more careless about stripping the cows on Mondays than on other days. Morning and Evening Variations. — In England it is the custom to milk cows twice a day ; the quality is not the same at both meals, the evening milk being almost invariably richer in fat than the morning milk. In dairies where it is the custom to leave an interval of twelve hours between the milkings this is far less noticeable than in those where there is an interval of nine to ten hours between the morning and the evening meal, 128 NORMAL MILK. and fourteen to fifteen hours between the evening and the morning meal. Table XXIV., giving the monthly average of morning and evening milk respectively during 1896, will show the average difference. TABLE XXIY. — Composition of Morning and Evening Milk. Morning Milk. Evening Milk. Month. Specific Total Fat. 3-71 Solids Specific Total Fat. Solids Gravity. .Sol i.ls. 12-76 not Fat 9 05 Gravity. Solids. notFat 906 Januarv. . . . 1-0327 1 0324 13-16 4-10 February, . 10327 12-63 361 9 02 1 0324 13 02 4 00 9 02 March, 1-0327 12-63 3-61 9 02 1 0323 12-96 3 95 9-nl April, . I 0327 12-58 3 56 9 02 1-0325 12-93 3 90 9 03 May, 1 -0328 12-4-2 3-40 9 02 1 0323 1276 3 79 8-97 June, 1 -0323 12-31 3-42 8-89 10318 12-55 3 72 8-83 July. . . 1 0316 12-24 3-50 874 10312 12 50 3 si) 8-70 August . 10315 12-40 3-65 8-75 10313 12 69 3 96 8-73 September, 1-0321 12 61 371 8 90 1-0318 13 07 4 15 8-92 October, 1 0328 12-83 3-75 9-08 10324 13 23 4 17 9 06 November, 1 0329 12-89 3 78 911 1 1)325 13 27 4 17 9 10 ! December. . 1 -0327 12-87 3 80 9 07 1 03-24 1 0321 13-24 12-95 417 9 07 Average, 1-0325 12-60 3 63 8-97 3*99 8-96 Variations on Partial Milking. — The quality of the milk first drawn from the udder is very different from the last portions. Boussingault has recorded the following analyses of milk drawn from a cow in portions : — Portion 1 2 3 4 5 6 Total solids, . .... Bolide n"t til . . Per cent. Per cent. 10-47 10-75 1-70 1-76 s-77 8-99 Per cent. Per cent. Per cent. 10-85 11-23 11-63 2-lo 2-54 ; 814 8-75 8-69 8-49 Per cent. 12-67 IKS 8-59 Helton has also given a remarkable analysis of a partial milking; it contained only -20 per cent, of fat. It is sometimes noticed thai :i cow, through n is or nervousness, holds back her milk, especially if the surroundings Tims Dyer has recorded an analysis of milk obtained from ;i cow at an agricull oral show which contained 1 *85 per cent. of tat ; the next day the milk was normal, containing 3*64 per COLOSTRUM. 129 cent, of fat. Many, if not all, of the very low fats recorded in Table XVII. on p. 123 are due to this cause. Variations of Fat with Solids not Fat. — Speaking very generally, a high percentage of fat is accompanied by a high percentage of solids not fat. Vieth gives the following table : — Total Solids. Fat. Solids not Fat. Per cent. Per cent Per cent. Milk containing 12 o contains on the average 3-80 8 70 127 3 90 8-80 129 4-05 8-85 131 4-29 8-81 13-3 4-34 8-96 There are, however, very many exceptions to this rule. Fore Milk and Strippings. — The first portions drawn from the udder are known as "fore milk," the last portions as "strip- pings"; it is not unusual to find more than 10 per cent, of fat in strippings. ColOStPUm.— The name "colostrum " is applied to die secre- tion of the udder before (and immediately after) parturition. Lassaigne pointed out that an albuminous liquid commenced to form sometimes two months before parturition. This secretion, according to Houdet, often appears under two forms — a brownish, viscous, honey-like product, and a lemon-yellow, non-viscous liquid ; the two often co-exist in the same animal, the earlier milkings furnishing the lirst, and the later the second. The viscous secretion is curdled by heat, and precipitated by acetic acid, mercuric chloride, and alcohol, but not curdled by rennet. The analysis is Per cent. Water, 63-14 Soluble proteids, ...... 22*74 Colloidal ,, 14-12 Ash, trace The non-viscous secretion contained more water and less soluble proteids than the viscous secretion, and gave a barely appreciable precipitate with mercuric chloride and alcohol, but was coagulated by heat and acetic acid and unaffected by rennet. One hundred cubic centimetres contained Fat, "15 gramme Sugar, .... •80 Soluble proteids, . 1-38 Colloidal ,, . 4-39 Calcium phosphate, •11 Other salts, . -38 Total solids, . .7*21 ,, The composition of the fluid secretion approaches more nearly to that of milk. Four or five days before parturition the secretions are replaced by colostrum proper. 9 130 NORMAL MILK. True colostrum is an opaque yellow liquid of pungent taste • sometimes blood is present, which shows its presence by a reddish colour. It is curdled by heat, acetic acid, mercuric chloride, and rennet (though the action of this is not so rapid as with milk). It has a slimy, viscous appearance, and, if left to stand, has a tendency to separate into two layers. The proteids probably consist of casein, albumin, nuclein, and globulin, while lecithin, cholesterol, tyrosine, and urea are present. Albumoses and peptones have been found. The sugar ot colostrum consists of milk-sugar, dextrose, and, possibly, other sugars. The fat differs from that of milk • the melting point is high (40° to 44° C), and the amount of volatile acids low. Pizzi found that a few hours (3 to 6) before parturition the Reichert-Wollny figure of the fat was 4-4 to 4'7, and six hours after calving 6-2 to 6*3; a rapid increase was noticed, and in from three to six days a normal figure was reached. The ash of colostrum has, according to Fleischmann, the fol- lowing composition : — Per cent. Potash, 7 23 Soda, 572 Lime, ......... 34*85 Magnesia, . . . . . . . . 2 -06 Ferric oxide, ....... '."»'- Phosphoric anhydride, ..... 41'43 Sulphuric- ,, . . . . . . "16 Chlorine, . . . ' . . . . 11 "25 103-22 Less oxygen equivalent to chlorine, . . 3-22 100-00 The best defined characteristic of colostrum is the presence of the "corps granuleux " of Donne, which consist of flusters of cells like bunches of grapes. These are from "005 to *025 milli- metre in diameter, and are easily detected under the microscope. They do not disappear entirely from milk till three weeks after calving, .according to Henle. The specific gravity of colostrum is from 1-04(5 to 1079 at 15° C. (59° F.), and averages 1-068. Eugling gives the following composition : — Pet cent. P« cent. I'ri conl Water, . 76-60 l" <>7 4.H average 71-69 Fat, . 1-88 ,, 4 68 ,. 3-37 ( lasein ('.'), . . 2-64 ., 711 ,. \ >83 Albumin (?), . 11 is ,, 20-21 ,, 15-86 Bugar, A>li, 1-34 ,, 3*83 , , 2 is lis ., 2-31 .• 1 -7s COMPOSITION OF COLOSTRUM. 131 Change of Colostrum to Normal Milk. — The composition of colostrum changes rapidly after parturition. Houdet gives the following figures as illustrating the change : — Pat. Sugar. Soluble Proteids. Colloidal Proteids. Calcium Phosphate Other Salts. Six days before calving, Four ,, ,, ,, Immediately after ,, Per ct. •50 3 01 3-14 Per ct. 2 35 3-17 2-70 Per ct. •47 •45 •25 Per ct. 17-43 12-08 14-53 Per ct. ■44 •47 •46 Per ct. •36 •40 •42 These figures show a sudden increase in the amount of pro- teids over that contained in the fluid secretion described above. Houdet ascribes this to a diversion to the udder of nutritive material which up to this time had been supplied to the foetus. An increase of fat and a decrease of soluble proteids are also observed. The colostrum from another cow was examined at intervals after parturition with the following results (Table XXV.), which show the gradual transition into normal milk : — TABLE XXV. — Change of Colostrum to Normal Milk. Date. Sugar. Soluble Colloidal Calcium Other Proteids. Proteids. Phosphate Salts. Per ct. Per ct. Per ct. Per ct. Per ct. Per ct. Immediately after calving 5-69 3-30 •51 14-05 •51 •54 1 day ,, ,, 4-48 4 05 •93 5-21 •43 •43 2 days ,, ,, 5-70 4 32 1-9S 3-52 •43 •45 3 „ 7-40 4 26 2 41 3-45 •43 •40 4 „ 3-20 4 44 •56 5 20 •40 •30 6 „ „ „ 4-20 4-64 1-19 4-02 •38 •29 8 ,, 410 4 96 •48 3-56 •40 •30 14 ,, 3-85 5-03 ■58 3-74 •35 •36 Vaudin gives the following figures (Table XXVI.) as showing the composition of colostrum : — TABLE XXVI.— Composition of Colostrum. Date. Fat. Sugar. Proteids . Per cent. Calcium Phosphate Other Salts. Per cent. Per cent. Per cent. Per cent. Evening before calving, 1-30 1-52 23 70 •62 •47 { 6-32 2-17 1491 •63 •46 Immediately after J 3-84 2-37 20 10 •66 •39 calving (4 cows), ) 1-36 1-02 19 02 •61 •46 [ 2 42 2-86 17-68 •87 •34 Five days after calving, 5-18 4-07 4-35 •38 •49 132 NORMAL MILK. Colostrum differs from milk in containing less sugar, a fat which is very poor in volatile acids, and a high amount ot nitro- genous compounds. The nitrogenous compounds differ from those of milk. As methods for their separation are not known, this accounts for the discrepancy hetween the results of Eugling and Houdet. Milk containing colostrum is not used for dairy purposes ; at least four days should be allowed to elapse after parturition before the milk is employed for consumption. Generally speaking, the milk of newly-calved cows is poorer in fat than that of cows towards the end of their period of lacta- tion. Kiihn's experiments have shown that the casein also increases as the period of lactation advances, while the milk- sugar decreases ; the mineral matter also increases towards the end of lactation. Most of the analyses on p. 122 which show a high percentage of proteids were obtained from cows which were getting dry. The milk of cows in ill-health may have a very abnormal composition. Wynter Blyth has collated the information con- cerning these in his Foods, their Composition and Analysis (q. v.). They are, however, of interest from a pathological point of view, rather than of practical importance in dairying. Limits and Standards Of Milk - Society of Public Ana- lyst's Standard. — The Society of Public Analysts have adopted as lower limits for fat and solids not fat respectively, 30 per cent, by weight and 8 5 per cent, by weight, and these limits have been accepted as satisfactory by the great majority of analytical chemists of the country. These limits do not repre- sent the absolute minima yet found, as will be readily seen by referring to the figures previously quoted, but are limits below which mixed milk of a herd of cows may be reasonably expected not to fall. Vieth in discussing the question how far they could be applied to all milks has written : "My object is by no means to raise the cry that the standard adopted by the Society is too high ; on the contrary, 1 think it is very judiciously fixed, but, in upholding the standard of purity, it should not be forgotten that the cows have never been asked for, nor have given their assent to it, and that they will at times produce milk below standard. A bad season for bay-making is. in my experience, almost invariably followed by a particularly low depression in the quality of the milk towards the end of the winter. Should the winter be of unusual severity and Length, ihr depression will lie still more marked. Long spells of cold and Wet, as well as of heat and drought, during the time when cows ,ii e kepi on pasture, also unfa\ ourably influence the quality and, I may add, quantity of milk." According to the author's experience the limit of 3"0 per cent, for fat is certainly reasonable for the mixed milk of a whole VARIATIONS OP FAT IN MILK ON STANDING. 133 herd; such milk very rarely, if ever, falls appreciably below this limit. It is far more frequent, as is shown by Table XVI. on p. 122, for milk to contain less that 8 "5 per cent, of solids not fat; in the whole of these cases, the author has found that at least •50 per cent, of total nitrogen and -70 per cent, of ash was present, and this experience has received much confirmation. Smetham and some American observers have, however, found that even these limits are somewhat too high for the milk of Dutch or Holstein- Frisian cows. At the present time this breed of cows does not form a majority of English milch cattle ; on farms where they are kept other breeds yielding milk of higher quality are also milked. Triple Standard. — For all practical purposes the triple standard of 8 -5 per cent, of solids not fat, -50 per cent, of total nitrogen, and -70 per cent, of ash may be adopted for the purpose of judging whether a milk is of genuine composition or not. The figure for the ash is, however, liable to be increased by the addition of mineral substances added to the milk ; thus boric acid and borax, used as preservatives, and salt, added to mask the addition of water, would raise the ash ; estimation of the boric acid, which is absent in genuine milk, or of the chlorine, which does not exceed TO per cent., will show additions of this nature. The amount of ash insoluble in hot water is also a useful figure ; it amounts in milk to at least -50 per cent, and is very nearly equal to the total nitrogen. A milk should never be pronounced as watered on the evidence of the solids not fat alone, unless this is well below 8-0 per cent. ; a determination of the total nitrogen and of the ash at least should be made in addition; a judgment formed on the three determinations will be in all probability correct. Variations of Fat in Milk on Standing. — Were milk a homogeneous solution there would be no trouble in employing the limit of 30 per cent, of fat to detect the addition of skim milk, in the same rigid manner that the limits mentioned can be used to detect watering ; the fat globules of milk have, however, a natural tendency to rise to the surface and to thus cause an unequal distribution of fat in different portions of the milk. Table XXVII. will give an idea of the rate at which appre- ciable change in the composition of the milk occurs ; 12 gallons of well-mixed milk were placed in a churn with a tap at the bottom at 11.25 a.m., and a measure holding 7 quarts was drawn out every half-hour till 2.25 p.m. ; each of these quantities was analysed, as also the residue left in the churn (5 quarts) ; the milk was undisturbed throughout. 134 NORMAL MILK. TABLE XXVII. — Variations in Composition of Milk on Standing (Large Churn). Time. Specific Gravity. Total Solids. Fat. Solids not Fat. Per cent. Per cent. Per cent. 11.25 a.m. 1 -0324 12-69 3-71 S-9S 11.65 ,, 1 -0325 12-68 3-68 9-00 12.25 p.m. 1 0328 12-35 3 34 901 12.55 „ 1-0331 12-13 3-10 9-03 1.25 ., 1 0334 12 03 2-95 9-08 1.55 „ 1 0334 11-97 2-90 9-07 2.25 „ 1 0334 11 97 2-9(1 9-07 Residue. 1 -0283 16-65 7-87 8-78 In another experiment two small churns, such as are used in restaurants, each holding 12 quarts, were stood side by side; every quarter of an hour 1 quart was drawn from the tap and the amount of fat in each portion was estimated (Table XXVIIL). TABLE XXVIIL — Variations in Composition of Milk on Standing (Small Churns). Time. No. I. Start. 3-72 % fat. 3-72 % fat. 15 miu. 3-65 „ 364 ,, 30 ,, 3 72 „ 3li5 „ 45 ,, 3 45 „ 3-38 „ 60 „ 2-95 „ 2-85 „ 75 „ 2-85 „ 2'76 „ 90 .. 267 „ 2-67 .. 105 .. 2-63 .. 2-60 .. 120 .. 2-64 ,, 2-57 „ 135 .. 2-54 ,, 2*50 It is Been from the results of these experiments, which are typical of many, that milk left to stand remains approximately of the same composition for short periods only — not exceeding half an hour; bj continually drawing off the bottom layer, samples are obtained which become poorer and pooier in fat till the upper layer of cream is reached. A similar phenomenon is observed, if the milk is dipped from the top of a counter pan, as the following figures will show : — Three quarts of milk were placed in a pan: every half-hour one pint was removed by dipping from the surface ; and each portion was analysed (Table XXIX.). PRACTICAL ALLOWANCES FOR FAT VARIATION. 135 TABLE XXIX. — Variations in Composition of Milk on Standing (Pan). Time. Percentage of Fat. Start. 3-65 30 min. 3-75 60 ,, 4 40 90 ,, 4-15 120 „ 3-75 Residue. 2-80 Here again it is seen that the milk does not remain practically constant in composition for more than half an hour. Court of Queen's Bench Decision. — These figures were obtained under conditions which need never occur in practice ; indeed, the decision of the Court of Queen's Bench in the case of Dyke v. Cower makes it necessary that they must not occur, as it has been decided that a vendor is bound to sell milk in its natural state ; it is equally an offence against the law to sell milk which has been deprived of its cream by natural rising when the milk is undisturbed, and to sell that wilfully adulterated with skim milk. Practical Allowances for Pat Variation. — It is, however, fortunately not a matter of extreme difficulty for a vendor to comply with the spirit of this judgment; for instance, in the sale of milk from a counter pan it is easy to stir the milk every half hour, or, what is preferable, before serving each customer. When milk is delivered in the streets the churn can be fitted with one of the numerous arrangements for automatically keep- ing the cream mixed ; the action of these is, too, materially aided by the motion the milk receives from the movement of the cart or barrow when drawn along the streets. To ensure that the composition of the milk will not vary the minutest fraction perhaps demands more skill and attention than the average milk distributor possesses, but a practical compliance with the judg- ment mentioned above can and ought to be obtained. It is probably owing to the consideration of the natural tendency of cream to rise that the chemists of the Board of Inland Revenue, who are referees under the Sale of Food and Drugs Act, have adopted the limit of 2 75 per cent, of fat in milk, while their limit for solids not fat is the same as that adopted by the Society of Public Analysts. The difference between the two limits — 3-0 and 2*75 — is certainly ample to cover any changes which may take place in the milk during sale, and the referees have not, in the author's opinion, erred on the side of stringency. 136 NOKMAL MILK. It cannot be too strongly insisted on that these limits apply only to the mixed milk of a number of cows; the milk of a single cow may be below to a serious extent these figures. As this case is one which but rarely occurs — the sale of milk being almost entirely confined to the production of herds — it is not necessary to make any allowance for the greater variations of quality of the milk of individual cows. Appeal to the Cow. — In cases of doubt it is advisable to resort to what is known as " appeal to the cow," or the " stall or byre test." This consists in having the cow — or cows — milked in the presence of a responsible witness who can certify to the absolute genuineness of the milk, which is analysed and compared with the suspected sample. It is desirable, it possible, that the milk of the morning and evening meals should both be examined. To make the test as fair as possible, the cows should be milked by their usual milkers at the same time of day, and under the same conditions ; the test should be carried out at as early a date as convenient, and care should be taken that the meteorological conditions are nearly alike, as a poorer milk is yielded in warm, damp weather than if it is clear and frosty. The test should not be carried out on a Sunday or Monday, or on a public holiday or its morrow, unless the previous sample was taken on a similar day, as it has been shown that the irregularity in the time of milking — which occurs on such days — affects the quantity and quality of the milk : any serious divergence from the average quantity of milk yielded may be looked upon as throwing doubt on the reliability of the test. The witnesses must be specially careful in seeing that the cows are milked out, and that nothing occurs likely to disturb the equanimity of the cows, such as undue commotion or noise. If the milk is cooled, it is the duty of the witnesses to satisfy themselves that the refrigerator does not leak, as well as to see that all vessels into which milk is received are clean and dry. This test, if properly carried out by competent witnesses, is very reliable; if the suspected sample were genuine, milk will be yielded of approximately the same composition at the appeal to the cow; everything, however, depends on the competency of the wii nesses. Adulterations of Milk.- The chief adulterations of milk are — (1) The addition of water, which is sometimes masked by the use of a solid substance which is soluble. (2) The addition of skim or separated milk, or the removal of cream. Calculation of Added Water. — Watering is detected by the depression of the solids not fat, total nitrogen, and ask; if all three are below the limits given above, the milk may be ecu- ADULTERATIONS BY CANE SUGAR, ETC. 137 demned as watered. The amount of water added is best calculated from the solids not fat by the formula — Water = 100 - j^x 100, where S = solids not fat. This formula will give the minimum percentage of water added. It is only correct if the original milk contained 8 -5 per cent, of solids not fat. The probable amount can be calculated by using the mean figure for solids not fat 8*9, instead of 8-5, in the above formula. Another excellent method for calculating percentage of added water is to use the sum of the degrees of specific gravity and the fat as a datum. Water = 100 - ~^j- x 100, where G = degrees of gravity, and F = the percentage of fat. This will likewise give a minimum figure, and the probable amount can be obtained by substituting 36 for 34*5. The latter formula has the advantage that it is applicable without correction to milk which contains an excess or deficiency of fat, while the percentage of solids not fat is affected to some extent by variations in the fat ; the table on p. 134 will make this clear. The solids not fat vary from 8 -78 to 9-08, a difference of *30 or 3-3 per cent, of the solids not fat ; the sum of the degrees of specific gravity and fat only varies from 36-1 1 to 3635, a difference of "24 or "7 per cent, of the sum. Adulterations by Cane Sugar, &o. — Sometimes substances such as cane sugar, dextrin, or other carbohydrates or glycerine are added to mask the addition of water by raising the solids not fat ; these will be detected by the sweet taste, the deficiency in total nitrogen and the ash. . Cane sugar, dextrin, &c, can be detected by the discrepancy between the milk-sugar estimated by polarisation and that determined by Fehling's solution. Glycerine, if added to any appreciable extent, will render the total solids sticky, and on analysing the sample the water, fat, milk-sugar, proteids, and ash will in the aggregate be seriously below 100 per cent. It can be detected, and approximately esti- mated, by evaporating 25 c.c. of milk to a pasty consistency, treating with a mixture of alcohol and ether, and following the procedure of the "Somerset House" method of analysis; the alcohol-ether extract is evaporated and the residue exhausted with a little water and this again evaporated. If glycerine be present, a residue having a sticky consistency when cold will be left ; the weight of this, less that of the ash left on ignition, will approximately give the amount of glycerine. Starch has also been used ; this is detected by a blue color- ation being obtained with a solution of iodine in potassium iodide (see p 89). 138 NORMAL MILK. Brains and mammary tissue are said to have been used ; this is doubtful, but they would be shown at once by the large deposit obtained on centrifugalising the milk. Mineral adulterants have been employed. The use of chalk, which is popularly supposed to enter into the composition of adulterated milk, is probably hypothetical, as its insolubility would defeat the object of its use. Salt is detected in the ash by an increase in the chlorides above "10 per cent. ; an estimation of sodium should also be made, as milk does not contain more than -05 per cent. ; carbonate or bicarbonate of soda is also detected by the increased alkalinity of the soluble ash ; this does not exceed in genuine milk an amount equal to -Q2o per cent. NagCOg ; an amount appreciably exceeding this is due to addition of alkali. The alkalinity of the ash should be estimated N by titrating with — acid, using phenolphthalein as indicator ; 1 c.c. of the acid is with this indicator equal to '0106 gramme of NagCOg. Other mineral additions, such as boric acid, borax, fluorides. &a, may be added as preservatives, and not to mask the addition of water; the methods of detecting these will be given later. It has been alleged that salts of ammonia have been added to raise the total nitrogen. These would be detected by rendering alkaline with magnesium carbonate, distilling the milk, and testing the distillate with Nessler's reagent (an alkaline solution of mercuric chloride in potassium iodide). Calculation of Fat Abstracted. — The detection of adultera- tion by removal of cream can only be effected with certainty by the estimation of fat; if this falls below 2"75 per cent., cream has certainly been abstracted, and any percentage below 3#0 is extremely suspicious. From the table on p. 127 it is seen that the mean percentage of fat varies at different times of the year; a limit of 3*25 per cent, could be used from October to January with as much justification as a limit of 3*0 for the other months. The percentage of cream abstracted is calculated by the formula ni abstracted = 100 < 100 where F = percentage of fat. This formula givea a minimum percentage of fat abstracted; bbe figure 2*75 should not be used instead of 3 in the calculation, as this is used as a limit in order to allow for cream abstraction by the natural rising of cream in milk. The figure thus calcu- lated 18 almost always seriously below the truth; the probable amount can be calculated > » \- substituting 3*75 for 3, <»r. better Btill, the monthly average figure given in Tabic XXIII. on p. Il'7 for the month in which the analysis is made. If •■ appeal to the cow " has been made, or if the mean oompo PRESERVATIVES. 139 sition of the milk was approximately or exactly known, the figure representing the actual composition should be substituted for 3. The colour of the fat is of some aid in judging the amount of cream abstracted ; if it is very yellow, the milk is very likely yielded by Jersey cows, and a high figure — e.g., 4 — may be sub- stituted for 3. The colour of the milk itself is no guide, as it is frequently artificially coloured to give it an appearance of richness. Annatto was the colouring-matter chiefly used, hut this is now somewhat largely replaced by coal-tar colours. Artificial colouring-matters generally may be detected by precipitating the casein with acetic acid, washing well with water, and digesting with strong alcohol ; the casein carries down the colouring-matter and gives it up to the alcohol ; on evaporating this, and taking up with a little water, the colour can be detected. Annatto is unchanged by mineral acius, while many of the coal-tar colours turn pink. Preservatives. — In order to check the growth of micro- organisms in milk, and thus make it keep for a longer time than it otherwise would, preservatives are frequently added. The most common additions for this purpose are boric acid and its sodium salt, borax ; salicylic acid, either alone or mixed with borax and boric acid, and sometimes in alcohol or glycerol solution ; fluorides, such as sodium fluoride ; fluosilicates and fluoborates ; and formaldehyde. Benzoic acid and potassium nitrate have also been recommended, but they are comparatively weak antiseptics and are little, if at all, used. Objections. — The practice of adding preservatives is by many considered highly reprehensible, while others are warmly in favour of this course. Evidence that any well-marked inju- rious effect follows the consumption of milk containing small amounts of preservatives is not forthcoming. Hehner, Leffmann and Beam, and Cripps have shown that boric acid, even in con- siderable quantities, has no appreciable inhibitive effect on enzymes such as pepsin, trypsin, and ptyalin, which exist in the alimentary tract, and to which a part of the digestive process is due. They have none of them, however, ventured to claim that their experiments have more than a partial bearing on the question whether boric acid is injurious or not. On the other hand, the author has found a general consensus of opinion among medical men, who are specialists in infant feeding, that the presence of boric acid or its compounds tends to cause feeding troubles in young children. Salicylic acid is in rather a different category ; it is a well-known drug, and, when taken in moderate quantity, has been proved to cause injurious symp- toms ; its use is forbidden in France as a preservative ; it has also an inhibitive effect on enzymes. Formaldehyde is of con- siderable activity as a chemical agent and combines with proteids 140 NORMAL MILK. to form compounds of a different nature; there is considerable evidence that it venders the casein of milk less digestible, accord- ing to the experiments of Weigle and Alerkel, and Cassal. J lie Lancet lias elicited the opinions of a selection of scientists, who may claim to be authorities on physiology ; the general view was that there was not enough evidence to justify the forbiddance of preservatives in food, but that the fact of their presence should be notified ; many were in favour of limiting the quantities allowable to limits not stated, but to be defined after full investigation. To sum up, it seems that while healthy adults can take small doses of the preservatives usually employed in milk, there is evidence that young children are not unaffected. The practice must, therefore, be considered undesirable. The author's expe- rience has shown that in London, the use of preservatives in milk is entirely unnecessary ; no difficulty has been found, even in summer, in delivering milk to customers in a fresh condition. Cream and butter are on a slightly different footing to milk. While the last is chiefly consumed for its food value, cream and butter are chiefly taken to improve the taste of other foods, and are consumed in comparatively small quantities ; being, more- over, high in price, they may be considered as luxuries, and are expected to keep for a longer time than is naturally possible. It is readily seen that, under these circumstances, there is far more to be said in favour of the use of preservatives in cream and butter, than can be said when they are added to milk. Butter is defined by the Margarine Act as "the substance usually known as butter . . . with or without preservatives," and the use of preservatives is thereby legalised ; the Sale of Pood and Drugs Act, however, contains no such clause, and, in a case recently (Jan. 12th, 1898) decided at Pontypridd, the presence of an amount of boric acid beyond that necessary for preserving the butter has been held to be an adulteration. Advantages. — The advantages of using preservatives to the vendor are obvious ; they enable a perishable article to be main- tained in a marketable condition for :i longer time than it would otherwise remain so. As change from the action of micro- organisms is not entirely stopped, the advantage t . > t he purchaser is by no means so apparent, and there appears to be a well- founded public opinion against, the use of preservatives. Detection of Preservatives. The detection and estimation of boric acid have already been ■ ibed (p. "•">). Some idea as to whether boric acid or borax has been added can lie obtained by applying the turmeric test ( I) to a solution of asfa of milk in water, and ( 2 | to a Bolul ion of the ash in dilute DETECTION OF PRESERVATIVES. 141 hydrochloric acid. If test (1) gives no reaction, while test (2) gives a strong reaction, borax has been added ; if test (2) gives a reaction no stronger than that obtained by test (1), boric acid has been used; while if test (1) gives a reaction, while test (2) gives a stronger reaction, a mixture of the two is probable. These tests are far from absolute, owing to the difficulty of judging the strength of a reaction, and, further, owing to the fact that the ash of milk is usually feebly alkaline, which would cause some of the boric acid to be reckoned as borax. Occasion- ally, the ash of milk is acid, and some of the borax would then appear as boric acid. Nothing more than rough approximate results are claimed for this method. Farrington has shown that when boric acid is added to milk its acidity to phenolphthalein is four times as great as its acidity in aqueous solution ; if a milk is found to have a high acidity, say 40°, ami does not smell or taste sour or curdle on boiling, it is highly probable that boric acid is present Salicylic acid is best detected in the nitrate produced by adding mercuric nitrate to milk ; if much salicylic acid be present this will acquire a red colour after some time, and when shaken with a little amyl alcohol, the colour will pass to the amyl alcohol. A very much better test is to shake the filtrate at once with ether, and evaporate the ethereal solution. The residue is taken up with water, and divided into three parts ; to one a drop of dilute ferric chloride solution is added, and a violet coloration is developed in the presence of salicylic acid ; a second is tested with bromine water, a curdy yellowish precipitate is produced by salicylic acid, and the characteristic smell of halogen phenol derivatives produced ; the third part is evaporated to dryness with strong nitric acid, and the residue taken up with a few drops of water ; a yellow coloration is produced on adding ammonia if salicylic acid be present These reactions are not absolutely characteristic of salicylic acid, as phenol (carbolic acid) and other hydroxy -benzene deri- vatives behave in a similar manner. Fluorides are thus detected in the ash of milk. At least 25 c.c. of milk should be taken, and the ash treated in a platinum basin with a little strong sulphuric acid. Over the top of the basin a watch glass coated with paraffin wax, through which a few lines are scratched, is placed, and a piece of ice or some cold water is put into the concave depression. The basin is then gently warmed and the watch glass exposed to the action of the fumes evolved for ten minutes. In the presence of fluorides it is seen that the glass has been etched, after removal of the wax. Jf a drop of water is placed on the paraffin, away from the lines scratched through it, a white film of silica will be formed on its surface, if fluosilicates be present. If fluoborates 142 NORMAL MILK. be present, this drop of water will give a boric acid reaction ; in the presence of fluoborates both a fluoride and a boric acid re- action are given by the ash of the milk. Formaldehyde, which has been introduced of late years, is now frequently employed as a milk preservative. It is generally added as a 1 per cent, solution in water, which is made by diluting the 40 per cent solution known as "Formalin," "Formal," " Formol," or " Formine." When tirst introduced it was claimed that it could not be detected in milk, but a very large number of reactions for this substance have been worked out. The most characteristic test is that known as Hehner'a test, which is best carried out as follows : — The milk is diluted with an equal volume of water, and a little (Jl per cent, sulphuric acid run in so that it forms a layer at the bottom. In the pre- sence of formaldehyde a violet-blue colour appears at the junction of the two liquids, and the colour is permanent for two or three days. This test will detect, easily, 1 part of formaldehyde in 200,000 of milk. Milk, in the absence of formaldehyde, gives a slight "Teenish tinge at the junction of the two liquids, and on standing a brownish colour is developed, not at the junction of the two liquids, but lower down in the acid. This test is abso- lutely characteristic of formaldehyde, but is not given in the presence of large amounts of this body. Leonard has pointed out that pure sulphuric acid gives no reaction, but the presence of an oxidising agent is necessary ; he found that a trace of ferric chloride gave the best results ; it is better to use commercial acid than a purer form, as the necessary oxidising agent is present. As a confirmatory test, s >me of the milk may be curdled by dilute sulphuric acid and a little Schitf's reagent — a solution of rosaniline bleached by sulphurous acid — added to the filtrate in a test tube, which is corked and allowed to stand. In the pre- sence of an aldehyde a violet-pink colour is produced after a short time. Excess of sulphurous acid must be avoided in pre- paring the reagent, or the test may fail with small amounts. There are many confirmatory tests, which are best applied to the clear Bolution obtained by distilling the filtrate obtained by curdling the milk with sulphuric acid. 7>mith and Leonard have shown thai when milk containing formaldehyde is distilled, but a small fraction can be obtained in the distillate; if the milk be made alkaline, still less is obtained; but a very much larger proportion is obtained by distilling from an arid solution. This is probably due to the fact that formaldehyde combines with the proteids of the milk ; the more perfectly these are in a state of solution, the faster is the rate of combination. Combination is more rapid at high temperatures, but takes place at ordinary temperatures, and the total quantity added is never obtained; DETECTION OF PRESERVATIVES. 143 after a lapse of some time — several days — the formaldehyde dis- appears, and can no longer be detected. If Schiff's test is applied to the distillate, it must be rendered faintly acid beforehand with hydrochloric acid ; Hehner has shown that the distillate of milk gives a faint pink colour with Schiff's reagent after some time, but this disappears on the addi- tion of a drop or two of sulphurous acid, while the colour due to the presence of formaldehyde does not. He ascribes this to oxidation, but as it is equally well prevented by a little hydro- chloric acid, it appears that this explanation is not correct; it is probably due to traces of alkali dissolved from the glass. The following tests are a selection from the m my which have been devised : — (1) To the distillate add one drop of a dilute aqueous solution of phenol, and pour in some strong sulphuric acid down the sides of the tube. In the presence of formaldehyde a bright crimson zone appears at the junction of the two liquids. This test, which is also due to Hehner, is as delicate as the test previously described, and has the further advantage that it is obtained by formaldehyde solutions of all strengths. If there is more than one part of formaldehyde per 100,000, a white turbidity is obtained in the solution above the sulphuric acid while in strong solutions a white or pinkish curdy precipitate is obtained. Many hydroxy-derivatives of benzene, such as salicylic acid, resorcinol, and pyrogallol may be substituted for phenol. Quinol, however, gives not a red colour, but an orange-yellow one. Acetaldehyde gives an orange-yellow colour with phenol and sulphuric acid. (2) Boil the distillate with a solution of hydrazine sulphate, made strongly alkaline with caustic soda; a white precipitate suddenly appeal's if formaldehyde is present. (3) To a decigramme of diphenylamine add 2 c.c. of water, and sufficient sulphuric acid to dissolve it, and pour some of the distillate into the warm solution. In the presence of formal- dehyde, a white turbidity or precipitate is obtained, on further warming if necessary. The precipitate rapidly turns <*reen. This test, like the last, is characteristic of formaldehyde, but is not of such great delicacy as the former ones, and may not be obtained with milk containing only a small amount. (4) Heat some of the milk for thirty minutes on the water bath with a little sulphuric acid and a drop of dimethylaniline ; filter ; render alkaline with caustic soda ; and boil till the smell ot dimethylaniline has disappeared. Filter ; moisten the filter paper with acetic acid, and sprinkle lead peroxide on it. A blue colour is developed if formaldehyde is present. (5) To the distillate add a 3 per cent, solution of aniline. Formaldehyde produces a white precipitate, which is dissolved on boiling, but is deposited again on cooling. 144 NORMAL MILK. Preservation of Milk Samples. Where any special importance is attached to the analysis of any sample, it is an advantage to preserve the sample for refer- ence and further corroborative analysis. Preservatives are added to effect this. The following substances have been used : — Alcohol — Allen has suggested adding to the milk to be kept twice its weight of alcohol : his experience and that of Hehner show that analytical data can be obtained on the preserved milk (making allowance for the alcohol added) which agree with the original sample The objection to this method is that a large amount of a volatile substance is added, and a correction, the correctness of which depends on the amount of alcohol present, must be made. Chloroform. — When added in the proportion of 1 c.c. to 100 c.c. of milk it keeps the milk well for a short time. It has the advantage of dissolving in the fat and keeping the cream in an easily miscible condition. As Babcock and Russell have shown, it does not stop enz}rmic action ; hence changes in the proteids, due to this cause, proceed as if no chloroform had bees added. The correction to be applied is small. For keeping samples for a short period, say ten days, this method is good. Ether. — This preservative is nearly as good as chloroform ; it is, however, not quite so good a preservative and is more volatile. Terpenes, Thymol, Diehlorophenol. and Salicylic Acid. — These keep the milk, but allow the cream to rise to the surface, where it sets in a firm layer and is not easily redistributed. Hydrofluoric Acid and Fluoboric Acid. — The author has proved that these substances, when added to fresh samples in the proportion of \ c.c. to 100 c.c. of milk, keep them in good condition, and, after a year, analysis gives the same figures as those previously found. They curdle the milk, however, so that the sample must be well shaken to bring the precipitated casein into a line state of division ; a little of the bottle is dissolved and the ash is thereby slightly increased. The author has found this method to lie one, of the best. Formalin.- -The addition of formalin has many advantages. A very minute amount of the 40 per cent, solution need be added (2 drops per 100 cc), and no correction is necessary for so small a quantity. The formaldehyde, however, combines with the proteids, and raises the Apparent percentage of total solids and solids not fat. Bevan has also suggested that the milk-sugar is hydrolysed into dextrose and galactose, as he found the increase in total solids more than the total amount of formal- dehyde added. Potassium Bichromate, Mercuric Chloride, and Solid Antiseptics. — These add considerably to the weight of the THE ACTION OP HEAT ON MILK. 145 total solids and solids not fat, and cannot, therefore, be recom- mended. If fat only is to be determined they are efficient. Sterilisation may be resorted to. Certain changes take place, which do not usually interfere with the analysis. The cream rises and clots on the surface, so that it is not easy to obtain an average sample. Cold Storage. — Samples may be frozen and kept in a cold chamber, if one is available ; they keep for an indefinite period thus, but require carefully remelting and remixing. This method, which is not always available, is superior to all others, and should be resorted to in those dairies which possess a freezing plant and cold storage room. The Action Of Heat On Milk. — When milk is heated the following changes occur : — At about 70° C. a change takes place in the albumin ; it is not precipitated, bat is converted into a form which is precipitated by acids, magnesium sulphate and other precipitants of casein. At about 80° C. certain organised principles, the nature of which is not fully known, undergo a change. The presence of these principles in an unchanged form is shown by the following reactions : — They cause an evolution of gas from hydrogen per- oxide in the cold and give a blue colour with para-phenylene- diamine (para-di-amido-benzene), and l^'drogen peroxide. Other substances may be substituted for the para-phenylene-diamine, but, according to Leffmann, this substance is the most charac- teristic. Near 100° C. calcium citrate is deposited, and, by keeping at this temperature for some time, slight oxidation sets in, with the production of traces of formic acid and a marked reduction of the rotator}7 power of the milk-sugar ; a brown colour is produced at the same time. A deposition of salts and, perhaps, also of albumin takes place on the fat globules, which increases their mean density, causing them to rise slowly to the surface, when the milk is afterwards cooled ; during the heating the fat globules are expanded and may somewhat coalesce. If the surface of the milk is freely exposed to the air, a skin forms at temperatures exceeding 60° C. This has been stated to consist of casein, but has not the properties of this substance ; it is certainly of a proteid character, and there is some reason to suppose that it is an oxidation product. The taste and smell of milk are changed by heating to above 70* C. It is not known how far the action of heat on milk affects its digestive qualities. Milk which has been heated is curdled less readily by rennet than fresh milk, but there are good grounds for the view that this is due to the deposition of calcium salts rather than to any change in the casein. It has been claimed that sterilised or boiled milk is more easy of digestion than unboiled milk, but this, again, is possibly due to the fact that it 10 140 NORMAL MILK. is not curdled so easily in the stomach and does not produce so firm a clot. There appears to be no evidence that healthy adults digest boiled milk either more or less readily than unboiled milk. In one respect boiled milk is less to be preferred than fresh milk. From the evidence adduced by Barlow, it seems that children fed exclusively on sterilised milk have a scorbutic tendency. It has long been known that the absence of fresh food of any description is a predisposing cause of scurvy, but no substance has yet been identified as the agent which confers anti-scorbutic properties. It is of considerable importance to be able to distinguish between fresh milk, on the one hand, and " pasteurised " or "sterilised" milk, on the other. Condensed Milk. For convenience of transport, milk is deprived of the bulk of its water by evaporation under diminished pressure in a vacuum apparatus fitted with a condenser ; this is termed condensed or evaporated milk. It is made in two forms : sweetened con- densed milk, which is a preparation of milk and cane sugar ; and unsweetened condensed milk, which consists of milk evaporated •per se. The methods of manufacture are similar. In the manufacture of sweetened condensed milk 1^ lbs. of cane sugar are added to each gallon of milk, and the mixture heated to such a tempera- ture that it will commence to boil at once on being admitted to the vacuum pan. It is allowed to flow in slowly, the pump being kept working the whole time, and no heat is applied till all the milk is in the pan. By this procedure the gases of the milk are drawn out, and on applying heat the milk boils without frothing over. By carefully regulating the supply of heat to the pan, and cold water to the condenser, the milk can be boiled at an even rapid rate till sufficiently concentrated, a point which can be easily told by an experienced operator. The whole oper- ation is controlled by looking through a glass sight-hole let into the upper portion of the pan. The finished product has a density of about 1 "28 and weighs one-third of the original milk : it only occupies three-elevenths of the original volume — i.e.} 1 gallon <>( milk is evaporated to 24 pints. Commercial glucose is sometimes substituted for a pari or the w hole of t lie cane BUgar. Composition of Sweetened Milk. — The following analyses (Table X .\ X. ) will show the composition of sweetened condensed milks : — COMPOSITION OF UNSWEETENED MILK. 14i TABLE XXX. — Composition of Sweetened Milk. Authority. Water. Fat. Milk- Sugar. Cane Sugar. Per ct. Proteids. Ash. Total. Per ct. Per ct. Per ct. Per ct. Per ct. Per ct. Author, . . . 24-06 11-28 13 97 38 31 9 36 2-13 99-11 Pearmain & Moor, 26-10 10-84 14-68 36-93* 9-55 1-90 100 00 r leischmann, . 25-69 10 98 16-29 32-37 12-33 2 34 100 00 Pearmain & Moor, 29-87 1-17 14-68 41-54* 10-74 2-00 100-00 Author, . . 29 05 1-28 1491 40-07 10 63 2-33 98-27 29 23 •64 15-50 40-19 10 73 2-63 98-92 28-43 •36 16-88 39-27 11-73 2-58 99-25 The first three are condensed whole milks — i.e., the milk has been evaporated without previous removal of the cream ; the last four are condensed separated milk, the separated milk having been mixed with cane sugar and evaporated. These milks are not usually sterilised, as the large amount of dissolved matter and the small amount of water renders them unsuitable for the development of micro-organisms ; they keep for a long time without appreciable change. Composition of Unsweetened Milk. — Unsweetened con- densed milks are prepared in a similar manner, except that the addition of sugar is omitted. The composition of this product is shown by the following analyses (Table XXXI.) :— TABLE XXXI. — Composition of Unsweetened Milk. Authority. Water. Fat. Milk- Sugar. Proteids. Ash. Total. Per cent. Per cent. Per cent. Per cent.' Per cent. Per cent. Author, .... 63-47 10 22 1298 10-30 2 07 99-04 ,, .... 62 40 11-91 13-04 9-68 2-14 9917 ,, ... 63 07 10-86 13-38 9-80 221 99 32 Pearmain & Moor, 6196 10 67 15-50 9-57 2-30 100 00 Aschmann, . . 69-35 9-23 10-98 9 41 1-63 100-00 These milks have all been sterilised by heat. They have the analytical characters of sterilised milk. It is noticed that the totals of analyses of condensed milk almost invariably add up distinctly below 100 per cent. ; it is probable that the milk-sugar is underestimated. In condensed milk the layer of solution which is attracted round the fat globules by surface energy has probably a composition which is identical with the composition of the liquid in which the globules are suspended. When condensed milk is diluted with * By difference. 148 NORMAL MILK. water it is doubtful whether the liquid in this layer is diluted by the water, as it is held by a great force, and acts as though separated by a semi-permeable membrane, through which the dissolved solids must pass by osmose. As the milk is usually diluted with cold water, this process of osmose takes a consider- able time, and the whole of the milk-sugar is not obtained in solution, but a portion is taken down by the fat globules, when they are removed previous to the estimation of the miik-sugar. The same cause can be assigned to the fact that the fat globules in diluted condensed milk rise with such extreme slowness ; a dense layer round the globules increases its mean density, and makes this nearly approach the density of the serum. Dilution. — The directions on the label of sweetened condensed milk are often somewhat, misleading. For some purposes — e.g., for infant feeding — the directions given are to dilute with five or even seven parts of water. Supposing that these dilutions are performed by volume, the composition will be as follows : — Condensed Whole Milk. Condensed Skim Milk. With 5 Volumes of Water. With 7 Volumes of Water. With 5 Volumes of Water. With 7 Volumes of Water. ■ Fat, Milk-sugar, . Cane sugar, . Proteids, Ash, 2-02 2'57 7 33 183 •40 1-51 1 -93 5 50 1 -37 ■30 •21 3-20 S-.3 2 24 •63 •l(i 2-40 li 40 ros •40 Compared with the average composition of human milk (p. 323), which is Fat, Sugar, 3 3 (is Proteids, Ash, 1-5 •2 we see that there is a serious deficiency of fat, especially in the diluted condensed skim milk, and a great excess of total sugar. Food Value. — Runners lias stated that as a food i'-43 partsof BUgar are equal to 1 part of fat. Calculating the value of fat as sugar by this factor, we gel the following values for the food value of fat- and sugar : — Condensed W hole Milk. Condensed -Aim Milk. Human Milk. I is:' w it h 6 \ olumes, 1 I ill With 1 Volumes. low With .. \ olumes, 12-34 With 7 \ olumes, 9 23 STKRILISED MILK. 149 Only in the case of the condensed whole milk diluted with 5 volumes of water does the food value approximate to that of human milk ; it is doubtful, however, whether fat can be replaced entirely by cane sugar, especially for young infants. Milk Powders. — To prepare these, milk is evaporated to dryness in vacuo, and granulated. Two samples examined by the author had the following composition : — Per cent. Per cent. Fat 152 13'5 Milk-sugar, 21 '7 21 3 Cane sugar, . . . . . . 42 5 40 9 Proteids, 15-1 14"9 Ash, 33 3-2 Both had a slightly rancid odour and taste. When dissolved in water some of the fat was not emulsified. Sterilised Milk. Milk is a product which affords all the necessary nourishment for the growth of micro-organisms ; these not only develop pro- ducts which cause alteration of the milk — e.g., lactic acid and proteolytic enzymes — but also are in some cases injurious to health. They are destroyed by heat. Hence milk is frequently " sterilised " by heat, the object being to bring about the destruction of the micro-organisms. Many processes are used. Pasteur originally recommended heating to 70° 0. for a short time, a process which was sufficient to destroy all adult forms of pathogenic organisms and, practi- cally, all others. The spores, however, were left untouched and retained their vitality ; on cooling to the mean air temperature these developed into the adult forms and resumed their activity. To destroy the spores, a process of continued "pasteurisation" has been used. This consists of alternately heating to 70° C. for, say, twenty minutes ; cooling to a lower temperature and keeping at this temperature for a sufficient length of time to allow the spores to develop ; again heating to 70° ; and repeating this process many times. By this process, which is very tedious, the taste and composition of the milk undergoes but little alter- ation. It has been found that most spores can be killed by continued exposure at higher temperatures. The temperature of boiling water is one much used, as it can be easily attained, but higher temperatures are sometimes resorted to by heating the milk under pressure ; the higher the temperature, the shorter the time necessary to kill all microbial life. Another method 150 NORMAL MILK. adopted is to alternate successive short periods of heating to high temperatures with intervals during which the milk is kept at the ordinary temperature. Numerous modifications of these methods liave formed the subjects of patents. Analytical Characters. — As, practically, no milk sterilised by successive heating to a temperature not exceeding 70° C. is sold commercially, it will be sufficient to describe the methods for characterising milk which has been heated above the coagu- lating point of albumin. The most marked characteristic distinguishing sterilised milk from new milk is the state in which the albumin exists. As previously stated, it is probable that albumin exists in milk in combination with a base ; on heating milk, no coagulation of albumin takes place, but on acidifying, or saturating with mag- nesium sulphate, the albumin separates with the casein. The albumin appears to be changed from a soluble to a colloidal form. (Not more than T per cent, of albumin is found in sterilised milk in the soluble form.) The casein separates on acidifying in a more finely divided state. If the milk has been heated to 100° C. or a higher temperature for any length of time, the rotatory power of the milk-sugar undergoes a serious reduction, the cupric reducing power not changing to any appreciable extent. The milk also assumes a slight brownish colour, due probably to the formation of a "caramelised" body of low rotatory power. The citric acid of the milk is partially deposited as calcium citrate, in the form of gritty particles ; both calcium and citric acid undergo reduction in quantity. The cream rises with extreme slowness ; in three hours, prac- tically no cream is observed on the surface of the milk ; and after six hours, the layer is only about one-tenth of that given by new milk. If sterilised milk be allowed to stand for twenty- four hours or more the bulk of the cream will rise to the surface, but the quantity will be less than that yielded by new milk ; the cream will, however, contain a distinctly larger percentage of fat, about 40 per cent., as against less than 30 per cent, in the cream yielded by new milk. The following figures, which, together with those in Table XXXVI., were obtained by Boseley and the author (Tables XXXII., XXXIIL, XXXIV.) will illustrate the above facts : — COMPOSITION OF NEW MILK. TABLE XXXII. — Composition of Sterilised Milk. Sterilised Milk allowed to stand for Six Hours. 151 No. Fat in Milk. Cream. Fat in Cream. Fat in Skim Milk. Per cent. Per cent. Per cent. Per cent. 1 •4-30 1-3 23 3 4-05 2 3-80 0-7 22 -.3 3-67 3 4 25 1-8 20-6 3 95 4 4-10 1-9 24 7 3-70 5 5 35 2-8 31-4 4-60 6 3-62 0-3 TABLE XXXI U. — Composition of Sterilised Milk. Sterilised Milk allowed to stand for Twenty-four Horn's. No. Fat in Milk. Cream. Fat in Cream. Fat in Skim Milk. Per cent. Per cent. Per cent. Per cent. 1 4-30 7-0 46-8 1-10 2 3-80 6 0 418 1-37 3 4 25 8-8 39-0 •90 4 4-10 8-7 41 0 •58 5 5-36 11*1 41-4 •85 6 3 62 0-8 3-48 TABLE XXXIV.— Composition of New Milk. New Milk allowed to stand for Six Hours. No. Fat in Milk. Cream. Fat in Cream. Fat in Skim Milk. 1 Per cent. Per cent. Per cent. Per cent. 1 4-05 9 2 17-4 2-70 2 4-20 11*2 16 5 2-65 3 3-90 9-8 159 2 60 4 3-70 9-8 18-0 2-15 5 4-45 13 5 16-8 2 30 Table XXXIV. showing the behaviour of new milk is pro- duced here for the sake of comparison. The samples 1 to 5 are from the same cows which respectively yielded the samples with corresponding numbers in the tables illustrating the behaviour of sterilised milk. 152 NORMAL MILK. Condensed unsweetened milk, which has been diluted to the original volume with water, lias all the analytical characteristics of sterilised milk. This is in no way due to the fact that it has been condensed, but is owing to the sterilising process that it has undergone. There appears to be no good method of dis- criminating between condensed milk diluted with water and sterilised milk. If a water containing large amounts of nitrates has been used for diluting the condensed milk, a strong diphenyl amine reaction will indicate the probability that water has been added ; this test is not of a sufficiently absolute character to be relied on. This is to be regretted. The subject has been con- sidered of sufficient importance by the British Dairy Farmers' Association to induce them to offer a gold medal for the dis- covery of such a method. Detection of Sterilised Milk in New Milk. — To distinguish new milk on the one hand from milk which has been sterilised on the other, the following methods may be employed : — (1) Place 100 c.c. of milk in a graduated cylinder (or till a "creamometer ") and allow it to stand for six hours at a tem- perature of 60° F. (15-5° C.) ; note the percentage of cream. If less than 2 -5 per cent, of cream for each 1 per cent, of fat in the milk has risen to the surface, the milk may be considered suspi- cious. If the quantity of cream falls markedly below 2 per cent, for each 1 per cent, of fat, it is highly probable that sterilised milk is present. (2) Estimate the albumin by the method of Hoppe-Seyler or. better, those of Sebelein or Duclaux. If less than *35 per cent, is found, sterilised milk may be considered to be present. (3) Estimate the milk-sugar by the polariscope, and also gravimetrically in duplicate ; if the difference between the two estimations be more than -2 per cent., it will be corroborative evidence of the presence of sterilised milk. (■I) To about 5 c.c. of milk add as much powdered para- phenylene-diamine as will lie on the point of a knife and shake well ; on the addition of a drop or two of a 10-volume solu- tion of hydrogen peroxide fresh milk gives a blue coloration ; "pasteurised" milk gives a similar reaction, not, however, so marked; while "sterilised" milk gives no coloration within 10 minutes. A mixture of " sterilised " and fresh milk will give the characters of " pasteurised milk. The hydrochloride of meta phenylenediamine may be sub- stituted with advantage for the para-compound. The coloration is paler, and not quite so quickly developed. I'.y shaking with an equal volume of amyl alcohol the blue substance is dissolved in the alcohol layer, and tin- test is thus rendered more reliable in the presence of substances which modify the tint (c.r/., formal- dehyde). DETECTION OF STERILISED MILK IN NEW MILK. 153 A cultivated palate may also detect a boiled taste ; this will certainly he noticed with "sterilised" milk. No good method for the estimation of citric acid is at present worked out, nor are there sufficient data to make an estimation of value. An estimation of lime is also not of much value in affording evidence of the presence of sterilised milk, as the vari- ations of this constituent are too great, and the difference too small between the amount in new milk and that in sterilised milk to allow of reliable deductions being drawn. It is doubtful whether a proportion of sterdised milk much below 30 per cent, could be detected with certainty when mixed with new milk. The proportion of sterilised milk should be deduced from the percentage of soluble albumin by the following formula : — „ . , .,. , ... •-!- percentage of soluble albumin ,„_ .Percentage of sterilised milk = - — x 100. This is based on the supposition that new milk contains ••! per cent, of albumin, while in sterilised milk the albumin has been removed. The estimation of albumin is the most reliable test. There are many causes which influence the rising of cream, such as the temperature to which the milk has been warmed or cooled; the size of the fat globules, which varies with the stage of lactation ; and the acidity of the milk. No quantitative deduc- tions can be drawn from observations of the rate of the rising of cream. The fall in specific rotatory power of milk-sugar is by no means constant, as milks sterilised side by side may show very appreciable variations in this respect. Tests other than the estimation of albumin must be considered as merely corroborative and of qualitative value only. It must be remembered, however, that no sharp distinction can be drawn between milk which has been raised to a tempera- ture over 70° 0. for a short period, and which is naturally not sterilised in the true sense of the term, and milk which has been heated for a sufficient length of time to destroy all microbial life. For this reason, a milk should not be reported as sterilised, solely on the result of a very low percentage of albumin, if neither the " creamometer " nor the para-phenylene-diamine nor "milk- sugar" tests give corroborative indications. It is probable that the milk, in this case, has been merely scalded. The following. figures (Table XXXV.) by 0. H. Stewart show the percentage of albumin found in milk raised to various tem- peratures : — 154 NORMAL MILK. TABLE XXXV. — Percentage of Albumin in Milk at Various Tempkratukes. Time of Heating. Soluble Albumin in Fresh Milk. Soluble Albumin in Heated Milk. Per cent. Per cent. 10 minutes at 60'' C, •423 •418 30 „ ,, ,, •435 •427 10 ,, „ 65° C, 395 •362 30 „ „ „ •395 •333 in „ ,, 70° C, ■422 •269 :so ., ,, .. ■421 •253 10 ., ,, 75°C, •380 07 30 „ „ „ •38 05 Id ,. ,, 80° C, •375 none 30 ,, ,. „ ■375 none The following analyses (Table XXXVI.) will show to what extent the methods above described can be depended on : — TABLE XXXVI. — Comparative Analyses of Mixed Fresh and Sterilised Milks. Percentage Sterilised. c 2 s 5 Cream 1-ut ■ 2 < GO 3 % o ^r Oh 3 o < Calc. from Cream. c 3 c '3 c 1 . 3 O — "32 1 p. C. 3 86 p. c. 7 2 p.c. 1-87 p. c. •30 p. c. 4-85 p.c. 4 65 33 29 25 2 410 96 2 34 •34 4 79 4-68 < irnuine 3 3-90 7-5 1 -92 •29 4-79 4 64 28 26 27 4 3-70 4 3 111) 16 f 7". 4 57 56 ill 60 5 1-10 74 1-81 •26 30 31 35 6 I -00 7 5 1-88 27 30 28 32 7 3-75 7*9 2-11 •35 ( tannine The Action Of Cold on Milk Composition.— When milk is exposed t<> a low temperature it partially freezes. Like other aqueous solutions the freezing poinl is below that of water, and is about '55* C. (•*51° F.), estimated in the Beckmann apparatus. The frozen portion has not the samr composition as t lit* milk from which it was prepared, bul contains a larger quantity of water. The following analyses (Table XXXVIL)will show the composition of the ice and liquid portion respectively : — COMPOSITION OF FROZEN" MILK. 155 TABLE XXXVII. — Composition of the Solid and Liquid Portions of Frozen Milk. Liquid Portion. Melted Ice. Percentage of Ice Formed, 1"2 pei cent. Specific gravity, . 1 -0320 1-0245 Per cent. Per cent. Water, 96-72 9163 Fat, .... 411 240 Proteids, 3 56 2-40 Sugar, .... 4-87 3 05 Ash. .... •74 •52 Percentage of Ice Formed, 2 per cent. Specific gravity, . 1-0330 1-0190 Per cent. Per cent. Water, 87-10 91 -83 Fat, .... 3-87 2 56 Proteids, 3 21 2-28 Sugar, .... 5-08 2-89 Ash, .... ■74 •44 Percentage of Ice Formed, 2 25 pe • cent. Specific gravity, . . 1 "0330 1-0180 Per cent. Per cent. Water, 87-21 92-46 Fat, .... 357 2-46 Proteids, 3 50 1-96 Sugar, .... 4-98 2 72 Ash, .... •74 •40 Percentage of Ice Formed, 10 per cent. Specific gravity, . 1 -0345 1 -0090 Per cent. Per cent. Water, 85 62 96 23 Fat, .... 4-73 123 Proteids, 3 90 •91 Sugar, .... 4 95 142 Ash, .... ■80 « It is seen that no appreciable difference between the ratio 'of the sugar to the proteids and the ash is found in the two series of analyses, showing that no separation of any constituent except water takes places during freezing. It is seen that the greater the percentage of the ice separated, the more dilute is the melted ice ; this is best seen by calculating the solids not fat (Table XXXV III.). 156 NORMAL MILK. TABLE XXXVIII.— Composition of Frozen Milk. Percentage of ice, Solids not fat, Equal to percentage of water (approx.), 1-2 6-17 30 2 0 561 38 225 5-08 43 10 2 64 70 As all these samples were taken from churns in which milk was brought up to London, the percentage of ice may be taken as roughly indicating the temperature below freezing point to which the milk was exposed, the time of exposure to the low temperature having been approximately the same in all cases. It appears that the lower the temperature to which milk is exposed the more dilute will be the ice after melting. Composition of Melted Frozen Milk. — The difference in composition between frozen and unfrozen milk may have some importance, should samples be taken under the " Sale of Food and Drugs Act," in very cold weather ; should an excessive proportion of ice be present in the portion sold to the inspector the sample may, though originally genuine, have the composition of watered milk. Vieth has recorded an interesting experiment on the freezing of milk: — Two gallons of milk were exposed to a temperature of - 10° C. (14° F.) for three hours; longer time than this did not render any more milk solid. Ice was formed on the bottom and sides of the vessel employed to contain the milk and a funnel- shaped cavity in the centre was filled with liquid. The ice was found to consist of two layers, one of cream, and the other of skim milk ; these were separated as completely as possible and the liquid portion also poured off. The results of analysis were : — TABLE XXXIX.— Composition of Frozen Milk (Vieth). Ice. Liquid Portion. Cream. Skim Milk. Proportion, 8'8 per cent. t>4'7 per cent. 26 6 percent. fie '_t.i\ ity, 1 0100 1 0276 1 -0625 Percent. Per cent. Pet cent. Water TIM 92-10 80-64 1 • 19-23 88 517 Proteida, .... •j ci 2-80 5 38 Milk -sugar, 3-33 3-96 7-77 Ash (Hi l-is 16 100-18 100 -01 Anoi Iht ♦• \ [><• ri m< u i Leave almost identical figures. COMPOSITION OF FROZEN MILK. 157 It is probable from these experiments that milk exposed to a temperature of - 10° C. will always give a liquid portion having the composition given above. The tigures also show that milk cannot be frozen in blocks, from which pieces can be cut off and melted for use, without modifying the composition to a serious extent. The author has had the opportunity of examining three samples of milk which had been frozen for transport and re- melted (Table XL.). The samples were taken under such conditions as would represent the retailing of the milk. TABLE XL. — Composition of Frozen Milk. 1. II. 1 III. Specific gravity, 1 0385 1-0270 1-0325 Per cent. Per cent. Per cent. Total solids, 13-60 1013 11-68 Fat, .... 3 29 2-70 2 86 Ash, •84 •62 •74 Solids not fat, . 1031 7-43 8-82 No. I. has the composition of com entrated milk, No. II. of a watered milk, and No. III. of a slightly skimmed milk. Attempts are being made to introduce frozen, or partially frozen milk, into the English market from Holland and other foreign countries. The above figures show what may be some- times the composition of milk as retailed, unless extreme care be taken in melting the imported product. 158 THE CHEMICAL CONTROL OF THE DAIRY. CHAPTER IV. THE CHEMICAL CONTROL OF THE DAIRY. CONTENTS. — Duties of the Dairy Chemist — The Testing of Milk— Deter- mination of .Specific Gravity — Estimation of Total Solids — of Fat and Butter — The Control of Milk during Delivery — The Solution of Analytical Problems — Cause of low and high Specific Gravity — of Sweet Taste — of "Poor" Milk — of unusual Taste and Smell — of Milk being Curdled — of Milk being Thick— Nature of Sediment — Skim Milk — Cream. Duties Of the Dairy Chemist.— The duties of the dairy chemist consist in the following : — (1) To see that the milk at or from the farms is of good quality, containing a full percentage of cream, is not tampered with by the employes, and is in good condition. (2) If milk is sold by retail, to see that the milk sent out is of good quality, and, by analysing samples taken without notice from the employe in charge of the milk, to ascertain that it is delivered in the same condition as it left the dairy. (3) To see that cream separators, churns, &c, are worked in the most efficient manner, by examining the various products, and to obtain such figures representing their composition as will allow of accounts being kept of the manufacturing processes. (■4) To ensure that all products derivt d from milk are of good quality. (5) To specially investigate products deemed unsatisfactory, and to elucidate the cause for dissatisfaction. (6) To make chemical examinations of water supplies, disin- fectants, &c., so as to ensure that sanitation is carried out by reliable means. (7) To advise on chemical questions that may arise '.;/., the .suitability of metals for the construction of dairy apparatus, the examination of waters or boiler compositions for steam produc- tion, the analysis of feeding stuffs and fertilisers, dec. A description of the duties of a dairy chemist must necessarily be somewhat hypothetical, as the conditions in different dairies differ exceedingly from each other. In large dairies the chemist an official wholly responsible for bis own department, and under the control of no one excepl the proprietor. It is not advisable thai he should have any direct control of the business. SAMPLES AND SAMPLING. 159 his functions being those of a scientific adviser ; a good dairy chemist should have had a practical experience in dairying, so that he may be able to apply his scientific knowledge to the various points that may arise from time to time. In smaller dairies, the manager or other person may undertake the functions of chemist, and these must be arranged so as to interfere as little as possible with his other duties ; this may introduce variations in the plan of work described, by curtailing it, but the general procedure will remain the same. The main duties of the dairy chemist are to see that the milk received from the farms and supplied to the public is pure and contains its due proportion of cream ; that the cream and butter are of good quality and of uniform composition ; that the skimmed or separated milk is as poor as possible in fat; and that the water used is free from pollution ; as also to elucidate the complaints of the customers by examining the product com- plained of. Samples and Sampling. — The main difficulty in keeping a uniform quality of milk is due to the rising of cream whenever milk is allowed to be at rest. The attention of the chemist should be devoted to studying the conditions under which the milk is distributed in the dairy to which he is attached, and to discover how to prevent this separation of cream during distri- bution. For the proper performance of his duties he must be provided with samples of milk at all possible stages, from the entrance of the milk into the dairy till the final return of the small quantities of milk left after distribution ; these samples should, if possible, be examined at once and before the milk has passed to the next stage of delivery. This is only practicable in large dairies where the chemist has no other functions. It is advisable that the persons employed in sampling the milk should be under the control of the chemist as far as this duty is con- cerned, as upon the proper sampling of the milk the whole value of his work depends. In certain cases where more value thin nsual is attached to the examination, the chemist should person- ally supervise, or evei perform, the sampling. The samples may be divided into two kinds, bulk-samples and samples taken during delivery. In the former case, the object to be attained is to take a sample in which the various constituents shall bear the same relative proportion in the sample as in the bulk. In the latter, the bulk from which the sample is taken will be of known composition, and the object of taking the sample is to test the person from whom it is taken ; no attempt must then be made to take an average bulk sample, but the person giving the sample should furnish it in the same manner as he would furnish milk for sale. The taking of the latter class of samples presents no difficulty; the only precaution to be observed is that the bottle into which the sample is poured is clean and dry, and that 160 THE CHEMICAL CONTROL OF THE DAIRY. it has a well-fitting cork. The proper sampling of a large bulk of milk is by no means easy ; the bulk to be sampled will be, in most cases, a churn, and these may be sampled as follows. The sampler stands at the side of the churn and places one foot against the bottom for greater power; he then inserts a stirrer (a flat board 6 inches wide and long enough to reach to the bottom of the churn, and provided with a handle) into the churn, keeping it against the side towards him ; he pulls the handle towards him, so that the end is moved along the bottom to the other side of the churn, and raises the stirrer, keeping the end against the side of the churn and the handle as near to himself as possible in such fashion as to lift up the lower layer of the milk ; this operation should be repeated ;tgain and again. The stirring should be brisk, and should continue for half a minute or more. An iron rod carrying a perforated tin plate is often used for the purpose of stirring the milk ; the stirring is performed by working the stirrer up and down. The "milk thief," a trough with a small opening in it, is also employed. The milk to be sampled is made to pass along the trough, and a little trickles out of the hole into a convenient receptacle beneath. This method gives fairly representative samples and requires no labour. Small quantities of milk may be mixed by pouring to and fro from one vessel to another. The sample should then be taken by means of a dipper or, better, by a sampling tube. This consists of a long tube open at both ends, the lower being flat; a flat plate is attached to a rod which runs down the middle of the tube, so that by raising the rod the plate can be pressed against the bottom of the tube enabling it to contain liquid. To take the sample the tube is lowered slowly into the churn, the plate being kept away from the bottom to allow the milk to rise ; when the milk has com- pletely filled the tube the rod should be raised, and the tube withdrawn to prevent the exit of the milk ; the sample can then be transferred to a convenient receptacle by placing it under the tube and depressing the rod. Another method of sampling bulks of milk, which is scarcely less exact than the preceding, is to tip the contents of the churn into a strainer with sides, the slope of which causes the milk to be thrown from side to side at an angle "i" 45°. The milk timls an exit through the wire gauze ;it the sides of a circular well, which should dip into a small tank of such size that the milk rises to the tup of the wire gauze : a hood at the, back prevents spilling and facilitates mixing. The sample should be taken from the tank with a dipper or sampling tube. This method of sampling has the advantage of removing any particles ol straw, dust ot food, ivc.. thai may be found in the milk, [f the tank be provided With a tap the milk CM! then lie run oil'. TESTING. 161 The most convenient receptacles for the samples from bulk are ordinary half-pint milk cans. In large dairies, the milk is received from different farms, and it is convenient to legibly stamp the name of the farm on its own sample can ; sample cans should be provided and marked for all the samples it is desired to take regularly, and the use of unmarked cans, cans marked with paper labels, and cans marked with another designation should be avoided, if possible. Testing. — The tests applied to milk should be of two kinds, simple tests done in the dairy, and a more extensive examina- tion in the laboratory. The only test sufficiently convenient for use in the dairy is the estimation of the specific gravity. This will be sufficient to detect any gross adulteration. The taking of the specific gravity of every churn should be invariably performed, as this indication alone will be sufficient to detect gross adulteration, and it will also give a rough indication of the quality of the milk. For this purpose it is most convenient to employ a thermo-lactometer, or lactometer and thermometer combined in one instrument ; the specific gravity should be cor- rected to 60° F. by means of Table LXXIII. It is not generally necessary that the chemist should personally take these specific gravities. This may be left to a foreman or other intelligent person who has been trained to this work under the supervision of the chemist. The instructions given to the foreman should be, to pass all milk of a specific gravity lying between certain limits, unless special instructions to the contrary in certain cases are given; these limits maybe from 1 034 to 1-031, 10305, or 1*030, according to circumstances ; but in special cases higher or lower limits may be used. Should the specific gravity of any churn fall outside these limits, the foreman should be instructed to take samples with special care, and send them at once to the laboratory to be further tested ; the milk in this case should be put on one side and not used until the report of the chemist has been received. As it is possible that a dispute, perhaps in a law court, may arise with respect to these special samples, the fore- man should be instructed to seal both the sample, and the churn from which it was taken, so as to prevent any possibility of the milk l>eing tampered with. This preliminary testing lias been found to give satisfactory results in the author's experience. In all cases where adulteration of milk before arrival at the dairy has been definitely proved, the specific gravity test revealed that the milk was not of normal quality. As an example of a case in which it was necessary to depart from the usual instruc- tions given to the foreman, the author has found, in the case of the milk received from one particular farm, that the milk had a specific gravity as low as 1-029. As the genuineness of this milk was proved beyond a doubt, the lower limit for the milk derived from this farm was fixed for a certain period at this 11 162 THE CHEMICAL CONTROL OF THE DAIRY. figure. It will not be necessary to teach the foreman to read the lactometer closer than half a degree, as tins is an approxi- mation quite sufficient in practice. Undoubtedly, the most perfect control over the milk would consist in the analysis of the milk in every churn before it is used, and the rejection of those churns in which the milk does not come up to the standard of purity adopted. This is, how- ever, hardly practicable in a large dairy, as the milk must be dealt with and sent out as soon as it arrives, and the time for analysis is short. It has been found that the time required for handling a churn of milk — i.e., straining and transferring to the vessel in which it is sent away from the dairy — is about 35 seconds, and the quickest analysis, other than the taking of the specific gravity, occupies at least two minutes ; so that to test each churn in this way would mean delaying the handling of the milk to an extent which is incompatible with the proper working of the dairy. The testing of the milk in the laboratory that has passed the specific gravity test, must, therefore, be done after the milk has been disposed of. It has been found that it is not necessary in this case to test the milk in every churn, as the results are for guidance as to the quality of milk that may be expected from different sources, and one sample per day from each farm is sufficient for this; the morning and evening meal should be sampled alternately. If adulteration is detected, or if the milk is of abnormal quality, the whole of the churns from that particular farm should be tested. It is also desirable to test the whole of the churns from each farm at intervals, say once a month, in order to see that the difference between them is not excessive. No strict rule can be laid down for the taking of samples ; the chemist must use his discretion, based on experi- ence, as to what samples he will have taken. Sample Cans. — It has been found most convenient to put the samples in half-pint cans. One of these should be provided for each sample that is regularly taken, and the designation of the sample should be legibly stamped on it in full, abbreviations being avoided as much as possible, as they are liable to create confusion. The lids of these cans should fit well, and they should not be filled more than three-quarters full, to obviate as far as possible the risk of spilling in transit. The samples, after being taken, should be placed in a box or tray made to contain twenty-four cans, or any other convenient number, in which they can be transported to the laboratory. The trays should have a strong handle in the middle, and it is desirable that they be also furnished with a lid which can be locked or sealed, so as to prevent any tampering with tin- samples in transit. The duty of conveying the samples should lie entrusted to one man who should be made responsible for any spilling of the contents. A tray holding t went y-fbur cans is not too hear; to be carried ANALYSIS OF THE SAMPLES. 163 steadily, and there is no reason why any of the milk should be spilt. If the sampling is performed at a distance from the laboratory, the use of 6-ounce bottles is more reliable ; a case to contain these should be provided. It is, of course, necessary for the chemist to see that the sample cans are in good repair; any which leak, or have ill-fitting lids, should be replaced at once. The cans or bottles before being handed over to the samplers should be quite clean and dry ; the cans should be washed with hot water and dried, and when not in use, kept with the lids open. If bottles are used a lai'ge stock should be kept, and they should be well washed with warm water and allowed to drain for a couple of days; this will be found to dry them suffi- ciently. Analysis of the Tamples. — The cans should be brought at once to the laboratory and the lid of the tray opened ; the samples are then to be arranged in alphabetical or numerical order, or in any way that may be most convenient ; a methodical system in this respect will be found to minimise any chance of •error in dealing with large numbers of samples. The procedure must vary in different dairies ; if the samples are very few, the samples taken at different times of the day may be left till a sufficient number have accumulated and all examined at once. In this case, it is necessary to preserve them in a cool place, especially in summer ; but where the time can be found it is preferable to make two or three series of analyses a day. An examination of the lids of the cans should be made to see if any of the milk has been splashed upon them, and if it is not possible to obtain a new sample the portion adhering to the lid should be washed down into the can with some of the sample. The analysis should comprise the following data : — Specific gravity, fat, and total solids, and (by difference) solids not fat. The specific gravity should be estimated by means of a lactometer. The fat may be estimated by the Leffmann- Beam or similar methods, or may be calculated from the total solids and specific gravity. The total solids may be estimated by evaporation, or may be calculated from the fat and specific gravity. The choice of how the analysis is to be conducted will depend upon the time available. The most reliable mode of work is to estimate both fat and total solids, but it requires a considerable amount of time; the quickest method is to estimate total solids and specific gravity, and to calculate the fat, while it is, perhaps, more satisfactory to estimate the fat and to calculate the total solids, as the fat is the most valuable constituent of the milk, and also because the accuracy of this estimation by the Leffmann-Beam method is rather greater than the accuracy of the total solid determination. In some dairies payment is made according to the amount of fat in the milk ; in this case, the fat estimation should certainly be made. 164 THE CHEMICAL CONTROL OF THE DAIRY. The Testing of Milk. In this chapter methods requiring less attention in detail, and suitable for the use of persons who have not had a thorough analytical training, are described. The results obtained by these methods have not the rigid accuracy which can be obtained by the best gravimetric methods, but determinations approximating sufficiently nearly to the truth can be made, to enable them to be used in practical work. Determination of Specific Gravity. Lactometers. — This is invariably done in milk-testing by lactometers (see p. 54) * the lactometers used in dairy work are of two kinds, the thermo-lactometer and the ordinary lactometer. The thermo-lactometer (Fig. 4) consists of a stem on which is marked a double scale, one part reading the specific gravity, and the other the temperature on the enclosed thermometer ; a cylindrical body ; and two bulbs, the upper one being the bulb of the thermometer, and the lower one (containing mercury or shot) serving for the adjustment. By its means the temperature and specific gravity can be read off from the same instrument. The ordinary lactometer consists of a stem carrying a scale on which the specific gravity is read ; a cylindrical, or globular, body * and a bulb containing mercury or shot. Soxhlet's lactometer (Fig. 5) contains a scale from 25° (1-025) to 35° (1*035) divided up into suitable divisions (h or yL). Vieth's lactometer has a globular body ; it requires a smaller bulk and depth of milk than Soxhlet's, and is suitable for taking the specific gravity in a half-pint can. The scale reads from 25° to 35°. Quevenne's lactometer has a scale from 15° to 40°, and is marked to show proportions of water added to milk and skim milk respectively. This auxiliary scale is useless. Another form of lactometer, the name of whose inventor is deservedly lost in oblivion, has a scale from 0 to 1U0, 0 being equal to a specific gravity of 1*000 (water), and 100 being equal to a specific gravity of 1*021). It is of no practical use in milk testing. Still another form is marked M at 1*029, and W at 1*000, the intermediate space being divided into quarters ; this form is a mere toy. An instrument has lately been put on the market, which con- sists of a glass tube in which is enclosed a bulb of specific gravity 1*029, which Boats in milk above this specific gravity, but sinks when the specific gravity is reduced below tins figun by watering, by warming, <>r by excess of cream. It provides h harmless form of amusement, bu1 is of no practical use. LACTOMETERS. 165 The best lactometers for use in milk testing are the therino- lactometer, Sox h let's, i and Vieth's. i"*^'"'] The thermo-lactometer cannot be made very small nor very delicate on account of the en- closed thermometer, and re- quires a comparatively large bulk of milk ; it is thus more suitable for testing in the dairy than in the laboratory, where samples are often limited. It has, however, the advantage of not requiring a separate ther- mometer and a separate opera- tion to determine the tem- perature. Vieth's lactometer can be used in a can and, if the samples are received in cans, as is often the case in a dairy laboratory, no transference of the sample is necessary. Soxhlet's lactometer has a wider scale, and may be con- veniently used when greater accuracy is required. Galaine's self-correcting lacto- meter has a metal ball completely filled with chloroform attached to the bottom, the object being to obviate the necessity of cor- rection of the specific gravity for temperature ; the expansion of the chloroform was supposed to compensate the expansion of the milk. Though excellent in theory, it has proved disappoint- ing in practice. The following directions are due to Vieth : — Use of Lactometer. — In order to determine the specific gravity, the milk is poured into a vessel at least ^ in. greater in diameter than the widest part of the lactometer, and deep if Fig. 4. Fig. 5. Thermo- Soxhlet's lactometer. Lactometer 166 THE CHEMICAL CONTROL OF THE DAIRY. enough to allow the instrument to float. A cylindrical glass jar (Fig. 6), with foot, is the most suitable vessel for the pur- pose if Soxhlet's lactometer or the thermo lactometer be used ; Vieth's lactometer may be used in a can or tin cup. The lacto- meter is gradually lowered into the milk to the 25th degree, care being taken that the instrument is entirely wetted by the milk and that no air adheres to it. When released, the lactometer will move up and down, and after a little while become stationary. That degree of the scale which coincides with the surface of the milk is then noted. It will be observed that, where the milk touches the vessel and the stem of the lactometer, the surface is not level, but, in consequence of the adhesion of the milk to the glass, forms a curve. There is no difficulty, however, in ascertaining the exten- Ision of the curve sufficiently near, | 30 '^Si 11 and this has to be allowed for in -==^|| reading off the specific gravity. When using instruments of ordinary size, the curve will be found to extend to about one-half degree. Lactometers indicate the exact specific gravity at a temperature of 60° F. It is, therefore, necessary, as soon as the position of the lactometer has been noted, to remove the instru- ment from the milk, immerse a ther- mometer, and ascertain the tempera- ture. If the temperature is found to be 60° F., the observed specific gravity is correct, but should the temperature of the milk be higher or lower than 00 F., the specific gravity must be corrected by the aid of the Table in the Appendix which is used as follows I Find the temperature of the milk in the uppermost horizontal line, and the observed specific gravity in the tir.^t or lasl vertical column ; in the same line with the latter, and under the temperature, is given the corrected specific gravity. For example- Supposing the temperature to be B l" and the specific gravity •">! . the specific gravity corrected io 60 P. is 32-9 I '0329; or if the temperature ii 66 and the Fig. 6. i .I., .in. ESTIMATION OF TOTAL SOLIDS. 167 specific gravity 29°, the corrected specific gravity is 29-8° = 1-0298. Never take the specific gravity of a milk without also noting the temperature and correcting to 60° Fahrenheit. Instead of reading from the bottom of the curve and making a mental allowance, the lactometers may be read from the top of the curve and a definite figure (ascertained by a few carefully- conducted experiments) added on. As soon as the specific gravity and temperature have been taken, the corrected specific gravity from the table should be entered in the book provided for the purpose of recording the results. It is not necessary to enter the specific gravity in full, but only the three significant figures ; thus a specific gravity of 1*0325 may be entered simply as 325 or 32*5. Though the determination of specific gravity has been de- scribed first, it is found that it is convenient in practice to proceed as soon as work is commenced with the estimation of total solids, as this is an operation which proceeds alone. Only in those cases where the sample is so small that the lactometer will not conveniently float, if the quantity necessary for total solid estimation has been removed, is it usually convenient to take the specific gravity first. Estimation of Total Solids. A number of dishes or capsules, each marked with a separate number and previously weighed, and a pipette marked to dis- charge 5 grammes of milk of a specific gravity T03- at a tem- perature of 60° F., are necessai'y. The dishes should be, if possible, of platinum, and at least 1| inches internal diameter, flat bottomed, and with a rim about | of an inch wide ; this rim should be considerably wider at one side so as to form a lip on which the number should be legibly stamped. These dishes weigh about 12 grammes and cost about 25s. each. They may, however, be replaced by porcelain dishes of about 2£ inches diameter, glazed all over ; these may be marked by scratching the number on the side with a new file, painting this over with a solution of platinum chloride, wiping off the excess, and igniting the capsule ; the number will be marked in platinum. The dishes must be previously weighed on a balance accurate to 1 milligramme, and the weights recorded on a table which should be kept in tbe balance case. It has been found in prac- tice that, if the dishes be carefully cleaned, monthly weighings of the dishes are sufficient, the average loss in this period for dishes used daily having been found to be about 1 to 2 milli- grammes. The dishes should be arranged in a shallow tray — a photo- graphic dish is suitable — according to their numbers from left 168 THE CHEMICAL CONTROL OF THE DAIRY. to right, six or seven in a row, beginning at the bottom — i.*., the side nearest the operator. This arrangement is chosen so that any milk accidentally dropped from the pipette will not fall into a dish which has been previously filled, but into an empty dish which can be easily wiped. The tray containing the dishes should he on the left of the tray in which the samples are placed. The samples should be arranged in order in rows, be- ginning at the left-hand bottom corner and going upwards — i.e., away from the opei'ator — and should, if in cans, have their lids turned back over the next sample can. The taking of samples for the estimation of total solids is much facilitated by having an assistant to stir the milk. The measurement of the quantities of milk for analysis is done as follows : — The assistant stirs No. 1 can, and when the cream has been mixed the chemist plunges the pipette into the milk and sucks it up till it enters the mouth ; it is advisable to throw away this first quautit\\ The milk is again sucked up, the finger placed over the end of the pipette, and the milk allowed to run down to the mark, care being taken that air hubbies are not included in the portion measured. The pipette is held over dish No. 1 and the finger removed ; the milk runs into the dish, and the drop adhering to the end is removed by touching it against the side of the dish ; the last drops must not be removed by blowing. Meanwhile the assistant has closed can No. 1 and stirred can No. 2, from which 5 grammes are measured in a similar manner, without, however, washing out the pipette ; this is transferred to dish No. 2, and the whole of the samples are taken similarly. The next step is to enter the designation of the samples and the number of the dish into which each has been placed in a book provided for that purpose ; the tray containing the dishes is then conveyed to the water-bath. The water-bath should be of copper, about 6 inches deep, and provided with a lid contain- ing a suitable number of holes in which the dishes can rest ; the number of these will vary with the number of samples to be daily examined ; it is convenient to have a projecting collar about a quarter of an inch deep round each hole, as this facili- tates the putting on and removal of the dishes, and each should be provided with a lid. If steam is laid on, the bath should be heated by means of a coil laid in the bottom, through which the steam circulates ; the exit of this coil should be connected with a condenser, and the condensed steam serves to supply the laboratory with distilled water. [f steam be not laid on, the bath must be supported on an iron support at such height as to allow of a burner being placed underneath; in either case an arrangemenl foi keeping the water level constant in the bath is ary. After the dishes have hern for about an hour on the bath, provided it has been boiling briskly, it will he noticed that a WEIGHING. 169 distended skin has formed on the surface of the milk ; this must be broken with a needle mounted in a handle, care being exer- cised that no portion of the skin is brought away on the needle. The object of this is to prevent the milk drying in flakes, which may be blown away by draughts, and the estimation lost. Should the dishes be forgotten, or should any other reason pre- vent the stirring being done at the proper moment, a few drops of water may be added to the milk residue, which will have the effect of making the flakes settle down and adhere to the dish. When the dishes have been on the water-bath for three hours, they should be taken off, placed on a tray having two or three thicknesses of blotting-paper on the bottom to remove adhering drops of water, and transferred to a water-oven or air-bath. The important point about the water-oven is that it has an even draught passing through it ; the form of air-bath devised by Dr. Adams of Maidstone is suitable, though the cover is a little troublesome to remove. The dishes are placed upon wire shelves one above the other, and it is convenient to have ten or twenty dishes on each shelf. If a good draught be maintained in the water-oven or air-bath, it is not necessary or advisable to keep this at a higher temperature than 9(T to 95° C. After three hours drying in the air-bath, the dishes should be weighed. Weighing. — Ten basins (or any number that can be con- veniently placed in the balance case at one time) should be removed from the bath, placed on a tray and conveyed to the balance case, and there allowed to cool for a few minutes. Platinum basins cool very much faster than porcelain, and much time is saved by their use ; when cool, they should be weighed to the nearest milligramme, the weight entered in the book opposite to the number of the dish ; the weight of the empty dish (from the table of weights) should be subtracted, and the weight of the milk residue will be the difference between the two weights ; this also should be entered in the book. As 5 grammes of milk were taken, the residue, multiplied by 20, will give the percentage of total solids in the milk. If the samples arrive in the laboratory in sample bottles and not in cans, a somewhat different mode of procedure must be adopted. A number of cylindrical tins without lids (of such a size as to hold the contents of a sample bottle) and a lactometer are necessary. The bottles and dishes are arranged in their proper order and entered in the book, as before. As many bottles as there are tins are shaken, so as to mix the cream, and emptied into the tins ; 5 grammes are taken from each and placed in the dishes, but before the milk is poured back into the bottle or otherwise emptied from the tin, the temperature and specific gravity should be taken ; the remaining samples are then similarly treated in their proper order. The drying and weighing is performed as before. 170 THK CHEMICAL CONTROL OF THE DAIRY. Stokes' Rapid Method. — Stokes recommends a modification of Gerber and Radenhausen's method. A pipette is used which delivers 2-5 grammes of milk, and the milk is run into flat- bottomed porcelain basins about 3 inches in diameter. The numbers are marked on the basins with copper paint, which paint, on ignition, forms an indelible blue mark. When all the basins are rilled, two or three drops of a 10 per cent, solution of acetic acid in alcohol are sprinkled over each. The alcohol spreads itself over the surface of the milk, and the acid precipi- tates the casein. Under these circumstances, drying proceeds very rapidly. The basins are placed on the water-bath till apparently dry, a matter of a few minutes only, and are further dried for about an hour in the water-oven or air-bath. They are then weighed, as before. The difference between the weight of the basin with the residue and the weight of the basin alone, multiplied by 40, gives the percentage of total solids. In the author's experience this method has a tendency to give results slightly above the truth ; it has, however, the advantages of rapidity and of requiring very little attention. Estimation of Fat. For the estimation of fat in a rapid manner, with an accuracy sufficient for milk control, a centrifugal method must be used. The Leffmann-Beam, the Babcock, and the acido-butyrometric methods, together with Soxhlet's areometric method, will be described in detail. The Babcock Method. — This method was the pioneer of the methods chiefly employed at the present day. It was devised by 8. M. Babcock, and it depends on the solution of the casein and other solids not fat of milk in sulphuric acid, and on the subsequent separation of the fat by centrifugal force. This method has proved to be one ot the greatest advances in practical milk testing yet made, and the name of Babcock must be placed high among dairy chemists, the more so because, unlike most other inventors, he sought no personal profit from his discovery, but gave it freely for the use of all. Though the method is being supplanted by methods on the Leffmann-Beam principle, the lustre of Babcock's name sutlers no diminution from this fact, these methods being but the legitimate offspring of a worthy parent. "•'•'• The only machine on the English market for performing the Babcock method is the Lister-Babcock. Embrey, Tichborne * The author feels thai .> description of the Babcock method would he incomplete without •> tribute to Dr Babcock, The author made his ac- quaintance 1 1n on l'Ii a scientific conl roversy, ami found him t he beel type of mi elfish investigator, Becking noi gain but the good of mankind. Mi labours were made possible by Ins position as chemisl t«> the Wisconsin E ipei mi' ni St., 1 1, ,i, I,, America, MEASURING. 171 and Wilkinson have investigated the method with this machine and find the results somewhat low, but Woll has shown that the speed of whirling recommended by the makers of the machine must be increased from 600 revolutions per minute to from 700 to 1200; when this is done the results are accurate and no arbitrary correction need be made. AMOTHIaua* • ClOIWETtO Fig. 7. — Lister-Babcoek Milk Tester. The machine is figured in Fig. 7, and is of strong and simple construction. It is provided with a cover to prevent accidents in case of the bottles breaking. The following directions for the Babcock process are those supplied with the Lister-Babcoek machines : — " Measuring. — If the pipette is not dry when used it should be filled with the fluid to be tested, and this thrown away before taking the test sample. " If several samples of the same are taken for comparison, the samples should be poured once 1'rom one vessel to another after each sample is measured. Neglect of this precaution may make a perceptible difference in the results, through the separation of cream, especially when the sample examined is rich. " Persons who have had no experience in the use of a pipette will do well to practise a short time by measuring water into a test bottle before attempting to make an analysis. The manipu- lation is easily acquired, and with a little practice fluid may be measured nearly as rapidly with a pipette as with a measuring glass, and with much greater accuracy. " When the samples have been sufficiently mixed, the pipette is filled by placing its lower end in and sucking at the upper end until the fluid rises above the ring round the neck ; then remove the pipette from the mouth and quickly close the tube at the upper end by firmly pressing the end of the index finger, first wetted, upon it to prevent access of air; so long as this is done the fluid cannot flow from the pipette. Holding the pipette in a perpendicular position, with the mark on a level with the eye, carefully relieve the pressure on the finger so as to 17l' THE CHEMICAL CONTROL OF THE DAIRY. admit air slowly to the space above the fluid. When the upper surface of this coincides with the ring round the stem or neck, the pressure should be renewed to stop the flow. Then proceed as follows for " New Milk. — Place the point of the pipette in the mouth of a milk test bottle held in a slightly inclined position so that the milk will flow down the side of the tube leaving a space for the air to escape without clogging the neck, and remove the finger, allowing the milk to flow into the bottle. After waiting a short time for the pipette to drain, blow into the upper end to expel the milk held by capillary attraction in the point. •' Measure 17"5 cubic centimetres of pure sulphuric acid of specific gravity between 1-831 and 1*834 by means of a small glass measure, and pour into test bottle, giving the bottle a turn so as to wash down any milk which may adhere to the neck of bottle, shake gently till all curd is dissolved, then place in machine and whirl 10 minutes at speed denoted on machine. Fill up bottle to mark 7 with hot water from water can, then pour hot water (temperature about 200° F.) into bottom of ^_s — machine about half an inch deep, and wliirl again for 2 — y minutes. Place bottle in hot water can (temperature 150° F. to 200° F.), allow this to stand a few minutes and ^^ measure extreme limits of fat column. Each complete ^d 1 division of 5 lines = 1 per cent, of fat, and the single -*-^- lines = -2 per cent., the percentage being denoted by figured long lines. " Cream. — Take a pipette full of cream up to line round neck, and let this quantity run into a small glass or jar, and then take exactly the same quantity of pure water of about the same temperature as the cream and thoroughly mix the two together, after which a pipette full of this mixture should be taken and put into one of the cream test bottles (the remainder may be used for another test or thrown away). Great care should be taken to get this mixture correct. •' .\basure 17-5 cubic centimetres of pure sulphuric acid of specific gravity between 1*831 and 1*834 by means of a small glass measure, and pour into test bottle, giving the bottle a turn so as to wash down any cream which may adhere to the neck of bottle, shake gently till all curd is dissolved, then place in machine and whirl 10 minutes at speed denoted on machine. Fill up bottle to mark 25 with liot water from water can, then pour hot water (temperature about 200° F.) into bottom of . machine about half an inch deep, and whirl again for 2 - y minutes. Place bottle in hoi water can (temperature 150° F. to 200° F.), allow this to stand a t'.w ininutrs and measure extreme limits of tat column. Bach complete J_ division of .r> lines = 2 per cent, of tat, and the single ' lines = *4 per cent., the percentage being denoted by REVOLVING DISC. 173- figured long lines, or for cream read double — that is, if the fat is from 2 to 24, leaving 22, the fat would be double that per cent. — that is, 44 per cent. " Separated Milk. — To test skimmed milk it is necessary to take 2 pipettes filled up to the ring, and place it in a skim milk test bottle, and to this add 2 measures each 17*5 cubic centimetres of pure sulphuric acid of specific gravity between 1*831 and 1 *834 by means of a small glass measure, and pour into test bottle, giving the bottle a turn so as to wash down any milk which may adhere to neck of bottle, shake gently until all curd is dissolved, then place in machine and whirl 10 minutes at speed denoted on machine. Fill up bottle to mark 2 with hot water from water can, then pour hot water (temperature about 200° F.) into bottom ^^ — - of machine about half an inch deep, and whirl again for "j" 2 minutes. Place bottle in hot water can (temperature ^^ 150° F. to 200° F.), allow this to stand a few minutes and measure extreme limits of fat column. Each complete -' | division of 5 lines = 1 per cent, of fat, and the single — — lines = TO per cent., the percentage being denoted by figured long lines. "Acid. — The best method of obtaining sulphuric acid of suit- able strength is to take 1 measure of water in an earthen jug, and then pour in very gradually 9 measures of the strongest sulphuric acid (pure) procurable, then on allowing mixture to cool to 60° F., and putting in the acidimeter provided, it should so float that the surface of the liquid is between the two red lines on the stem, which lie close together, and encircle the scale, the upper line corresponding to a specific gravity of T831, and the lower one 1 "834. " Cleaning the Test Bottles. — The bottles should be emptied while hot, afterwards rinsed twice with cold water, and then inverted to allow of draining. They are then ready for another test. "Working and Oiling Machine — Turning.— This should be commenced gradually, and increased until the speed as indi- cated on revolving disc is attained. " Oiling. — The oil must be of good quality. The vertical spindle and surfaces are oiled from the cup on top of disc. The bearing close to bevel wheels is oiled through tube which will be found in casting under revolving disc. The other bearings are in plain sight. A drop or two of oil is sufficient. Do not flood it. " Revolving Disc. — This must be well fixed to spindle by set pin, the spindle at the same time being pushed up from under- neath the frame so as to prevent the bevel wheels from engaging too deeply one in the other. Should the machine work a ittle hard at any time, this will most likely be the sole cause." 174 THE CHEMICAL CONTROL OF THE DAIRY. The Leffmann-Beam Method, and Modifications. — Leff- mann and Beam, realising that the time of whirling necessary in Babcock's method was a serious objection, experimented with a view to shortening this. They finally decided on the use of amy] alcohol as a means of assisting the fat to rise, and were thereby enabled to reduce the time of whirling. The same idea was also independently worked out at the Vermont Experiment .Station, but it appears that Leffmann and Beam were the pioneers in this direction. It is usually employed in conjunction with the Beimling machine. The method has been subjected to a close investigation by the author, and is of considerable accuracy. The Beimling Machine. — This consists of a cast-iron frame- work carrying a vertical spindle ; on this is a small bevelled cog- wheel, which engages a larger bevelled cog-wheel on a horizontal spindle turned by means of a handle. In the larger machines n second spindle and set of cogs is introduced (Fig. 8). Fig. 8. — Beimling' s Separator. On the top of the vertical spindle two, three, or six arms extending radially are fixed. To the ends of each of these are pivoted one or usually two cups, in which the bottles are placed. When thi' handle is turned, the cogs cause the Bpindle and the arms carrying the cups to rotate. For one turn of the handle, the vertical spindle turns eleven times. Centrifugal force causes the cups to assume a horizontal position when rotating, and they return to the vertical when the machine is at rest. The bearings are all plain, which causes a considerable APPARATUS. 1 75 amount of friction ; the centre of gravity of the rotating system is placed very high, which causes vibration, due to imperfect balancing, to be marked. The air resistance at high speeds is somewhat great. These are serious faults but are capable of improvement. The two-bottle Beimling machine is the only machine on the market, to the author's knowledge, in which the bottles assume a hori- zontal and radial p jsition when rotating ; in the larger sizes the bottles are nearly, but not quite, radial. This position is advan- tageous, as it allows of the most rapid separation of the fat from the acid liquid. Apparatus. — The test bottles consist of flat-bottomed flasks with a sloping upper portion terminating in a graduated neck. The bottles (English make) hold 29 c.c. ; the necks are made of glass tube 5*96 mm. in internal diameter, and are so graduated that 80 divisions = l-475 c.c. These dimensions are according to a specification laid down by the author, and differ slightly from those prescribed by Leffmann and Beam. The pipettes used are — 15 c.c. for milk, 9 c.c. for sulphuric acid, 3 c.c. for amyl alcohol mixture, 4*5 c.c. for cream, and 10*5 c.c. for water. Automatic measuring apparatus and burettes may be also used for measuring the acid and amyl alcohol. The author has devised a burette specially for the measure- ment of sulphuric acid and other corrosive liquids. It has been found, in practice, that ordinary burettes are liable to be filled to overflowing, and that considerable inconvenience is caused by spilling strong sulphuric acid. An ordinary burette with a three-way tap is used, and to the tube, for filling from the bottom, a wider tube, }f in. in diameter and 3 ins. long, is fused. An india-rubber cork is inserted in this, and through it is passed a long glass tube bent as a syphon, which serves to convey the acid from a stock bottle above. In the top of the burette an india-rubber cork is fixed, through which passes a tube going almost to the top of an air chamber of glass; to the bottom of the air chamber a glass tube of small bore passes upwards so far as just to enter into the stock bottle. The illustration (Fig. 9) will make the construction clear. The conditions necessary for satisfactory working are : — 1. The capacity of air chamber and tube leading to stock bottle must not be more than i of the capacity of the burette. 2. The bottom of the stock bottle must be well above the top of the tube leading into the air chamber. The tube leading into the air chamber must be adjusted to the mark on the burette equal to its capacity. 176 THE CHEMICAL CONTROL OF THE DAIRY. The burette is used as follows : — The tap is turned so that the liquid enters and fills the burette. As it reaches the upper portion, it passes up the tube and overflows into the air cham- ber, from wliich it is forced up the tuhe leading to the stock bottle. When the liquid reaches a height cor- responding to the level of the liquid in the stock bottle, the liquid ceases to run, and the burette is automatically tilled to the zero point. When the tap is turned the liquid runs out, air bubbling in from the stock bottle, and mea- sured quantities may be taken. After the liquid has been run out as far as desired, the tap is turned, and the liquid enters the burette. The liquid in the air chamber is forced back into the stock bottle, and the burette automatically fills itself. The burette can be made of 9 c.c. capacity, but it is much quicker to employ a graduated burette of much larger capacity than any form of automatic measuring apparal us. The advantages claimed for this burette are — (1) Automatic tilling to zero point. (2) One turn of the tap mil\ required to lill and to measure. (3) [mpossibilitj of spilling '•.<■. pipette : if it is thicker than this, it must be diluted with separated milk. Two t.raki-r.s or tin pots are counterbalanced on a rough balance Fig. 10. Neck of Bottle. TESTING OF SOUR MILK. 179 turning to -01 gramme; in one of them, about 25 grammes of cream are placed, and separated milk is run into the other till the weights are equal. The cream and separated milk are mixed together, and the mixture can be measured. The measurement is performed as follows : — Fill the pipette with cream by sucking at the top, and close it with the finger ; hold the pipette vertically, and allow the cream to run down till the upper surface is on a level with the mark ; turn the pipette to a horizontal position and wipe the stem ; then return it to the vertical and, holding the point over the neck of a test bottle, allow the cream to run out freely ; after the quick succes- sion of drops has ceased allow three more drops to run. Add 10*5 c.c. of water and proceed as in analysing milk. Calculate the results from Table XLL, using column 3 for undiluted cream and column 2 for diluted cream. TABLE XLI. — For Estimating Fat in Cream. Reading. Diluted. Undiluted. Reading. Diluted. Undiluted. 8-5 63 8 32 0 1 6-7 49 8 25 -0 8-4 63 0 3] -6 6 6 49 0 24 6 8 3 62 2 312 6 5 48-2 24-2 8-2 614 30-8 6 4 47-4 23 8 8-1 60-6 30 4 6 3 46 6 23 4 8-0 59 9 30 0 6 2 45-9 23 1 7 9 59 1 29 6 61 45-1 227 7-8 58-3 29 2 6 0 44 4 22 3 7-7 57 "6 28-9 5 9 43 6 219 7 6 56-8 28-5 5-8 42-8 215 7-5 56 0 28-1 5-7 42-1 211 7 4 55 3 27-7 5 6 414 20 8 7-3 54 5 27-3 5-5 40 6 20-4 7-2 53 7 26-9 5 4 39 -8 20 0 7-1 52-9 26-5 53 39-1 196 7 0 52-1 26-1 5 2 38-3 19-2 6-9 51-4 25 8 5-1 37-5 18-8 6 8 50 6 25-4 5-0 36 -7 185 Testing of Sour Milk. — Weigh in a small beaker about 15 grammes of the sample which has been previously well mixed by whisking with a brush formed of fine wires ; pour as much as possible into a test bottle and re-weigh the beaker ; the difference will give the weight of the milk taken ; add sufficient water to make up to 15 "25 grammes and proceed as in analysing milk. Calculate as follows: — Multiply the reading by 15 25 and divide by the weight taken ; the result will be the percentage of fat in the sour milk. 180 THE CHEMICAL CONTROL OF THE DAIRY. Testing of Clotted Cream, Cheese, and Butter. — Weigh the bottle and transfer to it about 1 to 1*5 gramme of butter, 2 grammes of clotted cream or 3 grammes of cheese, and weigh again. Butter should be melted in a closed vessel at a tempera- ture of 40° C. (104° F), and, after shaking, about 1^ c.c. sucked up in a tube which will just enter the neck of the bottle ; the butter should be blown in as completely as possible. Clotted cream should be well mixed and sucked up in a tube in the same way as butter, and either blown or pushed in with a wire. Cheese should be cut up into small pieces, which can be dropped in. Add sufficient water to make up the weight to 15-25 grammes and proceed as in analysing milk. Cheese requires rather longer shaking than other products, but gives equally good results. If desired, cream may be weighed instead of being measured. The calculation is performed as for sour milk. The above directions differ in some respects from those given by Leffmann and Beam. The author has had, however, some years practical experience of the methods described and is con- vinced of their accuracy. A stand for the bottles is to be recommended ; this may conveniently be made of wire rings into which the bottles fit, with a flat plate for a bottom ; the bottles can then be easily carried about. To clean the bottles : empty while hot in a convenient re- ceptacle, and wash twice thoroughly with hot water ; if neces- sary, run a brush down the neck. They are conveniently washed in the stand. Never leave pipettes dirty. Failures and their Probable Causes. — The only failures likely to happen are : — 1 . Dark layer of fat. 2. Fluffy layer under the fat. 1. If the acid be too strong, or the temperature too high. < ti- the mixture left too long before whirling, the fat may be dark. The remedy is obvious. 2. A fluffy layer under the fat is often caused by allowing the milk and acid to stand too long unmixed. It may sometimes be due to a bad quality of amy] alcohol. Crit on the bottom of the bottles may cause fracture while in the machine. Fracture may also occur from too sudden a stoppage after the whirling is completed. Modifications of the Leffmann-Beam Method. — The Leff- mann-Beam method has been subjected to considerable modifica- tion ; thus Paterson and, later, Gerber have used amy] alcohol alone without hydrochloric acid. Gerber's Acido-butyrometric Mothod.- This is essentially the Leffmann-Beam method, the chemical principles of which have been adopted. The use of hydrochloric acid as e solvent THE TESTER WITH CATGUT ACTION. 181 for the amyl alcohol has been, however, discarded, following Paterson. Gerber employs a test bottle, which he terms an " acido- butyrometer," which differs from that employed by Leffmann and Beam; it is a modified form of Marchand's lacto-butyrometer and, like this, is closed with a cork. A definite strength of sulphuric acid is prescribed (90 to 91 per cent.), and rules for testing the acid and amyl alcohol used are laid down. Gerber has shown considerable ingenuity in adapting the method of Marchand to that of Leffmann and Beam, and the method is reliable. The acido-butyrometers are usually whirled in Gaertner and Hugershoff's machine or in that of Lister, which are practically identical, but no reason exists, except trade interests, for not employing any other form of machine. The following comparative statement will show the differences of detail between this and the Leffmann-Beam method : — Leffmann-Beam. Gerber. 1. Test bottles are tlasked-shaped. Test bottles are butyrometer-shaped. 2. 96 per cent, sulphuric acid is 90 to 91 per cent, sulphuric acid is used. used. 3. A mixture of amyl alcohol and Amyl alcohol alone employed. hydrochloric acid employed. 4. Fat read off cold. Fat read off at 60° to 70° C. 5. Bottles are used open. Bottles are stoppered. There is no practical advantage in either method. The original Leffmann-Beam is somewhat more rapid, while the Gerber modification requires rather less skill. Both are equally accurate. I. The Tester with Catgut Action for Four and Eight Samples (Gaertner and Hugershoff's Patent). Description. — A steel spindle, running in two ball bearings, the upper with ten balls and the lower with seven, is supported in a well-stayed frame, which can be fixed to any table by means of a screw clamp. On top of the spindle is a boss, on which two discs with screw threads are fastened, which hold the disc-plate for the reception of four or eight samples. The cover is screwed on to the spindle by means of a loose milled-headed nut and the machine is ready for use. If the machine is destined for fre- quent use, it will be best to fix it to a strong bench and not to a movable table ; to further strengthen it, two screws may be put in through the holes in the frame and the tester will then not be transportable (Fig. 11). The bearings can be adjusted by means of the brass collar in the upper one which is held in place by two screws ; this should be so arranged that the spindle runs easily without play, and when this is found to be the case, the screws should be tightened 182 THE CHEMICAL CONTROL OF THE DAIRY. Fig. 11. -fiaertner and Hugershoff's Milk Tester. to hold the collar in place. The bearings should be oiled with good machine oil, care being taken that the oil which runs down the spindle is wiped off. To rotate the machine, put the metal end of the catgut into the hole in the spindle, wind the string around, by turning the disc plate back- wards till the handle is close to the spindle. Pull the handle with full strength, the whole weight of the body being brought to bear, and as the string unwinds the machine is rotated ; when all the string is unwound the end comes out of the hole, and the machine rotates freely. If clean and well oiled it will run for ten minutes. To stop the machine, take hold of the milled-headed nut of cover firmly and it will screw itself off; then press the edge of the under disc-plate gently with the finger till it stops. Do not stop it with a jerk. II. The "Excelsior" Gearing. — This can be fitted to 8- or 24-sample machines. It consists of a hollow cylinder fixed to the frame carrying a hollow double pulley, in?ide which the spindle can rotate with- out touching. Round the lower portion of the pulley is coiled a spring, and in the opposite direc- tion round the upper a strap is wound, which passes through an opening in the cylinder; on tin strap is clamped a stop-plate, which serves a double purpose — (1) to prevent the spring from pulling the strap too far, and (2) to lift the pulley, which is capable of a Blight vertical movement, when the strap i^ wound home. At the bottom of the pulley is a pawl, which, when the stop-plate is pulled out. engages a ratchet wheel on the Bpindle and which is lifted with the pulley when the stop-plate is I ig. 12 Mitt T< ■■ THE "rapid" gearing. 183 home so that the spindle runs freely. The machine is rotated by pulling the handle on the end of the strap rapidly to and fro fifteen to twenty times, when a high velocity is obtained ; the strap and stop-plate are then allowed to go home and the machine runs alone. If the speed slackens, it can be increased by a few further pulls. This gearing is only recommended for 24-sample machines. Large machines are made to run by steam power (Fig. 12 J. III. The "Rapid." Gearing. — In this, a loose pulley sur- rounds the spindle ; it runs on a separate bearing and is, when not in use, kept up by a spring. A. strap passes round the loose pulley, and when this is pulled (in a slightly downward direction) the pulley is brought downwards ; two bevelled teeth engage two similar teeth on the spindle and cause the machine to rotate. When the strap is pulled back (in a slightly upward direction) the spring forces the pulley up and the machine rotates freely. By pulling the strap rapidly backwards and forwards, a high rate of speed can be obtained. The 2-bottle machine differs in construction from the others in not having the disc-plates, which are replaced by two arms, carrying cups; these cups are larger than the cups used in the larger machine and have a cover ; the test bottles fit completely into them and are surrounded by warm water. The machine is fitted with the "Rapid" gearing and has plain bearings ; this causes continvial driving to be necessary. The machine cannot be left to run alone. None of the methods of driving the Gaertner-Hugershoff machine are satisfactory. The catgut requires a strong pull and is liable to soon wear out, if the metal end comes off; if it is required to rotate a second time, the machine must be stopped. The " Excelsior " gearing has a weak point in the spring, which breaks and is difficult to repair ; the strap also sometimes breaks, and cannot be replaced without some trouble. The " Rapid " gearing makes an unpleasant noise, and a great deal of the power employed to drive the machine is wasted in friction. It is far better to discard the methods of driving sold with the machine and to employ a yard of blind cord (of the best quality), one end of which is fixed into a wooden handle. This is given one or two complete turns round the spindle ; the handle is held in the right hand and the loose end in the left. The cord is pulled with the right hand, just sufficient tension being kept on the end with the left to make it bite. At the end of the stroke, the left hand is brought up near the machine to loosen the cord round the spindle, otherwise there is danger of the cord winding up. 184 THE CHEMICAL CONTROL OF THE DAIRY. The cord is now pulled back with the left hand keeping it quite loose — i.e., letting the right hand go back quite freely. The pulling with the right hand is repeated, and continued till the speed is high enough. It is advisable to stop up the hole in the spindle, as it causes the cord to wear. Should the cord wear out and break, it can easily be replaced at an infinitesimal cost. This method of driving was worked out in the author's laboratory by Boseley and Rosier. The Lister Machine. — This has practically the same form as the Gaertner-Hugershoff machine, but does not include the " Excelsior " or " Rapid " gearings, which are covered by patents. The frame is of different construction and is S-shaped. Round the spindle a small brass pulley is fixed * (in the 24-bottle machine a ratchet is added), and it is driven by a string wound round this by Boseley and Rosier's method, which, how- ever, was independently applied bv Lister (Fig. 13). It has the following advantages over the Gaertner - Hugershoff machine : — (1) Lower frame and, therefore, less vibration. (2) Better metal used for bearings; therefore lasts longer. (3) Is easier to drive. The 2-bottle machine has the arms hinged, and clamped in place by a screw, instead of having them in one piece ; it is more easily portable. Apparatus, &c — 1. The acido-butyrometer is a glass vessel closed by an india-rubber cork, and with a graduated neck divided into ninety divisions; one division Milk sugar, t :;i Proteida 3*36 AbI -70 Solids n'.t fat B*40 The sediment obtained by centrifugaliaing contained much mucus and cells from the udder. It was concluded thai the milk waa the product of a cow in ill health. It is evident that [f dirty water baa been added to milk, an THE SOLUTION OF ANALYTICAL PROBLEMS. 203 evil smell and taste may occur; no further example nefd be given of this. Turnips and other substances eaten by the cow or, what is more likely, handled by the milker, may communicate a taste to the milk. The action of certain organisms may have a similar effect. The author is unacquainted with chemical methods of identifying these causes. Problem VI. — To determine reasons for milk being sour or curdled. Example a. — The acidity was 17*5°, and the cream in clots. The analytical figures were : — Specific gravity, 1 03.':>3 Total solids, Fat, . Ash, . Solids not fat, Soluble albumin, Taste, 1273 per cent. 3-56 ,, •76 „ 9-17 ,, none, boiled. The milk had been boiled and the cream allowed to rise and clot, giving the milk a, curdled appearance. Example b. — The milk was curdled, and the whey was analysed. Acidity, 43-1° Total solids, 6 "25 per cent. Fat, 1-05 Ash, -48 ,, Solids not fat, 5 -20 From the low percentage of solids not fat and ash of the whey, it was concluded that about 15 per cent, of water had been added, and there was some probability that this water contained an acid. Example c. — The milk was curdled and the whey analysed. The analytical figui-es were : — Acidity, 35 2° Total solids, ...... 7 '46 per cent. Fat, "88 Ash -60 ,, Solids not fat, ...... 6*58 ,, It was concluded from the normal percentage of solids not fat and ash of the whey, that nothing had been added and that the milk had become sour by natural causes. Example d. — The milk was curdled and the whey analysed. It was slightly bitter and gave the biuret reaction. The analytical figures were : — Acidity, 20-8° Total solids, Fat, . Ash, . Solids not fat, 11 "13 per cent. 3 03 •69 „ 8-10 „ 204 THE CHKMICAL CONTROL OF THE DAIRY The alkalinity of the ash to phenolphthalein was equal to •025 per cent. Na.,CO,. It was concluded that the milk had been peptonised, and was insufficiently alkaline. Example e. — The milk was curdled and the whey analysed. The following were the analytical figures : — Aridity. Total sdI ids. Fat, . Milk-sugar, Ash, . Solids not fat, 26-2° 9 '42 per cent. 1-27 „ 5 53 ■60 8-15 The milk was not bitter, but gave the biuret reaction. It was concluded from the low acidity and the high milk- su^ar that lactic fermentation was not the cause of curdling ; from the biuret reaction being obtained, it was concluded that an enzyme was the cause. Milk is often alleged to be sour because when used for making milk puddings and custards with eggs, a clear whey runs out. The curdling of the milk is due to the coagulation of the large amount of albumin of the egg on baking. The following is an analysis of a whey from rice pudding : — Total solids, Pat, . Ash. . Solids not fat, 17 "07 per cent. ■82 1685 It was very sweet and contained much cane sugar. Problem VII. — To determine the reason for milk being thick. Example a. — The analytical figures were : — L0262 L7'92 per cent. 9-36 Specific gravity, Total solids, Fat, . Ash, . Solids not fat, •71 8-56 This sample contained an excess of cream, which made it appear thick. Example b. — The sample gave a blue colour on adding iodine solution. It was thickened with starch (or flour). Example c— The milk was thick and, on dipping a glass rod into it and lifting it out, a stringy mass adhered to it. < >n putting the rod (which had been sterilised) into a bottle con- taining sterilised milk, the latter acquired the same property in twenty-four hours. The milk was "ropy." Problem VIII. To determine the nature of sediment. In cases of this description, the milk should be placed in tubes and centrifugalised ; as much milk as possible must be decanted, SKIM MILK. 205 distilled water added, and the tubes again centrifugalised ; this procedure should be repeated till the water is clear. The sedi- ment is examined microscopically. Vegetable cells, if clear and sharply defined are usually due to the bark of hay and the dust of cake given to the cattle during feeding time. If indistinct and stained yellowish or brownish, these usually indicate cow-dung. Small hairs, cotton and woollen fibres usually show the pre- sence of household dust. Crystalline particles usually indicate road dust. In this case a little of the deposit is placed on a slide and warmed with dilute hydrochloric acid, which is evaporated nearly off; a drop of water is added and also a drop of a solution of potassium ferrocyanide. A blue colour, due to iron, is obtained from road dust. Skim Milk. — The term " skim milk " is applied to milk from which the bulk of the cream has been abstracted. Two ways of abstracting the cream are practised : (1) by allowing the milk to stand, taking advantage of the force of the earth's gravity to separate the cream ; (2) by employing centrifugal force to attain the same object. Distinction between Skimmed and Separated Milk. — A distinction has been drawn between skim milk obtained by these two methods ; that obtained by setting the milk being called " skimmed milk," and that obtained by centrifugal force "separated milk." The distinction is one of degree, not of kind, as, were it possible to keep milk without chemical change for an indefinite period, the same result would ultimately be obtained by either method. The following are the characteristics of skimmed and separated milks : — Skimmed Milk Separated Milk Contains the solids not fat of the Contains the solids not fat of the whole milk, partially changed by whole milk, practically un- the action of micro-organisms. changed. Contains usually more than -4 per Contains usually less than "3 per cent, of fat. cent, of fat. Contains a portion of the solid im- Is free from the solid impurities purities of the milk. of the milk. Rising of Fat Globules. — The globules of fat rise through the milk because they are lighter than the milk serum. If we have globules of fat of radius r, the force impelling it to rise will be proportional to the weight of an equal bulk of milk serum less the weight of the globule, or = x . 1 7T rs . {ds - dy) . g, where x is a constant varying with the units adopted for r, d and df. 7r is the ratio of the circumference of a circle to its diameter, r is the radius of the globule, and g is the acceleration due to gravitation. *2' >6 THE CHEMICAL CONTROL OF THE DAIRY. 4-n-2W! If the globule is acted on by centrifugal force, the expression 3600 must be substituted for g. r = velocity in revolutions per minute, b = distance of globule from the centre of revolution. The globule does not, however, rise freely ; at the velocity at which the globules move the resistance is very nearly proportional to the surface of the globule, which is equal to Air r-. The time taken by a globule to pass through a given layer of milk is therefore inversely proportional to the square root of the cube of the radius. It is evident that as the globules start from rest they must move with an accelerated motion. When a body falls freely, the space passed over in a given time is expressed by the formula s = hat'i; the motion of small globules in a liquid is not expressed by this formula as the resistance of the liquid, which increases as the cube of the speed tends to reduce the velocity ; it is evident that equilibrium will be after a short time established when the resisting force is equal to the impelling force, and if the latter be •nnstant the motion will be uniform. It is readily seen that the equation — = r~ x id - dj (i .-. k will hold when the milk is at rest. t * /' " a = space passed over by a globule. t = time. '/, — specific gravity of the milk serum. df= ,, „ ,, tat. ff = acceleration due to gravitation. k = coefficient of viscosity. If submitted to centrifugal force, it is evident that the speed of a globule ranno: be constant, as the centrifugal Force tending to move it varies with the distance of the fat globule from the centre of revolution. If we assume that the resistance is very threat (a condition nearly attained with small globules), the equation fur globules submitted to i ifugal force is da 7 , , . . , *»* '•" >> — = r k(^_^k*x-s— The connection between the space passed over in the passage through the separator and the time taken La given by integrating this equation between limits denoting the poinl of entry and exit from the separator. The factor A varies with the temperature, being Larger the hotter is the milk. In centrifugal machines the ease with which the cream can escape 1m- also an influence on the factor, and this becomes especially importanl if the of the cream is adjusted by widening or narrowing the exit. ■ be amount of cream left in I he separated milk is determined by tin- amount of globules which travel a certain distai in a given time, we can derive the following formula, assuming the ratio of various sited globules t.. be constant. The percentage of t.it left in the milk by any separator calculated by the formula : — SKIM MILK. 207 f=axb«° t) where f = percentage of fat in separated milk, F = ,, ,, cream, t = temperature in degrees Centigrade, m = number of gallons per hour, v = ,, revolutions per minute. a, b, and c are constants for each separator. b usually varies from 1 -035 to 1 -05. c „ ,, from 1-00 to 105. c is appreciable, chiefly with separators in which the adjustment of the thickness of the cream is made at the cream outlet — e.g., in the Alpha separator, in which c has the value 1 "04 to 1 -05. The following results were obtained with a separator, for which the following formula was applicable : — 2 * J = 8155 x 1-046 <40 " (> x 1-0471 F x ^-. F t. in. v. /• / calc. Per cent. Degrees. Gallons. Revolutions. Per cent. Pei cent. 15-5 32 350 5600 05 04 42-0 32 350 5600 12 13 51-0 32 350 5600 175 194 52-6 32 350 5600 210 207 563 32 350 5600 247 246 65-0 32 350 5600 330 369 60-4 38 350 5600 22 228 621 38 350 5600 25 247 51-0 32 240 5600 14 14 53-0 27 350 5600 30 27 42 0 32 325 5200 15 14 70-0 76 120 5600 07 07 The constant a depends on the following conditions : — 1. Size of drum and thickness of the layer of milk. 2. The specific gravity of the milk serum and of fat. 3. The units in which the variables are expressed. The constant b chiefly depends on the viscosity (internal friction) of the milk serum ; also, to a slight degree, on the cubical expansion of milk serum and milk fat, and on the friction of the liquid against the drum. The constant c depends on the viscosity of cream and on the friction of the cream against the sides of the outlet. It is naturally advantageous for a, b, and c to be as low as possible. To obtain a low, the drum should be large and the layer of * For temperatures above 40° the expression b should be used. m or 1-046 m 208 THE CHEMICAL CONTROL OF THE DAIRY. milk thin ; the discs placed inside the drum in the Melotte and Alpha separators make the layers of milk very thin and therefore decrease a. To obtain h low, the exits, and especially the cream exit, should be as large as compatible with the proper working of the separator ; and the tubes, through which the skim milk and cream leave the drum, as short and as straight as possible. To obtain c low, cooling of the cream inside the drum should be avoided, and the cream exit large. Separators in which the adjustment of the thickness of cream is performed at the cream exit havt* a large c. It is more difficult to express the results obtained by allowing milk to stand by a definite formula. Here we have not a definite space through which the globules of fat must pass, as in the cream separator, where the layer of milk is always of constant thickness ; the space is determined by the depth of the layer of milk set. In the formula j = r't -x (dg - cff) (j x k it is apparent that k, s, and (d - d)g are all constants for a given space provided the fat globules all have the same density and the equation may be written t = —? , where c is a constant. ?.4j Taking the diameter of the largest globules as "01 mm. and the smallest as -0016 mm., we calculate that the smallest globules will take about fifty times as long to pass through a given space as the largest; the author deduces from his experi- ments that the largest fat globules move at the rate of 15 mm. per hour. If we assume that the total weight of fat globules of any size, is equal to the total weight of lat globules of any other size, in an ordinary cream tube we may expect roughly the following figures : — In ."> hours about 35 per cent, of total fat will be found in the cream. ., 1<» ,. >> 65 ,, ,, ,, ,, ,, ,, 24 ,, ,, 85 ,, ,, ,, ,, ,, while from three to four days should elapse before the whole of the fat is found in the cream. From t be equal ion s f - = '•■' [dt '',) g ■ h it will be readily seen thai il the density of the hi varies the time will lerably affected. The density of solid fat al 60* F. (15*5 C.) is aboul '•'•'•: the density of liquid fal it aboul ■'j'2 at the same temperature ; and, as the experiment! in CONTROL OF SEPARATORS. 209 Appendix A show, it is highly probable that the solidification of the fat is a process which takes time. The difference between the specific gravity of milk serum and milk fat is also accen- tuated at temperatures above 60° F. ; it is probable that when milk is rapidly cooled, the fat globules do not so easily attain the lower temperature as the serum. It would appear, theoreti- cally, that there is a considerable advantage in setting milk for cream immediately after milking, and that the fat globules will rise at a much more rapid rate than if the milk is cooled and kept for some time. The experiments of Babcock completely substantiate this view ; he finds that delaying the setting for even a short time materially affects the percentage of fat in the skim milk. Composition of Skim Milk. — Skim milk differs practically from whole milk in the percentage of fat. In milk from which the cream has been removed by skimming very wide variations are found in the percentage of fit; it varies from -4 per cent, to over 2 per cent. Much lower percentages are found in separ- ated milk, and the limits, '05 per cent, to -3 per cent., are very rarely overstepped. By the removal of the fat the percentage of other solid constituents are slightly raised in amount ; this is caused by the constituents which were contained in 100 parts being left in about 96| parts, by the removal of i!l parts of fat. The following is the average composition of separated milk: — Water, . . . . . . 90 50 per cent. Fat, -10 Milk-sugar, 4-95 ,, Casein, ....... 315 ,, Albumin, ....... "42 ,, Ash, 78 „ Control of Separators. — The most important point in the control of separators is the estimation of the fat left in the separated milk. A separator leaving a proportion of fat appre- ciably higher than that deduced from the formula given above is working badly, and the cause should be at once investigated. It is important that the speed is properly maintained, that the milk is at the right temperature, and that the exit tubes are not clogged up ; the chemist should make a practice of visiting the separators daily while they are running and of checking the speed and temperature of the milk. At least one sample of separated milk should be tested from each "run" of the separ- ator; these samples should be taken from the skim outflow tube, at some period of the run, preferably not immediately after starting. A further means of controlling the separators is to compare the total weight of the fat in the cream, separated milk, and the milk left in the drum after separating, with the total weight of the fat in the milk separated. This is done by weighing each 14 210 THE CHEMICAL CONTROL OF THE DAIRY. product, multiplying the weight by the percentage of fat and dividing by 100. The total weight of fat in the cream and separated milk should be nearly equal to that in the milk, the difference representing loss in separating ; the average loss should not amount to more than 2 per cent, of the total fat in the milk. Separator Slime. — After running a separator a viscous sub- stance is found on the inside of the drum. It is usually of a dirty white colour; but if the milk contains much solid impurity, as happens most frequently in the winter, it may be distinctly brown. This by no means consists, as is often considered, of dirt and cow-dung, though it naturally contains these impurities if present in the milk. Microscopical examination shows it to contain — 1. Inorganic impurities — i.e., dust gathered during transport, and earthy matters due to uncleanliness. 2. Vegetable matters derived from the dust of the food given to the cattle — e.g., bark of hay, fine particles of cake, &c. ; in many cases portions of leaves with stomata developed may be identified. Other portions of the vegetable matter have the cell walls considerably disintegrated ; these have probably passed through the alimentary tract of the cow, and indicate the presence of cow-dung. 3. Substances derived from the cow ; hairs are often found ; much pavement epithelium from the udder of the cow, and possibly abo from the hands of the milkers ; and empty sacs (gland cells), which form a very large portion of the slime. (If the cow was in ill-health, mucus, blood, and pus may be present.) Micro-organisms are very numerous; should the cows be afflicted with tuberculosis of the udder, Bacillus tuberculosis may be found here. The following composition is assigned to separator slime by the author and by Fleischmann, respectively : — Author. Fleisrliniann. Per cent. Per cent. Water, .... . 6624 67-8 Fat, •50 11 ('.l-i in (or analogous body), . . 22 (approx.) 25 9 Milk-sugar, .... • '5 \ . 7-75 / 21 Other organic matter, . Ash, . 3-01 3-6 It is doubtful whether the substance returned as casein is really this body ; it is undoubtedly a mixture of several pro- teids, including Storch'a mucoid proteid. The. following is the composition of the ;ish : — Total ■' . Ii, 301 per cent. Soluble ash, '186 ,, In oluble ash, ...... 2-844 ,, consisting of Silica, . Iron oxide and alumina Lime, . Magnesia, Alkalies, Phosphoric anhydride, SEPARATORS. 211 "171 per cent. •012 „ •654 „ •225 ,, 559 „ 1-233 „ There are "675 equivalent of lime and "325 equivalent of magnesia to 1*506 equivalents of phosphoric anhydride, showing .that the insoluble ash consists chiefly of (Oa, Mg) (Na, K) P04 like the insoluble ash of milk. The quantity of separator slime amounts to about *04 parts to 100 parts of milk separated, and varies within comparatively narrow limits — *02 to *08 — unless the milk is very dirty, when it may even reach -15 ; in the last case the slime was brown and very gritty. It has been argued that the removal of the slime purifies the milk to such an extent, that its keeping qualities are enhanced. This opinion is probably founded on observations of the number of microbes contained in the slime ; but though a greater relative quantity are found than in the milk, the numbers left in the cream and separated milk are not appreciably diminished. Practice has, however, shown that a mixture of cream and separated milk in their original proportions keeps no better than the milk from which they were separated. Attempts have been made to remove the impurities in milk by filtration ; straining through a fine wire sieve and through tine muslin or swansdown is always practised in dairies; this removes the grosser impurities — i.e., hairs, large vegetable fibres, &c. — but the quantity removed in this way does not exceed ■0025 per cent. In Denmark and Germany, and lately in a few dairies in England, filtration through layers of gravel and sand is practised ; this method, which adds considerably to the labour of handling the milk, owing to the necessity of washing the gravel and sand with caustic soda, followed by water, sterilising, and drying, fails to remove any more from the milk than simple straining or upward filtration through muslin or swansdown. Separators. — It is not within the province of this work to give a description of the various cream separators that are in use. A few points only, which may aid in the choice and use of separators, and which may be said to come within the province of the dairy chemist, are touched upon. (See table on p. 224.) Before any advice on the choice of separators can be given, it must first be ascertained to what use they are to be put. A sepai'ator eminently adapted for producing cream destined to be churned into butter is not necessarily the best for making cream for sale as such ; a separator may produce a good thin cream, and yet not work satisfactorily when thick cream is desired. 212 THE CHEMICAL CONTROL OF THE DAIRY. When separating cream for churning a somewhat thin cream is made. The great point to be aimed at is to obtain the maxi- mum percentage of fat in the cream, and to leave as little as possible in the separated milk. For this purpose frequent examinations of the separated milk should be made, and a standard of, say, "15 per cent, of fat should be fixed ; if more is found, the cause should be enquired into. If the cream is "pasteurised " as soon as it is separated, as is the case when it is to be "soured" by means of a pure ferment, no special attention need be paid to the temperature of the cream leaving the separator. If, on the other hand, it is to he l"i_'. is. Burmeister and Wain Separator. allowed to stand tor some length of time at the temperature at which it, Leaves the separator, it becomes of importance to see that it is not too w arm. Closed separators- /.''., those which have a cover over the whole of the upper pan, leaving only an opening sufficient to allow the milk to enter — '.'/., the Alexandra (Fig. 17) deliver cream, if anything, slightly 'Warmer than the milk which Hows Fig. 17. — Alexandra Separator. [To fact p. 212. 2. 6a 7a 9a 10a 13c. 15. Explanation of Parts. Float for regulating inflow of milk from large receiving tin. Top tin cover with cream outlet. Bottom tin cover with skim milk outlet. . Steel cylinder in which milk is separated. Screw for regulating thickness of cream. Cast-steel spindle with ball-shaped head. Steel ball for footstep bearings, on which spindles Nos. 13c, 88, and 89 rest. Receiving tin bracket. Spindle for receiving tin bracket. Thumb nut for receiving tin bracket. Receiving tin with tap. Handle spindle. Steel pawl pin for handle. Steel spring for handle. Gun-metal ring for handle. Steel grub screw for handle. Iron quill pin and washer for handle. Wood quill for handle. Crank casting for handle. Footstep bearing for No. 13c. Steel set pin with lock nut for bearing 81a. Steel pinion on spindle carrying leather wheel. Leather wheel on spindle No. 88. Steel pinion for main spindle 13c. Steel spindle for carrying leather wheel and pinion. Steel spindle for bevel pinion and spur wheel. Neck bearing. Tin cover and inlet funnel combined. Strainer and inlet regulator combined. India-rubber ring for top bearing. Bevel wheel on handle spindle. Steel taper pin holding 118 to 47. Lubricator for handle. Grub screw for holding 87 to 13c. Bevel wheel. Spur wheel. SEPARATORS. 213 in ; a difference of 2° F. has sometimes been noticed. Such separators are at an obvious disadvantage. Open separators — i.e., those which have no cover at all — e.g., the Burmeister and Wain machines (Fig. 18) — permit of a con- siderable cooling of the cream, owing to the currents of air pro- duced ; it is by no means unusual to find that the cream is from 12° to 20° F. cooler than the milk. Semi-closed separators — i.e., those which have a cover over the upper part, but the opening of which is sufficiently large to allow of air being drawn in — e.g., the Alpha (Fig. 19) — stand intermediate in this respect be- tween the other two classes, the •cream being 4° to 6° F. cooler than the milk. If the cream is to be pasteur- ised, the separator which gives the " smoothest " cream is to be preferred, as the "lumps" are liable to melt into a fatty layer, which prevent uniformity in the butter. It cream is made for sale as such, the object to be aimed at is to obtain the most viscous or "thickest" product; smooth- ness should also be aimed at. The latter quality is obtained by taking off the cream as near to the centre of the separator as possible, and consequently as small an air space as practicable is allowed in the centre ; for this reason the more modern separ- ators are either of the closed or semi-closed varieties. The cream should also be allowed to flow out with as little friction as pos- sible ; the " open " separator of Burmeister and Wain, in which the layer of cream is cut off from the interior by a sharp edged tube, fulfils the last condition to the least extent; while those separ- ators which allow the cream to flow out through a hole are in this respect the best. Experiment points to the conclusion that cream is most viscous in proportion to its percentage of fat, when the largest quantity of fat is left in the separated milk ; this is probably clue to a difference in the mean size of fat globules, as it is Alpha Separator. 214 THE CHEMICAL CONTROL OF THE DAIRY. the smaller globules that remain in the separated milk. It is not altogether an advantage to insist on a very small percentage of fat in the separated milk when cream is made for sale. Cream, when used as such, is judged entirely by its taste and viscosity, and, other things being equal, that containing least fat is the most suitable for use ; for instance, cream low in fat is compara- tively high in proteids and, when used in tea, combines with a greater proportion of tannin. Separators, as a rule, do not work well if the cream amounts to less than 10 per cent, of the milk ; if it be desired to take off less than this — i.e., to make a thicker cream — the quantity of milk that a separator will cream must be seriously reduced, if a low percentage of fat in the separated milk be desired. Thus, when taking off cream in quantity equal to 6 per cent, of the milk, a separator of a nominal capacity of 300 gallons per hour will not run more than 150 gallons per hour. This is probably due to the fact that the viscosity of the cream is so great, and consequently the friction against the sides of the exit so much increased, that the cream does not all escape. As the pressure is great and the contents of the bowl must find an exit, a portion which should pass through the cream exit is obliged to flow out through the separated milk tube. Those separators in which the adjustment of the separati >r is performed by restricting the outlet of cream do their work less satisfactorily than those in which the flow of separated milk can be varied. There are few, if any, separators on the market in which the cream outlet is sufficiently large to allow very thick cream to flow away with sufficient freeness. The closer the exit of cream is to the middle of the drum, in which the tube feeding the milk is placed, the worse they are for running thick cream. The figures quoted in the table on p. 224 show this to a remarkable degree. Of separators in which the adjustment is performed at the cream exit, the Russian is closer built than the Alpha and shows a higher percentage of fat in the separated milk. The Alexandra and the modified Burmeister and Wain are adjusted by regulating the quantity of separated milk ; they both show a low percentage of fat when running thick cream. The modified Burmeister and Wain has the largest exit for cream, and will separate a quantity of milk approximating closer to its nominal capacity than any of the others, when thick cream is made. Cream Composition. — The name cream is given to the layer which rises to the surface when milk is allowed to stand. This layer consists essentially of the fit globules, together with a proportion of the aqueous portion of milk. Qualitatively, it has the same composition as milk ; quantita- tively, it contains a higher proportion of fat, the other consti- tuents being correspondingly depressed. COMPOSITION OF CREAM. 215 It is by many accepted as a fact that cream contains a larger proportion of solids not fat to water than the milk from which it was derived ; and various explanations of this have been put forward. Thus a membrane round each fat globule has been alleged to exist by some {e.g., Storch and Bechamp); others have considered that the proteids are concentrated in the aqueous layer formed round each globule by surface tension. The author's experiments have indicated that the ratio of solids not fat to water in cream is the same as that in milk. It is true that in some cases a distinctly higher ratio has been found, but it has been noticed that in these cases ample opportunity for evaporation of the water has been afforded, either by leaving the cream on the surface of the milk for some length of time in a dry atmosphere, or by pasteurising it, without any precautions to prevent evaporation ; indeed, evidence of evaporation has been obtained by noting the quantity of, cream before and after pasteurising. In cases where precautions have been taken to prevent evaporation, no evidence of a higher ratio has been obtained. In the following analyses (Table XLIII.) the solids not fat have been calculated by dividing the percentage of water by 100 and multiplying by 10"2 (except in No. 2 where 100, and No. 9 where 104 has been used), this being the average ratio in the milk from which these creams were prepared. The calculated ash is ^ of the calculated solids not fat: — TABLE XLIII. — Composition of Cream. Solids not Solids not Ash No. Total Solids. Fat. Fat, calc. Diff. Ash. calc. Diff. Per cent. Per cent. Per cent. Percent Percent 1. 32-50 6-83 6 90 + -07 •57 , -57 2. 37o9 614 6 24 + -10 •52 -52 3. 50-92 5 02 5 01 - -oi •42 i -42 4. 55 05 465 4-59 - 06 •38 -38 5. 55-18 4-77 4-57 - -20 •39 -38 -:oi 6. 55-97 4 47 4-49 + -02 •38 -37 -01 7. 56-37 4-40 4-45 + 05 •38 -37 -•01 8. 57 99 4-17 4-28 + -09 •41 -36 -•05 9. 68-18 3 30 3-31 + -01 •28 -28 In cream No. 1 the proteids were also estimated, and found to be 2-60 per cent., while the figure calculated on the assump- tion that they are 37 -8 per cent, of the solids not fat, as in milk, is 2*58 per cent. The statement that cream contains a higher proportion of solids not fat to water than milk, though to some extent due 216 THE CHEMICAL CONTROL OF THE DAIRY. to the evaporation of water which takes place, is probably also due to the methods of analysis employed. Thus it is known that when butter fat is heated in contact with air for some hours an increase of weight is noticed As cream contains from 25 to 50 per cent, of fat, an apparent increment in the total solids of from -1 to -3 per cent, may be noticed. If the fat be estimated by a method which avoids a long heating, and the solids not fat deduced by difference, the increment will swell the amount of solids not fat. Many analyses of the fat in cream have been made by methods which do not completely extract the fat ; the solids not fat are thus still further increased. The following is an analysis of a thick cream : — Water, . Sugar, . Proteids, Ash, . 99-70 The following table will show the amounts of milk-sugar, proteids, and ash contained in 100 parts of water compared with those contained in milk ami separated milk (see Mean Composition on pp. 120 and 209) :— 39-37 per cent 56 09 ,, 2 "29 ,, 1 -.-.7 ,, •38 )5 Cream. Milk. Separated Milk. Milk-sugar, . Proteids. Ash, .... Per cent. 5-81 3-99 •97 Per cent. 5-45 3 90 •86 Per cent. 5 47 3-94 •86 It is impossible to give an average composition of cream, as the variation of the fat is enormous ; the author has obtained cream containing 9 per cent, of fat as a minimum, and 68 per cent., and even slightly more, as a maximum. As milk has been known to contain as much as 12 per cent, of tat (from Jersey cows), it follows that no sharp distinction between milk and cream can be drawn. Attempts have been made to lix a standard for cream, but without success. Thus a London vestry, on the advice of their analyst, decided not to recognise as cream any product containing less than 25 per cent of t'at ; the absurdity of this is shown by the tact that, while much of the Cream sold in London contains between 40 and oil percent, of fit. being prepared by a separator, cream made by the Swarti process but rarely comes up to the standard proposed. Ash. — It has been alleged that the ash of cream is practically \'v<- from chlorides : this, however, is not in the author's experi- DENSITY OP CREAM. 217 ence correct ; the ash of cream differs in no respect from that of milk. The following is the composition of the ash of cream according to Fleischmann : — Potash, Soda, Lime, Magnesia, . Iron oxide, Phosphoric anhydride, Chlorine, Less oxygen equivalent to chlorine, 28-381 per cent. S-679 23411 3-340 2-915 21 735 14-895 103-356 3-356 100-000 The percentage of fat varies inversely as the density of the cream. A formula connecting the two can be deduced from the formula expressing the relation between specific gravity, fat, and total solids in milk. T = -2625 ^ + 1-2 F. Assuming that the solids not fat (S) are in the ratio to the water as 10-4 : 100, then and 100 - F = S T = F + 10-615 100 - F 100 + 9-615 F 10-615 substituting in the formula 100 + 9-615 F 10 615 1-2 F = -2625 ~ 10-615 3-123 F = 100-2-7S6 F = 32 0 - -892 G D G D' Density. — It is impossible to test the specific gravity of a cream containing more than 30 per cent, of tat with a hydro- meter direct ; but if it is diluted with an equal weight of separated milk the hydrometer can be used as with a thinner cream. To calculate the specific gravity of a thick cream from that of a mixture with an equal weight of separated milk, the following formula mav be used : — 218 THE CHEMICAL CONTROL OF THE DAIRY. c = specific gravity of cream. 8= ,, ,, of separated milk. m — ,, ,, of mixture. 8 X 7)1 Cream containing 25 per cent, of fat decreases in specific gravity -00027 or -27° for each 1° F. above 60° F. Table XLIV. shows the results obtained by calculating the fat from tbe specific gravity. TABLE XLIV. — Calculation of Fat in Cream. Specific Gravity. Fat Estimated. Fat Calculated. Per cent. Per cent. 1 0035 29 2 28-9 1 0057 27 3 26-9 1-0070 26-2 25-8 1 -i M IS.", 24-8 24-5 1 0090 2-1-0 24 1 10110 22-4 22-3 10125 214 21 1 10130 20-8 20 6 1-0210 13 3 13-7 Specific Gravity of Separated .Milk = «. Specific Gravity of Mixture = m. Fat Estimated. Fat Calculated. Per cent. Per cent. 1-0367 10053 55-5 54 7 1 -0367 10041 57-7 56 -3 1 0364 10081 49-8 490 The specific gravity of cream is affected by the state in which the iat globules exist; if they are in the solid state, the specific gravity will be very appreciably higher than if liquid. The formula given above assumes that they are solid : if, however, the cream has been separated at a temperature above the melting poinl of the fat, the globules are liquefied, and do not at once assume the solid state on cooling. For this reason the method of calculating the fat from the specific gravity is liable to give at times very discordant results. These figures show that, though the estimation of the specific gravity of a cream is scarcely exact, enough to serve as a means of analysis, Li is a useful corroborative figure. Considering the sources of error the agreement is very good, and serves as a further proof thai cream does no1 contain a larger proportion of solids not fal to water than milk, Vietb finds that cream containing l<> per cent, fal has, at a CLOTTED CREAM. 219 temperature of 175° F., a specific gravity of -960 and gives the following table : — Cream containing 30% 40% 50 % Fat. Gives at 185° F. asp. gr. , . ., 175° „ „ 165° „ •971 •975 •979 •956 •960 •964 •941 •945 •949 A sample of froth taken from the surface of cream running from a Burmeister and Wain separator had the following com- position : — Water, .... 48 "41 per cent Fat, . 4544 Milk-sugar, .... 2-86 Proteids, .... 1-89 Ash, ..... •40 It does not differ in its chemical composition from cream. The froth, however, always contains more fat than the cream. Clotted Cream, or cream prepared by the system practised in Devonshire and Cornwall, has been examined regularly in the Aylesbury Dairy Company's laboratory since 1886. Table XLV. gives the average yearly results, together with the maxima and minima found. TABLE XLV. — Composition of Clotted Cream. Date. Water. Fat. Ash. Solids not Pat. Per cent. Per cent. Per cent. Per cent. 18S6 36 11 57 36 •52 6 53 1S87 36-94 55 51 •58 7-55 1888 35 '54 57 09 •57 7 37 1889 36-69 56-69 •53 6 62 1S90 3516 58-35 •52 6 49 1891 33-95 59-30 •54 6 '75 1S92 35-63 56 27 •58 7-52 1893 30-77 61-49 •60 7-74 1894 31-59 60-25 •69 8-16 1895 33 19 58-21 •71 8-60 1896 32-36 5916 •68 8-48 1S97 33 36 58-22 •70 8-42 Average, . . 34-26 58-16 •60 7 52 Maximum, . 44 84 71-37 1-17 1 1 -70 Minimum, 21-08 44-29 •42 5 03 It is seen that the ratio of solids not fat to water is very much •_'20 THE CHEMICAL CONTROL OF THE DAIRY. higher in clotted cream than in milk, due to the evaporation which takes place from the surface during heating. Roughly speaking, the ratio of solids not fat to water is double the average ratio in milk. The ratio of ash to solids not fat is very neatly the same in clotted cream as in milk ; it is, however, slightly lower. This is partly, if not entirely, due to the fact that on heating milk certain salts of calcium, probably chiefly citrate, are deposited, leaving a smaller proportion in the milk and also in the cream derived from it. For dairy control work it is but rarely necessary to estimate the percentage of solids not fat, a determination of the fat being sufficient. This may be done by one of the centrifugal methods described, or it may be deduced from the percentage of total solids. For this purpose it is assumed that the proportion of solids not fat, to water in milk is constant, an assumption which causes no appreciable error in cream analysis. It is found that on the average 100 parts of water contain 10 4 parts of solids not fat (seep. 217); we may assume that the water in cream contains the same proportion of solids not fat, and estimate the fat by deducting the percentage of water multiplied by ■ 1 0-4 from the total solids. The following formula will express this relation : — Lei then T = total solids and F = fat, F = 1-104 T - 10 4. The following table (XLVI.) may be used: — TABLE XLVI.— PvATio of Fat to Total Solids in Cream. T.,tal Solids. Fat. Solids not hat. Total Solids. Fat Solids not Fat. Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. 60 55 8 4-2 44 38 2 5-8 .->!) 54-7 !•:: t:; 37-1 5 9 58 53 6 44 12 36 0 (5 0 57 .v.';. 4-5 41 ::i 9 6-1 56 61 l III 40 :::;s 6-2 .-,.". 50-3 17 39 32 7 6-3 54 in 2 IS 38 31-6 64 53 »>■! 1 9 .".7 304 6-6 62 I7«i 6-0 36 29 3 6 7 51 15-9 .VI 36 6 s 60 lis ::i '27 1 (i 0 i:i 13-7 5 :i 33 26*0 7-0 IS 12 6 •VI 32 24-9 71 17 1 ! '5 31 •_•;;■ s 7-J 16 to l 5-6 30 22-7 7-:< (.-) 5-7 29 21-6 71 This table is no< applicable t<> clotted cream. THE THICKNESS OF CREAM. 221 The Thickness of Cream. — The thickness is the factor by which cream is usually judged when used for direct consumption. This can be quantitatively estimated by the method generally employed for the determination of " viscosity" — i.e., noting the time taken for a given volume of cream to flow through a tube of constant size. The viscosity of a liquid depends on the internal friction — i.e., the friction of molecules passing each other ; the viscosity or internal friction of cream is not quite of the same order as that of a homogeneous liquid ; in the latter case, the molecules are of equal size (or nearly so), and very small in comparison with the diameter of the tube through which the liquid passes. The viscosity of cream depends on two factors — the internal friction of the very small molecules of the milk serum, and the friction between the comparatively large fat globules. As the fat globules have an appreciable size compared to the size of the tube, we cannot expect the laws to be of the same kind as those governing the viscosity of a liquid composed of molecules of infinitely small size. The actual and relative size of the globules will also have considerable influence; thus if we have two creams identical in chemical composition, in one of which the relative size of fat globules is much larger than in the other, the "viscosities" will differ. It is not possible to compare the thickness of cream by making a determination of the percentage of fat in a sample. It is possible, however, to make a comparison of cream which contain globules of relatively the same size. For instance, if cream be diluted with the separated milk, which is practically free from fat, the thickness can be deduced by making deter- minations of fat. The law connecting thickness or viscosity and amount of fat is expressed by the following empirical formula — V = lO^-3, where V = the viscosity, F, = the volume of fat in 100 volumes of cream, and x = a, factor dependent on the units in which the viscosity is ex- pressed, and on the relative size of fat globules. The volume of fat in 100 volumes of cream may be calculated from the percentage of fat (by weight) by the following formula — _ 1-07527 Fx 100 '" 0-11F + 96-5 This is true at a temperature of 60° F. (15-5° C), and maybe used without appreciable error at other temperatures. The following two series will illustrate the exactitude with which the formula agrees : — ogg THE CHEMICAL CONTROL OF THE DAIRY. Series I. , Calc. Calc. Calc. by Weight. by Volume. Viscosity. Viscosity. Percent. Fat by Volume. Per cent. Fat by Weight. 62 8 62 9 65 4 1516 157-6 65 3 603 62 9 88-0 90-3 628 60 2 57 • - 603 5.V2 52-7 60 6 58 0 52 6 55 3 21 2 21-4 55 3 52-6 Series II. 61-4 63 95 170 165-8 64 05 61 5 53-7 56 4 31-5 33 3 56-1 53 4 46-0 48-7 9-8 9 6 48-9 45 2 The agreement is within the limits of experimental error. Instead of the formula given above, which includes a calcula- tion of the percentage by volume of fat, the following approxi- mate formula may be used — V = lO***1 where F is the percentage of fat by weight. For small differ- ences the results by the two formula? agree sufficiently well. A practical method for the dilution of cream to constant thickness may be founded upon the above formula. To take the viscosity of a cream, a 10 c.c. pipette with a fairly wide opening, marked with distinct lines both above and below the bulb, may be employed j it should be surrounded by a water jacket made of glass to ensure a constant temperature ; and the end should not project far beyond the jacket. Care must be taken that its position is always vertical during the test ; this may usually be ensured by clumping the jacket firmly in position and fixing the pipette by rubber corks. The position should be tested by a plumb line, made of cotton, passing through the pipette. The " viscosity " of the cream is represented by the number of seconds that the cream in the pipette takes to How from the mark above the bulb to that below, which can be determined with sufficient accuracy by any watch with a seconds hand, though it is preferable to use a stop watch. Care must be taken that the cream is free from lumps, or solid particles, and it may advantageously be filtered through muslin. The pipette should be clean and dry, and the cream should be allowed to remain in the pipette a few minutes before making the test, in order to ensure that its temperature is that of the jacket. It will be found in practice thai it La better to use water of the mean daily t .nipei.it lire in the jacket than water at any constant temperature, because a purchaser is not in the habit of reducing cream to a temperature of (say) 60 F. before passing judgment on its thicknt THE THICKNESS OF CREAM. 223 At the same time that the viscosity is estimated a determina- tion of the fat should be made by one of the methods recom- mended (pp. 178 and 187). The relation between viscosity and fat can be calculated by the formula given above, which may be expressed, for practical use, as log (log V) = 3 log ( njy796^) + 1°g x> Or, log (log V) = 2-7 log F + log x,. A standard viscosity must be fixed, which evidently must be determined by each operator to suit his apparatus, and the con- ditions under which it is necessary to work ; the value of log x or log x having been found from the determination of viscosity and fat, the percentage of fat which will correspond to the stan- dard viscosity can readily be calculated. If a be the percentage of fat found in the cream, and b the percentage of fat which will be contained in the cream of standard viscosity, the cream may be reduced to standard viscosity by adding to each 100 parts 100 ( — — j parts of separated milk, or 100 ( , - .] parts of milk containing/ per cent, of fat. The figure 3 '5 may generally be used for/ without appreciable error. As an example the following result may be taken : — V = 170 log v = 2-23045 log (log v) = log 2-23045 = -34839 F = 61 -4 107-527 F TfF^96-5-W J° log 63-95 = 1-80584, and 3 log 63-95 = 5-41752 then 5 41751 = -34839 + 5-06913. Now let the standard viscosity be 25. log 25 = 1-39794, and log 1-39794 = -14550 therefore, 5-21463 = -14550 + 5-06913 now 521463 = 3 x 1-73821 = 3 log 54-7, and the percentage of fat in cream reduced to standard viscosity is 52 '0 per cent, by weight, or 54 -7 per cent, by volume. Now a = 61-4, and 6 = 520 then 100 (A^X\= 19'4 \b-3-5) that is, to each 100 parts of cream 19 "4 parts of milk must be added to reduce it to standard thickness. By the formula V = 10a;/ 7 the percentage of fat calculated in the cream of standard viscosity is 51'7, which is a figure sufficiently close for practical purposes. 224 THE CHEMICAL CONTROL OF THE DAIRY. Artificial Thickening of Cream. — Cream has been arti- ficially thickened by the addition of various foreign substances; thus, gelatine, isinglass, and substances of like nature have been employed, but without great success, as the cream thus treated has an appearance markedly different to that of genuine cream. The following method, due to Stokes, may be applied to detect gelatine in cream : — To 10 grammes (approximately) of cream add 25 c.c. of water and 2 c.c. of AViley's acid mercuric nitrate solution (p. 78), and shake well ; filter through a dry filter. In the presence of much gelatine the filtrate cannot be obtained clear, and it is not essential that it should be so. On adding a saturated aqueous solution of picric acid a yellow precipitate is formed in the presence of gelatine; if the quantity of gelatine be but small, the precipitate does not form at once, but the solution becomes turbid, and precipitates after a lapse of some minutes. Starch, which has been gelatinised bv heating, has also been used; this, of course, is readily detected by the characteristic blue coloration given with tincture of iodine. Of comparatively recent introduction is " viscogen," which is a solution of lime in cane-sugar syrvip ; the addition of a small amount of this sub- stance has a remarkable effect in increasing the thickness of cream. The following table shows the results obtained with various types of separators ; the experiments with thin cream were made by Vdeth in Hameln, and those with thick cream by the author at the Aylesbury Dairy Company. The Balance and the Alex andra separators are very similar, and the two series are cum parable: — - - - - a Name of Separator. j Speed. Revs. Burmeister & Wain, ,,l-r mi" A A, . . . 2700 Alpha II., . . 56(10 Balance, . . 7000 Capa- city. Galls. pel hr. 2+7 257 169 Yield of Cream. Perct. 12-18 12 97 Percentage of FaJ in trated Milk. 274 343 ! 267 15 05 •03 •50 ■25 •30 Avar- age. ■24 •10 •I.'. a ! 2 « t J s. ■- a - z. a H Burmeister & Wain, B modified), Alexandra I., Alpha I , . Russian, 4000 80 6 0 118 •08 •30 8000 ISO 6 0 233 ■OS •30 6600 250 6-0 67 •08 •34 7800 120 6 0 12 15 •38 ■15 ■1 i ■19 THE DECOMPOSITION OF MILK. 225 CHAPTER V. BIOLOGICAL AND SANITARY MATTERS. Contents. — The Decomposition of Milk — Micro-organisms — Action on Milk — Pathogenic Organisms — Conveyance of Disease — Water Supply — Inspection of Source — Analysis of Water — Bacteriological Examin- ation — Summary of Sanitary Precautions — Products formed from Milk by Micro-organisms. The Decomposition of Milk — Micro-organisms. — The decomposition of milk is due to the action of micro-organisms. The description of their life-history, and the means of separating and identifying them belong to the science of Bacteriology. The following slight sketch will, however, be found of use to the dairy chemist : — Classification. — Micro-organisms belong to the vegetable kingdom and are classed among the fungi ; they are divided into Schizomycetes or fission-fungi. Saccharomycetes or yeasts. Hyphomycetes or moulds. The Schizomycetes are again divided into families according to their shape and mode of growth : — Bacteria ; short rod-like forms forming no spores. Bacilli ; rod-like forms forming spores. Spirilla ; curved rod-like forms. Micrococci : round forms occurring singly. Dip/ococci ; „ ,, „ double. Staphylococci: ,, ,, in bunches. Y Streptococci; ,, ,, growing in chains. Sarcinm ; , , ., ,, in groups. Leuconostoc ; thread-like forms. Cladothrix ; branching forms. The distinction between these forms is by no means absolutely defined ; thus many species forming spores with difficulty or only under certain conditions, which were formerly classed as Bacteria, are now called Bacilli. Some organisms grow as micrococci, streptococci, spirilla, and leuconostoc. Action on Milk. For the purposes of the dairy chemist micro-organisms may be classed according to their action on milk, as follows : — 15 226 BIOLOGICAL AND SANITARY MATTERS. Those acting on milk-sugar (a) producing lactic acid ; (/>) ,, butyric acid ; (c) ,, alcohol. Those acting on proteids (a) curdling milk without acidity and not dissolving the curd ; (b) curdling milk without acidity and afterwards dissolving the curd ; (c) peptonising the proteids without curdling the milk. Those producing coloured substances. Those having no action on milk. We may also place in another class those which are pathogenic. Milk is a model food for micro-organisms, for it contains in an assimilable form all those compounds which are necessary for the sustenance of life. It has been shown by experiment that it is possible to obtain milk which is quite free from micro-organisms. It is necessary, however, to reject the first portions drawn, as these contain micro-organisms which have found their way down the duct of the teat. The last portions are practically sterile, and it is highly probable the few organisms found were due to accidental contamination of the milk during its passage from the teat into the sterilised bottle into which it was drawn. Practically speaking, all the organisms found in milk fall in after milking ; in certain diseases — e.g., tuberculosis of the udder — the Bacillus of tuberculosis is not derived from external sources, but passes from the diseased tissue into the milk. Generally speaking, micro-organisms only develop between the temperatures of 4° C. (39° F.) and 50° C. (122° F.) ; each organism has an optimum temperature — i.e., one at which its development and action are most rapid ; this varies from 12° C. (53-6° F.) to 40° C. (104° F.) in different species; the optimum temperature of pathogenic organisms and of most of those acting on milk is about blood-heat. Among other conditions which regulate their development are (1) the amount of acid present in the milk — thus the organisms which produce lactic acid are paralysed in their functions when more than about 1 per cent, has been produced; and (2) the presence or absence of oxygen, Some organisms can do without oxygen, and are called anaerobic; others require it for their life processes, and are designated aerobic Lactic Fermentation. — The most commonly observed effect of the action of micro-organisms is the souring of milk. This is due to a numerous class of organisms, chiefly bacteria and bacilli, which convert the milk-SUgar into lactic acid. The chemical equation f<,v this change usually given is C„H„Oi, OH, 4C,11,()3. The change, however, never proceeds in this delightfully simple manner, certain quantities of carbon dioxide being ORGANISMS WHICH PEPTONISE THE MILK WITHOUT CURDLING. 227 always produced ; by keeping up a free supply of oxygen a very large proportion of car lion dioxide can be obtained. Some lactic ferments give an amount of lactic acid agreeing approxi- mately with the above equation ; others produce notable amounts of alcohol and other products. Other organisms, again, produce very small quantities of lactic acid and large amounts of other substances. Hueppe has studied this class of organisms minutely and has described many species ; few of these form spores and are destroyed with comparative ease by heat ; generally speaking, their optimum temperature is about 35° C. (97° P.). Butyric Fermentation. — When this takes place the milk coagulates without the development of acidity, but the milk becomes alkaline ; a bitter taste is acquired, the precipitated casein is redissolved, and butyric acid is formed ; an unpleasant smell is usually developed. This fermentation, which does not readily occur if lactic acid is developed, appears to be also caused by many micro-organisms, which attack both milk-sugar and casein. When this fermentation takes place, the solid portion of the milk is reduced to a very much greater extent than by the lactic fermentation. Alcoholic Fermentation. — This does not readily occur in milk. As already mentioned, small quantities of alcohol are produced as bye-products by some organisms ; ordinary yeasts Saccharomyces cerevisice, &c, do not cause fermentation of milk- sugar, but one species of Saccharomyces is known which converts the bulk of the milk-sugar into alcohol ; this is found in kephir grains, together with organisms producing lactic acid and others acting on the proteids. Curdling Organisms. — These organisms act on the casein by the secretion of an enzyme, which resembles rennet in its action ; these are usually bacilli, which readily form spores and are difficult to kill by heating. Organisms which Curdle without Acidity and Redissolve the Curd. — This class is a very large one; the organisms act by the secretion of enzymes having proteolytic functions analogous to pepsin and trypsin. Many of the organisms producing butyric acid belong to this class ; among the most noticeable of which are the hay- and potato-bacilli. Organisms which Peptonise the Milk without Curdling. — This class is probably more numerous than has been described; they also act by the secretion of a proteolytic enzyme. It is rare to find milk which shows their characteristic behaviour, as there are generally other organisms present which curdle the milk. When cultivated in sterile milk, no action is at first apparent, but the milk gradually becomes more and more trans- parent till it assumes an appearance like a liquid jelly. The author has separated an organism of this class from "mazoum," an Armenian preparation. 2l'8 BIOLOGICAL AND SANITARY MATTERS. Chromogenic Organisms — Milk " out of Condition." — Several organisms have the property of producing coloured substances ; these, and one or two other classes, are the chief causes of milk being "out of condition." Blue Milk. — Sometimes the formation of dark blue patches on the surface of milk, having the appearance of a drop of blue- black ink which has fallen in, is noticed. This is due to an organism called B. syncyanus or B. cyanogenus ; when cultivated alone a grey colour is produced, which turns an intense blue on the addition of acids ; the blue colour is only noticed if the milk be sour with lactic acid. Red Milk. — This is occasionally due to the action of micro- organisms ; it is usual to ascribe the formation of red milk to Micrococcus prodigiosas, which forms an intense blood-red sub- stance, but it is doubtful whether this organism is commonly the cause. The colour is usually of a far more pinkish tinge, and is due to the pink yeast, Micrococcus rosaceus, Bacillus lactis erythrogenes, or Sarcina rosea. The organism causing a red colour varies according to the district, and only one organism is usually found in any district. A red colour in milk may be due to the presence of madder in the food eaten by the cattle, but far more frequently arises from the presence of blood ; this is produced by a diseased state of the udder, but far more frequently by some slight local damage, through a kick or a blow resulting in the breaking of a small blood-vessel in the udder. Yellow Milk. — An organism which curdles milk and redissolves the curd to form a yellow liquid has been described as Bacillus synxanfhus ; there are probably several organisms which produce a yellow colour ; all seem to have proteolytic functions. Yellow milk is very rare, though it is very common to see dirty vessels which have contained milk become quite yellow. Green milk, violet milk, and hitter milk have been found to be produced by micro-organisms. Bitter principles may be derived from the food of the cattle, and some, though not all, of the butyric ferments give rise to a bitter taste. Peptones produced from casein may also be the cause of bitterness. Ropy Milk. — INI ilk occasionally, instead of remaining liquid, becomes a thick slimy mass; if a glass rod is dipped into milk which has become ropy and withdrawn, a portion of the milk adheres and can be drawn out in long threads. Sometimes this action is confined to the cream on the surface, but with other organisms the whole milk becomes ropy. Soapy Milk. After a few hours milk has been known to acquires fishy odour, alkaline reaction, and soapy taste. Ilerz regards this as due to a disease of the cow, and lias found that Buch samples haves bigh ipecific gravity ; Weigmann has iden- tified an organism, which be also found in the Btraw used litter, which gave a soapy taste t<> milk. PATHOGENIC ORGANISMS. 229 Moulds. — White mould (Oidium lactis) is very commonly found on sour milk ; it forms a tough white skin on the surface, which is entirely formed by the hyphse and mycelium of the mould. A brown mould, which penetrates down into the milk, is sometimes observed. Green mould, Penicillium glaucum, also grows on milk and is the colouring agent of some cheeses — e.g., Roquefort and Gorgonzola. Pathogenic Organisms — Conveyance of Disease through Milk. — If, as already mentioned, a cow is suffering from tuber- culosis of the udder, the bacillus passes into the milk. It has been proved that the organism retains its toxic properties, and to this cause the bulk of cases of infantile tubercular intestinal disease can be traced. Tuberculosis is by no means an un- common disease in cows. Evidence was given before the Royal Commission on Tuberculosis that in Copenhagen and Berlin, where all animals before being slaughtered are systematically examined by veterinary experts, the percentage of oxen and cows affected with tuberculosis was 17*7 and 15-1 per cent, respectively of the total number examined. In many herds the number exceeds this ; on one farm as many as 80 per cent, of the cattle were affected. In a large proportion of the cattle the disease did not affect the milk-produciug organs, and in these the milk did not contain the tubercle bacillus ; in a very noticeable proportion the milk was, however, affected. As there is no certainty that the disease may not spread to the udder, even though the bacillus be not detected in the milk, the presence of tuberculosis in a cow should always be taken as a sign of danger. On the Continent and in America this subject has received much more attention than in this country, but now that the report of the Royal Commission on Tuberculosis is completed, it may be expected that legislation will follow, which will mini- mise this cause of infection. An obvious means of preventing infection by tuberculosis is to remove the diseased cattle, and only use healthy cows as the source of milk supply. As the tubercle bacillus is comparatively easily destroyed by heat, pasteurisation of milk may be resorted to to destroy the organisms ; keeping the milk for a quarter of an hour at 70° C. (162° F.) will practically remove the source of infection. Another, but less satisfactory means, is to mix the milk with that of healthy cows and trust to Providence for the presence of sufficient lactic acid organisms to destroy the tubercle bacilli ; even if they are not destroyed, they are sometimes so diluted that they have no toxic effect on healthy adults, though children and persons weakened by disease or predisposed by heredity to consumption may be affected. Other diseases — pleuro-pneumonia, foot and mouth disease, and scarlatina (or an analogous skin disease) — may be derived 230 BIOLOGICAL AND SANITARY MATTERS. from the cattle. These are much less common than tuberculosis and less insidious, as the symptoms can be detected with com- parative ease in the cows. Practically speaking, tuberculosis is the only disease which needs to be guarded against by systematic veterinary inspection. Conveyance of Disease through Contamination of the Milk. — The labours of the late Ernest Hart in collecting statis- tics have conclusively shown that typhoid, cholera, scarlet fever, and diphtheria can be conveyed through milk. There are practically two causes: (1) the occurrence of the disease in the milkers and those handling the milk and their families ; and (2) the presence of the organisms to which the malady is due in water used for " cleansing " the utensils or for adulterating the milk. The epidemics of scarlet fever and diphtheria which have been spread through milk have almost all been due to the milk being handled, shortly after milking, by those either affected with the disease, or living in the same house with sufferers. The remedy is, of course, obvious ; a rule should be made in every dairy that all employes who feel unwell should absent themselves from their work, and pay an immediate visit to a medical man ; if any members of their families be ill, medical advice should be similarly obtained; and if the disease be infectious, the employe must be at once suspended from duty, and not allowed to go near the dairy. It is found in practice that this regulation can be carried out (1) By the employer providing for the services of a medical man. (2) By the payment of full wages to any employe' who is suffering from infectious disease, and suspended from duty. (3) By a distinct understanding that the breaking of the regulation by an employe means instant dismissal without notice. Water-borne Diseases. — Typhoid and cholera, which are essentially water-borne diseases, have, in the majority of cases investigated, been due to the use of contaminated water for the cleansing (sic) of dairy utensils; the small amount of water left on the sides of the vessel is sufficient, if the water contain virulent germs, to infect the milk ; even more so does this occur if the practice of washing out the dairy vessels with a little water after milking, and adding this to the milk, prevails. The precautions against this form of infection arc also obvious, though more difficult to carry out in practice than those mentioned al>ove. Water Supply. A water supply which is not contaminated, <>r Liable to con- tamination, and b good system of sanitation is necessary. Before milk is supplied from B farm or dairy the water supply must be CHEMICAL ANALYSIS. 231 rigidly investigated. The investigation may be conveniently divided into three parts. (1) Inspection of source. (2) Chemical analysis. (3) Bacteriological examination. Inspection of Source. The following sources of supply are almost always satis- factory : — (1) Deep artesian borings. (2) Deep wells passing through an impervious stratum — e.g., chalk. (3) Springs fed by an uninhabited watershed — e.g., springs in the sides of hills. Public water supplies, mountain rills, and wells sunk in open ground remote from habitations are very frequently — but by no means always — of a satisfactory nature. On the other hand, shallow wells near dwellings, ponds, small brooks, and wells in pervious strata — e.g., coral ragstone — are usually unsatisfactory. The following points must be considered to be highly unsatis- factory : — The proximity of privies, cowsheds, &c. ; the trend of the lands from habitations to the source ; faulty conditions of the sides of a well (otherwise satisfactory), which may allow surface drainage to enter ; and, except in the case of springs on the sides of uninhabited hills, a marked diminution of the supply after drought, and increase after rain. It is advisable to ascertain the geological formation, and whether artificial fertilisers are much used in the vicinity ; if this is done to a large extent, some of the chemical evidence may be discounted. Chemical Analysis. Taking of Samples. — At least half a gallon of water must be taken for the analysis; a "Winchester quart" bottle is con- venient for this purpose. The first portions — say, 10 to 20 gallons — should invariably be rejected, and the bottle should be rinsed with the water, filled nearly full, care being taken to avoid undue aeration, and despatched to the laboratory as quickly as possible. The following data should be obtained : — Colour. — This should be observed in a layer at least 12 inches in length ; a yellowish-green tint is always suspicious, and points to sewage contamination ; a brownish or brownish- yellow indicates vegetable products, not necessarily harmful, but usually undesirable. A nearly colourless water, with a faint blue or bluish-green tinge, is shown by most good waters. Smell. — A small wide-necked bottle is half filled with the 232 BIOLOGICAL AND SANITARY MATTERS. water, which is warmed to about 60° C. (140° F.) ; the water is shaken, the stopper removed, and the smell noted. Foul smells show badly polluted waters; a peculiar sweetish unpleasant odour is often given by waters containing sewage. Few waters are absolutely devoid of smell when tested thus; for instance, waters from the Oxford clay sometimes smell of petroleum, and a smell of pines is not uncommon in wooded districts. Analytical Figures — Total Solids.— 250 c.c. (or 100 c.c.) are evaporated in a weighed basin, and dried to constant weight in the water-bath. Loss on Ignition. — The residue is ignited over a very small name ; the smell of the vapours given off should be noted, as polluted waters often give an unpleasant smell. Much blacken- ing indicates a large amount of organic matter; if nitrates are abundant, red nitrous fumes may be observed. Chlorine. — 100 c.c. of the water are placed in a white porcelain basin, 1 c.c. of a 1 per cent, solution of pure potassium chromate added, and silver niti-ate (4-7887 grammes AgNOa per litre) run in till a faint reddish colour is produced. The quantity of silver nitrate required to give a similar tint with 100 c.c. of distilled water is subtracted, and the difference represents milligrammes of chlorine. Free and Albuminoid Ammonia. — 250 c.c. of water are placed in a stoppered Wiirtz flask, to the delivery tube of which a condenser is connected ; the condenser must be a good one, and drawn out at the end, so that the diameter of the opening does not exceed 1 millimetre. If the water be distinctly alkaline to methyl orange, nothing need be added; but if not, a little freshly ignited sodium carbonate must be dropped in. A flame is placed under the flask, and about 125 c.c. of the water distilled and collected in a stoppered bottle. As soon as the flame is placed under the flask, about 250 c.c. of distilled water are placed in a flask and brought to the boil (or nearly so) ; the flask is removed to the bench, 10 grammes of caustic soda added, and, when dissolution of this is complete, about 1 gramme of potassium permanganate dropped in. This solution of alkaline permanganate is boiled, while the distillation is proceeding, at SUch a rate, that its bulk, when 125 c.c. have distilled from the flask, should be just about sufficient to make up the original volume. The alkaline permanganate solution is added to the Wiirtz flash : and a further 1 L'."> C.C. are distilled oil', and collected in a Becond stoppered bol I le. The first bottle contains the \'rvv (or saline) ammonia, and the rid the albuminoid (or organic) ammonia. The contents of the bot t les are well mixed, and 50 O.C. of each are placed in n N easier cylinder, 2 c.c. of Nessler solution added, and the tint in each of t hem matched 1 . \ placing a known volume STANDARD AMMONIUM CHLORIDE SOLUTION. 233 of standard ammonium chloride solution in a Nessler cylinder, making up to 50 c.c. with distilled water free from ammonia, adding 2 c.c. of Nessler solution. The waters must be allowed to stand for five or ten minutes before the final comparison is made, as the colour does not develop instantaneously. After a little practice, it will be found easy to make an approximate match of tints at the first trial. It is not necessary to do this exactly. If the cylinder which contains the distillate is of approximately the same depth of shade as the standard, a little may be poured from the darker cylinder till the colours are matched ; the positions of the cylinders should be several times reversed before finally deciding that they are equal, as a shadow may be cast on one cylinder more than the other and make it appear darker than it really is. If the cylinder containing the distillate is the darker, and some of the solution has been poured from it, the calculation is performed as follows : — Let x = the weight of ammonia equal to the amount of standard ammonia solution taken, y = the amount of solution poured out, and % = the total amount in the cylinder ; then the weight of ammonia in 50 c.c. of the distillate = x x , and the amount of ammonia obtained from 250 c.c. of water is found by multiplying by the total volume of the distillate, which should be measured, and dividing by 50. If the cylinder containing the distillate is the lighter, and some of the solution has been poured from the standard, the calculation is slightly different : — Let x = the weight of ammonia equal to the amount of standard ammonia solution taken, y = the amount of standard solution poured out, and z = the total amount in the cylinder containing the standard solution ; then the weight of ammonia in 50 c.c. of the distillate = x x — . Nessler Solution. — Dissolve 35 grammes of potassium iodide in 100 c.c. of water; next dissolve 17 grammes of mercuric chloride in 300 c.c. of water ; reserve a little of the potassium iodide solution and add the mercuric chloride solution to the rest, till a permanent precipitate is formed ; then add the remainder of the potassium iodide solution and cautiously drop in mercuric chloride solution, till a faint permanent precipitate is left. Dissolve 160 grammes of potassium hydroxide in water, add this solution to the mercury potassium iodide solution and make up to 1 litre. The solution is more sensitive if a little more mercuric chloride solution is added. The solution is left to settle and the clear portion decanted for use. Standard Ammonium Chloride Solution. — Weigh out -3146 gramme of pure ammonium chloride, and dissolve in 100 c.c. of 234 BIOLOGICAL AND SANITARY MATTERS. ammonia-free water ; dilute 10 c.c. of this to 1 litre with ammonia- free water for use. 1 c.c. = -00001 gramme NH3. Ammonia-free "Water. — Boil ordinary distilled water in a flask to half its bulk and cool in an atmosphere free from ammonia. Nitric Acid. — Place about -01 gramme of diphenylamine in a porcelain basin, add 1 c.c. pure sulphuric acid, and mix ; run two or three drops of the water down the sides of the basin, so that they will flow over the surface of the acid. In the presence of nitrates a blue colour will be developed. From the amount and depth of coloration produced a rough idea of the amount of nitric acid present can be formed, which will be useful in the quantitative estimation. Measure 1 c.c. of the water by an exact pipette into a porcelain basin and evaporate to dryness on the water-bath ; measure also a known volume of the standard potassium nitrate solution into a porcelain basin and evaporate to dryness. To each add 1 c.c. of a sulphuric acid solution of salicylic acid (2 grammes of salicylic acid dissolved in 100 c.c. of pure sulphuric acid) and heat for five minutes on the water-bath. Dilute to about 20 c.c. with distilled water, make alkaline with ammonia, and dilute to 50 c.c. Compare the colours produced in Nessler cylinders and calculate in the same manner as directed under Free and albuminoid ammonia. Standard Potassium Nitrate Solution. — Dissolve 185 grammes of pure potassium niti'ate in 1 litre of water ; dilute 10 c.c. to 1 litre for use. 1 c.c. = -00001 gramme N2Or. It the chlorine be high, the method just described gives results seriously below the truth and the following method may be used : — Place about 200 c.c. of water in a wide mouth stoppered bottle with three pieces of copper-zinc couple. Leave for twenty-four hours in a warm place ; then take 100 c.c. and distil oft" 50 c.c. of this, after making alkaline with sodium carbonate. Estimate the ammonia in the 50 c.c. (or an aliquot part, 5 or 10 c.c. diluted to 50 c.c. are often sufficient) in the manner previously directed. The ammonia found (less the free ammonia present) multiplied by 3-2 will givse the nitric acid (as N I I i Preparation of Copper-Zinc Couple.— Cut a number of pieces of sheet zinc 4" x 1", and im rse them successively in 2 per cent, caustic soda solution, distilled water, '2 per cent. sulphuric acid solution, and distilled water, keeping them for about two minutes in each solution and agitating them. Place t Ikih in 3 per cent, solution of crystallised copper Bulphate till a firm black deposit is obtained; well rinse them in distilled water, without undue handling] and preserve in a stoppered botl le filled with strong alcohol. Nitrites. — Dissolve about ■<)•"> gramme of meta-plicnylene- AMMONIUM MOLYBDATE SOLUTION. 235 diamine in dilute sulphuric acid (10 c.c.); add 10 c.c. of water and allow the mixture to stand. A pink coloration is produced, if nitrites be present. Oxygen absorbed from Permanganate. — Clean out a stop- pered bottle with chromic acid and rinse well with distilled water. Take 250 c.c. of water, add 10 c.c. of dilute sulphuric acid and 10 c.c. of standard potassium permanganate solution, mix, and keep at a temperature of about 80° F. (27 •4° C.) for four hours. Add a crystal of potassium iodide and titrate with standard sodium thiosulphate solution till only a faint yellow colour remains ; then add a little starch solution and continue the titration till the blue colour disappears. To 250 c.c. of distilled water add 10 c.c. of sulphuric acid and 10 c.c. of potassium permanganate ; and titrate with standard sodium thiosulphate solution (2 grammes per litre).* The difference between the amounts of sodium thiosulphate solution used, divided by the amount of sodium thiosulphate used for the sulphuric acid, potassium permanganate and distilled water, and multiplied by -001 will give the weight of oxygen absorbed by 250 c.c. of water. Dilute Sulphuric Acid. — Mix 100 c.c. of pure sulphuric acid cautiously with 300 c.c. of water, cool to 80° F., and add so much potassium permanganate solution that a faint pink tinge remains after four hours. Standard Potassium Permanganate Solution. — Dissolve •395 gramme of pure potassium permanganate in 1 litre of dis- tilled water. 1 c.c. = -0001 gramme oxygen. Starch Solution. — Make an emulsion of "5 gramme of starch in 2 c.c. of water and add this to 50 c.c. of boiling water. Boil for five minutes and cool. Phosphates. — Dissolve the ignited residue from the total solid estimation in a little dilute nitric acid ; evaporate the solution to dryness in a porcelain dish, and take up with 1 c.c. of dilute nitric acid, filter the solution, and wash the filter paper with very small amounts of water. Add to the filtrate, which should not exceed 2 or 3 c.c, an equal bulk of ammonium molybdate solution and warm to 60° C. (140° F.). A yellow- coloration is called a " very faint trace" of phosphates, and a distinct precipitate a "very heavy trace." Ammonium Molybdate Solution. — Mix 14 c.c. of strong ammonia (sp. gr. "880) with 28 c.c. of water, and add 10 grammes of molybdic acid and stir till all is dissolved. Add this solution, slowly and with constant stirring, to 125 c.c. of nitric acid (sp. gr. 1 -2) ; stand the solution in a warm place for a few days and decant the clear solution for use. A slight deposit may form on keeping. * The addition of a little, say "05 gramme, salicylic acid will render this solution permanent. -36 BIOLOGICAL AND SANITARY MATTKKS. Interpretation of Results of Water Analysis.— Good waters contain, generally speaking : — Total solids, .... 20 to 30 parts p«r 100,000. Chlorine. . . . . . 1 to ■_> ,, ,, Free ammonia, . . not more than -001 ,, ,, Albuminoid ammonia, ,, ,, -010 ,, ,, Nitric acid, .... 0 to 2 ,, ,, Nitrites, . . . . . none. They absorb less than -1 part per 100,000 of oxygen, and arc practically free from phosphates. The total solids may be higher than the limits named, in chalk waters and in mineral waters. A high chlorine content may be due to beds of rock salt — e.g., in Cheshire — or to admixture with salt derived from the sea (near the coast) ; it is, however, usually due to sewage. Deep well waters often contain large amounts of free ammonia; and water which has passed through iron pipes may also contain free ammonia and nitrites. A high albuminoid ammonia is usually very undesirable, though not conclusive of pollution by sewage ; pools into which dead leaves fall may give rise to high albuminoid ammonia. Nitric acid is a most reliable datum ; any amount above 3 or 4 parts per 100,000 is certainly due to pollution. The presence of nitrites is always unfavourable, except when the water lias passed through iron pipes. The amount of oxygen absorbed does not give much infor- mation as to whether a water is polluted with sewage ; high figures are often due to vegetable matter. The proportion of oxygen absorbed to albuminoid ammonia is often a useful datum. Where vegetable contamination has taken place the oxygen absorbed is ten times (or more) the albuminoid ammonia; in polluted waters it is usually less. The presence of phosphates is usually regarded as an un- favourable symptom ; this may, however, be due to the use of artificial fertilisers ; the nitric acid may be increased from this cause. If waters known to be pure from the same district and from the same geological formation can be obtained, the water can be compared with them; any marked increase in the figures found must be regarded as evidence of pollution. By this means evidence of contamination is often obtained which would be difficult, or almosl impossible, to acquire from chemical analysis alone. It must be remembered in comparing waters with ■ "district itandard thai in the autumn the figures for free and albuminoid ammonia, nitric acid, ami oxygen absorbed usually are Blightly higher t han al ol her t inn b of I he \ ear. BACTERIOLOGICAL EXAMINATIONS. 237 For further information on the subject works on :< Water Analysis " must be consulted. It must be borne in mind that the judging of water supplies is not a subject that can be learnt from books entirely, but that prolonged experience is necessary to properly interpret the results obtained. Bacteriological Examinations. A very simple examination is all that is usually necessary. A sample of the water for bacteriological examination must be taken in a sterilised bottle ; a six-ounce stoppered bottle is plugged with cotton wool, and the stopper is wrapped in cotton wool and tied to the neck ; the bottle is sterilised for three hourk at a temperature of 150° C. (350° F.). The sample is best taken directly after the sample for analysis has been obtained ; the plug of cotton wool is removed and the bottle filled with water without being rinsed; then the stopper is quickly removed from its cotton wool wrapping and inserted in the bottle. The examination must be commenced with as little delay as possible ; and, if the sample has to be forwarded by post or rail, it should be packed in ice. The examination usually consists in making a gelatine culti- vation at 22° C. and an agar cultivation at 37° C. Preparation of Nutrient Media — Nutrient Gelatine. — 120 grammes of gelatine (Coignet's Extra Gold Label) are dissolved in 1 litre of water on the water-bath ; 5 grammes of Liebig's extract of meat and 10 grammes of peptone are added, and dissolved by further heating ; the whites and shells of two eggs, stirred up together to make an intimate mixture are next added, and the heating on the water-bath continued till the liquid is cleared. Small quantities of sodium carbonate are now added, with constant agitation, till, on testing with delicate litmus paper, a faint alkaline reaction is obtained. The liquid is now filtered, the filter being kept warm, and the clear filtrate is ready for use. Portions of 10 c.c. are placed in tubes 4 inches long, 1| inches in diameter, with a neck |-inch in diameter, whicli have been previously plugged with cotton wool and sterilised by heating for three hours at 150° C. (350° F.). The nutrient gelatine in these tubes is sterilised by heating to 100° C. (212° F.) in steam for fifteen minutes on four successive days. Nutrient Agar. — Seventeen grammes of finely divided agar are substituted for the gelatine. The preparation is otherwise con- ducted in the same manner. The filtration is, however, much more difficult and the agar is never so brilliantly clear as the gelatine. If a steam turbine tester is available, it is better to centrifugalise the agar, in tubes of sufficient size to fit into the machine, at the highest rate of speed that the tubes will 238 BIOLOGICAL AND SANITARY MATTERS. bear, for an hour. The solid matters are removed by centri- fugal force, and the agar is clearer than can be obtained by filtration. Prepare also a number of test tubes, each containing 9 c.c. of distilled water ; plug these with cotton wool ; and sterilise. The tubes containing nutrient media and sterilised water must be covered with a rubber cap to prevent evaporation. Procedure. — Sterilise a pipette delivering 1 c.c. by heating to 150° 0. (350° F.), or by heating all over in the flame of a Bunsen burner. As soon as this is cool, open the bottle containing the sample, and take out 1 c.c. Add tins to one of the tubes con- taining sterilised water and replace the plug immediately. Take out another 1 c.c. and add this to a tube of nutrient agar, which should have been previously liquefied and allowed to cool to 50° G. (122° F.). Replace the plug of cotton wool, mix the water and the nutrient agar, and cool under the tap, rolling the tube between the fingers so that the agar is solidified in an even layer over the sides. "With another sterilised 1 c.c. pipette add 1 c.c. of the mixture of water with sterilised water to a tube of nutrient gelatine, which has been previously liquefied by heating and cooled to about 27° C. (80° F.). Replace the plug of cotton wool, mix the water and the nutrient gelatine, and cool under the tap if the water be cold enough, or by rolling on a block of ice. The gelatine must be spread in an even layer over the sides of the tube. Place the agar cultivation in an incubator kept at about 37° C. (or 100° F.), and the gelatine cultivation in an incubator kept at about 22° C. (or 72° F.) ; after two and a-half days the number of colonies that have developed are counted. The best method of counting is to hold the tubes over a black surface; mark each colony with a dot of red ink, and count the dots. It is usually advisable to divide the surface of the gelatine tube into sections by lines drawn in red ink and to count the colonies in the section separately. [f the water is suspected to be bad, a smaller amount of water may be taken, -5 c.c. or even "2 c.c. If it is supposed that the water is good, the amounts taken may b<> increased. The quan- tities given will, however, usually serve. Many of the colonies on the gelatine will be found to have liquefied the medium, and, if the Counting is delayed, the liquid may run down and con- taminate the Other portions. The author has found that if the colonies are counted in two and a half days, no practical incon- venience is found from this source. Interpretation of Results. The growth of any large number of colonies on the agar, cultivated at 37° C. (or 100' V.), must be considered as a ?erj unfavourable sign, as the ordinary water organisms ;ire almost all destroyed at this temperature, while SUMMARY OF SANITARY PRKCAUTIONS. 239 the organisms found in sewage, including pathogenic organisms, grow well under these conditions. A few colonies, say 5 to 10 per c.c, may, however, be found in good water. The colonies liquefying gelatine are usually those of putre- factive organisms, and any great proportion is undesirable. The number of organisms growing on gelatine varies greatly with the source of the water. Water from deep wells should be almost sterile and certainly should not give more than 100 colonies per c.c. ; any number exceeding this may be taken as indicating contamination with surface water. Surface waters which are not contaminated may contain many more organisms, as many as 2,000 per c.c, and often a large number of these (25 per cent.) liquefy gelatine ; such waters are generally found to contain organic matter derived from decaying leaves and other vegetable matter. All waters giving an appreciable number of organisms on nutrient agar and a number of organisms running into many thousands on gelatine may be condemned as unsatisfactory. By the combined information from inspection of the source, chemical analysis and bacteriological examination, a usually reliable opinion can be made of the purity of the water ; it is even more reliable, if the data are compared with those obtained on waters of known purity from the same district and of the same character. For other methods of bacteriological examination and for the separation and identification of individual species, works on bacteriology must be consulted. Summary of Sanitary Precautions.— The following re- commendations were made by a commission held under the auspices of the British Medical Journal : — 1. That all milking be carried on in the open air, the animals and operators standing on a material which is capable of being thoroughly washed, such as a floor of concrete or cement. Such a floor could be easily laid down in any convenient place which can be found. The site chosen should be removed from inhabited parts as far as possible, and should be provided with a plentiful [and pure] water supply. 2. That greater care be expended on the personal cleanliness of the cows. The only too familiar picture of the animal's hind- quarters, flanks, and sides being thickly plastered with mud and faeces is one that should be common no longer. 3. That the hands of the milker be thoroughly washed before the operation of milking is commenced, and that, after being once washed, they be not again employed in handling the cow otherwise than in the necessary operation of milking. Any such handling should be succeeded by another washing in fresh water before again commencing to milk. 4. That all milk-vendors' shops should be kept far cleaner 240 BIOLOGICAL AND SANITARY MATTERS. than is often the case at present. That all milk-retailing shops should be compelled to provide proper storage accommodation, and that the counters, &c, should be tilpd. With reference to the last recommendation, it may be men- tioned that the regulations of the London County Council provide that all places where milk is stored shall have an impervious floor, and the walls shall be tiled or cemented for a height of 6 feet from the floor. The following additional recommendations are chiefly taken from the system adopted by the Aylesbury Dairy Company : — 1. The cows should be systematically examined by veterinary surgeons ; and those in ill-health removed, and their milk not utilised. 2. The sanitary arrangements of the dairy and health of the employes should be systematically examined by a medical officer, who should be empowered to insist on all unsatisfactory arrange- ments being instantly remedied, and, in default of this, should have the power to stop the milk supply. 3. To ensure the proper carrying out of these regulations guarantees should be given that no financial loss should result from suspension of the milk supply owing to infectious disease, while very heavy penalties should be imposed for contravention of sanitary regulations. 4. All water used for cleansing dairy utensils should be previously boiled, to destroy disease germs if acciden- tally present ; and, if possible, the vessels themselves should be steamed. If the only available water supply be not above suspicion, an immunity from the consequences of its use may be attained by filtration through a Pasteur-Chamberland filter. This consists of one or more tubes of unglazed porcelain of a special quality, through which water will pass, but which keeps back micro- organisms. It has been found that in course of time that certain micro-organisms will grow through the filter, but it appears to be firmly established that pathogenic germs are not among these. To secure efficient working, these filters should be frequently cleaned, and it is advisable to sterilise them by Bteaming from time to time. They have the advantage of being easily tested, as when efficient they will not, when wet, allow air uinler a pressure of 10 lbs. per square inch to pass ; while, if defective, i passage is afforded at any place which will allow miero-orL.r:nii>iiis to traverse the filter. Products formed from Milk by the Action of Micro- organisms. Besides butter and cheese, in the manufacture of which micro-organisms play an important part, several prepara- tions are made from milk; among these may be mentioned komiu . l.ephir. and ma/.oiim. KOUMISS. 241 Koumiss. — This preparation was originally made from mare's milk by the Tartars. It is a product of combined alcoholic, lactic, and proteolytic fermentations on milk. Its production first from mare's milk is probably due to the fact that the sugar of this milk very easily undergoes alcoholic fermentation. The following analyses of mare's milk koumiss are by Vieth :— 1 Day Old. 8 Days Old. 22 Days Old. Per cent. Per cent. Per cent. Water, .... 9143 9212 92-07 Alcohol, . 2-67 2 93 2-98 Lactic acid, •77 1-08 1-27 Sugar, 1-63 •50 •23 Casein, •77 •85 •83 Albumin, . •25 •27 •24 Albumoses, •98 •76 •77 Fat, . 1-16 112 130 Ash, . •35 •35 •35 Koumiss is now very largely made from cow's milk by the selection of special organisms. The following analyses of various kinds of koumiss have been made by Vieth on the preparations of the Aylesbury Dairy Company. The carbonic acid present has not been taken into account; it is, however, always present (except in the earlier stages) in sufficient amount to render the koumiss highly effer- vescent ; hence, the preparation has been termed " milk cham- pagne " on this account. The term "casein" includes dys-caseoses. Full Koumiss. 1 Day Old. 8 Days Old. 22 Days Old. Per cent. Per cent. Per cent. Water, .... 88-90 90 35 90-57 Alcohol, . •15 •94 104 Fat, . 1-35 1-36 138 Casein, 201 1 96 1-88 Albumin, . •30 •23 •20 Albumoses, •34 •53 •77 Lactic acid, •34 •96 1-40 Sugar, 6-03 3-10 2-18 Ash, soluble, •17 •23 •23 ,, insoluble, •41 •34 •35 1G 242 biological and sanitary matters. Whey Koumiss. 1 Day Old. 8 Days Old. 22 Days Old. Per cent. Per cent. Per cent. Water, .... 89-74 90-63 9107 Alcohol, . •30 1 '03 1-38 Fat, . •11 •13 15 Casein, •15 •14 11 Albumin, . •39 •36 •32 Albumoses, •44 •49 •58 Lactic acid, •91 1-26 Sugar, 7-48 5-52 4 34 Ash, soluble, •37 •37 •37 ,, insoluble, ■42 •42 •42 Medium Koumiss. 1 Day Old. 8 Days Old. 22 Days Old. Per cent. Per cent. Per cent. Water, .... 87-55 88-39 88-62 Alcohol, . •29 •97 1-05 Fat, . 154 1-56 1-58 Casein, 146 1-40 1-30 Albumin, . •43 •25 •14 Albumoses, •48 •76 •97 Lactic acid, •68 1-20 1-67 Sugar, 6-80 4-70 3 90 Ash, soluble, •28 •32 •33 ,, insoluble, •49 •45 •44 Diabetic Koumiss. 1 Day Old. B hays iil.l. 28 Hays iil.l. Per cent. Per (int. Per cent. Water, .... 92-24 92*38 92-66 Alcohol, ■28 •:;;. •57 Fat, . . , •51 •:>•_> •61 1 ein, 2-19 213 2-06 Albumin, . •80 ■26 •is Albumoses, •:{(i i> •66 Lad i'' arid, ■7.-> •86 1 -2-2 Bugs*, Ash, soluble, 2-78 2-42 Mil •22 •J l ■26 ,, insoluble, . •37 •37 ■87 KEPHIR. 243 Russian Koumiss. 1 Day Old. 8 Days Old. 22 Days Old. Per cent. Per cent. Per cent. Water, .... 91-87 92 26 92-52 Alcohol, . •22 •45 •57 Fat, . •34 •33 •33 Casein, 232 2-17 2-03 Albumin, . •08 •07 •07 Albumoses, •32 •48 •63 Lactic acid, •06 •31 •56 Sugar, 3-95' 3-08 2-45 Ash, soluble, •46 •49 •49 , , insoluble, •3S •36 •35 The last preparation — made from skim milk — is not an article of commerce now. Wiley gives the following mean composition of koumiss pre- pared in America : — Water, . Carbon dioxide, Alcohol, . Lactic acid, Proteids, Fat, Sugar, . 89-32 per cent. •83 •76 •47 2-56 2 05 4-38 Koumiss has the advantage of being a food and a stimulant at the same time ; and is, for this reason, often prescribed by the medical faculty in cases of disease (e.g., gastritis) when no other food can be retained. Kephir. — This is a preparation of a similar nature to koumiss and is produced from milk by means of kephir grains. The following is the composition of kephir according to various authorities : — Konig (mean). Hammarsten. Vieth (an old sample). Per cent. Per cent. Per cent. Water, .... 9121 88 915 90 09 Alcohol, . •75 •720 •64 Lactic acid, 102 •727 •44 Fat, . 1-44 3-088 1-82 Sugar, 2-41 2-685 1-87 Casein, 2 83 2-904 2 90 Albumin, . •36 •186 •07 Albumoses, •30 •067 •45 Ash, •68 •708 244 BIOLOGICAL AND SANITARY MATTERS. Kephir differs from koumiss chiefly in the comparatively small amount of albumoses it contains, showing that, although the alcoholic and lactic fermentations have taken place, the proteolytic fermentation is very weak. Struve found in kephir grains : — Water, . Fat, Proteids, 11 "21 per cent. 399 51-69 The author has examined a " kephir powder," which had the following composition : — Water, 2 29 per cent. Milk-sugar, 88-90 Other organic matter, .... 7 '42 ,, Ash, 1-39 „ It appeared to be a mixture of milk-sugar with pulverised kephir grains. Mazoum. — This preparation, lately introduced from Armenia, where it has been made for centuries, has somewhat the appear- ance of clotted cream ; on warming, it separates into a liquid whey and an insoluble curd. The author has determined the following figures : — Fat, . Casein, Ash, . Organic solids, Ash, . Water, 6 '27 per cent. ) 2 56 „ > Curd. •04 5-00 •77 85-38 Whey. There was no evidence of albumoses in the whey. Mazoum appears to have been produced by the lactic fermen- tation of milk enriched with cream ; the sample examined was very fresh and proteolytic fermentation was not appreciable. An organism was separated from mazoum which gave colonies rapidly spreading on the surface of gelatine to 1 cm. or more in diameter, and which produced a slight putrid smell. This organism, which was a bacillus, slowly peptonised milk without curdling it, and finally transformed it into a semi-transparent liquid jelly. BUTTER. 245 CHAPTER VI. BUTTER. Contents. — Definition of Butter — Composition — Theory of Churning — The Proximate Analysis of Butter — The Analysis of Butter Fat — Preparation of the Fat for Analysis— Recapitulation of Properties — Estimation of Volatile Fatty Acids — Saponification Equivalent — Soluble and Insoluble Fatty Acids— Colour Tests for Adulterants — Behaviour of Butter Fat with Solvents — Iodine and Bromine Absorption — Heat Evolved by Sulphuric Acid — Physical Examination of Butter Fat — Microscopic Examination — Density— Refractive Index — Viscosity — Melting Point — Detection of Adulteration of Butter — - Influence of Keeping on Butter — Buttermilk — Chemical Control of Churning Operations. Definition. — Butter is the substance produced by churning milk or cream, during which process the fat globules coalesce to form granules ; when freshly churned, butter has the appear- ance of a fine spongy mass ; but, after being worked, this assumes a structure homogeneous to the naked eye. Composition. — S torch gives the following mean composition to butter : — TABLE XLVII. — Composition of Butter. From Fresh Cream. From Ripened Cream. Fat, Water, .... Proteids, .... Milk-sugar, .... Ash, Salt, Per cent. 83-75 13-03 •64 •35 •14 2-09 percent. 82-97 13-78 •84 •39 •16 1-86 He further argues that the milk-sugar must all belong to the buttermilk, which fills the spaces betweeu the fatty portion ; and, from the composition of the buttermilk, calculates the pro- portion of water, proteids, and ash belonging to this. 246 BUTTER. TABLE XLVIII.— Composition of Butter. From Fresh Cream. From Ripened Cream. Per cent. Per cent. Fat, 83-75 82-97 Buttermilk, . 6 95 8-49 Water, . 631 7-74 Milk-sugar, . •35 •39 Proteids, •23 •29 Ash, •06 •07 Mucoid substance, 721 6-68 Water, . 6-72 6 04 Proteid, •41 •55 Ash, •08 09 Salt, . 2-09 1-86 Proportion of Solids not Fat to Water. — Vieth has shown that in butter the proportion of solids not fat to water remains, so long as no water is added, the same as that in milk — i.e., 100 to 10 ; he gives the following average analyses : — Composition of Different Kinds. TABLE XLIX. — Composition of Butters. Designation. Fat. Water. Curd. Salt. *£>"" Per cent. Per cent. Per cent. Per cent. English, . . . 86-85 11-54 •59 102 5 French, fresh, 84-77 1376 1-38 09 10 * ,, salt, 84 34 12 05 1-60 2-01 13 * German, salt, 85-24 12 24 117 1-35 10 Danish, ,, 83-41 13-42 1-30 1-87 10 Swedish, ,, 82-89 13-75 1-33 2 03 10 The following analyses by the author show the average compo- sition of French fresh butter (giving the amount of preservative), and of Australian butter: — Designation. Pat. Water. Curd. Sult Anhydrous Anhydrous r'^^ livr. Borax. Boric Add. Perct. Perct. Perct. Perot. Per ct. Perot. Perct. French, fresh, 83*92 14-33 1*38 ... -21 bs = *66 Australian, salt, 84-50 12-70 1*21 1 57 ... Table L. will give the number of samples in which the water falls between the percentages named. The analyses were made by Vieth, Schnepel, Boseley, Livett, CShaughnessy, and the author in the Aylesbury hairy Cnnijaiiy's laboratory. * i ontained bono acicL VARIATIONS OF WATER IN BUTTER. 247 TABLE L. — Variations of Water in Butter. English Butters. Foreign Butters. Percentages of Water. No. of Samples. Percentage. No. of Samples. Percentage. 7 to 8, . . 2 •3 8 „ 9, 5 •8 5 •4 9 „ 10, 14 2 2 13 ro 10 „ 11, 26 4-2 51 3-7 11 „ 12, 65 10-4 78 5-7 12 „ 13, 154 24-6 115 8-4 13 „ 14, 182 291 395 29 0 14 „ 15, 97 15-5 373 27 4 15 ,, 16, 50 8-0 241 17-7 16 „ 17, 21 34 71 5 2 17 „ 18, 4 -6 21 1-5 18- ,, 19, 3 5 1 1 19 ■„ 20, 2 3 Total, 625 1364 The above table contains butters of all kinds — fresh, salt, preserved, unpreserved, fresh from churning, and samples which had been kept for various periods. Variations in Percentages of "Water. — The following table (LI.) is taken from a paper by Faber on "Water in Danish Butter '' :— TABLE LI. — Variations of Water in Butter (Faber). No. of Samples. Percentage of Total. Percentages of Water. Summer. Winter. Summer. Winter. 9 to 10, . . 1 1 •o •1 10 ,, 11, 16 8 •8 •4 11 ,, 12, 136 20 63 10 12 „ 13, 335 138 16-8 7-2 13 „ 14, 534 431 26-7 22 3 14 ,, 15, 512 562 25-7 29 1 15 ,, 16, 287 447 144 23 2 16 „ 17, 124 205 62 106 17 „ 18, 39 95 2 0 49 18 „ 19, 13 20 •7 10 Above 19, 4 3 •2 •2 Total, 2001 1930 Average, 14U3'70 14-417, 248 BUTTER. Table LII. shows the effect of keeping on the percentage of water contained in the butter; fresh and salt butters, which were all prepared at the Aylesbury Dairy Company, are kept separate. TABLE LII. — Variations of Water in Butters on Keeping. Percentages of Water. Percentages of the Total Number falling betw the Limits Named. ;en Fresh Butters. Salt Butters. Less than 12 hours old. 24 to 48 hours old. Less than 12 hours old. 24 to 48 hours old. 10 to 30 days old. 18 to 19, 1-3 17 ,, 18, ... 2-5 16 „ 17, 17 150 3-8 15 „ 16, 103 100 22-5 51 3-6 14 „ 15, 313 150 25 0 12-6 13 „ 14, 32-8 35-0 25 0 34-1 10 7 12 „ 13, 20 7 40'0 7-5 38-0 28-6 11 „ 12, 3 4 1-3 5-1 42-9 10 ,. 11, 13 10 7 9 ,, 10, 3-6 Average percentage of water, ! 13 79 1354 14-74 13-33 1-2 00 Taking butters from twenty-four to forty-eight hours old to represent commercial butter, it is seen that salt butter contains rather less water than fresh butter. The contrary is usually Stated ; but this is not according to the author's experience. Fresh butter loses its water chiefly by evaporation, and it is seen that this loss is small ; salt butter also loses water by brine running out. It will usually be noticed that salt butter looks wet on being cut, while fresh butter rarely has this appearance. Action of Salt. — The action of salt, which is added both to give a flavour and as a preservative, seems to be as follows : — It first dissolves in the buttermilk left in the butter, and forma a strong solution, which curdles the, buttermilk, giving an insoluble precipitate of proteid matter and a clear whey. The salt solution has a smaller viscosity than the buttermilk ; hence, a smaller layer is condensed round the particles by surface energy, so that there is liquid which is very loosely held in the butter; this gradually runs out, and gives rise to the wet appearance of salt butter. It is noticed that the liquid which runs out, or is THEORY OF CHURNING. 249 squeezed out, of salt butter is always clear and transparent, while the liquid squeezed out of fresh butter is usually milky. By warming to a temperat-ure near the melting point of the fat considerable quantities of water can be mixed with butter. In the preparation of "pickled" butter this fact is taken advan- tage of to add large amounts of salt by working in warm brine. Butter treated in this way does not lose its water easily, as an emulsion of fat and water is thus produced. Storch has shown that by the action of certain micro-organisms such a condition (of the proteids?) is produced, that large amounts of water are retained and cannot be worked out. In this case an emulsion is produced, which contains large numbers of very minute water globules. These butters are designated "thick," and are rare in England. Theory Of Churning". — Several theories have been put forward to account for the phenomenon of churning. Thus, Fleischmann holds the view that the globules of fat in milk are in a superfused condition, and that churning is simply the phe- nomenon of solidification ; with the recognition of the fact that the globules are solid at low temperatures this view is untenable. Soxhlet holds that churning consists in the rupture of a solid membrane, which he believes exists round the fat globules ; as the existence of such a membrane appears hypothetical, this view cannot be accepted. Storch attributes churning to the gradual rubbing off of a semi-solid membrane of "mucoid sub- stance," and this hypothesis has much to recommend it; the whole of the evidence points to the existence of a layer, which is not solid, round the fat globules. As previously stated, the author cannot reconcile Storch's theory that this layer consists of "mucoid substance" with known facts; but it appears very highly probable that there is a layer, the composition of which is for the present purpose immaterial, i*ound each fat globule. As it is improbable that this layer is elastic, the effect of the impact of one fat globule on another will be to squeeze out the layers between them, and bring the globules within the sphere of each other's attraction. In this way nuclei will be formed, which will, on continued churning, increase in size ; as the nuclei get larger and larger, the resistance, owing to fluid friction on their surfaces, will gradually bear a smaller and smaller proportion to the force tending to bring them to the surface, and, at a given moment, the butter will "come." This theory is in accord with all the known facts. By microscopical examination of cream during churning the formation of nuclei of irregularly shaped masses of fat globules is noticed. As an irregular mass will occupy a greater apparent volume than a sphere, the transformation of spherical globules into irregular nuclei should be attended with thickening of the cream, which is in accord with the facts ; as the nuclei increase in size, the 250 BUTTER. layer condensed by surface energy round them will rapidly become less, so that the cream will gradually decrease in thick- ness ; this decrease in thickness of the cream should take place later than the increase mentioned above, which is also the case. When the butter is taken from the churn it is in fine grains, which are the nuclei referred to. On working, the fat globules are brought still closer to each other, and the butter is formed into a nearly homogeneous mass ; small amounts of liquid are, however, left distributed throughout the mass, and as these liquid globules are very small and contained in a medium which, though solid, is still viscous, they are by surface energy trans- formed into spheres. The microscopical examination of butter shows a number of spherical globules of aqueous liquid in a nearly homogeneous medium consisting of fat ; there are, how- ever, many fat globules left, which, by careful examination with little light (best by dark stage illumination), can be made out. The whole of the globules usually seen, which are of all sizes, consist of aqueous liquid ; in many cases where the globules are of sufficient size for the surface energy to become small, they cease to be spherical. The reason that butter always does, and must, contain water is that the aqueous liquid present is finely divided, and assumes a spherical condition. It is impossible by pres- sure from the outside to remove small spheres from a homo- geneous medium. It appears certain, from the experiments of Storch on the density of butter, that the density of the fat is the same as that of butter fat in the solid state; it is, therefore, solid in butter. This view is nearly universally accepted. Vieth, however, holds that it is liquid, because all the globules which are visible are spherical ; it appears probable that he has overlooked the fact, only recently pointed out by Storch, that all the globules visible by the usual microscopical examinations are water globules. With the recognition of the fact that butter is an approxi- mately homogeneous fatty substance, the reason for its change of consistency by alteration of temperature at once becomes apparent. To churn butter of the right consistency it is neces- sary that the fat in the cream shall be of that consistency. As pointed out in Appendix A, the fat in cream which has been warmed very slowly solidifies. If the cream has been kept at a high temperature, as in summer, it is necessary to churn at a lower temperature than if the cream has been kept ai a Lower temperature, as the effeel on the consistency <'t' the fit of cream of cooling for -.i long time ai ■■> fairly low temperature is the same as that of cooling lor a shorter time at a lower tempera- ture. THE PROXIMATE ANALYSIS OF BUTTER. 251 Temperature of Churning. — The best temperatures for churning are as follows : — Recently separated cream (quick churning), about 8° C. (46 "4° F.) ,, ,, (slow churning), ,, 13° C. (55-4° F.) Sour cream, winter, . ....,, 18° C. (64*4° F. ) „ summer, , 13° C. (55-4° F.) If the butter is churned at too high a temperature, it will contain more water than at medium temperatures. Butter- churned at very low temperatures also contains more water than at medium temperatures ; this appears to be due to the fact that in the one case the fat is too liquid, and in the other too solid, for the maximum effect of squeezing out the watery portion on working to be attained. Butter which is quickly churned by violent impact also has a tendency to contain more water than that churned more slowly. This may be explained by the hypothesis that if the nuclei are quickly formed several globules of fat may coalesce simultaneously and enclose more buttermilk than if they coalesced singly. When the cream churned is very sour the solids not fat may contain precipitated casein ; in this case the ratio of solids not fat to water is high. If the temperature at which the butter is churned and worked be too high, very large percentages of water (up to 50 per cent.) may be found ; this may be very materially reduced by cooling the butter for several hours and re-working. Various substances — rennet, pepsin, sodium carbonate, &c. — have been used to increase the yield of butter; this effect is attained by increasing the water contained in the butter. Preservatives in Butter. — Besides salt, various other sub- stances are used as preservatives ; the most usual are mixtures of borax and boric acid, though formalin, salicylates, sulphites, and potassium nitrate have also been employed. The Proximate Analysis of Butter. — The proximate analysis of butter indicates, not whether the sample is genuine or otherwise, but its condition, and affords some clue as to its mode of preparation. The usual data to be determined are water, solids not fat, fat, and salt. Preservatives are usually only tested for qualita- tively, but sometimes a determination may be made. It is also occasionally of interest to determine the actual curd. Water. — The most important datum is the percentage of water. As the water is not always equally distributed through- out the mass of butter, especially in butters which have been salted, it is necessary to take precautions to obtain a fair sample — a matter of some difficulty. It is not advisable to use a scoop, as water is liable to be squeezed out while forcing it into the lump. Perhaps the fairest way of sampling is to cut the lump 252 BUTTEK. in two halves, and to take a piece near (not at) one top corner, a second piece in the middle, and a third near the opposite bottom corner. The three pieces should he placed in a wide- mouthed stoppered bottle, melted at as low a temperature as possible, and violently shaken till the mass is nearly solid. If the analysis is to be commenced at once, suitable quantities may be poured out while the butter is still in a semi-liquid condition, and weighed as soon as possible. The water by this means is equally distributed throughout the sample, and a small quantity will be representative of the whole sample. In the case of well- made fresh butter the differences in the distribution of water is small, and a single sample taken from any part of the lump will represent with fair accuracy the whole bulk. Where extreme accuracy is not desired, the melting and shaking of samples of fresh butter may be omitted. The water in butter may also Vie mixed by warming to such a temperature that the butter begins to lose its consistency, and stirring vigorously with a stout glass rod. The mixing of salt butter should not be omitted if accuracy is a desideratum. The following methods are used for the determination of the water : — 1. About 10 grammes are weighed out into a small porcelain basin provided with a glass stirrer. This is place 1 over a very small flame, or on a sand-bath, and the butter carefully, but vigorously, stirred till all signs of frothing cease. The tem- perature must be so regulated that spirting is avoided, and that the "curd" does not become appreciably browned by the heat. The basin and its contents are, after cooling, weighed ; the loss of weight indicates water. 2. A basin is filled with pumice, which is broken in pieces about the size of a small pea, washed, and ignited ; 2 or 3 grammes of well mixed butter are weighed in, and the basin placed in a drying oven at 100° 0. (21'J° F.), through which a good draught passes. At the expiration of an hour the basin is cooh'ii and weighed, and then replaced in the oven for n further half hour ; weighings are made at the expiration of succeeding half hours till the weight ceases to diminish. The lowest weight obtained is taken as that of the dry butter. The difference between this weight and that of the original butter is taken as water. 3. Four to five grammes of butter arc weighed into a wide- mouthed flat-bottomed conical flask, which is placed in a water oven and shaken i-\>ry ten minutes for the first half hour, after which it is shaken every halt" hour. At the expiration of four hours i' is ended, weighed, and returned to the bath for another hour: it' t here In- any loss, the drying is oontinued till an hour's drying does not cause any diminution of weight. I. Prom 2 to -.1 grammes of well mixed butter are weighed SOLIDS NOT FAT AND SALT. 253 into a Hat-bottomed basin about 2-f inches diameter. This is placed in the water-oven till just melted, and 1 to l.\ c.c. of strong alcohol are added; the basin is replaced in the water- oven, and weighed after two hours. The loss represents water. Of the four methods, the first is the most expeditious, and is nearly as accurate as the others ; the second is the most accurate ; the third is the most convenient if solids not fat and salt are also estimated; while the fourth is fairly accurate, rapid, and requires no attention. No one of the four methods has, however, any great advantage over the others. Solids not Fat and Salt. — For the estimation of solids not fat and salt the residue from the determination of water is taken and melted at a low temperature. A solvent for the fat, of which ether is perhaps the best, though chloroform, amyl alcohol, and others may be also used, is poured on, the whole well mixed, and allowed to stand in a warm place till the solvent is quite clear. The solution is carefully decanted and a fresh portion of the solvent poured on the residue, and, when clear, poured off. Four or five successive treatments are sufficient to remove the whole of the fat. With a little practice the operation may be so performed that none of the solids not fat are poured away with the solvent. The residue is placed in the water-oven, and dried to constant weight; the weight represents solids not fat and salt. Salt. — To estimate the salt the residue is treated with hot water and filtered, the filter together with the residue washed, and the filtrate, or an aliquot portion of it, is titrated with a standard silver nitrate solution, using potassium chromate as indicator. It is essential that the solution should be cold before titration, and the silver nitrate solution should be standardised on pure sodium chloride. The strength should not be deduced from the amount of silver niti'ate present, as Hazen, and, later, W. G-. Young, have pointed out that the amount of silver used is always greater than that theoi-etically required to combine with the chlorine From the amount oi silver nitrate solution used the weight of salt is readily calculated. It is convenient to make the silver nitrate solution of such strength that 1 c.c. = •005 gramme of sodium chloride. Solids not Fat. — The weight of salt found by titration is subtracted from that of the residue left after the extraction of the fat, and the difference represents the solids not fat. Fat. — The fat is best estimated by subtracting the total of the watei', salt, and solids not fat from 100; though the solvent may be evaporated and the fat actually weighed, if desired. Curd. — An estimation of the actual curd present can be made by submitting the residue, left after estimation of the fat, to Kjeldahl's process for the estimation of nitrogen (p. 105), and multiplying the nitrogen found by 6*38. The milk-sugar may 254 BUTTER. be estimated in a portion of the solution used for the titration of the salt by one of the methods given for the determination of milk-sugar (p. 82). These determinations are rarely required. Ash. — In place of an estimation of the salt, an ash deter- mination is often made, and the ash taken as salt. The results are, however, always slightly above those obtained by titration, as butter itself, to which no salt has been added, gives a small ash ; preservatives, such as borax, will also swell the weight of the ash. Preservatives. — The preservatives most largely used in butter consist of a mixture of borax and boric acid ; sulphites and nitrates have also been used, usually in conjunction with borax or boric acid ; formalin has been recommended, but appears to be rarely used. These should be tested for in the aqueous portion which sinks to the bottom on melting the butter at a low temperature. The reaction with turmeric paper applied to the liquid direct will show the presence of free boric acid. If no reaction or a feeble one be obtained, a little of the liquid may be acidified with very dilute hydrochloric acid, and tested with turmeric paper. A pinkish-brown coloration, turned greenish-black by dilute alkali, will show the presence of boric acid in combination (as borax). It will usually be found, if the butter is preserved in this way, that a reaction is obtained from the liquid itself, and a much stronger one alter acidifying. The presence of sulphites may almost always be detected by the smell of sulphurous acid developed on acidifying. Nitrates may be found by the diphenylamine test. For the quantitative estimation of preservatives 50 grammes of butter should be placed in a stoppered cylinder, 50 c.c. of chloroform added, and the mixture gently warmed till perfect mixture takes place. A quantity of water, which will, with that present in the butter, make up 50 grammes, is added, and, after shaking, the cylinder is put aside to allow the aqueous portion to separate. Each cubic centimetre of the solution will contain the preservative in 1 gramme of butter. For the estimation of boric acid Thompson's method is the most convenient (p. 76). As butter is practically free from phosphates, the process for their removal may be omitted, and tlif titration performed on the solution without any treatment j the result will be the total boric arid, free and combined. If it be desired to estimate borax and boric arid separately, it is best to evaporate an aliquot portion of the liquid to dryness several times with methyl alcohol, and to titrate the boric acid in the te ; 1 part BoOa in the residue equals 2*886 parts oi dry borax. The results obtained do not necessarily indicate the quantity of borax and boric acid originally added, as the presence of .-nid and .alkali in t lie butter may cause the formation of borax or boric acid in situ. A more useful result may be obtained by THE INTERPRETATION OF RESULTS. 255 dividing the total B203 by "56, a figure based on the fact that commercial preservatives contain approximately about 5G per cent, of boric anhydride. Another method of estimating borax is to calculate the total alkalinity to methyl orange as borax, but this method is liable to be erroneous should other substances — alkaline to methyl orange — be present. An estimation of the total sulphurous acid may be made by distilling a portion of the liquid with dilute hydrochloric acid, passing the gas evolved into decinormal iodine solution, and titrating with sodium thiosulphate ; 254 parts of iodine convert 64 parts of SO., into sulphuric acid. The gas evolved may also be passed into bromine water, and the sulphuric acid formed estimated as barium sulphate, of which 233 "5 parts represent 64 parts of S02. The solution from which the sulphurous acid has been distilled may be advantageously evaporated to dryness after making alkaline and ignited, and the sulphuric acid estimated in this ; the sulphuric acid present is probably due to the oxidation of the sulphite. Nitrates may be estimated by one of the methods described under " Water Analysis." If much salt be present, the copper- zinc couple method, or Crum's method, should be employed. Formalin cannot be estimated with any degree of exactitude, as it gradually enters into combination with the proteids present, and only the residue of uncombined formaldehyde, which gives no clue to the original amount, can be determined. If adulteration is suspected, it may be of interest to mici'o- scopically examine the residue left after removal of the fat ; adulterants, such as starch, mineral matters, &c, which it is alleged have been used, would be thus detected. This form of adulteration is of extreme rarity. The Interpretation of Results. — There* is a general con- census of opinion among authorities that butter at the time that it is placed on the market should not contain more than 16 per cent, of water ; in many cases where this figure has been markedly exceeded successful prosecutions under the "Sale of Food and Drugs Act " have been instituted. There is only one class of butter in which there is the slightest difficulty in getting the water down to 16 per cent. — the Irish pickled butter. This butter, though considered unappetising by the majority, finds considerable favour among the town workers of the Midlands and North. From its mode of preparation — the working in of strong brine at a somewhat elevated temperature — it is neces- sarily liable to contain a somewhat large percentage of water. Seeing that warm brine is worked into the butter, with the object of producing an article for which there is a public demand, it is doubtful whether such a proceeding can be considered an adulteration, though were water worked in in the same manner 256 BUTTER. it would undoubtedly be a contravention of the law. It, there- fore, behoves us to distinguish between them. It is advisable to always calculate the solids not fat and salt, not only as percentages, but also as parts per 100 parts of water present. The following table will show the characteristics of various classes of butter : — Class. Per cent. Water. Parts per 100 parts of Water. Designation in North of England. Solids not Fat. Salt. Fresh, unwashed, ,, washed, . Salt, unwashed, ,, washed, . Pickled, . . . Mixed with water, 12 to 16 12 „ 16 10 ,, 16 10 „ 16 May be high. 8 to 12 3 ,, 10 8 „ 12 3 „ 10 Rather low. >> > > none. \ none, f 5 to 25 \ 5 ,, 25/ 35 „ 40 Less than 25. Almost unknown. Mild. Salt. The figures given are not intended as absolute limits, but rather as indicating the composition of by far the greater number of samples met with. It is seen that the pickled butters contain a very large amount of salt in proportion to the water present. This fact is of great use in distinguishing them from samples which have been purposely watered. It is frequently stated, even by " experts," that salt butter contains more water than fresh. Unless the term "salt butter" is applied exclusively to pickled butter, this statement is contrary to fact, as it is found that if, after churning, the butter is divided into two parts, one being worked as fresh, and the other imme- diately salted, the percentage of water is almost identical in the two samples ; after standing, the salt butter will be found to lose water by running out, while the fresh butter undergoes no such loss. It will be found that salt butter when placed on the market contains on the average less water than fresh butter. A high percentage of water does not appear to have any etfect on the keeping qualities of the butter; a large percentage of solids not hit or curd seems to be distinctly inimical to its good pres'-rv.it ion. Speaking broadly, butters containing about 13£ per cent, of water have the best flavour. When the limits ot 1 '2 percent. on one hand, :«nd 15 per cent, on the other, are passed, a distinct falling-off in quality is usually found. To this rule, however, spl ions are numerous. During very hoi weather, if the butter is rerysoft when taken out lit' the churn, there is a difficulty in working the water < • u t nfficient extent ; during very oold weather the butter may ■ hard that it cannol be efficiently worked. Iii both these the water may somewhat exceed 16 percent. An organism THE ANALYSIS OF BUTTER FAT. 257 has been described which produces changes in the cream which prevent the water from being worked out, but it is fortunately not frequently met with. The Analysis of Butter Fat— Preparation of the Fat for Analysis. — A portion of the butter is placed in a beaker and melted by exposing to a temperature not exceeding 50° C. (122°F.). The water, with a considerable amount of the other constituents, sinks to the bottom, leaving the fat (containing, however, particles of curd in suspension) as an upper layer. If the butter be genuine, fresh, and well made, the melted fat will usually appear transparent ; while if it be mixed with butter substitutes, rancid, or churned at a high temperature, or if it has been melted and re-emulsified, the fat frequently has a turbid appearance. The fat, with as little as possible of the other constituents, is poured upon a dry filter, which is kept at a temperature sufficient to prevent the fat from solidifying ; the clear fat, separated from all the other- constituents of butter, except a trace (-2 per cent.) of water and lactic acid, if present, is collected in a dry vessel. It is sometimes of importance to prepare the butter free from water. This may be done by shaking it with a little calcium chloride (free from lime) and filtering again. Chattaway proposes to remove the water by stirring in a number of pellets of filter paper, which have been dried in the water-oven. The author has found that, as far as the propor- tions of the volatile acids, insoluble acids and saponification equivalent are concerned, the fat is entirely unaffected by this treatment, though certain properties — e.g., rise of temperature with sulphuric acid — are slightly affected, owing to removal of the water. After filtration, the fat is rapidly cooled, so as to prevent partial solidification and to ensure the homogeneous nature of the sample. Recapitulation of Properties. — The following recapitulation of the essential differences between butter fat and other fats likely to be used as substitutes or for adulteration will serve to show the basis of the methods employed in the analysis of butter. Butter fat is characterised by the presence, in consider- able amount, of glycerides of the fatty acids of low molecular weight. The lowest and most important is butyric acid, but the whole of the members of the series CnB[27i+1COOH, in which n is an odd number from 3 to 17, are present in butter fat. A considerable amount of acids of the oleic series, of which not much is known, is also present ; of this series, the lower members are certainly absent, and the unsaturated acids are of a higher mean molecular weight than the saturated acids : it is probable that oleic acid is the chief representative of the series, and, possibly, higher homologues occur. It is not known with 17 258 BUTTER. certainty whether acids of other series occur in butter fat. The alcohol present is almost entirely glycerol. The pioneer in butter analysis was Otto Hehner, who demon- strated in 1872 that upwards of 5 per cent, of the fatty acids were volatile, and that the quantity of insoluble fatty acids was very much less than that yielded by nearly all other fats. The bulk of the methods at present in use are the legitimate out- come of Hehner's work. Perhaps the only method which is not derived from the first investigation of Hehner is that of von Hiibl, who showed that, by the action of an alcoholic solu- tion of iodine and mercuric chloride, a quantitative addition of halogen could be made to unsaturated glycerides, but in the simplification of this method Hehner has had a large share. Estimation of Volatile Fatty Acids. Reichert Process. — Hehner and Angell, after showing that butter contained more butyric acid than was (then) generally supposed, attempted to estimate this by distillation, but finally relinquished the method on account of discordant results, due largely to the bumping of the liquid and the use of too strong an acid. Perkins published a method for distilling the volatile acid ; he used oxalic acid to decompose the saponified butter, and distilled to dryness. Probably he did not obtain the whole of the acid. In the same year Reichert proposed to saponify 2 5 grammes of butter with caustic soda and alcohol, evaporate off the alcohol, add 50 c.c. of water and 20 c.c. dilute sulphuric acid, and to distil 50 c.c. in a weak current of air. This method, though Reichert himself calls it Hehner's method, is now known as the Reichert process. He showed that butters took a constant amount of deci-normal alkali for neutralisation, while fats and artificial butters took very small quantities — 0*3 c c, and cocoa- nut oil took about 3 c.c. ; he proposed 140 c.c. as the mean for genuine butters, and 130 c.c. as a limit; he showed also that N mixtures of butter and margarine took quantities of alkali equivalent to the amount of butter they contained. Moore in L 884, and Caldwell in 1886, both spoke favourably of the method, the former drawing especial attention to the fact that cocoanut oil, which is not detected by other methods, is shown by the Reichert method. MedicUB and Scherer used this method to show that butter, on being melted and allowed to cool, separates into portions OOntaining more and less volatile acids respectively. Alien showed that the distilling vessel did not exercise any influence on tie- results, bill thai there was a considerable loss on saponification in an open basin, and recommended a closed ESTIMATION OF VOLATILE FATTY ACIDS. 259 flask ; this loss was due to the formation of butyric ether, as had been already pointed out by Hehner and Angell. Wanklyn and Fox actually estimated the butyric ether formed by saponi- fying with a barely sufficient quantity of soda, but naturally always fell far below the total quantity. Munier proposed the use of an alcoholic potash solution for saponification and phosphoric acid to liberate the acids. The results found by various observers are given in the following table : — Name. No. of Sam plea. Limits. Reichert, 13 13 0 to 1495 Caldwell, (?) 127 „ 15-5 Schmitt, (?) 130 „ 14-3 Allen, . (?) 12-5 „ 151 Ambuhl, (?) 14 05 „ 15-55 Munier, . 66 9-2 „ 1405 Reichardt, 35 138 „ 14-7 Beckhurts, (?) 15-6 „ 17 5 Merckling, (?)' 13"2 ,, 13-55 Woll, . ia ' 12-0 „ 14-9 Cornwall and Wall ice. . 80 ' 11-3 ,, 151 Nilson, . (?) 9-27 ,, 20 5 Too much importance must not be attached to these figures, as they were obtained by the original form of the method (or very slight modifications) ; Munier's low results have been criticised by Wollny {post), and Nilson's have also been doubted, though on no very strong grounds. Nilson showed that disease may seriously reduce the volatile acids; one cow whose butter gave 16-85 c.c, after a few days' N illness yielded butter taking only 10*1 c.c. of yn alkali. His lowest result — 9 -2 7 c.c. — was obtained from butter prepared from the milk of a cow directly after parturition, and he shows that the quantity of volatile acids rapidly increases, and becomes normal a very short time after calving. Figures as low as 9-27 c.c. can then hardly be considered normal for commercial butter. Meissl proposed to saponify 5 grammes of butter-fat in a flask of about 200 c.c. capacity with 2 grammes of caustic potash and 50 c.c. of 70 per cent, alcohol, and to drive off the alcohol on the water-bath. The resulting soap is dissolved in 100 c.c. of water, and 40 c.c. of dilute sulphuric acid (1 to 10) are added and the solution distilled with a few small pieces of pumice; 110 c.c. are collected, filtered, and 100 c.c. titrated with deci-normal alkali. In common with Reichert and the earlier experimenters, he used litmus as an indicator, but the superiority of phenol- phthalein for this purpose soon became apparent to many. To N the number of cubic centimetres of — alkali used one-tenth is 260 BUTTER. added; he found thus that butters gave from 26*6 to 31-8 c.c, and fats and artificial butters about 3-0 c.c. Sendtner, as early as 1883, proposed 23 c.c. as the lowest limit. Hansenn proposed blowing into the flask in order to drive away the last traces of alcohol, and was one of the earliest to use phenolphthalein as indicator. This method was adopted by the Congress of Bavarian Analytical Chemists at Monaco in 1883; Meissl's limit of 26 c.c. was, however, considered not to be universally applicable, and 23 c.c. were taken. The Paris Municipal Laboratory also adopt it with the modification of saponifying in an open basin, transfer- ring the soap to a flask, and washing the basin with 100 c.c. of hot water; their limits are stringent — 26 to 33'5 c.c. The following figures are published : — Name. No. of Samples. Limits. Meissl, . . . 52 26-6 to 31-8 c.c. Sendtner, , , 55 240 ,, 328 ,, Hager, . . (?) 26 0 „ 31-0 „ Wollny, in a now classic memoir, studied the errors of the Reichert- Meissl process ; these are : — (1) Error due to the absorption of cai-bonic acid during the saponification (may amount to + 10 per cent.). (2) Error due to the formation of ethers during saponification (may amount to — 8 per cent.). (3) Error due to the formation of ethers during the distillation (may amount to — 5 per cent. ). (4) Error due to the cohesion of the fatty acids during distil- lation (may in extreme cases amount to - 30 per cent.). (5) Error due to the shape and size of the distilling vessel and to the time of distillation (may vary the results ± 5 per cent.). To avoid these errors he lays down the following method of working : — Five grammes of butter-fat are weighed into a round flask of about 300 c.c. capacity, with a neck 2 cm. wide and 7 to 8 cm. Long : 2 c.c of a 50 per cent, soda solution ami 10 c.c of !*6 per cent, alcohol are added, and the tlask heated for half an hour on the water-bath under a slanting inverted condenser: between the centre and the flask is a T piece, which is closed, the limb being turned upwards. At the expiration of half an hour the limb of tlir T piece is opened ami turned downwards, and the alcohol distilled off during a quarter of an hour; 100 cc of boiling water an added by the T piece, ai <1 the Bask heated on the water-bath till the soap is dissolved. The solution is allowed to cool to 50° or 60 , I" c.c of dilute Bulphuric acid (26 CC. to a litre ; 2 e.r. of soda solution should neutralise about 35 c.c. of this), and two pieces ot pumice the size of peas are added. ESTIMATION OF VOLATILE FATTY ACIDS. 261 The flask is at once furnished with a cork carrying a tube 0-7 cm. in diameter having, 2 cm. above the cork, a bulb 2 to 2-5 cm. in diameter; above this the tube is bent at an angle of 120°, and 5 cm. further on again at an angle of 120° ; this tube is joined to a condenser by an india-rubber tube. The flask is heated by a very small flame till the fatty acids are all melted, and the flame is then turned up and 110 cc distilled off in from twenty-eight to thirty-two minutes. The distillate is well mixed, and 100 cc are filtered off through a dry filter, 1 cc. of a 0 05 per cent, solution of phenolphthalein solution in 50 per cent, alcohol N added, and the solution titrated with y^ baryta solution. To the figure thus obtained one-tenth is added, and the amount found by a blank experiment subtracted ; the blank should not exceed 0 33 cc In order to render this method more sensitive, if possible, for the detection of small quantities of butter in margarine, Hehner proposed the use of 5 cc. only of alcohol, saponifying (almost instantaneously) in a closed flask, warming for five minutes with occasional shaking, and driving off the alcohol through a narrow tube in a cork, reduced pressure being applied towards the end, and the addition of 100 cc of water which has boiled at least half an hour. He finds the blank figure thus to be less than OT cc, and the same as that given by 100 cc of boiled water filtered through a dry filter ; other fats and oils give less than O06 cc, and no increase is observed in beating them on the water-bath with the soda solution for two hours. In order to facilitate the melting of the fatty acids, the author proposes lengthening the bulb tube, used by Wollny for distil- lation, above the bulb to 15 cm. and placing on it a small con- denser, through which water is kept running during the melting of the acids, this being removed during distillation ; the same results are obtained by the use of this apparatus as by Wollny's. Mansfeld saponifies in a closed flask for two hours on the water- bath with a solution of 56 grammes of potash in 100 grammes of water, no alcohol being used ; he operates otherwise as Wollny. His method gives the same results as that due to Wollny. His blank is -4 cc, and the extremes are 2442 to 33-15 cc for butters and 0-59 to 0-96 cc for margarines. Goldman distils the whole of the volatile acids in a current of N steam, collects 600 cc of distillate, and titrates with baryta. He finds as limits 36-24 to 43-20 cc for butter, and 080 to 0'92 cc. for margarine ; duplicates do not differ by more than 0-2 cc Two samples gave by this method 36-24 and 36-28 cc, and by the Reichert- Wollny- Mansfeld process 27-00 and 28-04 cc respectively. 262 BUTTEH. Leffmann and Beam saponify with 2 c.c. of caustic soda solu- tion in 10 c.c. of glycerine, heating over a naked flame with constant shaking. As in the reaction heat is evolved, care must be exercised ; they otherwise operate as Wollny. The results are about 0*2 c.c. higher than Wollny's. The Reichert-Wollny method is largely adopted in every country, and may be considered as a standard method. In England the proportions of the Reichert method with Wollny's precautions are much used; the author has determined the ratio between figures obtained thus and by the Reichert- Wollny method, and finds it to be 2-21 to 2-27, mean 2*23. The following limits have been found by various observers : — Name. No. of Samples. Limits. Allen, . 2 22-5 to 24 55 Stein, . (?) 25-08 ,,31 95 Mansfekl, 88 2442 ,, 33-15 Besana, 114 21-8 „ :.019 Sartori, 52 23 59 ,, 30 79 Vigna, . 23 20-68 ,, 31-79 Spallanzani, . 70 20 63 „ 30-6 Longi, . 26 22-55 „ 28-4 Maissen and Rossi, 20 21-56 „ 26-40 Mayer, . 20 20-3 ,, 33-5 Vieth, . 236 20-0 ,, 32-5 F. Jean, 1 2075 Vieth and Spallanzani have also found in samples obtained under exceptional circumstances, which cannot be considered as commercial butter, amounts as low as 14 -7 and 14*3 c.c. respec- tively. The average of the results of different observers (excluding Vieth, who searched for low samples) shows that out of K'O samples — 3 will probably give over 30 c.c. 85 ,, ,, between 30 and 26 c.c. 8 „ „ „ 26 „ 25 „ 3 ,, ,, under •_'."> c.c. The absolute lower limit must be fixed at L'O c.c. for butters, but all samples giving below 25 C.C. may be looked upon as suspicious, and with a probability of 3 to loo of Buch samples being genuine, 25 cc. may be adopted as a commercial limit. Lefimann and Beam's modification has the advantages over the Reicherl Wollny method of yielding a clear distillate and giving a sharper end reaction. Kreis' Modification of Roichert's Method. ELreis has substituted (>»r saponification by means of alkali, hydrolysis with strong sulphuric arid. Five grammes of fal are treated with I1* CC. Of Btrong Bulphuric acid and gently wanned. * 'i'i. ptional amples, and hence the figures are m>t repre i ntative o\ the ordinary composition oi butter fat ESTIMATION OF VOLATILE FATTY ACIDS. 263 Saponification rapidly proceeds and the fatty acids are liberated; the unsaturated acids are attacked, with the formation of sul- phurous acid. 100 c.c. of water are added; then a solution of potassium permanganate is added till a pink colour remains for a minute or two ; and the bulk is made up to 140 c.c. 110 c.c. are distilled and titrated as in the Reichert- Wollny process. This method offers no advantages over saponification by means of alkali, and its adoption can be in no case recom- mended. The Theory of the Reichert Process. — The total amount of volatile acids contained in butter is not obtained in the Reichert process, but a nearly constant fraction — certainly constant for the same sample when distilled under standard conditions. The work of Duclaux has led to the explanation of the reasons why the amount is so constant, and has elucidated the real significance of the Reichert figure. In the flask from which the butter is distilled there are (1) an aqueous liquid containing volatile acids in solution and (2) a layer of non-volatile fatty acids, also containing volatile acids in solution. From the experiments of Duclaux, the author has deduced the general formula expressing the rate of distillation of volatile fatty acids (see p. 46), 100(100 -x)° (100 - y) = 1(X)a.1 , if no condensation take place in the retort. For values of a greater than 1 condensation in the retort causes the apparent rate of distillation to be faster. As a, in tlie case of butyric and caproic acids, is respectively 2 and 4, it follows that increased condensation, either by exposing a greater condensing surface or by increasing the time of distillation, will give higher results ; this is in strict accord with the experiments of Wollny. The author has found that if, instead of merely collecting 50 or 1 10 c.c. and titrating the total distillate, smaller fractions are collected and titrated separately, the results do not accord with the general formula given above. That the disturbing influence is due to the solubility of caproic acid in the layer of insoluble fatty acids is shown by the experiments detailed below : — (1) Pure butyric acid was distilled as in the Reichert process; the fraction distilled over was very nearly that deduced from the rate of distillation of this acid (96-9 per cent, when 110 c.c. out of 140 were distilled). (2) The experiment was repeated, with the addition of 2-2 or 4 4 grammes of well-washed fatty acids of butter, which, when distilled alone, gave a mere trace of volatile fatty acids ; the results obtained were practically equal to those obtained in experiment (1) (97"2 per cent). This shows that insoluble fatty acids do not retard the distillation of butyric acid, and that the 264 BUTTER. solubility of butyric acid in water is great compared with its solubilitv in insoluble fatty acids. (3) Numerous samples of butter were fractionally distilled. The following are the mean results obtained expressed as per- centages of the total, the variations being small, not exceeding 1 per cent. : — Volume Distilled Percentage of Volatile from 75 c.c. Acid in Distillate. 20 c.c., .... . 463 22-25 ,, .... . 50-8 40 >l .... . 749 .-,() . 84-4 60 9 9 • • . . . 911 75 . 1000 (4) Experiments by Wollny, which agreed with those per- formed by the author, showed that on the average 87 per cent, of the total volatile acids were found in the distillate in the Reichert- Wollny process. (5) Duclaux has shown that when eight-elevenths (practically the same proportion as obtained in the Reichert- Wollny method) of the bulk of liquid are distilled, that the composition of the distillate is 1*8 molecules of butyric acid to 1 of caproic acid. Now, from experiments (1) and (2) we see that 97 per cent, of the total butyric acid is in the distillate ; therefore, the total 1 -S butyric acid is equal to — = 1*856 molecules for each 1 of caproic acid in the distillate. From experiment (4) we see that 87 per cent, of the total acids are in the distillate ; each 2*8 molecules in the distillate 2*8 correspond to ■— = 3*218 molecules of total volatile acid * of these, 1*856 molecules are butyric acid, and, therefore, 1*362 molecules caproic acid — i.e.. the volatile fatty acids of butter — have the following average percentage composition : — Butyric acid, Caproic ,, f>7*7 molecules or 51*7 per cent, by weight. (•_•:; „ 18-3 The following table gives the percentage of acid distilled, the calculated percentage of acid that should bo distilled if it were all butyric acid, and the percentage of caproic acid distilled (this is obtained by multiplying the percentage of butyric acid that should be distilled by , subtracting it from the figures 100 in column 2 and dividing by 12-3 Km ):- ESTIMATION OF VOLATILE FATTY ACIDS. 265 Volume Distilled. Percentage of Acid Distilled. Calculated for Butyric Acid. Percentage of Caproic Acid Distilled. 20 c.c, . 22-25 ,, . . 40 „ . . 50 „ . . 60 „ . . 75 „ . . 46 3 50-8 74-9 84-4 91-1 100-0 49-4 53 4 SO -7 90-5 96-7 100 0 42 1 47 3 66 9 761 S3 5 100-0 By interpolation in column 4 of the table above, the composi- tion of the vapour at the moment when each fraction was completed, is expressed as percentages of the strength of the liquid at the commencement of distillation (column 2). By dividing this by 4 (the ratio of strength of liquid to strength of vapour for caproic acid) the composition of liquid can be calculated (column 3). By multiplying this by the amount of liquid left in the flask, and dividing by 75, the percentage of total caproic acid in the liquid at the end of each fraction is found (column 4). The total percentage of acid in the flask is found by subtracting the percentage distilled from 100 (column 5). The difference between column 4 and column 5 will indicate the percentage of caproic a,cid dissolved in the insoluble fatty acids (column 6). Volume J Composition Distilled. j of Vapour. 1 Composition of Liquid. Per cent. Acid in Liquid. Percent, 1 *"•««*• in^it in Insoluble in Flask. ,FattyAcids. 20 c.c. . 22-25 „ . 40 ,, . 50 ,, . 60 „ . 75 ,, . 139 5 124-0 82-3 62-0 65 0 34-9 31-0 20-6 15-5 16-2 25-6 21-9 10-5 5-2 3 3 57-9 52-7 431 23-9 16-5 32-3 30-8 21-6 18-7 132 As the volume of insoluble fatty acids is constant throughout, the percentage of caproic acid dissolved therein is always pro- portional to the composition of the aqueous liquid. It is seen that the figures in columns 3 and 6 are sensibly identical, proving that the caproic acid is distributed between the aqueous and fatty layers respectively in a definite propor- tion. 75 c.c. of the aqueous liquid dissolve sensibly as much caproic acid as 2 "2 grammes of insoluble fatty acids, while the solubility of butyric acid in insoluble fatty acids compared to that of water is small — in fact, negligible. This explains why the apparent rate of distillation of volatile 266 BUTTER. acids in the Reichert process is less than the rate of the less volatile acid — butyric. It also explains satisfactorily why Wollny found more volatile acid in proportion distilled from 25 grammes of butter than from 5 grammes, the other conditions as to volumes of water, &c, being identical. There was a smaller proportion of insoluble fatty acids, and, consequently, a larger proportion of caproic acid in the distillate. In the case of mixtures of butter and other fats, where the amount of insoluble fatty acids is varied but slightly from that found in butter, it is found, in accord with the present view, that the volatile acid distilled over is very nearly proportional to the percentage of butter present. As so large a percentage of volatile acids are distilled under the conditions of the Reichert process, the effect of condensation is practically small ; still it cannot be entirely neglected, and the practice of Wollny in laying down exact conditions of work- ing has a sound theoretical basis. To illustrate this fact it may be mentioned that the author has found that the ratio of the figures obtained in the Reichert process (where 2-5 grammes of butter are dissolved in 75 c.c, and 50 c.c. distilled) to those of the Reichert- Wollny process (where 5 grammes of butter are dissolved in 140 c.c.) is on the average 2-23. The ratio of the figures obtained by the Reichert process to those obtained by dissolving 25 grammes of butter in 70 c.c. and distilling 55 c.c. 2-17 is only, however, - . This is due to the greater condensation n the flask used for distiiling the larger quantity. Estimation of Saponification Equivalent, or alkali neces- sary for complete saponification. Koettstorfer's Method. — Kcettstorfer proposed to utilise the fact that butter required a greater amount of alkali for its com- plete saponification than most other fats. The method is performed as follows : — A standard alcoholic solution of sodium hydroxide is prepared by dissolving 25 c.c. of the 50 per rent, solution of caustic soda recommended by Wollny (p. 260) in 1 litre of strong alcohol ; after a day's repose, during winch a little salt set tleS out, the solution is clear and lit for use. This solution, which should lie approximately semi- normal, is standardised againsl semi-normal hydrochloric acid. About - grammes "t the tat are weighed out into a small flask, 25 c.c. of the alcoholic Boda solution run in from a pipette, the flask connected with an inverted condenser, and the contents gently boiled lor fifteen minutes. During the boiling the alcoholic soda solution is standardised; 25 <■.<•. of the solution are measured from the same pipette, which i- allowed to drain for the same length <>f time as before, and titrated with semi normal hydro- chloric acid a little phenolphthalein being added as indicator. ESTIMATION OF SAPONIFICATION EQUIVALENT. 267 The number of cubic centimetres of hydrochloric acid solution should be noted. It is advisable to perform this operation in duplicate. The flask containing the saponified fat is discon- nected from the condenser, a few drops of phenol phthalein solution added, and the liquid titrated with semi-normal hydro- chloric acid till the pink colour just disappears. The number of cubic centimetres used, subtracted from the number required by the 25 c.c. of soda solution alone, will give the equivalent of the alkali required for saponification * this, multiplied by -02805, will give the weight as alkali calculated as potassium hydroxide, KOH ; and the figure thus obtained multiplied by 100 and divided by the weight of fat taken will express the "potash absorption " as percentages. It is also advisable to calculate the "saponification equivalent'"' (a term due to Allen), which is really an expression of the mean molecular weight. This is calculated from the number of cubic centimetres of normal acid, the definition of a normal solution being that it contains, or is equivalent to, in 1 litre a weight in grammes equal to the equivalent of a substance. It is, therefore, necessary to calculate the weight of fat which would be saponified by alkali equal to 1 litre of normal hydrochloric acid. Let W = the weight oi fat taken. And V — the number of cubic centimetres of semi-normal hydrochloric acid equivalent to the alkali required for saponi- fication. Then the saponification equivalent is expressed by 2000 W The relation between " potash absorption per cent." (K) and "saponification equivalent'"' (S) is expressed by the formula „ 5610 Instead of a pipette, the alcoholic alkali may be measured from a burette or automatic measuring apparatus, and the saponification may be conducted in a closed flask. An open flask or basin should not be used, as ethyl butyrate, an inter- mediate product of saponification (p. 36), is volatile ; this would cause a low value to be obtained. According to Kcettstorfer, the potash absorption varies from 22-15 to 23-30 per cent, in genuine butters, with an average of 22*70 per cent. His experience has been confirmed by numerous observers. The saponification equivalent varies from 253 -3 to 240-8, the average being 247-1. Other oils and fats have a potash absorption of 19-0 to 19-9 per cent., with an average of about 19 '5 ; or a saponification equivalent of 2953 to 282-0, with a mean of 287*6. Cocoa-nut and palm-nut oils yield, however, figures which are very different, 24-62 to 26-84 per cent. 2G8 BUTTER. Estimation of Soluble and Insoluble Fatty Acids — Hehner and Angell Method. — Hehner and Angell, having relinquished the distillation of the volatile fatty acids (see p. 258), turned their attention to the estimation of the insoluble acids. At the date at which the process was devised the use of alcohol for the saponification of fats was unknown, and they saponified the butter by heating for a considerable length of time with a strong solution of caustic potash in water. This method was inconvenient, as it was found that the molten fat floated on the surface of the solution, and, being attacked with difficulty, required long boiling before saponification was com- plete. It was difficult to boil such a mixture, because bumping occurred, and this caused a certain amount of loss. Hehner and Angell's original figures were somewhat lower than those now generally accepted. Turner, shortly after the publication of the method, suggested that alcoholic alkali should be substituted for the aqueous solution formerly used. The method is performed as follows : — About 3 grammes of the fat are weighed out into a large basin, and saponified by about 1 gramme of potash (or its equivalent of soda) dissolved in about 10 c.c. of alcohol. On gently warming, an odour of ethyl butyrate is noticed, and saponification rapidly proceeds. When, on addition of a few drops of water, no cloudi- ness is seen, the alcohol is evaporated on the water-bath, the soap is dissolved in 50 to 100 c.c. of hot water, and hydrochloric acid is added to slight excess. The insoluble fatty acids which are liberated float on the surface in a curdy mass, and the basin is gently heated till these melt and become clear. A filter, which has been previously dried in the water-oven, is placed in a weighing tube and weighed, the weight of the empty tube being subtracted from the total. This is placed in a tunnel, wetted with hot water, and the insoluble fatty acids filtered through this. The basin can be washed quite clean by means of a jet of boiling water and the fatty acids entirely transferred to the filter. The washing is continued on the filter, care being taken to direct the jet of boiling water so that the liquid acids are well Btirred up ; at least a litre of water should be used in the washing. If the filter paper is of good quality, and thoroughly wetted beforehand, none of the fatty acids will run through ; if, however, it is noticed that oily drops fioal on the Burface of the filtrate, these may, if not too numerous or Large, be allowed to solidify, and can then be picked out and added to the main quantity. When the washing of the fatty acids is completed, the funnel, with the filter, should be immersed in cold water up to the level of the top of the fatty acids to solidity them. The filter and its contents Bhould then be taken out, placed in a weighed basin, and dried in the water-oven. Alter two hours the basin should be weighed, replaced in the water-oven for half ESTIMATION OF SOLUBLE AND INSOLUBLE FATTY ACIDS. 269 an hour, and again weighed. If a loss is found to have taken place, a further half hour's drying should be given. It is important not to prolong the drying too much, as the fatty acids have a tendency to oxidise and to increase in weight at a tempera- ture of 100° C. The weight of the basin and the filter sub- tracted from the total weight will give the weight of the in- soluble fatty acids. This method has been submitted to numerous modifications ; Muter prefers to conduct the whole operation in a flask. Instead of washing the fatty acids on a filter, he allows them to solidify in the flask, and pours off the aqueous solution. Hager proposes to add a known weight of wax, picks out the lump, dries, and weighs it. Fleischmann and Vieth advise that the washing should be continued till at each succeeding washing the colora- tion produced by the addition of a few drops of litmus solution to a few cubic centimetres of the filtrate is not changed. Cassal has devised an ingenious flask, which has a tap at the bottom so that the liquid can be run off, leaving the fatty acids in the flask ; washing can be thus much expedited, as hot water can be added, the fatty acids shaken up with the water, and the water run off. Modification by the American Association of Official Agricultural Chemists. — The following method has been adopted by the American Association of Official Agricultural Chemists : — Reagents required. — Decinormal sodium hydroxide. Alcoholic potash. Dissolve 40 grammes of good caustic potash, free from carbonates, in 1 litre of 95 per cent, redistilled alcohol. The solution must be clear. Semi-normal hydrochloric acid accurately standardised. Indicator. — One gramme of phenolphthalein in 100 c.c. of alcohol. About 5 grammes of the sample are weighed into a saponifi- cation flask (250 to 300 c.c. capacity of bard, well annealed glass, capable of resisting the tension of alcohol vapour at 100° C. ), 50 c.c. of the alcoholic potash solution added, and the flask stoppered and placed in the steam-bath until the fat is completely saponified. The operation may be facilitated by occasional agitation. The alcoholic solution is always measured with the same pipette, and uniformity further secured by allow- ing it to drain the same length of time (thirty seconds). Two or three blank experiments are conducted at the same time. In from five to thirty minutes, according to the nature of the fat, the liquid will appear perfectly homogeneous. Saponification being then complete, the flask is removed and cooled. When sufficiently cool, the stopper is removed and the contents of the flask rinsed witli a little 95 per cent, alcohol into an Erlenmeyer flask of about 200 c.c. capacity, which is placed on the steam 270 BUTTER. bath, together with the blanks, until the alcohol is evaporated. Titrate the blanks with semi-normal hydrochloric acid. Then run into each of the flasks containing the fatty acids 1 c.c. more of the hydrochloric acid than is required to neutralise the alkali in the blanks. The flask is then connected with a condensing tube, 3 feet long, made of small glass tubing, and heated on the steam-bath until the separated fatty acids form a clear stratum. The flask and contents are then cooled in ice- water. The fatty a rids having quite solidified, the liquid contents of the flask are poured through a dry Alter into a litre flask, care being taken not to break the cake. Between 200 and 300 c.c. of water are next brought into the tlask, the cork with its condenser tube re-inserted, and the flask heated on the steam-bath until the cake of fatty acids is thoroughly melted. During the melting of the cake of fatty acids, the flask should occasionally be agitated with a revolving motion, but so that its contents are not made to touch the cork. When the fatty acids have again separated into an oily layer, the flask and its contents are cooled in ice-water and the liquid filtered through the same filter into the same litre flask. This treatment with hot water, followed by cooling and filtration of the wash water, is repeated three times, the washings being added to the first filtrate. The mixed washings and filtrates are next made up to 1 litre, aliquot parts titrated with the deci- normal sodium hydroxide, and the total acidity calculated. The number so obtained represents the volume of decinormal sodium hydroxide neutralised by the soluble acids of the butter fat taken, jihis that corresponding to the excess of the standard acid used — viz., 1 c.c. The number is, therefore, to be diminished by 5, corresponding to the excess of 1 c.c. of semi-normal acid. This corrected volume, multiplied by "0088 gives the weight of (fatty acids calculated as) butyric acid in the amount of butter fat saponified. The flask containing the cake of insoluble acids and the paper through which the soluble acids were filtered are allowed to drain and dry for twelve hours, when the cake, together with u much of the acids as can be removed from the filter paper, is transferred to B weighed glaS8 dish. The tunnel and Biter are then Bel in an Erlenmeyer flask and the filter washed thoroughly with absolute alcohol. The ilask is rinsed with the washings from the filter paper, then with pure alcohol, and these trans* I to fli1' glass dish, which is placed in the steam-l>ath. After the alcohol bas evaporated, the residue is dried for two hour.-; in an air bath al 1 00 < '.. cooled in a desiccator, and weighed. It is heated in the air-bath for two hours more, cooled and weighed. If the two weighings are decidedly dif- ferent, a further heating for two hours must be made The residue is the total insoluble acids, of the sample. ESTIMATION OF SOLUBLE AND INSOLUBLE FATTY ACIDS. 271 Johnstone's Modification. — A method for the estimation of soluble fatty acids which the author has found to work vei-y well is one which was first suggested by Johnstone, though in an imperfect form. 4 to 5 grammes of butter fat are weighed out and saponified, as directed under the estimation of saponification equivalent, by a sufficient excess of alcoholic alkali. The excess of alkali is titrated with semi-normal hydrochloric acid and the potash absorption calculated. The soap solution is washed out of the flask into a basin and the alcohol evaporated. Acid is added and the insoluble fatty acids filtered and washed, as pre- viously directed (an unweighed filter paper being used). Instead of cooling down the fatty acids, they are washed by warm alcohol into a 100 c.c. flask, and, after cooling, the bulk is made up to 100 c.c. with alcohol and well mixed. 25 c.c. of this solution are pipetted into a weighed basin, the alcohol evaporated and the fatty acids dried and weighed ; 50 c.c. are titrated with alcoholic alkali solution, using phenolphthalein as indicator, till a faint pink colour appears. The alkali used is calculated into its equi- valent of semi-normal solution ; this multiplied by 2 is subtracted from the amount of semi-normal acid equivalent to the alkali used for saponification. This figure multiplied by 44 and divided by the weight of butter taken will give the percentage of soluble fatty acids calculated as butyric. This method has the advantage of taking but little time, and gives, besides determinations of the saponification equivalent, insoluble, and soluble fatty acids, an estimation of the mean combining weight of the insoluble fatty acids ; a figure which is occasionally of value. This is cal- culated in the same way as the saponification equivalent of a fat. Blunt's Modification — Blunt uses the fatty acids left in the flask after a distillation by Reichert's process for the estimation of the insoluble fatty acids. It is necessary, however, to wash out the condenser, as some of the insoluble acids are slightly volatile, and to add these, and the acids which are found in the distillate, to the quantity left behind in the flask. Morse and Burton's Modification. — Morse and Burton, instead of weighing the insoluble fatty acids, titrate them with alcoholic alkali very much in the manner above described, and express both the soluble and insoluble fatty acids in terms of the alkali necessary to combine with them calculated as per- centages of the total alkali necessary for saponification of the butter. This method has the advantage of rapidity and of not necessitating that the strength of the alkali solution shall be accurately known, but it is a decided advantage to know the weight of the insoluble fatty acids. Attempts have been made to measure the volume of the insoluble fatty acids, but, owing to the difference in density and difficulty of making accurate measurements, this method has not proved satisfactory. 272 BUTTER. The variation of insoluble fatty acids is from 85-5 per cent. {Bell and Menozzi) to 90 0 per cent. {Reichardt, Cornwall, and others) in genuine butters ; the soluble fatty acids calculated as butyric vary from 7-0 per cent, to 4-0 per cent. Most other fats give about 95-5 per cent, of insoluble fatty acids and traces only of soluble fatty acids. Cocoa-nut and palm-nut oils are, however, exceptions to this, yielding from 82 to 85 per cent. Specific Colour Tests for Adulterants. Baudouin's Test for Sesame Oil. — This test consisted, origin- ally, in shaking the melted fat with a solution of cane-sugar in hydrochloric acid. Villavecchia and de Fabris have modified this by using a solution of 2 grammes of furfuraldehyde in 100 c.c. of alcohol to replace the sugar; 10 c.c. of the melted fat are shaken thoroughly with 10 c.c. of hydrochloric acid and "1 c.c. of the reagent ; a red coloration indicates the presence of sesame oil. This reaction is very delicate, but is not entirely conclusive. Certain colouring matters — e.g., turmeric and certain aromatic dyes — give a red coloration with hydrochloric acid alone, and, in the presence of these, sesame oil cannot be detected, as the colour due to sesame oil would be masked by that yielded by the dye. Furfuraldehyde and hydrochloric acid alone, after some time, yield a reddish colour ; hence a slight pinkish tinge gradually appearing must not be taken to indicate sesame oil. Spampani and Daddi have shown that the milk of goats fed with sesame oil yields butter which »ives this test. Hehner and Fiber were, however, unable to obtain it with butter pre- pared from the milk of cows fed on sesame cake. Becchi's Test for Cottonseed Oil. — This test was originally performed by heating the fat with a solution containing silver nitrate, alcohol, etlier, nitric acid, amy] alcohol, and rape oil. The reagent has been frequently modified. Be van prepares the reagent by boiling silver nitrate with amyl alcohol, and cooling the solution. Equal parts of this solution and of the fat are heated in a test tube on a boiling water-bath for ten minutes; a brown or black coloration indicates cottonseed oil. Tins test is by n<> means conclusive of* the presence of added cottonseed oil, as tlie milk of cows fed on large proportions of cotton cake yields butler which will give a brown coloration. "Wellmann's Test for Vegetable Oils.— The reagent con- sists of a solution of sodium phospho-molybdate. It may be prepared bv saturating 5 grammes of molybdic acid with sodium carbonate solution, adding I gramme of sodium phosphate, eva- porating to dryness and fusing. The mas. is dissolved in boiling water, and concentrated nitric acid (6 to 7 ae. I is added till the yellow shade is permanent. The solution is then made up to 100 c.c. BKHAVIOUK OF BUTTER PAT WITH SOLVENTS. 273 One gramme of fat is dissolved in 5 c.c. of chloroform and shaken with 2 c.c. of the reagent for one minute. A green coloration (changing to blue on addition of ammonia) is formed in the aqueous layer when vegetable oils are present. Cocoa-nut oil is not, however, detected by this means. Behaviour of Butter Fat with Solvents. Critical Temperature of Solution. — Crismer recommends that several drops of the melted and filtered fat be introduced into a small tube several millimetres in diameter by means of a capillary pipette. A slightly greater volume of alcohol is added and the tube sealed and fastened by a platinum wire to the bulb of a thermometer ; it is then heated in a bath of sulphuric acid till the meniscus separating the two layers becomes a horizontal plane. At this point the thermometer is withdrawn from the bath, and turned sharply two or three times until the liquid becomes homogeneous, after which it is replaced and the tem- perature allowed to fall slowly, the thermometer and tube being constantly shaken. The temperature at which a marked turbidity is produced in the liquid is the critical temperature of dissolution. If absolute alcohol be employed an open tube may be used. When examining butter fat it is necessary to estimate also N the acidity by titrating 2 c.c. with — alkali and adding the figure thus obtained to the critical temperature. Crismer has shown that the critical temperature varies with the percentage of insoluble fatty acids. The following table will show the variations : — Critical Temperature. Alcohol -8195 sp. gr. Critical Temperature. Absolute Alcohol. Insoluble Fatty Acids. Below 100° 100° to 108° 108° ,, 118° 118° ,, 124° Below 54° 54° to 62° 62° ,, 72° 72° „ 78° 86 to 88 88 „ 90-5 90 ,, 933 93 „ 955 The Reichert-Wollny figure may be calculated by the formula R-W = 129° - critical temperature (with alcohol of sp. gr. *8195). = 835- ,, ,, „ absolute alcohol). Valenta's Method — Solubility in Acetic Acid. — Valenta showed that there was an enormous difference in the tempera- tures at which various fats and oils dissolved without turbidity 18 '274 BUTTER. in acetic acid. By the work of Allen and Hurst it was shown that the strength of acid made a considerable difference. Chattaway, Pearmain, and Moor have investigated the sub- ject and recommend the following procedure for butters : — 2*75 grammes of butter fat which has been previously dried (preferably by mixing with dried pellets of filter paper and filtering through a dried filter) are weighed into a test tube provided with a stopper ; 3 c c. accurately measured of acetic acid (containing 99'5 per cent. C.2H402) are run into a tul>e, and this is placed in a beaker of water. The water is gradually heated and the tube shaken till the solution is clear ; the water is then allowed to cool gradually and the temperature at which a turbidity appears in the tube is measured by a thermometer held in close proximity. By slightly warming up and cooling down again, a second determination can be obtained. Undue heating of the sample should be avoided, both in the preparation of the fat for analysis and during the performance of the test. They give figures as follow : — Maximum. Minimum. Average. Butter fat, . 39-0°C. 29 0°C. 36-0°C. Margarine, . 97 '0°C. 94-0° C. 95 0°C. E. W. T. Jones prefers, instead of using an acid of estimated strength, to test it against a standard sample of butter, and to dilute the acid so that it gives a temperature of turbidity of 60°. Margarine then gives about 100°. Hehner has found that this test depends almost entirely on the glvcerides of the saturated fatty acids present, as these are almost completely deposited on allowing the acetic acid to cool. The Iodine and Bromine Absorption. Von Hiibl's Method and its Modifications.— This method depends on the fact that acids of the oleic, linolic, and linolenio series contain unsaturated bonds, and. under suitable conditions, combine with iodine and bromine. For the iodine absorption, it has been shown by \on Hub! that it is in asary to have mercuric chloride present. 1 1 is process has received numerous modifications, but few, if any, are real improvements. The process is worked as follows: — Reagents [odine solution. Dissolve 25 grammes of iodine is 5U0 c.c. of 95 per cent, alcohol. Mercuric chloride solution. Dissolve 30 grammes of mercuric chloride in f)00 c.c. of 95 per cent, alcohol, and decant from the insoluhle residue, or filler, if necessary. THE IODINE AND BKOMINE ABSORPTION. 275 Equal volumes of the two solutions are mixed at least twenty- four hours before the test is made. Decinormal sodium thiosulphate solution. Dissolve 25grammes of pure sodium thiosulphate solution and 1 gramme of salicylic acid in 1 litre of water. Allow this to stand a few days and filter. This solution is permanent and does not alter in strength. To standardise the solution, about '25 gramme of resublimed iodine is accurately weighed in a small stoppered flask, about 2 grammes of potassium iodide and 2 c.c. of water are added, and the flask gently shaken till the iodine is dissolved. The iodine solution is diluted with water, transferred to a larger flask, and titrated with the sodium thiosulphate solution till the yellow colour just disappears. This operation is repeated two or three times. The mean strength of the iodine deduced from these experiments is noted on the label of the bottle. A 10 per cent, (approximate) solution of potassium iodide and a starch paste solution, made by pouring an emulsion of 1 gramme of starch in a little cold water into 200 c.c. of boiling water, and boiling for ten minutes; if a little mercuric iodide be added, this solution is permanent. The process is performed as follows : — About "5 gramme of the fat is accurately weighed in a glass stoppered flask holding at least 100 c.c. ; 10 c.c. of chloroform or, better, carbon tetra- chloride are added, and the flask gently rotated till the fat is dissolved ; 20 c.c. of the mixed iodine and mercuric chloride solutions are next added and the whole well mixed. The flask is now put aside in the dark lor three hours. At the same time one or more blanks — i.e., flasks containing 10 c.c. of chloroform or carbon tetrachloride and 20 c.c. of mixed iodine and mercuric chloride solutions should be put aside with the tests. After three hours, 10 c.c. of potassium iodide solution are added to each flask, and the contents are w ashed out into a larger stoppered bottle with distilled water. The standard thio- sulphate solution is run in with continued shaking till only a faint yellow colour remains; a little starch paste is added, and the thiosulphate solution run in, drop by drop, till the blue colour disappears. The quantity of thiosulphate solution used for the flask in which the sample was placed subtracted from the mean of the blanks will give the equivalent of the iodine absorbed. This, multiplied by the strength of the solution, will give the weight of iodine. By multiplying this by 100 and dividing by the weight of fat, the percentage of iodine absorbed is obtained. The following examples will make the mode of calculation clear : — 276 BUTTER. Experiment 1. Weight of fat taken, -5006 gramme. Titrated with 2648 c.c. of thiosulphate solution. ,, .'. W< sight of fat taken, 4991 gramme. Titrated with 20 55 c.c. of thiosulphate solution. Blank No. 1 took 43 35 „ „ * „ 43-45 „ Mean, 43"40 „ 1 c.c. of the thiosulphate solution was equal to •001187 gramme of iodine. Therefore -5006 gramme absorbed (43'40 - 26,48) x -001 1S7 gramme of iodine. = '2008 gramme or 4011 per cent. •4991 gramme absorbed (4340 - 26"55) x "001187 gramme of iodine. = -2000 gramme or 40-07 per cent. Bromine Absorption. — Instead of using a mixture of the iodine and mercuric chloride solutions, a solution of bromine in chloroform, or, what is far preferable, carbon tetrachloride may be used. Four c.c. cf dry bromine (this is best dried by shaking bromine with anhydrous calcium chloride, decanting, and distilling from a small stoppered Wurtz llask fitted with a good condenser) are dissolved in 1 litre of dry chloroform or carbon tetrachloride. The process is performed as above described, except that there is no need to wait three hours before titrating ; this may be performed at once. 20 c.c. of the bromine solution are sub- stituted for the 20 c.c. of mixed iodine and mercuric chloride solutions. It is advisable also to increase the amount of potas- sium iodide solution added to 20 c.c. or more. Gravimetric Method of Hehner. — Hehner has proved that the bromine absorbed may be estimated gravimetrically. The fat is weighed in a small basin, dissolved in carbon tetrachloride, a solution of bromine in carbon tetrachloride added, and the excess of bromine and the carbon tetrachloride evaporated on a water-bath in a good draught cupboard. The residue is freed from the last traces of bromine by adding several successive portions of carbon tetrachloride and evaporating them, and, finally, by drying in an air-bath maintained at a temperature somewhat above 100° C. The increase in weight multiplied by 1 "'7 = l\r;.v7."> will give the iodine absorption. 80 Thermometric Method. — Hehner and Mitchell have also devised a most ingenious means of rapidly and accurately cal- culating the iodine absorption, founded on the facl that when 1 molecule ol bromine combines with 1 molecule of unsaturated fai a definite amount of bint is liberated. One gramme of fat is weighed into a jacketed test tube about 1 inch in diameter and 6 inches long, from the jacket of which the air has been exhausted. 10 c.c. of chloroform are added, and the temperature noted; 1 cc of bromine is added, the HEAT EVOLVKD BY HYDROLYSIS BY SULPHURIC ACID. 277 mixture stirred with the thermometer, and the highest point to which the temperature rises is recorded. The difference between the initial and the highest temperatures multiplied by a factor will give the iodine absorption. The factor must be found empirically, as it varies slightly with each apparatus, ther- mometer, &c. It can be easily ascertained by submitting a few fats of known and varying iodine absorption to this test, and taking the mean relation between the difference of temperatures noticed and the iodine absorption. Hehner and Mitchell found in their experiments that the temperatures multiplied by 5*5 gave the iodine absorption. The thermometer used should be a good one, capable of reading to Ty C. ; the same thermometer and test tube should always be used. When the apparatus has been once standardised this method forms a rapid means of estimating the iodine absorption. The bromine should be measured in a 1 c.c. pipette, having a bulb filled with soda lime in its upper portion ; unless this is done, the fumes of the bromine are apt to prove very unpleasant. Heat Evolved by Hydrolysis by Sulphuric Acid. The Maumene Test. — When fats are acted on by strong sulphuric acid a series of reactions takes place. The fat is first split up to fatty acids and glycerol, which combines with the sulphuric acid. The saturated fatty acids (stearic series; are not further affected, but the unsaturated fatty acids undergo sulpho- nation and other changes. Of these, the oleic series, which has only one saturated bond, is acted on to a less degree than the linolic and linolenic series, which contain two or three bonds respectively. Each of the actions which takes place evolves heat, and, by measuring the rise of temperatures which takes place, an index of the total amount of heat evolved is obtained. Modification by Thompson and Ballantyne. — This test is due to Maumene, who measured the heat evolved on mixing 10 c.c. of sulphuric acid with 50 grammes of an oil or fat. His original method was faulty, in that he did not rigidly prescribe any strength of acid nor form of apparatus. Thompson and Ballantyne propose to compare the heat evolved on mixing 10 c.c. of sulphuric acid with 50 grammes of oil or fat with that evolved by mixing 10 c.c. of the same acid with 50 grammes of water in the same vessel. Taking the heat evolved by the water as 100, they term the figure obtained the "Specific Tem- perature Reaction" of the oil or fat. This method gives a very fair means of correcting for the differences of temperature observed when working with acids of differing strength and in different apparatus, and is convenient in practice. The author has examined with some care the results obtained by the use of acids of different strengths. The following series 278 BUTTER. will show that the effect of strength of acid can be corrected by a very simple calculation. These results were obtained with a pure olive oil. Strength of Acid. Rise of Temperature. Calculated for 100 per cent. 100 00 per cent. H2S04, . 47-2° 17*2 97-50 41 1° 16-6 96-64 39 3° 46 6° 94-93 35-6° 46-6 93-41) 32-6° 46 8° 92'85 31-4° 46 9° 9204 29 0° 46-3° Mean, 4(J-7" The results calculated for 100 per cent, acid were obtained by the following formula : — 21 "5 Rise of temp, x . T, „--: ^~z = rise of temp, witli 100 per cent. H2S04 - 78'5 per cen* acid Richmond. Modification. — The "author calculates the li Rela- tive Molecular Maumene" figure bv the following formula: — R.M.M. 21 T, = Rx- _ ■ x- 78*5 20 + A 20 195 K ; where R = observed rise of temperature. x = percentage of H2SO4 in acid. h — heat capacity of apparatus. K = potash absorption (per cent.). 25 grammes of oil were used and 5 c.c. of acid. The method is performed as follows: — A beaker ab< ut \\ inches in diameter and 3 inches deep is fitted, by means of a ring of cork, inside a slightly larger beaker; this is placed in a third still larger beaker, and the intermediate space packed with cotton wool. The heat capacity of this apparatus is next deter- mined; about 10 grammes of water are placed in the innermost beaker and the temperature noted ; about 25 grammes of water of higher temperature are milled, and the final temperature noted. The beat equivalent of the apparatus is calculated by the formula — where c-a h sheal capacity >>t apparal a , x=weigh1 <>i water placed in beaker. y=weigh1 ofhol water added. « temporal m e "t apparal us. b= temporal are "t li"t water, final temporal ore after mixing. X. a. ?/• grammes. grammes. lO'O 16 0° 26-5 100 17-5° 23-5 o-o 20-0° 35-1 THE PHYSICAL EXAMINATION OF BUTTER FAT. 279 The following experiments will show the nature of the value ofA:— b. r. h. grammes. 39 0° 31-2° 3 60 50-5° 38-5° 3 43 420° 40-0° 3-51 When the innermost beaker holds about double the volume of the oil and acid, its weight multiplied by '15 will give its heat capacity with considerable accuracy ; the beaker used above weighed 23-2 grammes; this multiplied by T5 gives 3-48. Twenty-five grammes of filtered and dried fat are weighed into the beaker, and the apparatus with thermometer, together with the acid to be used in a small bottle, and a 5 c.c. pipette, are placed in an incubator kept at 30° C. for at least half an hour, and the temperature noted. 5 c.c. of acid are added, and the mixture well stirred with the thermometer, till the tempera- ture ceases to rise. The difference between the initial tempera- ture and that finally attained is taken as the rise of temperature, and the Relative Molecular Maumene figure is calculated from this. The R.M.M. of butters varies from 33 0° to 34-55, with a mean value of 34 0°. The ratio . — '/ ' — = — , has been about iodine absorbed •633, varying from -615 to -649. Any increase in this ratio may be taken to indicate adulteration by vegetable oils. This method is occasionally useful, but is rather troublesome, and cannot be well recommended, except as an additional test in cases of doubt. It is very important that the fat be well dried. The Physical Examination of Butter Fat.- The most important physical properties are microscopic examination under polarised light, density, refractive index, viscosity, and behaviour on melting. Microscopic Examination under Polarised Light. — This method is founded on the fact that when a crystalline substance is placed between two crossed Nicol prisms the light undergoes rotatory polarisation ; the rays that would normally vibrate in the plane, which would cause total reflection, are caused to vibrate in a plane inclined to this, and the light consequently passes through the second Nicol prism. Substances which have no crystalline structure do noc cause any interference with the plane of vibrations. This method was first applied by Campbell Brown to detect adulteration of butter with foreign fat. The fat of milk when churned into butter is devoid of crystalline structure. The fats of which margarine is composed, having been melted and cooled, usually acquire a more or less pronounced crystalline form. It has been studied by Taylor, Pizzi, and others, and is fairly I'^O BUTTER. reliable. The following are the sources of error : — The presence of salt, salicylic acid, and other crystalline substances added to butter as preservatives, or accidentally mixed with it, will cause the light to pass, and may be mistaken for crystalline fat ; but a simple microscopical examination will usually reveal the nature of particles of this nature, and an experienced observer will rarely be misled. Butter which has been melted, re-emulsified, and rechurned will behave to this test as margarine, though no similar appearance is noticed in butter which has been kept just below the melting point for some length of time. Margarine which has been prepared by emulsifying the fat with skim milk with a good emulsor, separating the cream, and churning this with ordinary cream, behaves as butter, and Pizzi has succeeded in adding 30 per cent, of foreign fat to butter in this way without being able to distinguish it. Finally, rancid butter, and butter which has been at once churned from pasteurised cream at a low temperature, may sometimes give an appearance resembling margarine. It is apparent that this test must be used with reservation, but it is without doubt of use as corroborative evidence in cases where other analytical data are not absolutely conclusive. The method is carried out as follows: — The outer portions of a piece of butter are removed, and a piece about the size of a pin's head is transferred from the freshly exposed surface to a clean microscope slide. A cover glass is placed on the top, and the butter spread out by gentle pressure on the upper surface of the cover. The slide is placed on the stage of a microscope fitted with crossed Nicol prisms, and examined with a 1-inch objective. To exclude light from the upper surface a blackened cardboard tube may be placed over the slide in such a manner that the objective dips into it, and the light falling on the upper portion of the slide is cut off. When pure butter is examined the field is uniformly dark, and only with the greatest difficulty can any structure be distinguished. When margarine is present certain portions of the field have a bright appearance, and indistinct crystalline forms can be made out. It' any distinct and bright crystals are seen, the Nicol prisms should be turned parallel, ami the slide examined in that spot in order to see whether salt or other crystalline matter is present ; there is not much difficulty in distinguishing this owing to its greal refrac- tive power. The slide should be moved about to examine :ill parts of it, as, in eases of small amounts of adulteration, the margarine is not equally distributed throughout, and two or more portions from different parts of the sample tna\ be examined. \ a check, a Belenite plate (a crystalline form of calcium sulphate, which possesses the property of rotatory dispersion to a large extent) is next placed under the slide, the microscope THE DENSITY OF BUTTER FAT. 281 focussed, and the sample again examined. In this case the slide will be uniformly illuminated when the prisms are crossed, but will appear coloured ; the colour depends on the thickness of the selenite and the position of the Nicol prisms, hut when pure butter is examined the whole of the field appears of one colour. When margarine is under observation certain parts of the field are seen to be of a different colour. This modification is, when used by persons of absolutely normal vision, quite as delicate as the examination without selenite, but it cannot be generally recommended, as the per- ception of colour is a sense in which many people — more than is commonly supposed — are somewhat deficient, though not abso- lutely colour blind. The usual colours which selenite plates are constructed to give — red and green — are those which are least easily distinguished by the majority of those who suffer from weak colour perception. It is advisable, therefore, never to omit the examination without a selenite plate. It is, of course, essential to employ a good microscope, as any illumination of the slide, except by light which has passed through the polariser, will prevent the extinction of the field on crossing the Nicol prisms. Though it is impossible in practice to secure an absolutely dark field, this can be done with a good instrument and a cardboard tube over the slide with a near approach to completeness. Any marked illumination of the field when the Nicol prisms are crossed will greatly impair the delicacy of the test. The Density of Butter Fat. Butter fat, on account of the presence of glycerides of low molecular weight, has a greater density than the fats used for its adulteration. As it is more convenient and exact to take the density of a liquid than of a solid, the fat is almost invari- ably melted and the density determined at a temperature above its melting point. The methods of estimating the density have already been dis- cussed under the "specific gravity of milk" (p. 51), and (except that for butter a temperature considerably higher than that at which the density of milk is taken is employed) the same methods are employed. Expansion. — Two questions arise : At what temperature shall the density of butter be taken 1 How shall the results be expressed 1 The experiments of Skalweit have indicated the most favourable temperature. He took the densities of butter and margarine at various temperatures from 35° C. to 100° C, using Koch's incubator to keep a constant temperature. 282 BUTTER. His figures are as follow : — Temperature. Butter. Margarine. Difference. 35 C. •9121 •9017 0104 50° „ ■9017 ■8921 •OO'JO 60 .. •8948 ■8857 0001 7" .. ■ssT'.i ■8793 •0086 80° „ •8810 ■8729 •0081 90°,, ■8741 •8605 •0076 L00°„ •8672 •8601 •0071 Mode of Expressing Results. — These figures clearly show that hs the temperature rises the densities of butter and margarine tend to approach one another ; the widest difference occurs at 35° C. ; he, therefore, recommends that this temperature be adopted as the temperature at which the densities of butter should be determined. In England a large number of determinations have been made by J. Bell, Allen, Muter, and others at a temperature of 100° F. (37 "8° C), and this temperature is very near that found by Skalweit to give the largest difference. In America the temperature of 40° C. is used to a considerable extent, and the author has taken a large number of densities at 39 "5° 0. (owing to the use of a thermometer which read '5° too high). Estcourt proposed to use the temperature of boiling water (which he found to raise the butter fat to 97-8° C. (208° P.)), as being easily attained. Allen and others have warmly recom- mended this temperature, and find no difficulty in bringing the temperatur ■ up to '.'9° 0. There is a certain amount of confusion as to the manner in which densities are expressed. To ascertain the true density, the weight of a certain volume of fat should be divided by the weighl of 'he same volume of water at the same temperature and multiplied by the density of water at that temperature. This is very rarely done, so that few published figures are true densities. .Muiei- gives the term "actual density'' to the weight of a certain volume of fat divided by the weighl of the same volume of water at the same temperature ; densities expressed thus •">7 "8 are usually denoted by the Bymbol D — For density at 87'8", 37-8 35 or I» for density at 35", and the true density is often expressed as D or D I 4 THE DENSITY OF BUTTER FAT. 283 It is usual when densities are taken at the temperature of boiling water to express them in a different way. The weight of a certain volume of fat is divided by the weight of water displaced by a piece of glass which occupies the same volume at the same temperature, when it is cooled down to 60° F. (15-5°C.) This mode of expression may be denoted by the formula D in glass. Though apparently cumbersome this method of expressing results has certain advantages, as the instrument with which the densities are taken can be standard- ised at 60° F. (15-5° C), and can then be used at any temperature without requiring to be restandardised. It must be rememben d that though the expansion of glass is very nearly constant it is not quite so, and over a range of 85° C. appreciable differences may occur in the expansion of different instruments. If the glass be not well annealed, internal strains are set up, and these may be so accentuated at high temperatures as to cause dis- tortion and change of volume. It will be readily seen that the method of taking the apparent density in glass at the tempera- ture of boiling water is liable to greater experimental error than determinations at lower temperatures, and, as the experi- ments of Skalweit have shown, that the effect of experimental error is magnified at 100° C, owing to there being a smaller difference between the densities of butter and margarine at this temperature than at lower ones. It is desirable not to adopt this method where accui'acy is, as it always should be, a desideratum. On the whole, it seems desirable to adopt 100° F. (37*8° C.) as the standard temperature at which determinations should be made, because it is sufficiently near Skalweit's minimum to give a large difference between butter and margarine, and because a large number of experiments on genuine butters have already been made at this tempei-ature. Determination. — The density of butter is best determined by the pycnometer. This is filled with distilled water, and the weight of water which it holds at 37 S° determined. After drying, by placing in the water oven and drawing a current of air through it, it is filled with the fat and placed in water at 37*8° C. till the volume is constant; the temperature must be accurate to -1° C. if the result is required to be exact to the fourth place of decimals. The weight of fat divided by the weight of water will give the density at -. The Westphal balance may be employed, the apparent density of water at 37-8° must be determined, and the density of fat indicated by the instrument divided by this to obtain the density at „? „„. *284 BUTTER. The ilensity is also sometimes determined by a hydrometer. If this instrument be used, it should be tested in fats of known density, and its indications thus controlled. A. Meyer states that the height of the meniscus depends somewhat on the baro- metric pre.-sure, but the error due to this cause is not likely to exceed the experimental error of reading. Should the tempera- ture not be exactly 37-8° C, a correction of -0007 for each degree mav be added for temperatures above, and subtracted for temperatures below, 37-8° C. 100° It it be desired to take apparent densities at - „ in glass, the instruments should be standardised at 15"5°, and the density determined as above. The author has used a bulb of specific gravity *865 at 15-5* for the purpose of rapidly determining an approximate density. A test tube is filled with the fat, the bulb dropped in, and the tube placed in boiling water. If the bulb floats at the top, the density is above *865 ; and if it sinks, it is below. This has proved a fairly good rough test. The limits observed for pure butter are : — Maximum. Minimum. Mean. At .^o -9140 -9094 -91 IS •5/ O At y-^o (in glass) -8685 "8660 '8667 The fats usually employed as adulterants have a density at y^a-o of -^01 to -905, mean -903; and at ^.a (in glass) of -860 to '863, mean -861. Certain oils have, however, a higher density; thus, at ... ,„ 1 0 "D (in glass) — Palm-nut oil has a density of -st:? < locoa-nut oil, ........ -S74 CottlUI sect] nil, ....... '8726 Arachis oil, '863 up'' oil, ........ - s ( i 7 ."> Of these oils, palm nut and cocoa-nut oils can be readily detected (see Fat), while the other oils cannot be used alone, but must be mixed with fats of less density to obtain the necessarj consistency. With the reservation thai the oils mentioned above would cause somewhat abnormal results, the determination ol the ilensity of butter is a very useful test, and, though not reliable as a Bingle test, is of great use for corrobora < ive purposes REFRACTIVE INDEX. 285- Molecular Specific Volumes. — A method of calculating ■which will sometimes be of use is to deduce the specific volume by dividing the density into 1, and to multiply the figure thus obtained by the potash absorption and to divide the result by 195. The mean figure thus obtained for butter is 1-2766, and for margarine 1 *1641 at 37 -8° C. If the butter is adulterated with beet or other animal fat, the percentage of adulteration calculated with this figure will agree fairly well with that calculated from other determinations. If vegetable oils have been used, tlie percentage deduced thus is considerably more. Refractive Index. The Oleo - refractcmeter. — When light passes from one medium to another it only passes in a straight line when it falls perpendicular to the surface separating the two media. If it passes through at an angle to the surface, it is bent or refracted, and the ratio between the angle made by the path of the ray with the perpendicular to the surface in the first medium and the angle made by the path in the second medium •with the perpendicular is a constant; the ratio of the sines of the two angles is known as the index of refraction. As the sine of an annle of 90° is 1, it is seen that the ratio between the sine of the angle at which light is first reflected and 1 is the index of refraction ; this angle is termed the angle of total refection. As it is more convenient to measure this than to measure the two angles, and deduce the ratio of the sines, in practice the angle of total reflection is frequently measured. Miiller was the first to apply the determination of the refrac- tive index to the analysis ot butter. He allowed the butter to solidify slowly, absorbed the liquid portion with filter paper, extracted this with ether, and examined it in Abbe's refract o- meter, an instrument which measures the angle of total reflection. Skalweit examined this method and showed that it was important to operate at a fixed temperature. Owing to the difficulty of maintaining a fixed temperature in Abbe's refract ometer, this method was not much used till special instruments were devised. Amagat and Jean have devised an oleo-refractometer for deter- mining the refractive index of oils and fats (Fig. 20) ; it consists of a collimator, a hollow prism with sides inclined at an angle of 107°, and a telescope furnished with an arbitrary glass scale placed in the focus of the eye-piece. In the collimator is placed a piece of opaque substance, which cuts off the light from one- half of the field. If the prism and the space outside between the collimator and the telescope are filled with the same liquid, there will be no refraction. If, however, the prism contains a •_-s,', BUTTER. different liquid, ithe refraction will be indicated (in arbitrary decrees) by the position of the junction between th^ li^ht and dark halves of the field on the scale. Fi j . 20. — Oleo-refrad i imeter. A standard oil {huile type)* is supplied with the instrument, and the scale is so adjusted as tn read zero when this is placed in the instrument. The oil or fat to be tested is placed in the hollow prism and the position of the dividing line read off on the scale. The temperature is kept constant by means of a jacket, and is usually ir>°C. Jean gives the following method for testing butter: Melt from 25 bo ;>" grammes of tie- butter in a porcelain dish at i "Tin- is usually translated .1 "typical oil": the word "standard" is in",,- nearly equivalent \>> t be Frenob " type," than is " typioaL" BUTYRO-RKFRACTOMETER. 287 temperature not exceeding 50° 0. ; stir well with a pinch or two of gypsum, and allow to settle out at about the same tempera- ture. Then decant the supernatant fat through a hot water funnel plugged with cotton wool, and pour (while warm) into the prism. Observe the deviation at 45°. Genuine butter gives a deviation of about 30° to the left, while margarine gives about 15°, and cocoa-nut oil about 59°. L->bry de Bruyn has shown that genuine butters may show a deviation of 25° to the left. It is evident that the addition of a mixture of cocoa-nut oil and margarine would give a figure equal to that of butter. Muter has, however, shown that the figure given in the oleo- refractometer has a relation to the Reichert figure, which would be much disturbed by such a mixture. Muter's relation is expressed by the following table : — A deviation of - 36° is accompanied by a Reichert figure of 160. - 35° ,, „ 15-25. -34° „ „ H-5. - 33° „ „ 13-75. -32° „ ,, 13 0. -31° ,, „ 12-25. -30° „ „ 11-5. -29° „ „ 1075. Butyro-refraetometer. — Zeiss' butyro-refractometer(Fig. 21) measures the angle of total reflection and is a modification of the well-known Abbe refrac to meter. It consists of two prisms of glass, hinged so that they can be separated. The light enters at the bottom, passes through the prisms, aud is viewed through a telescope having a fixed scale in the focus of the eye-piece. The prisms are provided with a jacket, through which water, the temperature of which is indicated by a thermometer, is passed. A drop of the filtered fat is placed on the glass surface of the lower prism, spread evenly over it, and the prism closed ; the reflector is adjusted so as to reflect clear daylight or lamplight through the prisms, and the refractive index in scale degrees is read off. This instrument is extremely rapid, as a determination, in- cluding reading of the temperature and scale degrees, does not take more than a minute. After use, the instrument should be cleaned by rubbing off the fat with a duster, and polishing the prisms with a clean linen cloth slightly moistened with alcohol. Scale divisions may be converted into refractive indices by the following table (p. 288). There is a difference in the refractive index depending on the light used ; this is corrected in the instrument by making the prisms of different kinds of glass, so that when used with butter ordinary white light behaves as if it were simple light. Other fats (and adulterated butters) may be tinged at the edge with blue or red. In this case it is not easy to read the dividing line 288 BUTTER. Scale Division. Refractive Indices for the D line. Difference. 0 1 -4-220 10 1 -4300 8-0 20 1 -4877 7-7 30 1 -4452 7 5 40 1 -4524 7-2 50 14593 69 60 1 -4659 6 6 70 1 472.S 64 80 1 -4783 6 0 90 1 -4840 5 7 100 1 4895 5-5 I 21. — But VI I ' I'M EU t. 'Ill' til . BUTYRO-REFRACTOMETER. 289 accurately. The author is in the habit of using the sodium flame, obtained by heating sodium chloride in a Bunsen burner, as the source of light, and finds that absolutely sharp readings can thus be always obtained. The readings with butters do not differ, whether white light or sodium light be used. The refractive index varies -55 scale degree for each 1° C, and can be corrected by means of this factor if the temperature differs from that adopted as normal. The author has found that genuine butters vary from 43 '7° (in a sample giving a Reichert value of 16-0 c.c.) to 49*0° (in a sample giving a Reichert value of 10-5 c.c), and average 46-0° at a temperature of 35° C. The value 47 0° has been proposed as a practical limit. The equivalent at other temperatures of this limit is as follows : — Temperature. Scale Division. 1 Temperature. Scale Division 25° 52-5° 40° 44-2° 30° 49-8° 45° 41-5° 35° 47-0° 1 Some importance has been attached to the colour observed at the edge of the dividing line, and a blue colour has been alleged to be indicative of mai'garine. In the author's experience this property is valueless. Thus the sample giving a reading of 43-7° was tinged red, and that giving 49-0° was tinged blue, though both were authenticated as genuine butters. Margarine has a value of about 52° at 35°, cocoa-nut oil of 41°, and cotton-seed oil of 61°. The remarks made upon the oleo-refractometer apply equally well to the butyro-refractometer, except that the actual values are not identical. The author's experience confims that of Mansfeld, and shows that, while Muter's relation is, broadly speaking, correct, there are differences so large between the refractive index found and that calculated on the assumption that this property follows the Reichert value, that the rule cannot be depended upon. The refractive index is a property which is much more nearly related to the iodine absorption, or, in other words, to the unsaturated carbon atoms. Though a very convenient test, it has but little value alone, unless the value is below the average, 46° at 35° C. When a butter is adulterated with vegetable oils — e.g., cotton seed — its indications are of some value. It is also useful in detecting cocoa-nut oil, but its value is chiefly corroborative. A standard fluid (normal Jiiissigkeit) is supplied with the instrument, and the readings of the scale should be checked from time to time by its use. The point at which the dividing line should lie at 35° C. is marked in the instrument, and the 19 290 BUTTER scale should be brought to this point by means of a key just above the prisms. Viscosity. — Killing proposes to take the viscosity of butter fat as a test by running it out of a pipette, marked above and below the bulb, and records the time taken for the melted fat to flow from one mark to another. The instrument must be graduated with butters and other fats of known purity. He gives the following average times of flow: — Butter, 3 minutes 43£ seconds. Margarine, ..... 4 ,, 19 ,, Lard, 4 „ 28 Beef fat, 4 „ 33 Wender uses an apparatus called a fluidimeter. This consists of a U-shaped capillary tube having at one end an enlargement holding 10 c.c, and at the other an enlargement holding 2 c.c. ; the larger bulb is placed higher than the smaller ; liquid, there- fore, flows from it. A solution of the fat in chloroform is used ; the upper bulb is filled with this, the solution allowed to flow into the lower bulb, and the time noted which it takes to pass from the lower mark to the upper one on the smaller bulb. The time taken for chloroform to flow is also noted, and this is taken as 100. The viscosity of the fat is calculated by the following formula : — Let V = viscosity of the fat, x = percentage of fat in chloroform solution by volume, and T = the time taken divided by the time taken by chloroform, TT 100 T- 100 (100 -a;) then v = ! . x The average time for chloroform to fill the lower bulb was 20-04 seconds. Wender gives the following values as the mean figures at 20° C. (chloroform = 100):— Viscosity of pure butter, 344*3 ,, ,, margarine, 3732 It does not appear that this test has any greater value than other physical determinations. Behaviour of Butter on Melting. — When butter is melted at a temperature of about G0° C, the fat which flows from the aqueous portion is generally clear and transparent ; when margarine is melted, the fat is almost always cloudy. This has been used as a test for the purity of butter. It does not appear t<> depend on any property of the fit, but on the state in which the tat existed in milk, and the method of pre- paring the butter. Butters which have I d overworked invariably melt in a cloudy manner. DETECTION OF ADULTERATION OF BUTTER. 291 Druot has devised an apparatus for observing the behaviour on melting. It consists of a number of cups stamped in tin plate, in which pieces of the samples to be tested, about li grammes in weight, are placed. A piece of iron heated to about '60°, and of sufficient thickness to retain enough heat to melt the samples, is placed over the top, and left till the butters are melted. The appearance of the fat is observed, the polished surface of the tin plate materially aiding the observation. This method can only be classed as a rough means of deter- mining the purity of butter. Melting Point of the Fat. — Formerly some importance was attached to the melting point of the fat ; this, however, depends to some extent on the method employed in determining it. Butter melts at about 33° 0. ; and artificial butters are made up to melt at the same temperature. Among other physical properties which have been proposed are the determination of the heat of combustion, which differs materially in butter and other fats, and the relative transparency to the X rays. These methods are not, however, practical analytical methods. Detection of Adulteration of Butter.— The most useful and rapid preliminary test is examination with the butyro- refractometer. Any sample showing a refractive index of less than 46° at 35° 0. is most probably genuine, but may, however, contain cocoa-nut oil. The Reichert process should next be applied. Any sample requiring less than 9 c.c. of —-alkali for 25 grammes, or 20 c.c. for 5 grammes (Reichert-Wollny method) may be taken as adulterated ; samples requiring more than 12-5 c.c. or 28 c.c. respectively may be passed as genuine, though they cannot absolutely be certified as free from adul- teration. Any sample taking a volume of — alkali between the limits given above must be further examined. Baudouin's, Becchi's, and Wellmann's tests should be applied. A well- marked reaction with any or all of them will furnish strong presumptive evidence of the presence of margarine containing vegetable oils. The soluble and insoluble fatty acids, saponi- fication equivalent, and especially the mean molecular weight of the insoluble fatty acids should be determined. Cocoa-nut oil can be readily detected by the figures thus obtained. The ratio between the Reichert or Reichert-Wollny figure and the difference between the insoluble fatty acids and 95*5 is much depressed ; in butter the ratio is about R R-W S5^Tj = l'6 °r 95-5 "I = 3'5 (R = EeichGrt figUre' 292 BUTTER. R-W = Reichert-Wollny figure, and I = Insoluble fatty- acids) ; while cocoa-nut oil gives values of *35 and *75 respec- tively. The mean molecular weight of the insoluble fatty acids in butter is about 259 and varies but little from this figure, while the corresponding figure for cocoa-nut oil is about 200. The iodine absorption of cocoa-nut oil is also low, about 9 per cent. ; while butter absorbs about 34 per cent, of iodine. It is far more difficult to detect other adulterants, if present in small quantities. Genuine butters which are below the average in the Reichert figure give high insoluble and low soluble fatty acids, a high iodine absorption, and a low per- centage of potash absorbed. In the few samples that the author has examined the mean combining weight of the insoluble fatty acids has not been so high as would be expected. Thus the mean combining weight of the insoluble fatty acids is about 259, while the mean combining weight of the insoluble fatty acids of most adulterants is about 277. The Valenta test is also useful, and the density may be used as a corroborative test. Margarine. — It is advisable to calculate from the mean figures yielded by genuine butters and margarine the apparent per- centage of margarine present. If the percentage thus calculated from the mean combining weight of the insoluble fatty acids, the Valenta value, and the density be less than that calculated from the other determinations and, at the same time, the iodine absorption and refractive index are slightly high, it is probable that the butter is genuine. If the contrary is the case, and the apparent percentages from all the methods give approximately the same value, it is probable that the butter is adulterated. If, in addition, the colour tests for vegetable oils have given distinct reactions, the probability of adulteration is strength- ened. Though in the present state of science it is not possible to definitely certify many cases of small amounts of adulteration, for dairy control work the task is much simplified. The samples which must be regarded as suspicious can be reported as Buch, or even as adulterated, with a high degree of probability, and it will be frequently possible to trace such samples to their origin, by examining the fat of the milk of the cows which yielded the butter. Influence of Keeping on the Analytical Properties of Butter. — When butter is kept and becomes rancid 7ery pro- nounced changes take place in the coin pus it inn of the fat. These may Declassed under two leads hydrolysis and oxidation. If butter fat lie kept in the dark and out of contact with the air, it keeps indefinitely without change; but in the presence of light and air it becomes oxidised. ANALYTICAL PROPERTIES OF BUTTER. 293 The general course of change may be roughly indicated thus — (1) The fat is partly hydrolysed into fatty acids and glycerol. (2) The glycerol is oxidised to fatty acids of low molecular weight. (3) The unsaturated acids are oxidised, forming hydroxy-acids. The general effect of these changes is — The volatile and soluble acids are increased, the soluble in greater pro- portion than the volatile. The insoluble acids are decreased. The iodine absorption is lowered. The density and refractive index are increased. The potash absorption is increased. If the butter has been kept in its natural state, the butter fat obtained on melting may have properties materially differing from those indicated above, owing to the solubility of some of the products in the water still left in the butter. The soluble and volatile acids in the filtered fat may be lowered from this cause, and the insoluble acids increased. The change is not very rapid, and in the course of several weeks the changes are often not very pronounced. Bell has recorded the following figures for the changes in the insoluble fatty acids; the butter in this case was kept for the times indicated : — No. of weeks kept, . 12 7 7 6 8 6 Before keeping, per cent., 87-30 S7-80 85-50 87-40 87 -72 87-65 After ,, ,, 88-97 90-00 85-72 87-97 88-40 88-00 Per cent. Per cent. Per cent. 88-33 87-61 87-72 85-97 84-41 83-82 Vieth has made analyses showing the change in the insoluble fatty acids produced when butter fat is kept. In each case about a, year had elapsed between the two analyses. Per cent. Original insoluble fatty acids, 87 "43 Insoluble fatty acids, after keeping, 85 "07 The same observer has also examined old butter fat and old butter (kept for about ten years) which had not been previously analysed. The old butter fat was divided into two portions — one, com- pletely bleached, contained 83-52 per cent, of insoluble fatty acids ; and the other, which still retained a trace of its natural colour, yielded 83 -90 per cent. The results with the old butter were as follows : — Lower portion, . . 89 -28 per cent, insoluble fatty acids. ,, ,, washed, 89-33 ,, „ ,, Upper portion, . . 90 -94 ,, ,, ,, Allen and Moor have examined two samples of butter which had been kept for five and a half years. The following table gives their results : — 294 BUTTER. B. O. Fresh. Old. Fresh. Old. 1. 2. 3. ^ ■* 100° /■ 1 1 Density ._ _„ (in glass), . . Reichert-Wollnj*, .... Potash absorption, .... Soluble fatty acids, per cent. , Insoluble fatty acids, ,, Iodine absorption, .... 8640 22-51 22-16 4 44 90 44 40-0* •8634 14-43 2199 3 82 90 73 30-01 •8696 12-02 22-55 5-66 9070 27-17 •8730 L2-0J 22 88 5 80 90 00 25-08 •8641 24 55 22 09 4-68 9010 1 22-48 23-33 5-S9 85-78 25 57 Clayton lias analysed a butter which in 1879 gave in Hehner's hands 87'75 per cent, of insoluble fatty acids. His results were : — Melting Point. Density Kill' ' 15-5° (in glass). Insoluble Fatty Acids. Soluble Fatty Acids. Keichert- j Wollny. January, 1895, October, 1897, 33°C. •8742 Per cent. 85-72 Per cent 7-36 c.c. 22 36 Potash absorbed. Iodine absorbed. M«£f* Rancidity. January, 1895, October, 1897, Per cent. 2347 Per cent. 25-68 25 09 1 22° C. LOO grammes required KiO-3 c.c. normal alkali. Besana has examined twenty samples after keeping for various periods of time ; he estimated the Reichert- Wollny figure (Table LIIL). Vieth has examined a butter which had been kept more than ten years ; the fat then yielded the following Reichert- Wollny figures — 2G-2, 25*6, 2-V7, and 21/2 c.c. on different portions. lie has also examined butter tat which had been kept for eighteen monl hs. The results wriv : — Bre in, Old, 28"2o.c. 30 I c.c. 29*9 c.o. 29*5 c.c. (determined by the author). This figure w.i determined by the author on a duplioate sample. THE RICIIERT-WOLLNY FIGURE OF BUTTERS. 295 TABLE LIII. — The Reichert-Wollny Figure of Butters. No. of days Reichert-Wollny Figure. between first and second Difference. test. Fresh Butter. Rancid Butter. 173 27-70 27-42 -•28 171 27-28 26 98 -•30 170 27*50 27 28 -•22 169 27 51 27 64 + •13 164 27-43 27 75 + •32 162 28-49 28 30 -19 161 27-90 27 65 -•25 160 27-54 27 40 -14 157 27-72 27 31 -•41 157 28-49 27 97 -•52 134 2915 29 40 + •25 131 29-48 28 74 -•74 107 29-48 28 96 -•52 107 29 70 29 18 -•52 84 29-40 28 85 -•55 84 29 36 28 74 -•62 79 27-S7 •27 42 -•45 47 28-08 •28 30 + •22 46 27-86 27 75 -•11 46 28-85 28-96 + •11 Another example of butter fat well protected from the light N gave in July, 1888, from 31*6 to 32*1 c.c. of y-~ alkali. In — October, 188S, it gave 31 8 c.c January, 1889, May, 1889, September, 18S9, December, 1889, 32-1 „ 32-1 „ 31-8 „ 32-2 ,, April, 1890, July, 1893, >> 32 0 „ 339 ,, The last figure was determined by the author ; the others by Vieth. It is seen from the figures quoted above that the analysis of butter which has been kept for any length of time is a matter of considerable difficulty. Though in butter fat the volatile acids do not show any diminution, but rather an increase (due pos- sibly to the oxidation of the glycerol), in butter the reverse is usually the case. It is by no means improbable that, besides the solubility of these in the water contained in the butter, a portion is destroyed by the action of micro-organisms. The most reliable datum would seem to be the determination of the volatile acids on the butter itself without separation of the fat, subsequent determination of the fat, and calculation of the 296 BUTTER. Reichert figure on the actual fat present. The potash absorption does not appear to undergo much change. Buttermilk — Definition. — The term buttermilk is applied to the aqueous portion left after churning. It differs only slightly in composition from skim milk. As the cream used for churning is usually slightly sour, the buttermilk contains appreciable amounts of lactic acid ; it will also contain water or any other substance which has been added during churning. There is, in suspension, a considerable amount of Storch's mucoid proteid, which may be removed by passing it through a cream separator, when it is deposited on the sides of the drum. Composition. — The following composition of buttermilk from sweet cream is given by Storch : — Water, 89 "74 per cent. Fat, Milk-sugar, Proteids, Ash, 1-21 4-98 3-28 •79 Buttermilk from ripened cream has the following composi- tion : — Authority, . . . Storch. Vieth. Fleischmann. Water, Fat Milk-sugar,. Lactic acid, . Proteids, Ash, .... Percent. Percent. 90-93 90 39 •31 -50 4-58 4 06 (?) -80 3-37 3-60 •81 -7.5 Per cent. 91-24 •56 J 4-00 3-50 •70 Variations of Fat. — The author has found the amount of fat in buttermilk to vary from -15 per cent, to 5*60 per cent.; the last percentage is very unusual, and it is rare to find even as much as 2-0 per cent., percentages higher than this denoting that the churning has been inefficiently carried out. Ash. — The following composition is given by Fleischmann to the ash of buttermilk : — Potash, KsO, 24*63 per cent Soda, X....O 1 1 r>4 „ Lime, 1 !a< >, 1973 Magnesia, Mg< >, 3 66 Phosphoric acid, PjOj, . 29-89 Chlorine, CI, ..... 13-27 [ron oxide, &c, .... 47 102 99 „ I. oxygen - chlorine, 2*99 IIIO-HII CHEMICAL CONTROL OP CHURNING OPERATIONS. 297 Buttermilk has usually a slightly acid flavour ; it does not, however, taste quite like sour skim milk, but has a distinctive smell and flavour of its own ; it is not known to what this is due. On microscopic examination it is seen that the fat left is not entirely in globules ; there exist many small nuclei consisting of two or more fat globules. Chemical Control of Churning Operations.— The fat in the buttermilk from each churning should be estimated. Usually less than 1 per cent, of fat may be considered satis- factory, but if sweet cream is churned it is difficult to always keep within this limit. Any percentage of fat above 2 must be considered unsatisfactory, and the cause should be enquired into. This may be due to the use of cream which is too thick, mixtures of cream of different consistency and age, too high a temperature, or too rapid churning. The fat in the cream to be churned should also be estimated. It has been found that cream containing from 25 to 30 per cent, of fat gives the most satisfactory results. If the cream contains more than 40 per cent, of fat, the buttermilk is very high in fat, and a larger percentage loss is obtained. The weight of fat in the butter plus the weight of fat in the buttermilk should come within 2 per cent, of the weight of fat in the cream used. If a larger difference is found, a needless loss of fat is taking place, and the cause of this should be ascer- tained. Table LXXXIY (Appendix) gives the weight in pounds of butter which may be expected to be produced on churning cream varying in percentage of fat from 15 to 50. 298 OTHER MILK PRODUCTS. CHAPTER VII. OTHER MILK PRODUCTS. CONTENTS. — Cheese — Rennet — Classification of Cheeses — Composition — The Ripening of Cheese — Analysis of Cheese— Adulteration of Cheese — Other Products derived from Milk. Cheese. Cheese is prepared by the action of rennet on milk ; this separ- ates it into whey and curd ; the curd is finely divided, pressed to separate the whey and to consolidate it, and, usually, salted. From this, cheese is produced by ripening, which is due partly to the action of micro-organisms and fungi, partly (as Babcock and Russell have recently shown) to the action of an enzyme natural to milk. Action of Rennet. — The action of rennet is to split up the casein into a dyscaseose, the calcium compound of which is insoluble and which forms curd, and a soluble caseose ; the insoluble curd carries down with it a large proportion of the fat. Composition of Curd and Whey. — The following table will show the distribution of the various constituents of the milk when made into whey and curd : — Milk. w hey. Curd. Per cent. Pet cent. Per (Tut. Water, 87'10 80-60 6*50 Fat 3-90 30 3-60 \1 ill, sugai . . 4-7A 1-46 ■30 1 3-00 •»o 2*60 Allnimin, ■40 ■40 i race A 1 "76 (in •].-. The following is the composition of whry according to various authorities : — COMPOSITION OF CURD AND WHEY. 299 Fleischmann. Kbnig (average). Smetham. Vieth (from skim milk). Per cent. Per cent. Per cent. Per cent. Water, . 9315 93 38 93 33 93-00 Fat . •35 •32 ■24 09 Milk-sugar, 4-90 4 79 5-06 5-45 Proteids, . 1-00 •86 •88 •92 Ash,. •60 •65 •49 •54 The author has found the fat in whey to vary from *04 per cent, (from skim milk) to 1 *35 per cent., and the solids not fat to lie between 6 and 7 per cent., averaging 6-6 per cent., which contain — Milk-sugar, Proteids, . Ash, 5*0 per cent. 1-0 „ •6 On adding an acid to whey, a slight proteid precipitate (which is difficult of nitration) is obtained. On heating the acid whey, a soft curd of little consistency is formed ; this substance is a commercial article on the Continent. The composition of the whey and the precipitated curd (after acidifying and boiling) are given : — By Fleischmann. By Bochicchio. Whey. Precipitate. Precipitate. Per cent. Per cent. Per cent. Water, 93-31 68-5 68-47 Fat, .... •10 31 5 22 Milk-sugar, . 5 85 3 2 3 97 Lactic acid, . •8 Proteids, •27 22 1 18-72 Ash, .... •47 2 3 3-62 On boiling whey without acidifying, a precipitate of a similar nature also occurs; this appears to consist of coagulated albumin. Cheese is sometimes prepared by allowing the milk to become sour spontaneously, salting and pressing the curd, and allowing it to ripen. This variety of cheese is not considered of such good quality as rennet cheese. Fleischmann gives the composition of the whey thus obtained as follows : — 300 OTHER MILK PRODUCTS. Water, Fat Milk-sugar, . Proteid precipitated by acetic -acid, ,, ,, tannin, Ash Difference (lactic acid ?), 93 i 3 per cent. ■12 4-38 ■47 •59 •82 •49 Vietl) has shown that whey prepared in this way undergoes alcoholic fermentation much more readily than rennet whey. Rennet. — This substance is an enzyme produced in the stomachs of mammals ; it occurs in the human stomach, and the curdling of milk when ingested is due to this ; it is especially abundant in the young while still suckling. Preparation. — It is usually prepared from the fourth stomach of the calf. The stomachs are dried and kept for some time ; they are then cut up into small pieces and macerated in a 5 per cent, salt solution, usually containing boric acid, for some days ; to the solution a further 5 per cent, of salt is added, and the liquid filtered ; this forms extract of rennet. By adding more salt, the rennet is precipitated, and " rennet powder " is pro- duced ; this consists, essentially, of the ferment, together with other organic matter, and a considerable amount of salt. Properties. — Rennet acts on casein only in neutral or acid solution, and its properties are destroyed by alkalies. Like all enzymes it has an optimum temperature at which it acts best ; this has been found by Fleischmann to be 41° C. (105-8° F.). He gives the following table as showing the relative proportion of milk coagulated in a given time by the same quantity of rennet at different temperatures : — Temp. C. Proportion. Temp. C. Proportion. Temp. C. Proportion. 20° 18 36° S9 44° 93 25° 44 37° 92 45° 89 30° 71 38° 94 46° 84 31° 74 39 96 47° 78 32° 77 40° 9S 48° 7(> 33° 80 41° 100 49° 60 34° 83 12 99* 50° 50 35° 86 13 96 At the optimum temperature, and for several degrees on either side, the curd produced is very firm ; at low temperatures, L5 C. to 20° C, the curd is quite soft and flooculentj and when tin- temperature is raised t . • 50°, the curd again becomes very Soft. * Qiven aa 98 in original, but from the experimental data it appears that 99 ia more corn CLASSIFICATION OF CHEESES. 301 By heating rennet to temperatures much above 60° C. (140° F.} it rapidly loses its properties. The action of rennet is affected by the acidity of the milk ; the lai'ger the amount of acid, the more rapid the action ; the addition of water to milk causes it to be coagulated more slowly by rennet and the curd is less firm. By heating milk, the action of rennet is delayed, owing to the removal of some of the soluble calcium compounds. By the addition of soluble lime salts, the milk will be curdled by rennet in the usual manner. Testing of Rennet. — It is important to know what the strength of rennet preparations are — i.e., the amount of milk that will be curdled by 1 part in a definite time at a definite temperature. This may be estimated as follows : — 5 c.c. of a rennet extract or -5 gramme of a rennet powder are made up to 100 c.c. with distilled water. After thorough mixing, 1 c.c. is measured out by means of a pipette and added to 100 c.c. of separated milk of acidity 20°, which has been brought to a temperature of 35° C. ; the milk and rennet solution are immedi- ately well stirred and the exact time at which the rennet was added noted. The milk should be contained in a beaker, which is placed in a water-bath kept at 35° C, and gently stirred with a thermometer till it is found, by the path becoming visible, that the milk has coagulated ; the exact time which has elapsed from the addition of the rennet till the coagulation sets in is noted. The strength of the rennet — i.e., quantity of milk that will be coagulated by 1 part in forty minutes — is calculated by the following formula : — Let x = quantity of milk coagulated. p — proportion between milk and rennet taken. t = the time. Then x=^P. The value of p is 2000 when 5 c.c. was diluted to 100 c.c. and 1 c.c. taken, and 20,000 when -5 gramme was taken. If the time taken is less than five minutes, or more than ten minutes, it is advisable to make another determination, using a smaller or larger proportion of rennet to milk. Classification Of Cheeses. — Cheeses may be divided into the following classes : — 1. Soft Cheeses. — These are obtained by coagulating the milk with rennet at a low temperature (below 30° 0. or 86° F. ). The period of coagulation lasts a long time. As representative of these cheeses the following kinds may be mentioned : — Gervais made from cream ; Brie, Camembert, Pont l'Eveque, and Bondon (or Neufchatel) made in France ; and Stracchino made in Italy. 302 OTHER MILK PRODUCTS. -. Hard Cheeses. — These are obtained by coagulating at higher temperatures (30° C. or 86° F. to 35° C. or 95° F. ; they inav be again divided as follows : — (1) Cheese made from milk and cream — Stilt on. (2) Cheese made from whole milk — Cheddar, Cheshire, Dunlop, and Wensleydale made in England ; Port de Salut made in France ; Emmenthaler or Gruyere made in Switzerland, Edam in Holland, and Gorgonzola and Cacio Cavallo in Italy. (3) Cheese made from partially skimmed milk — Parmesan in Italy ; Derby, (xloncester, Leicester, and, sometimes, Cheddar in England ; Edam (usually made in this way) in Holland, and Gruyere in Switzerland. Skim milk cheese and cheese made from skim milk enriched by margarine are also made. A famous cheese, known as Roquefort, is prepared from sheep's milk ; Besana has shown that many sorts of cheese may be made from sheep's milk. Goats milk is also employed in cheese manufacture, but these cheeses are not important articles of commerce. In addition to rennet cheeses, cheese made from the curd precipitated by warming milk which has been allowed to become sour is also used. The only cheese made in England is cream cheese ; frequently an acid is added to the cream instead of allowing lactic fermentation to take place. A Swiss cheese, Glarner, and the German caraway cheese come under this category ; the latter is mixed with caraway seeds. Composition Of Cheese. — But little is known of the com- position of cheese. Most of the analyses made have included only water, fat, ash, and total nitrogenous substances either by difference or by estimation of the nitrogen and multiplication of this by a factor. In very few cases has the separation of the nitrogenous matters been attempted, and it is doubtful whether, where this has been done, much real information as to the character of the products has been obtained. The chemical knowledge of cheese must be pronounced to be in a much less satisfactory condition than thai of other milk product-. The following tables (L1V. to T/VTI.) will give the proximate composition of Nations cheeses : they will be useful as showing the most striking differences. Thus soft cheeses contain large amount- of water, and small percentages of fat and proteids ; cheeses mule from whole milk contain an amount of fat at least equal to the proteids, while skim milk cheeses contain usually less fat than proteids; in cream cheeses the fat greatly exi i he proteids : — COMPOSITION OF CHEESE. 303 TABLE LIV.— Cream Cheeses. 1. English cream cheese made without rennet. Authority. Vieth, . Snietham, Pearmain & Moor, Water. Per cent. 30-66 20-56 57-6 Fat. Per cent. 62-99 80-03 39 3 Proteids. Lactic Acid, &c. Ash. Per cent. 4 94 2 99 19 0 Per cent. •26 •57 Per cent. 115 •83 3 4 Vieth found the insoluble fatty acids of the fat to be- When fresh, 87-31 per cent. After 1 month, 87'12 88-02 „ 3 „ „ 4 » 2. Gervais cheese. Vieth, . Stutzer, . Author, . 87-96 87-58 Per cent. Per cent. Per cent. Per cent. 42-32 49-18 7-75 •27 44-84 36-73 1548 33-80 57-79 791 Per cent. •49 2 95 •50 TABLE LV.— Soft Cheeses. Authority. Water. Fat. Proteids. Lactic Acid, 5> 33-90 29 05 27-37 4-05 (English) Cameron & Aikman, 27*20 32-05 36-60 415 (American j» >» 28-09 22-52 45-75 3-64 (English) Muter, 29-70 30 70 35 00 •90 3-70 (American) ,, ... 33-40 26 60 3417 1-53 4 30 (English) Konig (average), 33 89 33-00 27-56 1-90 3-65 3. Cheshire. Smetham, . _._ 39-33 30 80 23-70 2-43 3-60 Pearmain & Moor, . 34-70 33-30 2610 4-30 Leffmann & Beam, . 30 4 25-5 36-1 4 80 4. Gruyere 'or- Ehnmenihal). FleiBchmann, . 361 29-5 28-0 33 31 Duclanz, . 36 00 29*29 30-84 3-87 Stut/i-r. . 33-01 30-28 31*41 .v:;o Pearmain & Moor, . 31-45 30-20 30-00 i -jo ( lameron & Aikm m, .".:•:: 1 26-47 31-33 3-42 Muter, 33-20 27-26 33-49 1 ;::. 4-70 Leffmann A Beam, , 32-d 28-0 36-1 i 8 Konig (average), 36-49 28 01 80-83 •72 3 '.15 "•. Cacio Cavallo. tori, . 19-76 .-{»;■: i 3412 8-70 .VI in 8pi< i & I •'■ Bit i. 23 67 26*49 29-28 17:::. l"_M COMPOSITION OF CHEESE. 305 TABLE LVII.— Skim Milk Cheeses. Authority. Water. Fat. Proteids. Lactic Acid, &c. Ash. Per cent. Per cent. Per cent. Per cent. Per cent. 1. Dutch. Duclaux, . 37 31 24-41 32 50 5-69 Pearmain & Moor, . 32-90 17-78 30-80 6-40 Konig (average), 37-35 24-61 32-40 5-65 Muter, 42-72 16-30 28-27 1*35 11-36 2. Gloucester. Cameron & Aikman, 28-62 23-67 43-54 4-17 Pearmain & Moor, . 35-25 25-80 30-05 4-80 Muter, 37-20 22-80 33-64 1-80 4-56 3. Grana. Duclaux, . 32-56 21-75 42-27 5-07 Konig (average), 3133 23 90 35-34 4-17 5-26 4. Parmesan. Duclaux, . 30-09 26 04 38-42 5 45 Konig (average), 31-80 19 52 41-19 118 6-31 Pearmain & Moor, . 32-5 17-1 43-6 6-2 Cameron & Aikman, 27-56 15-95 44-08 5-72 5. York (a soft cheese). Muter, 63-64 15-14 18E0 1-80 •92 Vieth, . 68-44 12-89 14-50 2-S8 1-29 Besides these cheeses, which are all made from cow's milk, the famous Roquejort cheese, made from sheep's milk, must be mentioned. Its composition is — Authority. Water. Fat. ' Proteids. Lactic Acid, &c. Ash. Konig (average), Pearmain & Moor, . Leffmann & Beam, . Muter, Per cent. 36-85 29 6 26-5 21-56 Per cent. ,30-61 30 0 32-3 35-96 Per cent. 25 25 28-3 32-9 24-52 Per cent. 1-90 ... •72 Per cent. 5 39 6-7 4-4 10-24 In the above analyses the figures under the term "proteids " include true proteids and their products of ripening, and, fre- quently, also such products as lactic acid. Proteids in Cheese. — Besides the analyses given on pp. 303-305, the following, in which an attempt has been made to distinguish between the various constituents, may be noticed. 20 306 OTHER MILK PRODUCTS. fa c S5 O o fa a O O o 63 < w - ^^ = 'C u -3 t> •* ----- r. /. a = ic i-cr. — >c re g Dsoooo t" isp oo — ej "OB3 i— ISO) "SO = 35 re re — 3) |0 v — r~ 3> —CIO ojg OBOiO C5 CO I- -g . J u © © © CC C3 — ' « — > « J gee cc cc fa 5 eo cq «p £ CI -^ CI fa -. — ci ci C5 X — CI CI -t S^ — — 1 s - 0) — - - = ri — - ai — a t. -t cc ci eo«o 3! — 2«W« CI — CC cc fa 1.2.8 1 JB N . N .- 3 3 o §i::::: 3 < o tc gpq 3 « ^j 8 lO CI — — -.3 35 CI "O^HrtWI^M g ooi-t'M i- >~ fa fa J J •- S oo — i cc >e cc r— lo 5 .3 5 ci i^ o re -.3 co co < fa -CKMOhO IQ « Tl 05 M S> IS O * ■-~f -tO-OWM o a — — i c-1 CI CI CI fa *J r cc ic i-c oo r— oo in "as -■f i"-iot^«o < _-Cl re -* -t IC :: IC fa ;-KI-MOt>-t- o 'C CO -f IC 13 -^ CI £ t--t O — •- iC 1 - 1- i -i • ■ • V- U 1— 1 — 1 u: O ri <3 o -S - o . •3 „ «n -£ - F - u c - 2 S >>§oa 2 e P b * cc K S - - DETAILED COMPOSITION OF CHEESES. 307 o 8 M . 0 F* O - » a * rs » a zpq J3 S^ 3 r-- m sg S co 01 >o tt p, £^h to t>. £5 P4W ft = co i-~ to gCO 1— 1 t— t.-* A O 0 •0 M *"e3 ' £-§ J * j i) 3 s S pqwo c> 5 fed g ■* 0 m 0 oOS t— CO CM £ <4 t,?OC10 ft .3 c SCO (M 10 0 3 3 a>CO tji CO O c« £©1 7* O © a 0 S 0 0 ft "1 8 g t- t- ©1 0 "iO!DOO ft £7* 0 0 p ft "oi ^J 0 g ©i co r^ no oi^ooffl 33 % iio 1^ ■* to ft ^ = O — ©1 to gOS O -H I© «1 fe **«-H ft ^ £©1 OS CO -* 'as 3 ©1 tO t— CO 02 Sco co -h ^h ft _j sci as 0 00 Og 0 rt< t^ in ^ JrO IO t-. tO (5JKS Tt* -* IQ aJ si 5 •n +3 M . ■*= CS £M «S ,Q jh a ,0) 0 as S -t3 to .S C t- -. t. ei O ^ PSOPhO ^ g >o ©1 0 0 0 OCI-10000 u — ' ©1 ©< — ' ©1 ft ■a j gto© CO 0 0 a S CO t^ 1© »© >© a t.p©J p©5 7* 0 0 0 ft S H «! $ p. O -H OS CO ©1 S ©1 0 ©i 0 0 ft J.O O O O O ft a— tjimoc 0 g— . -* CO cc 10 « ^O co ■<# m cx> O ftrt ^j = OS iOOO!(N *w «os 00 co to -* # ©) O r- Pm t, -h »f OS tO — 1 » co ©1 ©1 ©i ©i ft "aio — 1 0 OS to gt- cp p p >p £ t-O t^ to O ©1 » ■* CO CO CO CO ft 0 5 0 to •d to 3 a • • .as -o .gS y £> S T3 C - t- s u -g 3 b rt C Q w Pu O 308 OTHER MILK PRODUCTS. Steiben gives the following figures for Roquefort cheese : — Water. Fat. , Insoluble 1 Soluble Asn. Proteids. Proteids. Fresh, . Month in cellar, Old, Per cent. 49 66 36 93 23 54 Per cent. 27-41 31*23 40-13 Per cent. Per cent. 1-74 13 72 4-78 5()2 6 27 8 53 er cent. 6 93 20-77 18-47 It is seen that comparatively few analyses are available, and that they are insufficient to allow any definite conclusions to be drawn as to the connection between chemical composition and degree of ripeness. Heavy Metals in Cheese. — The presence of copper has been noted in cheese by Besana ; it is derived from the use of copper vessels. Stoddart has found metallic lead in Canadian cheese ; its presence appeared to be accidental. Allen and Cox have drawn attention to the use of sulphate of zinc in cheese manufacture ; this is called "cheese spice," and is used to prevent the formation of gas in the cheese by fermentation. The Ripening" Of Cheese. — The work of Freudenreich, Lloyd, Duclaux, Bochicchio, and Babcock and Russell has shed much light on the nature of ripening. Role of Micro-Organisms. — When the curd is precipitated by rennet it carries down with it the bulk of the micro- organisms present in the milk. The first of these to develop are the lactic acid organisms, which increase rapidly and trans- form the milk-sugar into lactic acid. Freudenreich and Lloyd have both come to the conclusion that these organisms arc the chief, if not the only, factor in the ripening of cheese. While it cannot be denied that they have some influence, it is hard to realise that lactic acid bacteria, which when grown in sterilised milk do not convert the proteids into albumoses and amido- compounds, should acquire this property in cheese. It appears to be an established fact, however, that the lactic acid organisms develop, rise to a maximum, and then gradually diminish. The acid they produce appears to be inimical to the growth of other Organisms. The ripening of cheese goes on concurrently with the growth of tho lactic acid organisms, and continues at an even rate while the organisms are decreasing. This shows that the ripening of cheese is not due to the direct action of micro- organisms. R61e of Enzymes. — Duclaux has recognised this, and attributes the ripening of cheese to enzymes (called by him "diastases") secreted by various organisms to which be gives the name Tyrothria; the enzyme would remain and be active alter the Organisms had died off THE ANALYSIS OF CHEESE. 309 Babcock and Russell have quite recently shown that milk itself contains a peptonising enzyme. By treating milk with a quantity of an antiseptic, such as chloroform, to check all microbial action, they found that a digestion of the proteids was still going on. They have isolated the enzyme from milk, and, finally, have prepared cheeses, which have been ripened under aseptic conditions. Though perfectly sterile, these cheeses show that the proteids are converted into albumoses, peptones, and amido-compounds just in the same manner as in normal cheeses. Babcock and Russell conclude that the action of the natural enzyme of milk is the chief factor in the manufacture of cheese, and consider that Freudenreich and Lloyd have been misled. The true part played by micro-organisms in cheese is probably the production of compounds in small quantities which give the characteristic flavours to the cheese. The Analysis of Cheese. A complete analysis of cheese includes determinations of the water, fat, ash, salt, proteids, primary products of ripening (as albumoses and peptones), secondary products of ripening (such as amido-compounds, ammonia, and nitrates), and lactic and fatty acids ; also, when present, milk-sugar. Few, however, of these determinations can be made with accuracy, though results which are of great utility can readily be obtained. In addition to the determinations mentioned, the fat may be examined as to its genuineness, and the proteids as to their digestibility. The earlier methods of cheese analysis consisted of the esti- mation of water, by drying at 100° C. (212° F.) to constant weight ; of fat, by extracting with ether ; of ash, by ignition ; and of casein, by difference ; this method has the advantage of simplicity, but gives no information as to the changes that have taken place during ripening. The following method will give fair results, and is easy of execution : — Richmond's Method— Water, Fat, and Ash.— Three to five grammes of cheese are weighed into a wide platinum dish and dried in the water-oven till the fat begins to run away from the cheese. The basin is then turned up, so that the fat collects at one side, and the drying continued for an hour or so. It frequently happens that no fat runs away from the cheese; in this case the turning up of the basin may be dispensed with. The basin is then removed from the oven, and treated several times with ether to remove the fat. The ethereal solution is collected in a flask, the ether evaporated, and the fat dried and weighed. The basin and its contents are replaced in the water- oven, and the residue dried to constant weight. The combined weight of the fat and residue subtracted from the original weight 310 OTHER MILK PRODUCTS. gives the water. It will be found that the removal of the fat facilitates drying, but it is difficult to remove the whole of the fat in this manner. The residue may now be incinerated at a low red heat, and the ash weighed ; in this the salt may be estimated by solution in water, and titration with silver nitrate solution, using potassium chromate as indicator. It is advisable to make a separate estimation of the fat. This may he done by Short's method, which consists in grinding up a few grammes of cheese with twice its weight of anhydrous copper sulphate, and extracting the mixture with ether in a Soxhlet extractor. Schleicher and Schull's thimbles are very convenient for holding the mixture. The Werner-Schmidt method is also applicable. To 2 or 3 grammes of cheese 5 c.c. of water and 10 c.c. of strong hydrochloric acid are added, and the whole boiled with constant shaking till all, except fat, is dissolved. The solution is cooled, about 25 c.c. of ether added, and the tube well shaken. After complete separation, as much as possible of the ether is drawn off, and a fresh portion added. After four or five repetitions of the same process, the extraction of fat is complete. The combined ether extracts are then evaporated, and the fat weighed. Proteids and the Products of Ripening. — About 10 grammes of cheese are well ground up in a mortar with ten successive portions of 20 c.c. each of hot water, the aqueous portions being poured off into a 250 c.c. flask. The grinding should be as thorough as possible, every lump of cheese being well crushed. After cooling, the solution should be made up to 250 c.c. and filtered. Twenty-five c.c. of the filtrate should be evaporated in a platinum basin on the water-bath, and dried in the water-oven to constant weight. This may be termed the " total soluble extract." The residue may he incinerated at a low red heat, and the ash of the soluble extract weighed. Twenty-five c.c. of the filtrate are diluted to about 100 cc., 5 c.c. of a solution of copper sulphate solution added (3 1 64 grammes to 500 c.c), and caustic soda solution added, drop by drop, till the precipitate settles in the form of curd, and leaves tin supernatanl liquid quite clear. After standing for some time, the precipitate is collected on a Gooch crucible, washed with water, and dried at 120° C. After weighing, the crucible is ignited, and the residue of copper oxide and phosphate weighed. The difference between the two weights may be taken as "primary products of ripening." The difference between this figure ami that of the "total soluble extract," less the ash, may be taken as ''secondary products of ripening." The difference between the "total soluble extract," less ash of Soluble extract, .uid the "solids not fat," less total ash, may be taken as proteids. THE ANALYSIS OF CHEESE. 311 The above method will be found to be fairly rapid and to give an insight into the composition of the proteid matter of the cheese. The separations between the different classes of proteid substances are, however, arbitrary. Thus it is assumed that all the insoluble "solids not fat" consist of proteid, and that all the products of ripening (and nothing else) are soluble. The dis- tinction between primary and secondary products of ripening is based on the assumption that primary products are precipitated as basic copper compounds, while secondary products give soluble compounds under the conditions given above. In the present state of knowledge it is impossible to identify and separate all the products of ripening ; therefore empirical methods which yield comparative results are necessary. Stutzer's Method. — If it be desired to obtain further in- formation, the method given above may be elaborated by some of the methods detailed below. Stutzer has recently published a study of the methods of cheese analysis, of which the following is an abstract.* Ash and Mineral Matter. — From 10 to 15 grammes of the cheese are burnt (preferably in a muffle) in a platinum basin. The weighed ash is dissolved in 250 c.c. of water and an aliquot portion used for the determination of chlorine (calculated to sodium chloride). The portion insoluble in water may also be dissolved in dilute hydrochloric acid and made up to 250 c.c; in a mixture of equal aliquot portions of each of these solutions the calcium and phosphoric acid may be determined. Water. — A weighed quantity of the cheese is mixed with washed, ignited, and sifted quartz sand. For most cheeses the proportions of 100 grammes to 400 grammes of sand are satisfac- tory, but with very rich cheeses 500 grammes of sand are taken. This sand mixture is used in all the estimations. For the deter- mination of the water, an amount of the mixture corresponding to about 3 grammes of cheese is dried to constant weight in the water-oven. Fat. — The dry residue from the water-determination is ex- tracted for twenty-four hours with water-free ether, which has been dried over sodium. Nitrogen — I. Total Nitrogen. — Ten grammes of the sand mixture are analysed by Kjeldahl's method (p. 105). II. Applicability of Copper Hydrate to the Precipitation of Albuminoids. — Formerly, Stutzer employed copper hydrate to separate proteids and their primary cleavage products from secondary products (amido-compounds, &c). He has since found that it only partially precipitates trypto-peptones (pancreas- peptone), and, extending his experiments to cheese, finds that there is sometimes a peptone present which is not completely precipitated. * Taken, with but slight alterations, from The Analyst for January, 1897. 312 OTHER MILK PRODUCTS. III. Phospho-tungstic Acid as a Precipitant. — The con- clusions of Bondzynski that phospho-tungstic acid is a suitable separating agent are confirmed. By its means the proteids and their primary cleavage products (albumoses and peptones) are separated from tlie secondary products (phenyl-amido-propionic acid, leucine, tyrosine, and other amides) and ammoniacal com- pounds, all of which Stutzer classes as worthless. The substances belonging to the first group may be further divided into — (a) Indigestible nitrogenous matters ; (b) Albumoses and peptones soluble in boiling water ; and (c) Proteids insoluble in boiling water. IV. Nitrogen in the Form of Ammoniacal Salts. — An amount of the sand mixture corresponding to 5 grammes of cheese is mixed with 200 c.c. of water and the ammonia dis- tilled, after the addition of barium carbonate. Magnesia and magnesium carbonate cause a partial decomposition of the amides. The author prefers to operate on a portion of the hot- water extract. V. Nitrogen in the Form of Amides. — This is taken to be the nitrogen belonging to those compounds in the cheese which are not precipitated by phospho-tungstic acid, and which are not ammoniacal compounds. An amount of the sand mix- ture, corresponding to 5 grammes of cheese, is mixed with 150 c.c. of water, and well shaken for fifteen minutes in a closed vessel. After standing for fifteen hours at the ordinary temperature, 100 c.c. of dilute sulphuric acid (1 vol. : 3 vols, water) are added, and phospho-tungstic acid so long as a pre- cipitate results. The liquid is filtered, the precipitate washed with dilute sulphuric acid until the filtrate amounts to 500 c.c, and the nitrogen is determined in 200 c.c. of tins. By deducting from the amount that previously found as ammoniacal nitrogen, the nitrogen present in the form of amides is found. VI. Indigestible Nitrogenous Substances. — The fresh mucous membrane of six pigs' stomachs is cut into small fragments and mixed with water and hydrochloric acid in a wide-necked flask in the proportion of 5 litres of water and 100 c.c. of 10 per cent, (by weight) hydrochloric acid to ea h stomach. At the same time, 2.1 grammes of thymol dissolved in alcohol are added as a preservative. The mixture is left for twenty-four hours, with occasional shaking, and then filtered through flannel, coarse paper, and fine paper successively. It necessary, the amounl "t hydrochloric acid in the extract is brought to exactly - per cent. As thus prep ired. the irastiic juice remains unaltered for months. Band mixture, containing •"> grammes ot cheese, is deprived of of Cheese (Stutzer). Camembert. Swiss. Gervais. Per cent. Per cent. Per cent. 50 90 33 01 44 S4 Fat, 27 30 30 28 36 73 Organic solids not fat, 18 66 31-41 15-48 Ash, The ash contained — 314 5-30 2-95 Calcium, ..... •03 1-56 •14 Phosphoric acid, .... •76 •82 •23 Sodium chloride, .... Total nitrogen, .... 2 21 1-56 •76 2-900 5 072 1 -923 Nitrogen as ammonia, •386 •188 •031 ,, amides, 1117 •459 •099 ,, albumose and peptone, . •ssr, •4:;.-. •298 ,, indigestible matter, •115 •119 166 ,, digestible proteids, Percentage of proteids dissolved by •397 3 871 1-329 gastric juice in 30 minutes, . 100 68 52 Percentage of proteids dissolved by gastric juice in 60 minutes, . 100 91 75 100 parts of nitrogen were present in the following forms : — As ammonia, ..... 13 0 3-7 1-6 ,, amides, ..... 88fi 9 0 5*2 Ibumose and peptone, 30-5 8-6 l.v.-, ,, indigestible matter, 4 0 2-4 8*8 ,, digestible proteids, I l-ii 76-3 69-1 The above analyses expressec 1 accord in g tn the uitlior's method give — Water. ...... .-.<>•'. in 88*01 14*84 I'.l 27 ::" 30-28 36 ::: :: I I 5-80 2*95 Proteids, ...... 3-27 25-46 12-78 Primary products of ripening,. ;, i:t 2-77 I'M ondary .. .... '.i 78 817 ■84 THE ANALYSIS OF CHEESE. 315 Table LIX. gives the results of the analysis of three varieties of cheese to illustrate the results of Stutzer's investigation. The nitrogen in the proteids multiplied by 6*38 will give, with fair accuracy, the amount of the proteids ; the nitrogen of the albumoses and peptone multiplied by 6-38 will approximate nearly to the amount of primary products of ripening. The author has calculated from the nitrogen given in Stutzer's analysis the proteids, primary and secondary products of ripening, in order to compare the method given above with that previously described. For most practical purposes the author's method will give as much information as that of Stutzer, if the following facts are borne in mind: — (1) The ripening of a cheese is shown by the proportion of primary and especially secondary products ; and (2) the digestibility of a cheese increases with its ripeness. Dliclaux's Method. — Duclaux has proposed the investiga- tion of the fatty acids developed by ripening as a means of judging a cheese. The-following are the methods used by him : — Water, Fat, Alcoholic and Aqueous Extracts. — 20 grammes of sand which has been previously dried, sifted, and ignited, are weighed out, and about seven-eighths are placed in an enamelled mortar ; 2 to 3 grammes of cheese, accurately weighed, are ground up with the sand to form a homogeneous mass, which should become nearly pulverulent. The mixture is introduced into a small calcium chloride tube, fitted with a plug of asbestos to prevent loss, and the basin rinsed out with the remainder of the sand. The tube with its contents are weighed, and placed in a bath heated to 50° or 60°, and a current of dry air passed through for some hours. After cooling, the tube is weighed and the loss noted as water. The fat is now extracted by carbon bisulphide (other solvents, such as ether or chloroform, may be used), the tube again dried and weighed, and the amount of fat deduced by difference. The tube may be similarly exhausted by alcohol, hot or cold water, and the loss of weight noted after each extraction. Ash and Salt. — A fresh portion of cheese is weighed out into a platinum basin, and ignited to obtain the ash ; in this, the chlorine is titrated with standard silver nitrate, using potassium chromate as indicator. Proteids and Products of Ripening. — About 10 grammes of cheese are weighed and intimately mixed in a mortar with about 10 c.c. of water; a very homogeneous paste is formed, and this is left for half an hour to ensure the perfect contact of the water with the solid matter. More water is added, little by little, the mixing in the mortar being continued till 100 c.c. has been added. The mixture is now filtered through a porous porcelain filter by means of reduced pressure ; in several hours 60 to 70 c.c. can be obtained. 316 OTHER .MILK PRODUCTS. Ten c.c. are evaporated in a platinum basin, the residue dried at 100°, weighed, then ignited, and the ash weighed. The difference will give the organic matter ; this is termed by Duclaux "caseone," and represents the products of ripening. The percentage may b; calculated with approximate accuracy, by multiplying by 100 + the weight of water in the amount of cheese taken, and dividing by one-tenth of the weight of the cheese. The remainder of the filtered liquid (50 c.c.) is brought, by the addition of water, to 150 c.c, and distilled into standard acid, to determine the free ammonia ; this determination is not very exact as ammonia is gradually liberated as the distillation proceeds ; hence it is usual to stop the distillation when 75 c.c. have distilled over. A little calcined magnesia suspended in 25 c.c. of water is next added, and about 50 c.c are distilled into standard acid for the estimation of combined ammonia. The residue in the distilling flask is rendered acid by the addition of a little sulphuric acid, and made up to 55 c.c. ; 40 c.c. are distilled oil', and the volatile acid received in standard alkali. The acid is calculated as butyric by multiplying the N number of c.c. of— alkali used by the factor "00975 (this lactor assumes that 90-2 per cent, of the total acid will be obtained under these conditions). He gives the following analyses : — Curd Two Days Old. CantaJ Cheese in B 1 condition. Old Cantal Cheese. Per cent. Water, 40 "7 Fat, 301 Proteids (insoluble), . . 20'0 ,, (soluble i>ut not ul- tra 1 .1.0, . . 4"1 (filtrable), . . : 4"3 Salt -8 Ammonia total, ... Volatile acids (as butyric), . Per cent. 44"4 23 9 13-7 8-3 :■•_' 2 5 Per cent. 36-26 34 70 1 1 09 13-60 2-23 ■90 ■27 Volatile Acids. The following proportions of volatile acids per 100 of fat are instructive: — 'i curd, ....... -04 per cent. Curd five days old, ..... "66 ,, .. eighl ' 2-33 Cheese from the Bame curd I w o months old, . 3 o • .nii.il chi ...... 3*2 lit from above rani id after one month, . 9'2 Salei i ■ hi • ■ I bittei . . . . s '8 ">dl. 2*0 < Iheese fivi l, . . . . . 71 - ADULTERATION OF CHKESE. 317 Devarda'S Method. — Devarda recommends for the deter- mination of water that about 10 grammes of finely-divided cheese should be dried in vacuo over sulphuric acid for twenty- four to thirty-six hours, and then for two to six hours at 100° C. until the weight becomes constant. In this way the bulk of water is removed at the ordinary temperature, and, whilst the method is fairly quick, there is no material loss of organic matter, such as occurs with long-continued drying at 100° C. Complete drying in vacuo is too tedious and often impracticable. The following examples show the accuracy of this process : — Name of Cheese. Loss of Water per cent Water per cent. •24 hours hi vacuo. A second 24 hours in vacuo. 3to6hrs. at 100°. Total. Dried at 100° C. Dried in vacuo. Romadur, Limburger, . . Gervais, . . . Limburger, . . (air-dried). 46 24 37-79 47-98 11-10 2-24 112 311 09 1-36 217 51-59 39-00 49 25 13 27 5192 39 38 • 49-36 1346 51-50 38-98 1 49 10 Adulteration Of Cheese. — The only forms of adulteration of any importance consist in the substitution of skim milk cheeses for whole milk cheeses, and the addition of fat not derived from milk to skim milk before making it into cheese. The former adulteration is detected by the estimation of fat and total nitrogen. In a whole milk cheese the ratio fat . . — : ttwz varies from 1 to 1*0: in a skim milk cheese total nitrogen x 6- I turbidity! nitrate, . . . . \ none. Behaviour with milk, not curdled. not curdled. not curdled. Ash, . . . per cent., •025 •048 •032 Junkets. — This preparation is made by adding cane-sugar to milk and curdling by rennet at a low temperature. It is a sweetish gelatinous substance, and is usually eaten with nutmeg and cream. Proteid Compounds. — The following products derived from casein are commercial substances : — Lacto-Somatose. — This consists of albumoses derived from casein by heating with superheated steam. Sanose. — A mixture of 80 per cent, casein and 20 per cent, albumoses. Nutrose. — The sodium compound of casein. Eucasin. — The ammonia compound of casein. Argonin. — The silver compound of casein. Lactoform consists essentially of casein precipitated by metallic salts and subsequently hardened by formaldehyde. It is employed in place of horn, ivory, ebony, amber, ■ tab. Proteid*. Starch. UUk-Sugar. Substances. i' Per caul i Percent. Percent. Percent, Percent. 5-93 25-91 B'02 19*50 B#70 ll"70 26 24, COMPARISON OF THE FAT OF DIFFERENT ANIMALS. 321 CHAPTER VIII. THE MILK OF MAMMALS OTHER THAN THE COW. Contents.— Classification of Milks— Human Milk— The Milk of the Buffalo — the Gamoose - the Ewe — the Goat — the Mare — and the Ass — Milk as a Food and a Medicine — As a Food for Infants. Classification. — Broadly speaking, the milk of all mammals may be divided into classes as under : — (1) Milks forming hard curds with rennet. This class includes the milk of the ewe, buffalo, goat, and cow. (2) Milks forming a very soft, or no, curd with rennet. In- cluded in this class are human milk, and those of the ass, mare, and mule. The composition of milk of all mammals, on the whole, re- sembles that of cow's milk — i.e., they all contain fat in the form of globules, sugar, proteids, and mineral matter. Marked differ- ences, however, occur in the composition of these bodies. Comparison of the Fat of Different Animals. — (a) Size of Globules. — The following table (LXI.) gives the results obtained by Pizzi : — TABLE LXI. — Size of Fat Globules in Mammalian Milks. Relative Number of Globules of the Sizes Named. Name of Mammal. •0127 mm. •0109 mm. •0090 mm. •0072 mm. 1 0054 mm. •0033 mm. •OOlSmm. •0009 mm. Woman, 0 o many many medium few v. few v. few Ewe, . . o few o medium > j medium few J5 Goat, . . v. few v. few few few >> > ? medium 3> Cow, . . . o o medium many ?) 5> v. few ,, Rabbit,* . many many few few v. few v. few v. few v. few Ass, . . . 0 v. few v. few many medium medium v. many j ? Mare, . . o i) medium medium few many many » » Sow, . . . o o v. few v. few ; v. few medium v. many many Bitch, . . o o many many medium j> v. few v. few Cat, . . . o o few few ,, few 5» >> Mouse,*. . many- many >> >> >) v. few >> > i The milk of the rabbit and mouse contained globules up to -01S1 mm. in diameter. 21 322 THE MILK OF MAMMALS OTHKK TIIAN THE COW. (6) Composition of Fat. — The following table (LXII.) gives the comparative figures for the composition of the fat of various mammals : — TABLE LXII. — Properties of Mammalian Fats. Name of Mammal. Melting Point. Solidifying Point. Reichert- Wollny Figure. Insoluble Fatty Acids. Refractive Index. Per cent. Woman, . 32° 22-5° 1-42 51-9° Ewe, 29° 12° 26-7-32-89 Goat, 30-5° 31° 26-1-28-6 Buffalo, . 38° 29° 25-4-39 Cow, 20-0-34 86 to 90 f43-7;-49-0° \ mean 46 5° Rabbit, . 16 06 Ass, . 13 09 Mare, 11-22 Sow, 28° 12° 1-65 Bitch, 1-21 Cat, . 4-40 Mouse, 2-97 I A sample examined by Allen contained 5'C 6 per cent. Porpoise, . 1 of volatile acid, having a mean combinin g weight of y 1047, and agreeing with valeric acid (m. c.w. 102) in ' its properties. Sugar. — The author has proved that the sugar of the milk of goat, the ass, and the gamoose (in summer) contains milk-sugar. With Pappel the author obtained analytical figures which showed that the sugar of the milk of the gamoose in winter differed from milk-sugar, and with Carter that the sugar of human milk did not correspond with milk-sugar. It is probable also that the sugar of mare's milk is not identical with milk- sugar. Proteids. — But little is known of the proteids of milk. It appears probable that the curd-forming milks contain the same proteids as cow's milk. The milks which do not form curd may differ in their proteids, but it is possible that the different reaction with rennet is due to a deficiency of lime, or to an alkaline reaction. The following milks have an alkaline reaction: — Human milk, the milk of the marc, ass, rabbit, sow, and cat. Composition of Milk. — Tabic LXII I. gives the mean composition of the milk of different mammals. Of these milks those of the cow, -oat, sheep, bullalo, mare, ass, and, in some countries (-.'/., Spain), sow are used for human consumption, ami, with tl xeeption of that of the sow, are HUMAN MILK. 323 worthy of a more detailed notice. Human milk, the natural food of infants, will also be dwelt on. TABLE LXIII. — Composition of Mammalian Milk. Water. Fat. Sugar. Per cent. Casein. Albumin. Ash. Per cent. Per cent. Per cent. Per cent. Per cent. Cow, .... 87 10 3-90 4-75 3-00 •40 •75 Goat, . 86 04 4-63 4-22 3 49 •86 76 Ewe, . 79 46 8-63 4-28 5 23 1-45 97 Buffalo, 82 63 761 4-72 3-54 •60 90 Woman, Mare, . 88 89 2 80 3 3 117 6-8 6 89 1-0 •5 2 30 1 84 Ass, Mule, . 9U 91 12 50 1-26 1-59 6-50 4-80 1-32 | -34 46 38 1-64 Bitch, . 75 44 9 57 3 09 6-10 5-05 73 Cat, . Babbit, 81 69 63 50 3 33 10-45 4-91 1-95 312 596 2 58 56 15 54 Llama, Camel, . 86 86 55 57 3'15 3-07 5-60 5-59 3 00 | -90 80 77 4-00 Elephant, 67 85 19-57 8-S4 3-09 65 Sow, . 84 04 4 55 313 7 23 1 05 Porpoise, Whale, 41 48 11 67 48-50 43-67 1-33 11-19 57 46 7-11 Human Milk — Appearance. — In appearance human milk has usually a chalky white, somewhat watery appearance ; some specimens, usually those high in proteids, have a marked yellowish tint. A red coloration, due to blood, has been noticed by Carter and the author. Properties. — The fat globules, according to Pizzi, vary in size from -009 mm. to "0009 mm. Carter and the author have observed also that they are, on the whole, smaller than those of cows' milk. The taste is rarely, if ever, sweet, but rather saline. The reaction to litmus paper is almost always alkaline. Composition. — Human milk appears to be more variable in its composition than that of the cow. This is probably due to the fact that, while the cow is forced to adopt regular habits and leads a life which is very regular, the many occupations and duties of woman do not permit of this. Table LXIV. gives the mean composition of human milk according to recent observers. 324 THE MILK OF MAMMALS OTHER THAN THE COW. TABLE LXIV. — Mean Composition of Human Milk. Leeds.* (64) Pfeiffer. (160) Luff. (12) Johanssen. (25) Carter and Richmond. (90) Lehmann. (40) Per cent. Per cent. Per cent. Per cent. Per cent. Per cent. Water, 86 69 88-22 8851 SS-H4 87-3 Fat, . 416 3-11 2-41 3-21 3-07 3-4 Sugar, 6 95 6-30 6.39 4-67 6-59 ti-4 Proteids, 2-02 1-94 2-35 1-10 1-97 1-7 Ash, . •22 •19 •34 •26 •2 TABLE LXV. — Variations in Composition of Human Milk During Lactation. Refrac- tive Water. Fat. Sugar. Proteids. Ash. Per ct. Index of Fat at 35°. Per ct. Perct. Per ct. Per cent. Colostrum (Pfeiffer), 85-75 2-38 3-39 8-60 •37 Milk that did not agree (C.tfci?.), 88-11 2-95 6-28 2 36 •31 54-3° Normal Milk, 4 to 6 days ,, 88-01 2-97 6-47 2-25 •30 53 2° ,, ,, 7 to 14 ,, ,, 88-21 3*06 6-62 1-85 •26 51-5° „ 15 to 29 „ „ N7-71 3-42 6-95 1-67 •22 51-4° ,, ,, over 30 ,, ,, 88-53 3 00 6 83 1-43 ■21 51-7° First Month (Pfeiffer), . 88-18 274 5-77 2-98 •_'• Second ,, ,, 88-22 3*37 6-33 2-04 •18 Third 88-90 2-71 6-43 1-99 18 Fourth ,, ,, 87-56 3*91 6 89 1-77 15 Fifth ss-77 3-36 7 33 1-45 •19 Sixtli ,, ,, ss-.si •_'■:«.) 6-83 154 •23 Seventh ,, ,, 89-43 3-28 6-89 1 -63 •is Eighth ,, 88-49 3-36 6*31 1-69 •16 Ninth s«. >■■_'.-. 2 41 6-62 1-54 •17 Tenth ,, „ st-7'.i 1-22 6-24 1-71 14 Eleventh ,, ,, 87*92 :{•">!» 6-66 1-47 •14 Twelfth ,, 86-71 5-30 6-09 1 -73 •16 Thirteenth ,, ,, 88-66 2-94 6-68 1-65 •15 ' Leeds gives the average composition as : — Water, 86-733 per out. 1-181 Sugar, ...... 8*986 Proteids, ...... l-.l!).-, „ Ash -Jul His figure , however, '1" QOt agree with tin- average deduced from his analyses, There i- internal evidence thai bis analyses are no1 so reliable as the other series and comparatively little weighl must be given i" bis i i four sample derived trom eighty women, some oi in int|i|. being the mixed mill* "t iui women. HUMAN MILK. 325 Water. Fat. Sugar. Proteids. Ash. 1st to 11th day (Leeds), 11th to 31st ,, „ 31st to 91st ,, ,, Over 91 days, ,, Per cent. 86-49 86 60 86-99 86-51 Per cent. 4-28 3-90 3-97 4-44 Per cent. 6-67 7-06 6-99 7-09 Per cent. 2 32 2-01 1-80 1-76 Per cent. •23 •20 •21 •22 Variation with Lactation. — There exist several series of analyses in which the time which has elapsed since parturition has been noted. Of these, the results of Carter and the author represent normal milks, those which disagreed with the child in any way having been excluded. The Tables due to Pfeiffer and Leeds contain all the analyses made by them without any eliminations (Table LXV.). Probable Mean Composition. — From the above results the following probable composition may be deduced for normal human milk after lactation has become regular : — Water, . . . . . . . • 88 "2 per cent. Fat, 33 Sugar, . . . . . . 6 "8 ,, Proteids, . . . . . .1*5 ,, Ash '2 Variation of Constituents. — The following maxima and minima have been found : — Per cent. Per cent. Fat, . . 9-05 (Pfeiffer), •47 (C. andR.) Sugar, . 8-89 (C. and R.), 4-22 (Pfeiffer). Proteids, . 5-56 (Pfeiffer), •85 (Leeds). Ash, . . -50 (C. and R. ), •09 (Pfeiffer). Composition Before and After Suckling. — The average composition of 37 samples taken before and 37 samples after suckling was found by Carter and the author to be — Before Suckling. After Suckling. Water, .... Fat, Sugar, .... Proteids, .... Ash Per cent. 88-33 2-89 651 1-99 •28 Per cent. 88 04 3-18 6-53 1-99 •26 In one case, where the secretion was excessive, the analyses before and after suckling were practically identical ; in another, where a very deficient supply was given, the fat differed greatly. 326 THE MILK OF MAMMALS OTHER THAN THE COW. Excessive Secretion. Deficient Secretion. Before After Before After Suckling. Suckling. Suckling. Suckling. Per cent. Per cent. Per cent. Per cent. Water, .... 87-40 87-36 90 59 87-65 Fat, .... 3-12 312 •98 4 07 Sugar, .... 6 68 6-70 6 52 6 31 Proteids, 249 2-51 1-71 1 77 Ash, .... •31 •31 •20 •20 In 15 cases the fat was higher before suckling than after suckling, and in 21 it was lower, while in 1 case it was identical. The cases in which the fat was higher before suckling than after were generally when the mother was in a prone condition, indi- cating that the separation of cream was largely mechanical. Comparison with Cow's Milk. — The following differences in composition of the various constituents from that of the cow have been noticed : — ]?at. — This is very low in volatile acids (see p. 322). It appears to contain free fatty acids ; Leeds noted that many of the fats extracted from the copper-proteid precipitate obtained by Ritthausen's process were tinted green ; Carter and the author confirmed this, and found the following percentages of copper oxide (CuO) in the fats thus extracted : — ■J-Sil 1-2! •87 •62 ■30 The copper could be easily removed by shaking witli dilute hydrochloric acid, and the fat behaved to copper salts in every way as if it contained free fatty acids. Carter and the author found the refractive index to vary from 58-4° (in a milk which upset the child, which finally died in convulsions) to 482° (in a milk on which the child throve remarkably well). The analyses of these two samples were : — Water. Fat. Sugar. Prottiils. Ash. Refractive Index. Per cent. VI-;, ( 87-1 Per ci nt. •87 3-96 Per cent. 519 711 Per nut. 1-02 I -6 1 Per cent. ■38 ■20 :.si (s.._. Sugar. — Carter and the author found that the sugar crystal- lised in rhomboid plates (nol the wedge-shaped crystals of milk-sugar), and had a specific rotatory power <>| ["|,, 18*7*. The sugar was estimated by difference in the milk, as it was found that polarisation and estimation by Fehling's solution MILK OF THE BUFFALO. 327 did not give satisfactory results. It was found that the gravi- metric results were from -56 to -98 per cent, below the difference, and averaged -71 per cent, below, while the polarimetric results were from -85 to 2-22 per cent, below the difference, and averaged 1*30 per cent, below. It was noted that by precipitating the sugar crystallised from water with dilute alcohol an amorphous substance separated, soluble in water. The [a]D of the organic solids of the mother liquor from which the sugar was crystallised was 26 '8°. These facts seem to indicate that more than one sugar was present. Proteids. — The proteids differ from those of cow's milk by not giving a curd with rennet, and by giving a much finer precipi- tate with acids. By the addition of calcium phosphate they can be made to approach much more nearly in behaviour to those of cow's milk. The proteids of human milk are not precipitated by copper sulphate from a solution neutral to phenolphthalein, but require a further addition of alkali ; the precipitate thus obtained yields a black ash, while the proteids of cow's milk precipitated from a neutral solution leave a green ash. Mineral Matter. — Harrington and Kinnicutt give the fol- lowing mean composition of the ash : — Per cent Unconibined carbon, •71 Chlorine, CI, . 20-11 Sulphurous acid, SO2, . 4-38* Phosphoric acid, P-,,05, . 10-73 Silica, SiO-2, . •70 Carbonic acid, C02, 7-97 Iron oxide and alumina (FeAl)203, •40 Lime, . . 15 69 Magnesia, 1-92 Potash, . 29-84t Soda, . . . . . 12-39t 104-85J Less oxys mn = chlorine 4-53 100-31J The presence of citric acid has been established, and is about •1 per cent. Bechamp describes a starch-hydrobysing enzyme. The author has established the presence of a proteolysing enzyme analogous to that described by Babcock and Russell in cow's milk. The Milk Of the Buffalo. — This has been examined in Europe by F. Strohmer, W. Fleischmann, and A. Pizzi. Composition. — They give the composition as — * Given in original as sulphur, 2 -19. t Given in original as potassium, 24 '77 ; sodium, 9*19 ; oxygen, 6*16. X The total is given in original as 100 "54. 328 THE MILK OF MAMMALS OTHER THAN THE COW. Strohmer. Fleisch- mann. Pizzi. Specific gravity, .... 1-0319 1-0339 1-0332 Water, .... per cent. 81-67 82-93 82-20 Fat, ....,, 9-02 7-46 7 95 Proteids, . . . ,, 3-99 4-59 4-13 Milk-sugar, . . . ,, 4-50 4-21 475 Ash, . . . . ,, •77 •81 •97 Strohmer draws attention to the high percentage of fat and the musk-like smell. It is white in colour, and the butter prepared from it has only a slight yellowish tinge. Fat. — The analytical figures for the butter fat are given by Strohmer as — Melting point. Solidifying point. Solidifying point of fatty acids. Potash absorbed. Reichert-Wollny figure. 31-3° 19-8° 37-9° 22*24 per cent. 30-4 c.c. and by Pizzi at melting point, 38*0°; solidifying point, 29-0°; Reichert-Wollny figure, 26 -2. Milk of the Gamoose — Composition. — The composition of the milk of the Egyptian gamoose or water-buffalo, which is the. same as, or very closely allied to, that found in India, South Africa, Hungary, and Southern Europe, has been studied by the author and A. Pappel. The average composition is — Specific gravity, Water, Fat, . Sugar, Casein, Albumin, Salts, Nitrogenous bases, A rise in specific gravity on standing was noticed, amounting to, in 6 hours, -0006 24 horns, -OiKiT One sample, however, showed a decrease. The fat was found to vary from 7'3fi to 5*15 per cent., and the solids not fat from 10-G7 to 1007 per cent. The average percentage composition of the solids not fat was — 'I. .... Proteids, .... Ah < it her nil i moes, Showing a ratio of sugar : proteid 1 -0354 84-10 per cent. 5-56 5-41 3'26 ,, containing nitrogen, •511 •60 •094 1-03 „{ " a*h'. ., •S5 •30 •09 ,, ,, nitrogen, •035 48'fi per ('('lit . ins 8 -2 I ■•"> ., B ih 6 : .r) : 1. MILK OF THE GAMOOSE. 329 The following formula was found to be applicable to gamoose milk :— T = -27 -=? + 1-191 F., indicating that the fat had a density of -934, and the solids not fat had a density of 1-589. The formula ~ = - -761 F + 4 L + 2-5714 P + 7*5715 A (see p. 65) was found to be applicable to the milk of the gamoose. Two series of investigations into the constituents of the milk were made, one daring the winter on milk yielded by a newly- calved gamoose, and the other during the summer on the milk of animals well on in their period of lactation. Notable differ- ences were found. Fat. — The fat gave the following figures on analysis : — Slimmer. Winter. Potash absorption, . . per cent. 23-17 22 04 Insoluble fatty acids, 86-9 87-5 Mean combining weight, 265-0 270 5 Iodine absorption, . per cent. 351 418 Soluble fatty acids, . • 5> 6-99 6 09 (calc. as butyric), Reichert-Wollny figure, . c.c. 34-7 25-4 Iodine absorption of fat, . per cent. 32-0 35-0 A winter sample of fat was found to contain -05 per cent, of sulphur and -01 per cent, of phosphorus. Casein. — The casein was prepared from the winter milk. The purest preparation contained 2-53 per cent, of moisture and -60 per cent, ash, the nitrogen calculated to the pure substance being 14-66 per cent, and the phosphorus -85 per cent. Other pre- parations, which were less pure, gave about 14 -4 to 14-5 per cent, of nitrogen. Though this casein was precipitated three times, and thor- oughly washed with water each time, and finally with alcohol and ether, it was perhaps not pure, as a solution was made in a minimum of caustic soda, and equivalent amounts of sodium phosphate and calcium chloride added • the nitrogen was esti- mated in this and in the precipitates obtained by (1) saturation with magnesium sulphate, (2) tannin, and (3) acetic acid at 40° C. Calling the nitrogen in solution 100, the following amounts were obtained by Magnesium sulphate, . . . . . . 95*2 Tannin, 96 '6 Acetic acid, . . . . . . . 94 -7 Albumin. — The albumin contained 15*75 per cent, of nitrogen, and is probably identical with that of cow's milk. 330 THE MILK OF MAMMALS OTHER THAN THE COW. Citric acid was identified by isolating it and determining the percentage of calcium in the calcium salt. A yellow crystalline mercury compound was isolated from the winter milk in too small a quantity for identification, but was in all probability derived from a nitrogenous basic substance. Sugar. — The sugar was prepared from the winter milk. Two preparations gave the following figures : — Influence on density. 3-94 3 94 ["Id. 48-66 49-10 Cupric reducing Water of power. crystallisation 73-6 4-77 73-9 4-82 Mucic acid was not obtained by oxidation with nitric acid. On treatment with acid the following figures were obtained : — £«1d. 53 74 Cupric reducing power, 101-0 figures approaching those given by dextrose. This sugar evidently differed from milk-sugar, and was named "Tewfikose." A second preparation was made from the summer milk ; it was examined by A. R. Ling and the author, and yielded the following figures. (For the sake of comparison figures yielded by milk-sugar, prepared by the same method, are given.) Gamoose Sugar. Milk-Sugar. 01 , 55-3° 55'1° Cupric reducing power, 79-7 79-5 Influence on density, 8*92 302 Milt bag point, 213° to 215° 214° to 220° Water oi crystallisation . per cent. 5-03 5-00 (calc.) Molecular weight (from freezing point), 341-7 342(calc.) ( larbon, . . per cent. :;:i-7.-> 39-60 Hydrogen, ,, 6-47 6-63 Mucic acid by oxidation with nitric acid, . • 32 32 By heating with phenylhydrazine acetate two compounds were formed— one readily soluble in hot water (melting point, 197°), and the second almost insoluble in hoi water, but Boluble in hot dilute alcohol (melting point, 218 to 219°). These compounds agree with phenyllactosazone and its anhydride. The acetyl derivative prepared by heating with acetic an hydride and anhydrous sodium acetate, and crystallising from alcohol melted al 75° to 80°. When crystallised from a mixture of 90 per cent alcohol and chloroform it melted al 88" to 95°. The solution in chloroform was nearly optically inactive ; if anything, Lightly loevo-rotatory. THE MILK OF THE EWE. 331 A determination of acetic acid in the acetyl derivative gave 71 -46 per cent, as against 70-79 calculated for an octacetyl derivative. The properties of the acetyl derivative agree exactly with octacetyllactose. The birotation ratio was found to be 1/6. All the properties without exception agree with those of ordinary milk-sugar. It appears that the sugar of the summer milk is " lactose " and not " tewfikose." Winter and Summer Milk. — There appears to be a distinct difference between the winter and summer milks, which may be summarised as follows : — Winter. Fat low in volatile acids. Contains "tewfikose." Summer. Fat high in volatile acids. Contains "lactose." The author has tried to find evidence that the sugar called "tewfikose" was a product of the action of reagents used in the preparation of milk-sugar, but has been unable to do so, manv preparations of milk-sugar having been made by the same method (including that from summer milk), always with the properties of milk-sugar. Analyses of the milk used to prepare " tewfikose" only added up to 99*3 percent., when the polarisations were cal- culated as milk-sugar, but gave a satisfactory approach to 100 when calculated as tewfikose. There appears to be no reason to reject the view that "tew- fikose " is a separate entity. The Milk Of the Ewe. — The following composition is given by different authorities : — TABLE LXVI. — Composition of Ewe's Milk. Authority. Water. Fat. Sugar. Casein. Albumin. | Ash. Per cent Per cent. Per cent. Per cent. Per cent. Pizzi, .... 80-42 9 66 437 4-40 1-10 Besana, . 78-23 9 50 5-00 6-26 101 Vieth, . . . 81-3 6-8 4-8 6 3 •s Bell, .... 752 11-3 36 8-8 11 Fleischmann, . 83-0 5 3 4-6 4 6 1-7 •8 (average) >■> 75-40 11-77 3-65 6-47 1-64 1-06 Raden herd) Piccardi, . . 82-46 6-10 3-95 5-56 1-01 9-3 The composition of colostn lm of e1 ive's milk is giv en by Voelcker as — 1 69-74 2-75 8-85 | 1737 1-29 332 THE MILK OF MAMMALS OTHER THAN THE COW. The following figures are given by Weiske and Kennepohl :- TABLE LXVII.— Composition of Ewe's Milk. Time Since Lnmbing. Water. Fat. Sugar. Casein. Albumin. Ash. Non- proteid Nitrogen. Per ct. Per ct. Per ct. Per ct. Per ct. Per ct. Per ct. \ hour, . 47-03 25 04 1-54 4-96 1S-56 119 "_'S 7 hours, 6193 16-14 3-53 7 48 961 •96 11 L9 ., . 76 53 8-87 5-24 5-27 2-93 •86 12 2 ilavs, 82-79 5 93 519 4-28 •82 •87 11 3 „ 82-93 619 4 37 4 54 •92 •95 10 4 ,, 83-48 569 4-31 4 64 •85 •96 10 5 „ 83 90 5 72 4 27 4-18 •60 •92 09 6 ,, 85-22 4-47 4-55 3-88 •70 •88 08 7 „ 84-40 4-61 5 09 4-04 •86 •90 07 8 „ 84-26 4-62 5-31 3 97 •73 •88 10 9 „ 84-39 4-71 541 4-49 •60 •90 •08 The specific gravity varies from 1-035 to L043. Besana gives the following table for correcting the specific gravity to 15° C. : — Temp. Correction. 5° to 10°, . . . Subtract 1-25 + -20 (10 - t )" ■25 (15 - t )° •30 ( / - 15)° 1 -5 + -32 ( t - 20)° 3-1 + -35 ( t - 25)° 4 So + -37 ( t - 30)° according to Besana, from not in accord with Pizzi's 11° „ 15°, 16° „ 20°, . . Add 21° „ 25°, 26 ,, 30°, 31° ,, 35°, The fat globules vary in size, •0047 mm. to -0309 mm. This is observations (p. 321). Sheep's milk throws up no cream if left to rest, owing to its great viscosity. The cream may, however, be removed by a separator, or by dilution with an equal bulk of water. The action of rennet does not differ from that with cow's milk, but the cuni is firmer. The Milk Of the Goat. — The following is the mean com- position given by various authorities : — TABLE LXVIII.— Composition of Goat's Milk. Authority. K;it. Sugar. Casein. Perot 3-20 344 .-!s Albumin. \-h. BLonJ e), Mo er .v Soxnlet, . Bleiflohmann, Aut hor, . Perct. 86-71 36 is B6'7fi B6-78 IVn-t. 1 7s t i:; is 3-78 r. i . t in. i 66 in 3-60 1 -49 Per < t. 1-09 •80 1-2 Perot, •78 •79 •7 •88 •87 8 M 1*10 THE MILK OF THE MARE. 333 None of the constituents differ sufficiently from those of cow's milk to need detailed notice. The fat is, however, very white, and the milk and butter have a smell of the goat. The Milk Of the Mare. — Most of our knowledge of mare's milk is due to Vieth, who carried out an extended series of observations on the stud of mares at the International Health Exhibition in London during 1884. The following is an abstract of his results : — TABLE LXIX. — Composition of Mare's Milk. Water. Per cent. 90-06 90-41 89 74 Mixed milk. Average, Maximum, . Minimum, Milk of individual mares. Average, . . . 90 "13 Maximum, . . . 90-46 Minimum, . . . j 89 '88 Milk of mares specially fed. Average, Maximum, . Minimum, Fat. Per cent. 1-09 1-44 •87 •94 1-18 •62 Sugar. Per cent. 6-65 6-82 6-30 6-98 6-70 7-21 Proteids. Per cent. 1-89 2-11 1-71 1-65 1-76 1-50 Ash. Per cent. •31 •34 •29 •30 •36 •26 89-22 1-48 7 03 1-99 I 89-88 214 7-28 2 20 88-24 1 1-18 6-67 1-70 i •28 •32 •24 j 90-7 1-2 5-7 2-0 92-53 2-45 7-26 3 00 j 89-05 •12 4-20 1-33 Eleischmann gives the following composition : — Average, Maximum, . Minimum, The following composition is also given : — Authority. Landowsky, . Biel, . Vieth gives the following composition of samples of con- densed mare's milk (containing cane-sugar 16 to 18 per cent.) 89-29 1-16 7-32 1-87 90-42 1-31 5-43 2-55 •4 1-20 •28 •36 •29 L, II., III., IV., 26-73 4-77 53-07 13-69 24-04 6-20 55-81 12-17 17-90 12 07 54-88 13-50 IS -80 10-08 54 09 15 23 1-74 1-78 1-65 rso Vieth describes the milk as of a chalky white colour, of sweet, and at the same time somewhat harsh taste, and of aromatic flavour. It had usually an alkaline reaction, the very few exceptions being neutral. 334 THE MILK OF MAMMALS OTHER THAN THE COW. As this milk undergoes alcoholic fermentation very easily, while cow's milk does not, there is reason to suppose that the sugar is not identical with milk-sugar. The Milk Of the ASS. — The milk of the ass is considered hy some authorities (e.g., Tarnier) to approximate more in com- position to human milk than that of any other animal ; it is used to some extent for infant feeding. The following is the composition given by various authorities: Authority. Water. Fat. Sugar. Casein. Albumin. Ash. Duclaux, Author, . Per cent. 90-70 89-77 Per cent. TOO IIS Per cent. 6-54 6-86 Per cent. ■99 Per cent. ■34 Per cent. •43 •45 I- 74 Pizzi has shown that the fat is somewhat low in volatile acids (see p. 322). The author has prepared the sugar and finds that it has a specific rotatory power [a]D = 52"5° (for hyd rated sugar), a bi- rotation ratio of 1"6, and corresponds in every particular with milk-sugar. The milk has a very feeble alkaline reaction ; rennet produces a very soft curd after a long time, and acids give a finely- divided precipitate. On boiling, it has a tendency to curdle and deposit flakes (coagulated albumin ?). It has a white colour and a sweet taste. Milk as a Food and a Medicine.— In considering the food value of milk, two points must be borne in mind ; first, its value in repairing the waste of the tissues ; and second, its value as a source of energy. As a food for infants it is required not only to repair waste of tissues, but to actually build them up. Composition of Constituents. — The following table gives the percentage composition of the three main constituents of milk : — Carbon. Per cent. 75-63 42-11 52-66 Hydrogen. Oxygen. Nitrogen. Per cent. 16-77 Fat, .... Sugar, .... Proteids, Per oent. 11-87 6-43 713 Per cent. 12-50 51-46 22-77 It is seen that fat, is the richest in carbon and hydrogen, proteids next, while sugar occupies the lowest place. Neither fa! nor sugar ean replace proteids, as these compounds form the only source of nitrogen, Pal and sugar being composed of the game three elements may replace each other, bttt it is evident MILK AS A FOOD AND A MEDICINE. 335 that in building up tissues containing high percentages of carbon and hydrogen, fat is a far more advantageous food than sugar. As a food for infants the value of milk largely depends on the fat present, and it is doubtful whether fat can be replaced by sugar without detriment to anabolic processes. As a food for adults, where the tissues are ready formed, milk may be regarded chiefly as a source of energy. From this point of view fat may be replaced by the iso-dynamic quantity of milk- sugar. Heat of Combustion of Constituents. — The following values for the heat of combustion of the constituents of milk are due to Strohmer : — Fats — Butter fat, 9231-3 calories per gramme Other fats, 9500 Sugar — Milk-sugar, . 3950 Cane-sugar, 3955 s> Proteids — Casein, 5858-3 „ ,, Albumin, 5735-2 „ ,, These values assume that complete combustion takes place, and that carbon dioxide, water, and nitrogen are produced. In the case of fat and sugar it may be fairly assumed that an approach to complete combustion takes place in the human body, and that carbon dioxide and water are excreted. The nitrogen of proteids is not excreted as nitrogen, but as com- pounds, of which urea may be taken as the type. Strohmer calculates that 1 gramme of average proteid yields •3428 gramme of urea, the heat of combustion of which is 2537 calories per gramme ; the heat of combustion of the urea from 1 gramme of proteids is, therefore, 869-7 calories, or, in round figures, 15 per cent, of the total heat of combustion. It is necessary, therefore, to deduct 15 per cent, of the heat of combustion of proteids in calculating iso-dynamic metabolic ratios. In round figures, the following will be the calories per gramme developed in combustion of the three constituents in the human body : — Calories. Fat, 9230 Sugar, 3950 Proteids, 4970 These figures are in the ratio of 2*38 : 1 : 1*26. The author proposes to calculate the ratio between the various constituents as follows : — Anabolic ratio — fat : sugar : proteids. ,, , , .. .. fat x 2-38 + sugar + proteids x T26 Metabolic ratio = ■ — A . , . proteids. Instead of the figures 2*38 and 1-26, the round figures 2*5 and 1*25 may be used without appreciable error. The author 336 THE MILK OF MAMMALS OTHER THAN, THE COW. believes that the above ratios will give a truer idea of the proportionate value of different constituents than the usual .... fat x 2-5 + sugar nutritive ratio, which is —t-j . proteids. Food Value. — We may now consider the food value of various milks. The ratios for human milk are — Anabolic ratio 2*2 : 4-5 : 1 Metabolic ratio, . . . • 11*3 For cow's milk — Anabolic ratio, 1*15 : 1*4 : 1 Metabolic ratio, .... 5*54 The marked difference of the two milks, due to the smaller amount of proteids in human milk, is very apparent. It is assumed in calculating these ratios that the constituents are all digestible ; this is approximately true with human milk. The same cannot be said of cow's milk, owing to a difference in the proteids ; the action of rennet, one of the enzymes of the stomach, on cow's milk results in the formation of clots of curd, which are not digested. If the fat has been partially churned in the milk, this also is not perfectly digested. Experiments have shown that children do not derive the most benefit from milk unless the anabolic ratio approximates to 2 : 4 : 1, and the constituents are in such a form that they are as finely divided as possible in the stomach. Milk as a Food for Infants— Artificial Human Milk.— Many preparations of artificial human milk, or humanised milk, are made ; they correspond in composition more or less exactly with human milk. The condition of the proteids necessary to produce a fine state of division in the stomach is attained — (1) By simple dilution with water, and addition of fat and sugar. (2) By removal of casein, and addition of fat and sugar. ('.i) By acting on the milk with a proteolytic enzyme — i.e., peptonising it, anil addition of fat and sugar. (4) By adding a preparation containing diastase and diluting it, and adding fat and BUg Various sugars are used, milk-sugar naturally being the most universally adopted ; while cane BUgar, and maltose, and other carbohydrates, resulting from the diastatic conversion of starch are added. The artificial feeding of children is to a large extent empirical There is strong reason bo believe thai few of the constituents of cow's milk are identical with those of human milk, though closely analogous ; yel i< bas been found that cow's milk suitably modified is an excellent food. MILK AS A FOOD FOR INFANTS. 337 Again, it is found that human milk decreases in proteids as lactation advances. The best results have been obtained in artificial feeding by an exact reversal of this rule. Peptonised Milk. — It is now conceded by the best authori- ties that the use of peptonised preparations is not an advantage, as, though the digestibility of the proteids is increased, it is at the expense of the development of the digestive organs. The value of milk in the treatment of disease lies in the fact that it is readily digestible, especially if diluted or modified so that the formation of hard curd in the stomach is prevented. As an example, it may be mentioned, that during the epidemic of typhoid at Maidstone in 1897, the Aylesbury Dairy Company sent many hundreds of bottles of humanised milk to the hospitals, which gave most satisfactory results, and provided a food which was readily retained and assimilated. Peptonised milk is also used in cases of gastric disorders. Vieth gives the composition of this product as : — Water, 89 -20 per cent. Fat, 3-41 Sugar, 3"80 ,, Casein, ....... "96 ,, Albumin, 07 ,, Albumoses. ...... 1*88 ,, Ash, -68 „ Diabetic Milk. — In cases of diabetes, Ringer has recom- mended a solution of casein in a mixture of salts approximating to those present in milk as supplying proteid nourishment ; and Overend has used a diabetic milk in which the milk-sugar has been almost entirely replaced by lsevulose with success. ~ The author found diabetic milk to have the following com- position : — Water, .... . 90 '50 per cent Fat, . 2-48 Lsevulose, . 441 Milk-sugar, •12 Proteids, .... . 244 Ash, .... •45 „ Koumiss is a remedial agent of great use in gastric disorders and many other diseases (see p. 243). It owes its value to the fact that it is, first, a food of great digestibility ; and, secondly, owing to the presence of alcohol, a stimulant. It is retained in cases where absolutely no other food can be given. 22 338 APPENDIX A. EXPERIMENTAL EVIDENCE THAT THE FAT IN CREAM IS SOLID AT LOW TEMPERATURES. As a means of determining this question the expansion of butter fat was studied, and the expansion of the fat in cream was compared with this. The expansion of a sample of cream was found to be : — Temperature C. True Densities D.-- 4 True Specific Volumes. 142° 1 0019S •99802 20-7° •99865 1 00135 27-9° •99400 1 -00604 38-4° •!'S763 101252 43-1° •98500 1-01523 47T •98245 1-01786 The cream had been left under the receiver of an air-pump for some time, and had stood for several hours at 14-2° C. before the densities were determined. The separated milk (which contained 08 per cent, fat) from the same milk from which the cream was prepared was also examined. Apparent Specific Gravity in Glass Temperature C. " i;|..^ (m glass). 15*3 10375 * 21 :: 1-0361 22 ■ t 1 -035S * 27 •"■ 1 -0342 29 3° i 0336 * :::, fl 10315 * 16 0 1 -0276 .-.i.i. L-0267 * i to eliminate aii bubbles; the experiments marked with an * was taken while the temperatnn eg, the others while it was falling, and 11 n al 16*8* after heating to 60 ; no change ticed. EXPERIMENTAL EVIDENCE. 339 From the above results the following true specific volumes were cal- culated : — Temperature C. Specific Volumes. Specific Volumes (calculated). 14-2° •96451 •96452 20-7° •96600 •96609 27-9° •96824 •96819 38-4° •97191 •97185 43 1° ■97371 •97373 47-7° •97570 •97571 The results were calculated by the formula : — Specific volume = -96203 + "000127 t + -00000335 P. It is seen that the difference is within the limits of experimental error, and a curve may be drawn (Fig. 22) with a bent lath which passes through all the points when temperatures and specific volumes are plotted against each other. It may be concluded that the expansion is regular between 14 2° and 50 "0°, and shows no break in continuity. From the specific volumes of cream and separated milk, that of the fat in cream may be calculated by the following formula : — „ . . , Sp. vol. of cream - -664 sp. vol. of separated milk op. vol. of fat= — — ^ . The following table gives the results thus obtained : — Temperature C. True Specific Volume of Fat. True Density of Fat. 14-2° 20-7° 27 9° 38-4° 431° 47-7° 1-0643 1-0712 1 -0807 1 0928 1 0973 1-1012 •9396 •9335 •9253 •9151 •9113 •9081 On plotting out the temperatures against the specific volumes of cream and of fat it is seen that it is impossible to draw a single curve with a bent lath, which will include all the points, without far exceeding the experi- mental error. In both cases, however, two curves may be drawn, which cut each other at about 32° C. ; the upper includes the three points above 32° C, which lie in a straight line ; and the lower, the three points below 32°, which do not lie in a straight line. No curve can be drawn which will include more than three points. There is conclusive evidence that a change takes place in the density at about 32° C. , and that the expansion, which is perfectly regular above this temperature, is of a different character below. The melting point of butter fat lies at about 32° C. The densities of fat which have been calculated do not necessarily represent the real densities, as they are affected by any error in the fat determination or by evaporation of the cream when exposed in vacuo ; these errors will not, however, affect the relative values appreciably. 340 APPENDIX A. EXPERIMENTAL EVIDENCE. 341 On p. 39 the densities and specific volumes of butter fat are given, and the specific volumes of the fat in cream are interpolated for comparison. Temperature C. Sp. Vol. of Butter Fat. Sp. Vol. of Fat in Cream. Difference. 15 0° 37-8° 39-5° 1-0753 (solid) 1-1041 (liquid) 11056 1-0651 1-0922 1 -0937 •0102 •0119 0119 A series of experiments on the expansion of butter fat in the liquid state were carried out. Temperature C. Volume (in degrees of dilatometer) Sp. Vol. (calculated). 38-5° 42-3° 45-5° 1566-2 1571-4 1575-6 1-0928 1 -0965 1-0995 The specific volumes were calculated by dividing by 1433'07, in order to give figures comparable with those determined for the fat in cream. On plotting out these figures and those for the specific volume of butter fat (corrected by subtracting -0119), it is seen that the whole of those referring to liquid fat lie on the straight line which represents the results above 32°. It is seen then that the expansion of fat in cream above 32° C. corre- sponds exactly with the expansion of liquid fat. It is seen also that the specific volume of fat in the solid state lies very close to the curve representing the points below 32°. Seeing that the densities of fat in cream correspond with the assumption that the fat is solid at temperatures below 32° and that the very marked change in the expansion occurs at the melting point of butter fat, the evidence is very strong and, practically, conclusive. Another sample of cream which had been treated in a similar manner was found to have a density of 1-0009 at 15 '6° C. ; this was heated to 50° C. and rapidly cooled, and its density after half-an-hour's cooling was found to be -9976 at 15 -5°. After a further two hours at this temperature it was found to have contracted very appreciably. From this experiment it appears that when the fat in cream is liquefied it returns but very slowly to its original volume, and it is probable that it remains for some time in the superfused condition and only slowly solidifies. It is by no means improbable that the density of cream which was determined at 14-2° is slightly too low from this cause, and that the reason of the slight divergence of the specific volume of butter fat at 15° C. from the curve is due to the curve being not correct owing to the fat at 14'2° not having assumed its real density. 342 APPENDIX B STANDARDISATION AND CALIBRATION OF APPARATUS. I. Weights. — A good set of weights is a sine qud non in a laboratory ; they should consist of the following : — 100, 50, 20, 10, 10, 5, 2, 1, 1, 1, grammes, and •5, -2, -1, -1, -05, -02, -01, -01 gramme, and some riders each "01 gramme. Select one of the weights, preferably a 10 gramme, as a standard ; mark one of the 10 grammes and one of the 1 gramme with a mark (') by means of a fine steel point ; mark another 1 gramme with a mark (") ; turn up one corner of a '1 gramme and of a 01 gramme. By this means the weights can all be distinguished from each other. See that the balance is in adjustment by swinging it without any weights in the pans ; if the pointer does not travel to an equal distance on both sides, alter the adjustment till this end is attained. After the adjustment, leave the balance for at least one hour and see if it is still in adjustment ; if not, repeat the process, handling the beam, &c. , as little as possible. When the balance is in proper adjustment, place the 10-granime weight on the right-hand pan, and the lO'-gramme weight on the left-hand pan ; they should very nearly balance, and the pointer should swing nearly equally on both sides ; if they do not balance, place the rider so that the balance is restored. The value of the lO'-gramme weight can now be obtained in terms of the 10-gramme weight, by adding the readings of the rider, if on the right arm, and subtracting, if on the left arm. Now reverse the weights, placing the 10-gramme weight on the left-hand pan, and the lO'-gramme weight on the right-hand pan, and repeat the weighing; the value of the lO'-gramme weight can bo obtained in terms of the 10-grammc weight by adding the readings of the rider, if on the left arm, and Buhtracting, if on the right arm. Owing to minute differences in the lengths of the arms it is not unusual to find a difference between the two values. The true value may be found by adding the two values together and dividing by 2. (It is i v oorreot, theoretically, to multiply the two values and take the square root, bu1 the values thus obtained are practi- cally identical with the arithmetical mean.) The t,,t dvalneofthe 5 + 2 + 1 + 1'+ 1 weights are similarly obtained, He value of the 20-gram me weight is obtained in a similar manner liy weighing it against the 10 + 1C, 10 + 6 + 2+ 1 + l' + l* or the 10' + 1 + 1' + 1" or, preferably, by weighing againsl all three series and taking the mean of the three values (which Bhould not differ appreciably). The \alue of the 60-gramme weight is obtained by weighing it against the 20+ 10+ 10' +6 + 2 + 1 + 1' ! r weights. The value of the 100-gramme weight is obtained by weighing il againsl the B0 20H 1<» i 10' i 5 + 2+ 1 i 1' i l" weights. The 5 gramme weight is now taken, temporarily, .as a standard, and the 2 + 1 + 1 + I" weights are weigh I I hat , and t he value of the series obtained in term- of the 6 gramme weight.. STANDARDISATION AND CALIBRATION OF APPARATUS. 343 The true value of the 5-gramme weight is obtained by the following formula : — Let 10 + x be the value of the series 5 + 2 + 1 + 1' + 1", 5 x a + y, the value of the series 2 + 1 + 1' + 1" in terms of the 5-gramme weight, and 5 x a the true value of the 5-gramme weight ; then 10 + x — 2 (5 x a) + y, 10 + x - y or 5 x a = -. Now, temporarily assume that the 1 -gramme weight is the standard, and ascertain the values of the 1' and 1" weights ; then ascertain the value of the 2-gramme weight by weighing it against 1 + 1', 1 + 1" or 1' + 1" or, preferably, against all three. The apparent values of the 2, 1, 1', and 1" weights in terms of the 1 -gramme weight will now be obtained. The true values are obtained as follows : — Let 1 x b be the true value of the 1-gramme weight, and 2(1 x b) + z, 1 x b + w, 1 x b + u, the values of the 2, 1', and 1" in terms of the 1-gramme weight ; then 2(1 x b) + z + 1 x b + 1 x b + iv + I x b +u = 5 x a + y, 7 5xa+v-3-i5-»i or 1x6 = i— . From the true value of the 1-gramme weight, the true values of the 2, 1'. and 1" weights are obtained. The values of the fractions of a gramme are obtained by the same process as the values of the 5, 2, 1, 1', and 1" weights. TABLE LXX.— Values of Weights. Weight. True Value. Correction. 100 100-0031 + -0031 50 50-0028 + -0028 20 199992 - -0008 10 10-0000 10' 9-9991 - -0009 5 5-0002 + -0002 2 2-0007 + -0007 1 •9989 - -oon 1' •9993 - -0007 1" 1-0001 + -oooi '5 •4997 - -0003 •2 •2002 + -0002 1 1001 + -oooi •1' •099S - 0002 •05 •0497 - -0003 •02 •0200 •oooo •01 •0097 - -0003 •or •0099 - -oooi Rider •0101 + -oooi 344 APPENDIX B. It is best to weigh the series "5, "2, "1, '1', '05, '02, "01, and "01' against the 1, 1', and 1" weights, and take the mean of the three values so obtained. When the weights have been standardised, a table should be drawn up in the above fashion (Table LXX.). II. Burettes. — Carefully clean out the burette with hot chromic acid mixture and rinse well with distilled water. Place it in a situation where sudden changes of temperature can be avoided, and fill it above the zero mark witli distilled water ; note the temperature of this, which should be as near as possible 60° F. (15 '5° C). Weigh an empty weighing bottle provided with a stopper ; cut two parallel slits abort - inches long and three-eighths of an inch apart in a card (a visiting card answers admirably), and bend this so that the burette passes through the slits, the narrow strip being in front ; adjust this so that the upper edge of the narrow strip is coincident witli the graduation next below the zero mark. Now carefully run out the water so that the lower edge of the meniscus coincides with the zero mark, cork up the burette and leave it for a few minutes ; after making sure that no alteration in level has occurred, adjust the card to the graduation next below the 5 c.e. mark, and run out slowly 5 c.c. into the weighing bottle, Weigh this and subtract the weight of the empty bottle ; the difference will give the weight of water occupying the volume between 0 and 5. After making sure that the level has not changed, adjust the card to the graduation next below the 10 c.c. mark and run out a further 5 c.c. into the weighing bottle ; weigh again, and subtract the weight of the empty weighing bottle ; the difference will give the weight of the water occupying the volume between 0 and 10. Repeat this process till the lowest mark on the burette is reached. The calibration of the burette should be repeated two or three times and the mean values tabulated. With a finely-divided rule measure the lengths of the divisions 0 to 5, 0 to 10, &c. ; multiply each of these lengths by the total weight of wat el- and divide by the total length, to obtain figures commensurate with the weights of water. Now plot out on squared paper two curves, one taking the scale readings as ordinates, and differences between scale readings and weights of water as abscissa;; the other taking scale readings as ordinates, and differences between scale readings and lengths of scale corrected as described above aa abscissae. If both curves are nearly straight, it shows thai the burette is made from B tube of uniform bore, and is correctly divided ; if the two curves have a marked curvature, bu1 coincide in form, it shows thai the lunette i made from a tube of uniform bore, bu1 incorrectly divided ; if the two curves do doI coincide it shows thai the tube is not uniform in bore. NOW, obtain the value of the weights of water contained in each 5 C.C., 0 to 5, 5 to 10, &c, by subtracting the weighl contained in 0 to 6 Erom thai contained in 0 to 10, &c, and the value of the lengths in a similar manner ; divide one value by the other and plot ou1 the values so obtained on squared paper, taking the mean scale readings (».e,, for the volume 0 bo 5 take 2*5) aa ordinate . and bhe values obtained bj tin- division as abscissas. This will give bhe curve of irregularity of bore ; if at any part of the curve it is noticed thai bhe irregularity is very gross, bhe volume i hould be obtained bj weighing the water; if bhe curve ia appreciably regular, it is evident that bhe errors of bhe burette must be due to incorrect division, and verj careful measurements of bhe lengths of divisions intermediate bet ween each 5 0.0. mark should be made : and it any very grave faults are found, the burette should be especially calibrated at that point. It il better, however, not to USe a burette of this descript inn. Table LXXI. will give tic figures obtained on a burette of fairly even bote, but badly dii idecL STANDARDISATION AND CALIBRATION OF APPARATUS. 345 TABLE LXXI. — Calibration of Burette. Scale. Weights of Water. Difference. Length (inches). Difference (corrected). Oto 5 4-918 -•082 1-752 -•022 Oto 10 9-940 -■060 3-550 + •016 Oto 15 14912 -•oss 5-329 + 001 Oto 20 19-896 -•104 7-1095 -010 Oto 25 24-8S0 -•120 8-890 -023 Oto 30 29-908 -•092 10-683 •000 Oto 35 34-849 -•151 12-436 -•087 Oto 40 39-817 - -183 14-204 -135 Oto 45 44-817 -•183 16-982 - -153 Oto 50 49-877 -•123 17-7775 -124 III. Pipettes. — Pipettes are used for measuring liquids by filling them to the mark and letting the liquid run out ; the following points should be noticed : — (a) The bottom of the meniscus should coincide with the mark. (b) The pipette should be held vertically while it is running out. (c) The liquid should always be allowed to run out in the same manner. Perhaps the best manner of allowing the liquid to run out is to allow it to flow as fast as possible, and, when empty, to touch the surface of the liquid with the point and to withdraw it at once. It may, however, be allowed to run out slowly, or a definite number of drops may be permitted to run out after the main portion is delivered. Whatever method is adopted during graduation must be strictly adhered to in practice. The graduation of pipettes is very simple ; they are filled with water as near 60° F. (15 '5° C. ) as possible, the contents run into a weighing bottle and the water weighed. The pipettes should be each etched with a number and the weight of water delivered tabulated for use. Pipettes used exclusively for delivering known weights of milk should be graduated with milk of l-032 specific gravity containing from 3 5 to 4-0 per cent. fat. In this case, the reading should be from the top of the meniscus, as the lower edge is invisible. IV. Flasks. — Flasks of capacity sufficiently small to permit of being weighed when full, are filled with water as near 60° F. as possible, and weighed. Each should be marked with a number, and the weight of water contained by each tabulated. Larger flasks (e.g. , litre flasks), if no balance sufficiently large is available, are graduated by the following method : — 10 successive portions of a little less than 100 grammes of water at about 60° F. (15"5° C. ) are weighed into the flask (best from a 100 c.c. flask). A beaker containing a little water, and a pipette are now weighed, and the litre flask filled to the mark by water from the pipette ; the beaker, pipette, and remaining water are now weighed ; the difference between the weights and the total weight of the ten portions added together will give the weight of water in the litre flask. V. Leffmann-Beam or Gerber Bottles.— These can be graduated with sufficient accuracy by using each to make determinations of fat in several samples of milk, in which the fat has been carefully estimated by a good gravimetric method (e.g., the Adams method). Those bottles which show a marked difference (i.e., more than "1 per cent.) should be rejected. The scale should also be measured with a finely-divided rule, and any bottles showing marked irregularities of graduation must be likewise rejected. 346 APPENDIX B. VI. Lactometers. — Lactometers are graduated by taking the specific gravity of several samples of milk which have had the density determined by a pycnometer ; the range of specific gravities should be fairly wide ; no lactometer showing differences of more than •0002 (•'2°) should be used, unless the differences are constant, when a constant correction may be applied. VII. Thermometers. — One thermometer should be specially calibrated, and this will then serve as a standard of comparison for others. The calibration is divided into two parts. (a) Calibration of scale. (I>) Determination of fixed points. (a) Calibration of Scale. — By means of a finely-divided rule the distances between the marks on the scale (e.g., 0 to 10, 10 to 20, &c. ; or 0 to 5, 5 to 10, &c.) are measured and tabulated. The mercury is allowed to flow into the stem, and at a point, which should be as nearly as possible 10° from the end, the tip of a fine flame is carefully applied ; by a gentle jerk a thread about 10° in length can be separated from the main portion, which is now allowed to flow back into the bulb. By gently tapping the tube, the thread is brought so that one end coincides with the zero mark, and the length of the thread is carefully measured ; the thread is next brought to the 10° mark, and its length carefully measured again ; and so on throughout the whole scale. By dividing the lengths of the thread when it is between each pair of points (0 to 10, 10 to 20, &c. ) by the distance between the same pair of points, the length of the thread in apparent degrees will be obtained ; the average of these lengths will give the mean length of thread in mean degrees. By dividing the length of thread between each pair of points by the mean length, the value of a degree between each pair of points in terms of B mean degree will be obtained ; and, on multiplying by ten, the distance between each pair of points in mean degrees will ne obtained. The values in mean degrees of the scale from 0 to 10, 0 to 20, CO io o CO o o 00 IO OS IO o o CI o CO iO -f CO -1 CM CM CM CI CI re co CO CO CO o CM •o CO •o o CO o o 00 IO iC o o CI o CO CO CM CI CI CM CI CM CI CO CO re t^ o o CI io CO ■o o CO o IO 00 lO Ci IO o o CI CO CI CI CM CI CI CI CI CI co CO CD •o o o CM lO CO ■o a CO a lO oo •o o CO rH CM CI CM ci CM CI CI CI re m IO CO IO C5 o a CI IO cc IO o o IO 00 »o Ci CO ~ Jj CI CM CI Cl CI CI CI CI ^ Hi •o GO a o o o CI lO eo lO o CO o I— IO oo CO 1-4 2 CM CM CM CI CI CI d CI CO o CO IO >o oo o o o o CI IO CO o CO o CO ^| [5 CM CM CI CI CI CI c< 0} o o io lO 00 o o o o CI IO co LO •<* o CO CO ~ ^ H CM CI CI CI CI CI iH ro o io o co IO Hi 00 a o o IO CI IO CO o IO CO CI CI CI CI CM o io CI IO CO o a CO >o »o 00 a o a IO CI IO CO CO CI CI CI CI a IO >o CM o -* o IO o CO lO lO 00 a o a iO CI a CI CI CM 00 o o IQ IO CM o o IO o CO IO ■o 00 8 e OJ CI CI I> o 95 a o IQ lO CM -r o lO lO CO •o iO 00 a o w © CI CO 1 - a o o IO IO CM a 8 IO CO IO 1- 8 w o o IO iO co IC 1- a OS 8 ■o IO CI 5 a >-. CO IO 1 - w o s o > 1 E ■* o m o m o m o in o m E • o CO o CO CO 1— 1 CO CSJ CO CM CO CO CO CO CO CO CO 1 \ ^ ^ Degrees of Lactometer. 75 76 77 78 79 80 81 82 83 84 85 i 21-6 ... 20 > 22-K ... ... 21 » 23-7 ... 22 > 247 23 } 25-7 24 5 26 8 25 f 27-8 27 9 28-0 28-2 28-3 28-4 28-6 28-7 28-9 29 0 29-2 26 ' 2S-9 29^ 2&-1 29-2 29;4 29-5 29-6 29-8 30-0 30 1 30 3 27 5 29-9 30-0 30-2 30 3 3Q-.4 30*6 po-^ >30 8 3L-0 31-2 31-4 23 i 31-0 31 1 313 31-4 31-5 31-7 31-9 32-0 32-2 32-3 32-5 29 I 32-1 32-2" >2-4 32 5 32 6 32-S 33 0 331 33 3 33 4 33 6 30 > 332 33-3 33 4 33 6 337 33 9 34-0 34-2 34-4 34-5 34-7 31 34 3 34-4 34 5 34 7 34 8 35-0 35 1 35 3 35 5 35-6 35-8 32 i 3B54 35 6 35 S 36-0 36 1 36 3 36 4 366 36 7 36 9 33 ! 36 4 * 36 5 36-7 36 9 37-0 37-2 37 3 37-5 37 7 37-9 38-1 34 2 37-4 35 36 TABLE LXXIII. — For Correcting the Specific Gravity of Milk according to Temperature. 0* «■' \" ■>* . t> 1 Dkurees of Thermumetkk' {Fahrenheit). 33 34 35 36 37 38 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 29-7 29-7 29 s 30-6 3U6 ::'!■: 31-6 31-5 31-6 32-4 32 4 32-5 3! -3 33-4 33-4 190 19-9 20-9 21-9 22-9 23 8 24S 28-8 267 27-7 'J SI, 29 v 3D-4 i'K ffl-4 36'4]36 5 :i7"4 28-6 281 2 _')i. 29 8 30(1 30 1 3HJ-30S 310 31-2 31-9 32-0 32-2 :i2:s 33-0 :;:; 1 33 3 33-4 34-0 U - 34-4 34 3 35 1 35 a 33 :, 35-6 36 3 36 4 36 6 367 37 3 3TB 37 7 37-9 13-59 13-71 13 71 I 13-83 14-08 14 20 14 33 1445 13-84 13 96 13-96 1408 14-09 14-21 14-21 14 33 14-34 14-46 I 14-58 14-46 14-58 14-70 14-59 14-71 14-83 1471 14-83 14-95 14-83 14-95 15-07 14-96 15-08 15-08 15-20 15-21 15-33 15-33 15 45 1546 15-58 15-58 I 15-70 15 82 15-94 16 07 1619 16-19 1 1631 16-32 16-44 16-44 16-56 16-56 16-68 1 16-80 16-68 16-80 1692 16-80 16-92 17-04 16-93 17-05 I 17-17 17-05 17-17 I 17*29 15-70 15-82 15-95 16-07 15 20 15 32 i 5 -45 15-57 15-70 15-82 15 94 16 06 1619 1631 16-43 16 56 1668 DIFFERENCE TABLE. 03 •01 •01 •05 •02 •02 •08 03 04 10 •04 •05 05 •06 06 •07 •07 •08 •08 10 •09 11 TABLE LXXIV.— For the Calculation of Total Solids from Fat and Specific Gravity (Riehmmufi Formula). Fat phb ■* ■i , 1 -2 •3 ■4 S 6 ■7 •8 •9 10 11 1-2 1-3 1-4 1-5 i -a 1-7 1-8 1-9 20 2 1 2-2 2-3 2-4 2-88 2-5 2 6 2-7 2-8 2-9 3 0 3 1 3-2 | 3-3 3-84 3-96 3-4 4-08 3 5 4 20 3-6 37 3-8 3-9 40 4-32 4-44 456 41- 4 SO 41 4-2 4-3 4-92 5 04 5 16 44 Gravity. l -; Fat. ■12 -24 •36 ■4S •60 -72 ■84 •96 108 1-20 1-32 1-44 1-56 1-68 1-80 1-92 2-04 216 2-2S 2 40 2-52 2-64 2-70 300 312 3 24 3-36 3-48 3-60 3-72 ^°! Total Solids PEE CENT. 22 0 5-652 .--:- 5-89 601 613 6 25 6-37 6-49 6-61 6-73 6-85 6-97 7-09 7-21 7-33 7-45 7-57 7-69 7-8 1 7-93 8-05 S-17 . 8-29 8-41 853 8-65 8-77 8-89 901 913 9-25 9-37 9-49 9-61 973 9-85 9-97 10 09 10-21 10-33 10-45 10-57 10-69 10-81 10-93 III 22-5 .-, 777 5*U 602 6-14 6-26 6-38 6-50 6-62 (1-74 6-86 6-98 7-10 7'22 734 7-46 7-58 7-70 7-82 7-94 8 06 8-18 8-30 8-42 8-54 8-66 8-78 8'90 9 02 9-14 9-26 9-38 950 9-62 9-74 9-86 9-98 1010 10-22 10-34 1046 10-58 10-70 lo sj 10-94 11-06 11 aa d 5-901 6*2 614 6 26 6 38 6-50 6-62 6-74 6-86 6-98 7-10 7-22 7 34 7-46 758 7-70 7-82 7-94 s (111 81S 8-3)1 8-42 8-54 s nil 8-78 8-90 9 02 9-14 9-26 9-38 9-50 9-62 9-74 9-86 9-98 10-10 10-22 10-34 10-46 10-58 10-70 Hi 82 10-94 11-06 Ills 11 23-5 6-027 6-i:. 6-27 6-39 6-51 6 63 6-75 6-87 6-99 7-11 7-23 7-35 7 47 7-59 7-71 7-83 7-95 S07 8-19 8-31 8-43 8-55 8-67 8-79 8-91 9-03 9-15 9-27 9-39 951 9-63 9-75 9-87 9-99 1011 10-23 10-35 10 47 lo .-.:. 10-71 10S3 1095 1107 1119 II 31 11 24 0 fi 153 6-27 6-39 6 51 6-63 6-7.". 6-87 6-99 711 7 23 7 35 7-47 759 7-71 7-83 7-95 8-07 8-19 s:!l 8-43 8-55 8-67 8-79 8-91 9 03 915 9-27 9-39 9-51 9-63 9-75 9-87 9-99 1011 10-23 10-35 1047 10-59 10-71 lo--:-, 10-95 11 "7 1119 11-31 11 43 11 245 6-278 6-4(1 652 6-64 6-76 bSS 7-00 7-12 7-24 7-36 7-48 7-60 7-72 7-84 7-96 8-08 8-20 8-32 s-44 8-56 8-68 SMI 8-92 9-04 916 9-2S 9-40 9-52 9-64 9-76 9-88 1000 10-12 HI 24 10-36 10 48 10-60 in 72 h. -i 10 96 U IIS 11-20 11-32 11-44 11 56 11 25 0 6*02 6-52 6-64 676 6-88 7-00 7-12 7-24 7-30 7-48 7-60 7-72 7 84 7-96 8-08 8-20 8-32 8'44 856 S-6S 8-80 8-92 9-04 9-16 9-28 9-40 952 9-64 9-76 9-88 1000 1012 10 24 10-36 104S 10-60 10-72 10-84 10-96 11 -us 11-20 1 1 -32 11 44 11-56 11 25-5 6 527 6-65 6-77 6 89 7 01 7-13 7-25 7-37 7-49 7-61 7-73 7-85 7-97 8-09 8-21 8-33 8-45 8-57 8-69 S-81 8-93 9 05 917 9-29 9-41 953 9 65 9-77 9-89 1001 1013 10-25 10-37 10-49 10-61 10-73 10-85 10-97 11 09 ,1-2, 11-33 1 1 -45 11 57 11-69 II si 11 260 6-652 6-77 6-89 7 01 713 7-25 7-37 7-49 7-61 7-73 7-85 7-97 8 09 8-21 8-33 8-45 8-57 8-69 8-81 8-93 9-05 9-17 9-29 9-41 9-53 9-65 9-77 9 89 10-01 10-13 10-25 10-37 10-49 10-61 1073 1085 10-97 11-09 11-21 11-33 11 45 1157 11-69 11-81 ll-.i; -- 26 5 6776 6-90 7 -ii2 7-14 7-26 7-38 750 7-62 7-74 7 86 7-98 8-10 8-22 8-34 8-46 S-5S 8-70 8-82 8 94 9-06 9-18 9-30 9-42 9-54 9-66 9-78 9-90 10(12 1014 10-2U 10-38 10-50 10-62 10-74 10-86 10-98 1110 1 1 22 11-34 1146 11-58 11 7o 11 82 11-94 12-06 .- 270 6-900 7-02 714 7-26 7-38 750 7-62 7-74 7-86 7-98 8 10 8-22 8-34 846 8-58 S-711 8-82 8-94 9-06 918 9-30 9-42 9-54 llllli 9-7S 9-90 10 02 1014 10-26 10-38 10-50 10-62 10-74 10-86 10-98 11-10 11-22 11-34 11 46 11-58 11-70 1 1 -82 11-94 12-06 - 2 37 5 7025 7-13 7-27 7 39 751 7-63 7-75 7-87 7-99 811 8'23 8-35 8-47 8-59 8-71 8-83 8 95 907 919 9-31 9-43 9-55 9-67 9-79 9-91 10 03 10-15 Hl-27 10-39 10 51 10-63 10-75 10-87 10-99 1111 1 1 -23 11-35 1117 11 59 11-71 11 S3 11-95 12 07 12-10 12-31 .- 280 7-150 7-27 7-39 7-51 7-63 7-75 7-87 799 8-11 8-23 8-35 8-47 8-59 8-71 8'83 8-95 9 07 919 9-31 9-43 9-55 9-67 9-79 9-91 10 03 1015 10-27 10-39 10-51 10-03 10-75 10-87 10-99 1111 11-23 11-35 11-47 11-59 11-71 11-83 11-95 12-07 1219 12-31 12-43 12 28-5 7-274 7-39 7-51 763 7-75 7-87 7-99 8-11 8-23 8-35 8-47 8-59 8-71 8-83 8-95 9-U7 919 9-31 9-43 9-55 9-67 9-79 9-91 1003 10-15 10-27 10-39 10-51 10-63 HI-7". 10 87 10-99 11-11 11-23 11-35 11-47 11-59 11-71 11-83 U-P5 12-07 1219 12-31 12-43 12-55 12 29 0 7-397 752 7-64 7-76 7-88 s-oo 812 s-24 8-36 8-48 8-60 8-72 8-84 8-96 9-08 9-20 9-32 944 9-56 9-68 9-80 9-92 10 04 1016 10-28 10-40 10-52 10-64 10-76 10-88 u-oo 1112 11-24 11-36 11-48 1 1 -60 11-72 11-84 11-96 12 D8 12-20 12-32 1244 12-56 . 12 29-5 7-522 7-64 7 76 7-88 8 00 812 8-24 8-36 8-48 8-60 8-72 8-84 8-96 9 08 9-20 9-32 9-44 9-56 9-68 9-80 9-92 10-04 10-16 10-28 10-40 10-52 10-64 10-76 10-88 u-oo 1112 11-24 11-36 11-48 11-60 1172 11-84 11-96 12 08 12-21 12 32 12 44 12-56 12-6- . 2 30 0 7 -647 7-77 7-89 801 813 8-25 8-37 8-49 8-61 8-73 8-85 8-97 9 09 9-21 9-33 9-45 957 ll -lid 9-81 9-93 10-05 10-17 10-29 10-41 10-53 10-65 10-77 10-89 11-01 11-13 11-25 11-37 1 1 -49 11-61 11 73 1 1 S5 11-97 12 09 1221 12 33 12-45 1257 12 69 12-81 12113 13 305 7-771 7-89 sill 8-13 8-25 8 '37 8-49 8-61 8-73 8-85 8-97 9-09 9-21 9-33 9-45 9-57 9-69 9-8] 9-93 10 05 1017 10-29 10-41 10-53 10-65 10-77 10-89 11-01 11-13 11-25 11-37 11-49 11-61 11-73 11-85 1 1 -97 1209 12 21 12-33 1-2-4. 12-57 12-09 1281 12 93 13-05 13 310 7-895 8-02 814 8-26 8-38 8-50 8-62 8-74 8-86 8-98 910 9-22 9-34 9-46 9-58 9-70 9-82 9-94 1006 10-18 10-30 10-42 10-54 10-66 10-78 10-90 11 02 11-14 11-26 11-38 11-50 11-62 11 74 1 1 -86 11-98 1210 12-22 1234 12-46 12-58 12-7" 12-82 12-94 13-06 13-18 13 31-5 8018 s-14 8-26 8-38 850 8-62 8-74 8-86 8'98 9-10 9-22 9-34 946 9-58 9-7(1 9-82 9-94 10 06 1IJ-18 10-30 10-42 10-54 10-66 10-78 10-90 11 02 1114 1 1 -26 11-38 11-50 11-62 11-74 11-86 11-98 12-10 12-22 12-34 1246 12-58 12-70 12-S2 1294 13-08 13-18 13-30 13 320 8140 8-26 8-38 8-50 8-62 8-74 8-86 8'98 910 9-22 9-34 9-46 9-58 9-70 9-82 9-94 10 06 10-18 10-30 10-42 1054 10-66 10-78 10-90 11-02 11-14 11-211 11-38 11-50 1 1 (12 11-74 use 11-98 12 10 12-22 12-34 12-46 12-58 1-2-70 12-82 12-94 13-06 13 is 13-30 13-42 13 32-5 ■ 264 B-38 8-50 8-62 8-74 8-86 8-98 9-10 9 '22 9-34 9-46 9-58 9-70 9-82 9-94 10-06 10TS 10-30 10-42 1054 10-66 10-78 10-90 1 1 02 1114 1 1 -20 11-38 11 50 1 1 -62 11-74 11-86 11-98 12-10 12-22 12-34 12-46 12-58 12-70 12 82 12-94 13-06 13-30 13-42 13 54 13 330 - 387 8-51 8-63 8-75 8-87 8-99 9-11 9-23 9-35 9-47 959 9-71 9-83 9-95 10-07 10-19 1(131 10-43 10-55 10-67 10-79 10-91 11 03 11-15 1 1 -27 1 1 -39 1 1 51 11-63 11-75 11-87 11-99 12-11 12-23 12-35 12-47 1259 12-71 12-83 1-2-95 13 07 1319 13 31 13-43 1355 13 67 13 33-5 8-509 8-75 8-87 8-99 9-11 9-23 9-35 9-47 9-59 9-71 9-83 9-95 10-07 10-19 10-31 1(143 10-55 10-67 10-79 10-91 11-03 11-15 11-27 11-30 11-51 11-63 1 1 -75 11 -S7 11-99 12-11 12-23 12-35 12-47 12 59 12-71 12 83 12 95 13 07 13-19 13-31 13-43 13-55 13-67 1379 13 34 0 8-631 8-75 S-S7 8-99 911 9-23 9-35 9-47 9-59 9-71 9'83 9-95 10-07 10-19 10-31 10-43 10-55 1(1117 10-79 1091 11 03 1115 11-27 11-39 1 1 -5 1 11-63 11-7.5 1 1 -87 11-99 1211 1-2-23 12-35 12-47 12-59 12-71 12-83 12-95 13 07 13 19 13-81 13-43 13-55 13-67 13-79 13-91 14 34-5 8-755 S-88 900 912 9-24 9-36 9-48 9-60 9-72 9-84 9 96 10-08 10-20 10-32 10-44 10-56 10-68 10-80 10-92 1 1 04 11-16 11-28 11-40 11-52 11-64 11-76 11-88 12-00 1212 12-24 12-36 12-48 12-60 12-72 12-84 12-96 13 0S 1320 13-32 13 44 13-56 13-68 13-80 13-92 14-04 14 350 8-878 B-OO 9-12 9-24 9 36 9-48 9-60 9-72 9-84 9-96 10 08 10-20 10-32 10-44 10-66 10-68 10-80 10-92 11 04 1116 11-28 11-40 11-52 11-64 11-76 11-88 12 mi 12 12 12-24 12-36 12-48 12-60 12-72 12-84 12-96 13-08 13-20 13 32 13-44 13-56 13-6S 13-80 13 92 14-04 1416 " 35-5 9-000 '.1-12 (124 9-36 9-48 9-60 9-72 9-84 9-96 10 08 10-20 10-32 10-44 10-56 10-68 10-S0 10-92 1104 1116 11-28 11-40 11-52 11-64 11-76 11-88 12-00 12-12 12-24 12-36 12-48 12-60 12 72 12-84 12-96 13-08 13-20 13-32 13-44 13-56 13 lis 13-80 13-92 W-04 14-16 14 -2S 14 38 0 9-122 924 9-36 9'48 9-60 '.1-72 9-84 9-96 1008 10-20 10-32 10-44 10-56 10-68 10-811 1002 11 04 1116 11-28 11-40 11-52 11 64 11-70 11-88 12-00 12-12 12-24 12-36 12 4S 12-60 12-72 12-84 1-2-96 13-08 13-20 13-32 13 44 13 56 18-68 13-80 13-92 1404 14 16 14 -2s 14-40 M 36-5 g i-44 9-36 9 48 9-60 9-72 9-84 9-96 10-08 10-20 10-32 10-44 10-56 10-68 10-80 10-92 11-04 1116 11-28 1 1 -41) -11-52 1 1 '64 1 1 7C. 11-88 12 00 1212 12-24 12 36 12-48 12-60 12-72 1284 12-96 13-08 13 20 13-32 13 44 13-56 13 OS 13-80 13-92 1404 14-16 14 2s 1440 14 52 14 37-0 9-366 949 9-61 9-73 9-85 9-97 10-09 10-21 10-33 10-45 10-57 10-69 10-81 10-93 1 1 ii.-. 11-17 11-29 11-41 1153 11-65 11-77 11-89 12-01 1213 12-25 12-37 12-49 12-61 12-73 1285 12 97 13-09 13-21 13-33 13-45 13-67 13-69 13-81 l :i 93 14 05 1417 14-29 1441 14-53 14 65 14 376 9'488 9-61 9-73 9-s.-, 9-97 1009 10-21 10-33 111-45 10-57 10-69 10-81 10-93 11-05 11-17 11-29 11-41 11-53 11-65 11-77 11-89 1201 1213 12-25 12-37 12-49 12-61 12-73 12-85 12-97 13-09 13-21 13-33 1345 1357 13-69 13-81 13-93 14-llj 1417 14-29 1441 14-53 14« 1477 14 ATION OP 10 TAL IM1LI IS Kl tou ± 11-38 11-50 1 1 -62 11 74 11-86 11-98 12-10 12-22 12-34 12-46 12-58 12-70 12-82 12-94 13-06 1318 13-30 13-42 13-54 13-66 13-78 13-90 14-02 14-14 14 26 14-38 14-50 14-62 14-74 14-86 1498 15-10 15-22 15-34 15-40 1.V5S 15-70 15-82 1 1 :S8 11-50 11-62 11 74 11-86 11-98 12-10 12-22 12-34 12-46 12-58 12-70 12-S2 12-94 13-06 1318 13-30 13-42 13-54 13-66 13-78 13-90 14 02 14-14 14-26 14 38 14-50 14-62 14-74 14 86 14-98 1510 15-22 15-34 15-46 15-58 15-70 15-82 15 94 11.50 11-62 11-74 11-86 11-98 12-10 12-22 12-34 12-46 12-58 12-70 12-82 1294 13-06 13-18 13-30 13-42 13-54 13-66 13-78 13-90 1402 1414 14-26 14-38 14 50 14-02 14-74 14-86 14-98 1510 15-22 15-34 15-46 15-58 15-70 15-82 15-94 1606 1 A3 11-75 11-87 11-99 1-211 12-23 12-35 12-47 12-59 12-71 12-83 12-95 13-07 13-19 13-31 13-43 1355 13 67 13-79 13-91 14-03 14-15 14-27 14-39 14-51 14 13 1475 14-87 14-99 1511 15-23 15-35 15-47 15 59 15-71 15-83 15-95 1607 16-19 n-75 1 -87 11-99 12-11 12 23 12-35 12-47 12 59 12-71 12-83 12-95 13-07 1319 13-31 13-43 13-55 13-67 13-79 13-91 14 03 14-15 14 27 14-39 14-51 14-63 14 75 14-87 14-99 15-11 1523 15-35 15-47 15-59 15-71 15 -S3 15-95 16-07 1619 16-31 11-87 11-99 12 11 12-23 12-35 1217 12-59 12-71 12-83 1-2-95 13 07 1319 13-31 13-43 13-55 13-67 13-79 1.1-91 14 03 1415 14-27 14-39 14-51 1*63 14-75 14 87 14-99 15-11 15-23 15-35 15-47 15-59 15-71 15-83 15-95 1607 1619 16-31 16-43 12-12 12 24 12-36 12 4S 12-60 12-72 12-84 12-96 13 OS 13 20 13-32 13-44 13-56 13-68 13-80 13-92 1404 14-16 14-28 14-40 14-52 14-64 14-76 14-88 15 00 1512 15-24 15-36 15-48 15-60 15-72 15 S4 15-96 16 08 16-20 16-32 16-44 16-56 12 12 12 24 12-36 12-48 12 60 12-72 12-84 12-90 13-08 13-20 13 32 13-44 13-56 13-68 13-SU 13-92 14-04 14-16 14-28 1440 14-52 14-64 14-76 14-88 1500 15 12 15-24 15-36 15-48 15-60 15-72 15-84 15-96 16-08 16-20 16-32 16-44 16-56 16-6S 12-24 12-36 12 is i-j 60 12-72 12-84 12-96 13-08 13-20 13-32 13-44 13-56 1368 13-80 13-92 14-04 14-16 14-28 14-40 14-52 14-64 14-76 14-88 15-00 1512 15 24 15-36 15-48 15-60 15-72 15-84 15-96 16-08 III -211 16-32 16-44 16-56 16-68 16 sn 12-36 12 -is 12-60 12-72 12-84 12011 13 08 13-20 13-32 1344 13-56 13-68 13-80 13-92 1404 1416 14-28 14-40 14-52 14-64 14-76 14-88 15 00 15-12 15-24 15 16 15-48 15-60 15-7-2 15-84 15-96 16 08 16-20 16-32 16-44 16-56 16-68 lti-S(l 16-92 12-48 1200 12 72 12-84 12-96 1308 13 20 13-32 13-44 13-56 13 68 13-811 13-92 1404 14-16 14-28 14-40 14-52 14 64 1470 14-88 15 00 15-12 15-24 15-36 15 43 15-60 15-72 15-84 15-96 1608 16-20 16-32 16-44 16-56 16-6S 16-80 16-92 17-04 12-61 12 -..', 12-85 2 '.'7 13 09 13-21 13-33 13-45 13-57 13-69 13-81 13-93 1406 14-17 14-29 14-41 14-53 14-65 14-77 14-80 1 15 01 1 15-13 15-25 15-37 15 49 15 61 15 73 15-85 15117 10 09 16-21 16-33 16-45 16-57 16-69 16S1 16-93 17-05 1717 12 7: 12-85 12-97 1 :-.!>■ 1 13-21 j 13-33 13-45 13-57 13-69 13-81 1393 14 05 14-17 14-29 14-41 14-53 14-65 14-77 14-89 15-01 15-13 15-25 15-37 15-49 15-61 15 73 15-85 15-97 16-09 lli-21 16-33 16-45 16-57 16 69 16-81 16-93 17 05 17 17 17-29 DIFFERENCE TABLE. * T. r. T. '1 03 m •01 -2 05 v2 ■02 •3 •08 03 •04 ■4 10 •04 -05 05 ■06 ■06 ■07 07 ,,i ■10 ■09 •11 TABLE LXXV. — For the Calculation of Total Solids fbom Fat and Specific Gravity (llehner and Richmond's Formula). Fat per cent. Specifl,' 1 ■2 ■3 •4 ■5 ■6 •7 -8 •9 10 11 1-2 1-3 1-4 1-5 1-6 1-7 1-8 1-9 2 0 2 1 2 2 2-3 2-4 2-5 2-6 2-7 2-8 2 9 3 0 3 1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 4 0 4 1 4'2 4-3 4-4 4-5 4 6 4 7 4 o Total Solids per cent. 24 0 6-21 6 33 (1-45 6-56 6 68 6-79 691 7 03 7-14 7-26 7 38 7-49 7-61 7-73 7-s-l 7 96 8-07 8-19 8-31 8-42 8-54 8-66 8-77 8-89 901 912 9-24 9-36 9-47 9-59 9-70 9-82 9-94 10-05 10-17 10-29 10-40 10-52 10-04 10-75 10-87 10-98 1110 1122 11 33 11-45 11-57 11< 24 5 6-34 0 46 6-57 6-69 6 80 6 92 7-04 7-15 7-27 7 39 7 50 7-62 7-74 7-85 7-97 8 09 8-20 8-32 8-43 8-55 8-67 8-78 8-90 9 02 9-13 9-25 9-37 9-48 9-60 9-72 9-83 9-95 1006 10-18 10 30 10-41 10-53 10-65 10-76 10-88 11 00 1111 11-27 11-34 11-46 11 58 11-69 IIS 25 0 647 O-.'.S 6-70 0 82 6-93 7 '05 7'16 7-28 7-40 7-51 7-63 7-75 7-86 7 -9s 8-10 8-21 8-33 8-45 8-56 8-6S 8-77 8-91 9 03 9 14 9-26 9-38 9-49 9-61 9-73 9-84 9-96 1007 10-19 10-31 10-42 10-54 10-66 10-77 10 -S9 11-01 1112 11-26 11-36 11-47 11-59 11-70 11-89 11-9 25 5 6-69 i; 7 1 6-83 6-94 7-06 718 7-29 7 41 7-53 7'64 7-76 7-87 7 99 Sll 8-22 8-34 8-46 8-57 8-69 8-81 8-92 9-04 915 9-27 9-39 9-50 9-62 9-74 9-85 9-97 10 09 10-20 10-32 10-43 10-55 10-67 10-78 10 90 11-02 1113 11-25 1 1 -37 11 48 11-60 11-72 11 S3 11-9.5 12") 26 0 6 72 e-84 6 95 7 '07 7-19 7 30 7-42 7-54 7'65 7-77 7-88 8 00 812 8-23 8-35 8-47 8-58 S-70 8 82 8-93 9-05 9-16 9-28 9-40 9-51 9-63 9-75 9-86 9-98 1010 10-21 10-33 10-45 10-56 10-68 10-79 10-91 11 03 1114 11-26 11-38 11-49 11 01 n-7:: 11-84 11-96 12-07 121 26 5 6-85 6-96 7-08 7-20 7'31 7'43 7-55 7-06 7-78 7-90 801 813 8-24 8-36 8-48 8'59 S-71 8-83 8-94 9 06 918 9-29 9-41 9-52 9-64 9-76 9-87 9-99 1011 10-22 10-34 10-46 10-57 10-69 10-80 10-92 11-04 11-15 11-27 1 1 -30 1 1 .Ml 11-62 11-74 1 1 -85 11-97 12-09 12-2)1 12 3 27 0 6-97 7119 7 21 7 '32 7 44 7 56 7 '67 7-79 7-91 8 02 814 8-25 8-37 8-49 8-60 8-72 8-84 8-95 9 07 919 9-30 9-42 9-54 9-65 9-77 9-Ss 10-00 10-12 10-23 10-35 10-47 10-58 10-70 10-82 10-93 11-06 11-16 11-28 11-40 11-51 11-63 11-75 11-86 1 1 -98 1210 1221 1233 12-4 27 5 7-10 7'22 7 33 7-45 7-57 7 -68 7-80 7-92 8 03 8-15 8-27 8-38 8-50 8-61 8-73 8-85 8-96 9-08 9-20 9-31 9-43 9-55 9-66 9-78 9-90 1001 10 13 10-24 10-36 10-48 10-59 10 71 10-S3 10-94 11-06 11 18 1129 11-41 11-52 11-64 11-76 11-87 11-99 1211 12 22 12-34 1246 12-5 28 0 V23 7 34 7-46 7-58 7-89 7'81 7! 13 8 04 816 8-28 8-39 8-51 8-63 8-74 8-86 8-97 9 09 9-21 9-32 9-44 9-56 9-67 9-79 9-91 1002 1014 10-25 10-37 10-49 10-60 10-72 10-84 10 95 11-07 1119 11 30 11-42 1 1 -54 11-65 11-77 II -s 12-00 12 12 1-2 23 12-3.5 12 47 12-58 12 7 28 5 7-36 7-47 7 59 7'70 7-82 7 94 8 '05 817 8-29 8-40 8-52 8-64 8-75 8 '87 8-99 910 9-22 9-33 9-45 9-57 9-68 9-80 9 -92 1003 1015 10-27 10-38 10-50 1061 10-73 ins:, Ill ill! 1108 11-20 11-31 11-43 11-55 1 1 -66 11-78 11-90 12-01 1213 12-24 12 30 12-48 12-59 1271 128. 29 0 7 -48 7-00 7-72 7-83 7-95 8 '06 8-18 8'30 8-41 8-53 8-65 8-76 8-88 9 -.00 9-11 9-23 9-34 9-46 9-58 9-69 9-81 9-93 10 04 1016 10-28 10-39 10-51 10-63 10-74 10S6 10-97 1 1 09 11-21 11 32 11-44 11-56 1 1 -87 11-79 1 1 -9 1 1202 1214 12-25 12 37 1-2 4'.' 12 60 1272 12-84 12-9 29 5 7-61 7-73 7-84 7 9li SOS 8'19 8'31 8-42 8'54 8-66 8-77 8-89 901 912 9-24 9-36 9-47 9-59 9-70 9 82 9-94 10 05 10-17 10-29 10-40 10-52 10-64 10-75 10-87 10-99 11 10 1 1 -22 11 33 1 1 45 11-57 11-68 1 1 -su 1 1 92 12-03 1215 12-27 12-38 12-50 12 02 12-73 12-85 1296 130 30 0 7-74 7-85 7 07 8 09 8-20 8-32 8'43 8'5o 8-67 8-78 890 9 02 913 9-25 9-37 9-48 9-60 9-72 9-83 9-95 10-06 10-18 10-30 10-41 10-53 10-65 10-76 10-88 11-00 1111 11-23 1 1 -34 11-46 1 1 -58 11 69 11 si 1 1 93 12114 12-10 12-28 12-30 1251 12-63 1274 12-86 1297 13-99 13-2 30 5 7-86 7-98 8-10 8-21 8 33 S45 8'56 8'68 8-79 8-91 9 03 914 9-26 9-3? 9-49 9-81 9-73 9-84 9-96 10-08 1019 10-31 10-42 10-54 10-66 10-77 10-89 11 01 1112 11-24 11-35 11-47 1 1 -59 11-71 1 1 -82 11-94 1205 1217 12-20 12-40 12-52 12-64 12 7.-> 12-87 12-99 1.1 HI 1322 13-3. 31 0 7-99 811 8-22 8 '34 8 '46 8-57 8 '69 S'81 8 92 9 04 915 9-27 9-39 9 -00 9-62 9-74 9-85 9-97 10-09 10-20 10-32 10-43 10-55 10-67 10-78 10-90 11-02 1113 11-25 11-37 11-48 1 1 -60 11-72 1 1 S3 nil.") 1206 12 IS 12-30 12-41 12-53 12 65 12 76 12-88 13-00 1311 13-23 13-34 13 41 31 5 8-12 8-23 8-35 8-47 8'58 8 70 8 '82 8-93 9 0S 9-17 9-28 9-40 9-51 9-63 9-75 9-86 9-98 1010 10-21 10-33 10-45 10-56 10-68 10-79 10-91 1103 1114 11-26 11-38 11-49 11-61 1 1 -73 11-84 11-96 12-08 1219 12 31 12 12 12-54 12-66 12-77 12-89 1301 13 12 13 21 13 36 13-47 13-5 32 0 8-24 8-30 8'48 8-59 8-71 8-83 8 114 !l'06 918 9-29 9-41 9 52 9-64 9-76 9-87 9-99 1011 10 22 10-34 10-46 10-57 10-69 10-81 10-92 1104 1115 11-27 1 1 -39 11-50 1 1 -62 11-74 1185 1 1 117 12 119 12-21) 12 32 12-43 12-55 12-67 12-7S 12-90 13 02 1313 13 2.-, 13-37 1348 13-60 13-7 32 5 8-37 8-49 8-60 8-72 S-84 8'95 9-117 1119 9-30 9-42 9-54 B-65 9-77 9-88 1000 1012 10-23 10-35 10-47 10-58 10-70 10-82 10-93 1105 11-17 11-28 11-40 11-51 11-63 11-75 11-86 11-98 1210 12-21 12-33 12-45 12 56 12-68 12-79 12-91 13 03 1314 13 20 13-38 13-49 13-61 1373 13* 33 0 8-50 861 8 73 8-85 8-96 9-08 9'20 9'31 9-43 9-55 9-66 9-78 9-89 1001 1013 10-24 10-36 10 -4S 10-59 10-71 10-83 10-94 11 06 11-18 11-29 11-41 11-52 11-64 11-70 11 -S7 1 1 -99 12 11 12-22 12-34 12-46 12-57 12-69 12-81 12-92 1304 1315 13-27 13-39 13-50 13-62 13 74 13-85 13-9 33 5 8-62 8-74 8 -SB 8-97 9 09 9-21 9-32 9-44 9-66 9-67 9-79 9-91 1002 1014 10-25 10-37 10-49 10-60 10-72 10S4 10-95 11 07 1119 1 1 -30 11-42 11-54 11-65 11-77 11-88 12 00 12-12 12-23 12-35 12-47 12-58 12-70 12-82 12-93 13-05 1317 18-28 13-40 1.: 51 13-63 13-75 13 86 13-9S 14K 34 0 8-75 8-87 8-99 9-10 9-22 9-33 9-45 9-57 9-68 9-80 9-92 1003 1015 10-27 10-38 10-50 10-61 10-73 10-85 10-96 11-08 11-20 11-31 11-43 11-55 11-66 11-78 11-90 1201 12 13 12-24 12-36 12-48 12-59 12-71 12-83 12-94 13-06 13-18 13 29 13-41 13-52 13-64 13-76 1387 13-99 14 11 14 i 34 5 8-88 9 00 911 9-23 9-35 9-46 !l-.-,S 9-69 981 9 93 10 04 1016 10-28 10-39 10-51 10-63 10-74 10-86 10-97 11-09 11-21 11 '32 11-44 11-56 11-67 11-79 11-91 12-02 12-14 12-26 12-37 12-49 12-60 12-72 12-84 12-95 13-07 13-19 13-30 13 42 13 54 13-65 13-77 13 ss 14-00 14 12 14-23 143. 35 0 9-Cll 912 9'24 0 36 9 47 9-r>9 9-70 9 82 9-94 10 05 hi it 10-29 10-40 10-52 10-64 10-75 10-87 10-99 1110 1 1 -22 11-33 11-45 11-57 11-68 1 1 -80 1 1 -92 12 03 121.-. 12-27 12-38 12-50 121,1 12-73 12-85 12 96 13-08 13 20 13 31 13-43 13-55 13-66 13-78 13-90 1401 14 13 1424 14-36 144? 35 5 9-13 9-25 9-37 9 48 9-80 9-72 9-83 9-95 10 06 1018 10-30 10-41 10-53 10-65 10-76 10-88 11 00 1111 11-23 11-35 ... 36 0 9-26 9-38 9-49 9-61 9-73 9-84 9-96 10-08 1019 10-31 10-42 10-54 10-66 10-77 10-89 11-01 11 12 11-24 11-36 11-47 .. 36 5 9-39 9-60 9-62 9-74 9-85 9 97 1009 10-211 10-32 10-44 37 0 9-51 9 63 975 9 86 9 '98 1010 1021 10-33 1045 10-56 37 5 9'64 9-76 9-87 9-99 1011 10'22 10-34 10-46 10-57 10 69 | - SOLIDS FROM Fat AND Specific Gravity (llehnt-i • and Richmond- % Fm inula ;• Fat pee OEHT. 3 0 3 1 3-2 3-3 3-4 3-5 3-6 3-7 3-8 3-9 4 0 4 1 4-2 4-3 4 4 4-5 4-6 4-7 4-8 4-9 5 0 6 1 5-2 5-3 5-4 5-5 5-6 5-7 5 8 5-9 ao 6 1 6-2 6-3 6-4 6-5 Total Solids per tent. 9-59 9-70 9-82 9-94 10-05 10-17 10-29 10-40 10-52 10-64 10-75 10-87 10-98 1110 11-22 11-33 11-45 11-57 11-68 11-80 11-92 12-03 12-15 12-27 12 38 12-50 12-61 12-73 12-85 12-96 . 130S 13-20 13-31 13-43 13-55 13-66 972 9-83 9-95 1006 10-18 10 30 10-41 10-53 10-65 10-76 KISS 11-00 11 11 11-27 11-34 11-46 11-58 11-69 11-81 11-93 12-04 1216 12-28 12-39 12-51 12-63 12-74 12-86 12-97 13-09 13 21 13-32 13-44 13-56 13-67 13-79 9« !>:»; 10 07 10-19 10-31 10-42 10-54 10-66 1077 10-S9 11 01 1112 11-26 11-36 11-47 11-59 11-70 11-82 11-94 1205 12-17 12-29 12-40 12-52 12-64 12-75 12-87 12-98 13-10 13-22 13-33 13-45 13-57 13-68 13-80 1392 9-97 10-09 10-20 10-32 10-43 10-55 10-67 10-78 10 90 11-02 11-13 11-25 11-37 11 48 11-60 11-72 11-83 11-95 12-06 12-18 1230 12-41 12-53 12-65 12-76 12-88 13-00 1311 13-23 13-34 13-46 13-58 13-69 13-81 13-93 14 04 1(1 in 1021 10-33 10-45 10-56 10-68 10-79 10-91 11-03 11-14 11-26 11-38 11-49 11-61 1 1 -73 11-84 11-96 12-07 1219 12-31 12-42 12-54 12-66 12-77 12-89 1301 13-12 13-24 13-36 13-47 13-59 13-70 13-82 13-94 HO.". 14-17 10-22 10-34 10-46 10-57 10-69 10-80 10-92 11 04 11-15 11-27 11-39 11-50 1 1 -82 11-74 11-85 11-97 1209 12-20 12-32 12-43 12-55 12-67 12-78 12-90 13 02 13-13 13-25 13-37 13-48 13-60 13-72 13-83 13-95 1406 14-18 14-30 10-35 10-17 Hr5S 10-70 10-82 10-93 11-05 1116 1 1 -28 11-40 11-51 11-63 11-75 11 86 U-9S 1210 12-21 12-33 12-45 12-56 12-68 12-79 12-91 1303 1314 13-26 13-38 13-49 1361 13-73 13-84 13-96 14 07 1419 14-31 1442 10-48 10-59 10-71 10-83 10-94 11-06 11 IS 11-29 11-41 11-52 11-64 11-70 11-87 11-99 1211 12 22 12-34 12-46 12-57 12-69 12-81 12-92 13 04 13-15 13-27 13-39 13-50 13-62 13-74 13 85 13-97 1409 14-20 14-32 14-43 14-55 liii,n 10-72 10-84 10 95 11-07 11-19 11 30 1 1 -42 11 .54 1 1 -6.". 11-77 1(-S8 12-00 12 12 12 23 12-35 12-47 12-58 12-70 12-82 12-93 13 05 1316 13-28 13-40 13-51 1363 13-75 13-86 13 98 14-10 14-21 14-33 14-45 14-56 14-88 1073 10 so 10-96 1108 11-20 11-31 1 1 -43 1 1 -55 1 1 -60 11-78 11-110 1201 1213 12-24 12-36 12-4S 12-59 12-71 12-83 12-94 13 06 1318 13-29 13-41 13-52 13-64 13 76 13-87 13-99 1411 14-22 14-34 14-46 14-57 14-69 14-81 10-S6 10-97 1109 11-21 11 32 11-44 11-56 11-67 11-79 11-91 12 112 12-14 12-25 12-37 12-49 12 60 12-72 12-S4 12-95 1307 13-19 13-30 13-42 13-54 13-65 13-77 13-88 14 00 14-12 14-23 14-35 14-47 14-58 14-70 14-82 14-93 10-99 II Hi 1 1 -22 11-33 1145 1 1 .IT 11-68 11-80 11 92 12-03 1215 12-27 12-38 12-50 12-62 12-73 12-85 12-96 13 OS 13-20 13-31 13-43 13-55 13-66 13-78 13-90 1401 1413 14 24 14-36 14-48 14-59 14-71 14-83 14-94 15 06 11-11 1 1 -28 1 1 -34 11-46 11-58 11-69 11 SI 11 93 12 04 12-16 12-28 12-39 12-51 12-63 12-74 12-86 12-97 13 09 13-21 13-32 13-44 13-56 13-67 13-79 13 91 14-02 1414 14-25 14-37 14-49 14-60 14-72 14-84 14-95 15 07 1519 11-24 11-35 11-47 11-59 11-71 11-82 11-94 1-2 05 12-17 12-20 12-40 12-52 12-64 12 75 12-87 1 12-99 13-10 13-22 13-33 13-45 13-57 13-68 13-80 13-92 1403 1415 14-27 14-38 14-50 14-61 14-73 14-85 14-96 15-08 15-20 15-31 11-37 11-48 1 1 -60 11-72 1 1 S3 11-95 1206 12-18 12-30 12-41 12-53 12-65 12-76 12-88 1300 1311 13-23 13-34 13 46 13-58 13-69 13-81 13-93 14 04 1416 14-28 14-39 14-51 14-63 14 74 14-86 14-97 15 09 15-21 15-32 15-44 11-49 11 lil 1 1 -73 11-84 11-96 12-08 12-19 12-31 12 42 12-54 1266 12-77 12-89 1301 13 12 13-24 13 36 13-47 13-59 13-70 13-82 13-94 14-05 1417 1429 14-40 14-52 14-64 14-75 14-87 14-99 1510 15-22 15-33 16-46 15-57 11-62 11 74 1185 11-97 12-09 12-20 12-32 12-43 12-55 12-67 12-78 12-90 13-02 1313 1325 13-37 13-48 13-60 13-72 13-83 13-95 1406 14-18 14-30 14-41 14-53 14-65 14-76 14-88 15 00 1511 15-23 15-34 15-46 15-58 15-69 11-75 11-86 1 1 lis 12 111 12-21 12-33 12-45 12-56 12-68 12-70 12-91 1303 1314 13 26 13-38 13-49 13-61 13-73 13-84 1396 14 08 14-19 14-31 14-42 14-54 14-66 14-77 14-89 1501 1512 15-24 15-36 15-47 15-58 16-70 15-82 II s: 11-99 12 11 12-22 1234 12-40 12-57 12-69 12-81 12-92 13 04 13-15 13-27 13-39 13-60 13-62 13'74 13-85 13-97 14 09 14 20 14-32 14-43 14-55 14-67 14-78 14-90 15-02 1513 15-25 15-37 15-48 15-60 15 72 15-83 15-95 12-00 1212 12-23 12-35 12-47 12-58 12-70 12-82 12-93 13 0.-, 1317 13-28 13-40 13-51 13-63 13-75 13-80 13-98 1410 14-21 14-33 14-45 14-56 14-68 14-79 14-91 1503 15-14 15-26 15 38 15-49 15-61 15 73 15-84 15-96 1608 1213 12-24 12-36 I-J-4S 12-59 12-71 12-83 12-94 13 06 18-18 13 29 13-41 13-52 13-64 13-76 13-87 13-99 1411 14-22 14-34 14-46 14-57 14-69 14-81 14-92 15 04 1515 15-27 15-39 15-50 15-62 15-74 15-85 15-97 1609 16-20 12-20 r_»::7 12-49 12-60 12-72 12-84 12-95 13-07 13-19 13-30 13 42 13 54 13-65 13-77 13-88 1400 14 12 14-23 14-35 14-47 14-58 14-70 14-82 14-93 15 05 15-17 15-28 15-40 15-51 15 63 15-75 15-86 15-9S 16-10 16-21 16-33 12-38 15 50 12 01 12-73 ... 12-85 12 96 1308 13-20 13 31 13-43 13-55 13-66 13-78 1390 1401 1413 ... ... 14 24 14-36 14-48 14-59 14-71 14-83 14-94 15-06 15-18 15-29 15-41 15-52 15-64 15-76 ... 15-87 15-99 1611 16-22 16-34 16-46 DIFFERENCE TABLE. 0. T. ■ T. 01 01 •1 113 112 ii2 ■2 ■05 03 ■OS ■3 •OS 04 ■05 •4 ■10 05 ■06 06 •07 07 •OS ■09 ■09 •10 350 APPENDIX C. - a - ft s; e g PS o «5 © o 10 CO o o © IO o o CM S CO OH CM CI en CM CI CI co CO CO 8 10 © CO o iO iO o © X IO © o o CI C) CI CM CM CI CI CM CM co co CD o 00 IO io o o CM © CO ■o IO © IO co IO © CO - ' j3 CI CM CM CI CM CM CM CI tO o 1- e CO OS © © CM IQ CO IO © © © iO CO CO 1-1 £j ^ CM CI CM CM CM CM CM rj< o CO o io iO © © © CM iO CO IO © © © CO ~" ' ~ --H ~ CM CI CM CM CM CM CO •o *l o CO O IO 00 11 © 2 © CM CO © IO © © CO CM CM CI CM CI 0} >-Cl CO IO o CO io ■o 00 © © © IO CM IO CO © CO — ~ ^ ^ J3 CI CI CM CM CJ H IO <-m IO CO o © CO 00 © © © IO CM >o co CO CM CI CM CI o o iq CM io CO © © so LI 1^ IO oo © © IO IO CM CO CI CM CI S 2 o — — o If) O IT) O m (N CM CO CO ■>* « CO CO CO CO CO CO USEFUL TABLES. 351 m © o 10 o CO o LO io io to o 00 o © lO o lO 10 "* "# -* ■># ■* ■* ■«* "# LO LO <# o OS lo o LO o CO o lO IO lO to © 00 o © IO o o CO -* -* # T* LO CO o CO o o io o CO o IO lO o 1^ o 00 LO © W CO CO ■* ■* *# TT ■*< **l >* -* o o © CO O CO CO CO -* -* ■* -* "# ■* ~* H lO io © 1^. o CO LO LO o © CM © co LO lO IO o O co co CO co ■* -# "* ■* ■<* <* o io lO IO o o CO LO © o o CM IO CO lO **< o to o CO CO CO co co M* r* ■* -* ■* 05 o CO LO o to o IO 00 IO © o o CM •o CO LO o 00 iO C5 © o CM lO CO ^ co co 2 CO 2 co CO tH -* -* 1> o o CM CO lO o to IO IO CO o o o lO CM ^ CO CO CO co co co co -f -t o CO LO OS o LO CM lO co o IO o to LO 1^ CO o o <# CM CO CO CO co co co CO "* "* w lO 00 o o o lO LO co o IO o to lO IO 00 o o ^ CM CO CO co CO CO CO co CO ■* <* ■o IO 00 o o o lO CM o o lO lO CD l^ o «t CM o LO CM o o lO IO CO LO ^ C5 CM CM CO CO co co CO co CO a O lO lO CO o o o lO lO CM o o lO lO to «* CM CM Ol CM CO co CO CO CO CO rH o o lO O CO o CO r-t CO rH CO CO CM CO CO CO CO CO <* CO CO 1 0 2. 3 ID bC -— a5 b hi m tfl M -u - efl 111 -- a v- rt 0) 01 .T, = 4-> o CO ^ ^ o ~" +J +J LO 0} o^ o +J fl - OJ •: XJ — o c3 X CO r- co IO gj ~ ao o eg TS y T3 352 APPENDIX C. TABLE LXXVLTI. — Fob the Calculation of the Total Solids of Skim Milk from the Fat and Specific Gravity. For Use in the Dairy Laboratory. Fat. Specific Gravity. T •2 3 •4 5 6 •7 •8 9 33 5 8-65 8-75 8-85 9-00 910 9-25 9-35 9-45 9-60 34 0 8-75 8-85 9-00 9-10 9 25 9 35 9 45 9-60 9-70 34 5 8-90 9 00 9-10 9 25 9 35 9-50 9-60 9 70 9-85 350 9-00 910 9 25 9 35 9 50 9-60 9-70 9 85 9-95 355 910 9-25 9-35 9 50 9-60 9-70 9-85 9-95 10-10 36 0 9-25 9 35 9 50 9-60 9-70 9-85 9-95 1010 10-20 36 5 9-35 9 50 9-60 9 70 9-85 9 95 1010 111-2(1 10-30 370 9 50 9 60 9 75 9 85 9 95 10-10 10 20 10 35 10-45 37 5 9 60 9 75 9-85 9 95 1010 10 20 10-35 1045 10-55 TABLE LXXX. — For the Conversion of Thermometry Scales. For the Conversion of Degrees Fahrenheit into Degrees Centigrade. Formula C = (F-32)xjj. Degrees Degrees Degrees Degrees Degrees Degrees Fahrenheit. Centigrade. Fahrenheit. Centigrade. Fahrenheit. Centigrade. 0 -17-78 51 10-56 7S 25-56 5 -15 00 52 1111 79 26-11 10 - 12-22 53 11-67 80 26-67 15 -9-44 54 12-22 90 32-22 20 -6-67 55 12-78 100 37-78 25 -3 89 56 13-33 110 43-33 30 -111 57 13-89 120 48-89 31 -0-56 58 14-44 130 54-44 32 0 59 15 00 140 60 00 33 0-56 60 15-56 150 65-55 34 111 61 1611 160 7111 35 1 67 02 16-67 170 76-67 36 2 22 63 17 22 ISO 82-22 37 2-78 64 177S 190 sT-Ts 38 3-33 65 is :;:; 200 93-33 39 3-89 66 18-89 210 OS Ml to 4 44 67 19-44 212 100 -00 41 5 00 68 20 00 220 104-44 42 6-56 69 20-66 230 110-00 13 (in 70 2111 240 115-55 n 6-67 71 21-67 •J.-.o 121-11 45 7 "22 72 22*22 •JO! 1 126-67 46 7-78 73 22-78 270 182-22 47 8-33 7) 23-33 280 137 78 48 s 89 75 23-89 2". t(» 143-33 49 9 44 76 ■'i ii 300 148-89 so 10-00 77 26-00 Percentage of Fat at IT'S" C. (Soxldet's Areometric Method.) t. ct. Spec. Grav. Fat. Per ct. Spec. Grav. Fat. Per ct. Spec. Grav. Fat. Per ct. Spec. Grav. Fat. Per ct. Spec. Grav. Fat. Perct. Spec. Grav. Fat. Per ct. JO 48 0 2 64 510 3 00 54 0 3 37 57 0 3 75 60 0 418 63 0 4 63 5] 48-1 2-66 511 3 01 54-1 3 38 57 1 3 76 604 419 63-1 4 64 $2 48-2 2 67 512 3 03 54 2 3 39 57 2 3 78 60 2 4 20 63 2 4 66 S3 48 3 2-68 513 3-04 54 3 3 40 57 3 3-80 60 3 4 21 63-3 4 67 S4 48-4 2-70 514 3-05 54-4 3 41 57 4 3-81 69 4 4-23 63-4 4 69 $3 48-5 271 515 3 06 54 5 3 43 57-5 3-82 60-5 4 24 63 5 470 $6 48-6 2-72 516 3-08 54 6 3 45 57 6 3 84 60 6 4 26 63 6 471 $7 48-7 2-73 517 3-09 54 7 3 46 57-7 3-85 60-7 4-27 63 7 4 73 $8 48-8 2 74 51-8 3-10 54-8 3 47 57-8 3 87 60-8 4 29 63 8 4-75 59 48 9 2-75 51-9 311 54-9 3 48 57 9 3-88 60 9 4-30 63 9 4-77 to 49 0 2 76 52 0 312 55 0 3 49 58 0 3-90 610 4 32 64 0 4-79 12 49-1 277 52-1 3 14 55-1 351 58-1 3-91 611 4 33 64-1 4-80 13 49 2 2-78 52-2 3 15 55-2 3 52 58-2 3-92 61-2 4 35 64 2 4-82 t4 493 2-79 52 3 316 55-3 3 53 58-3 3 93 613 4-36 64 3 4-84 15 49 4 2-80 52-4 3-17 55 4 3 55 58-4 3 95 614 4 37 64 4 4-85 16 49-5 2-81 52 5 3-18 55-5 3 56 58-5 3 96 61-5 4-39 64 5 4-87 17 49 6 2-83 52-6 3 20 55 6 3 57 58-6 3-98 61-6 4 40 64 6 4-88 40 49 7 2-84 52-7 321 55-7 3-59 58-7 3-99 617 4-42 64-7 4-90 30 49-8 2-86 52-8 3 22 55-8 3 60 58-8 4 01 61-8 4 44 64 8 4 92 51 49 9 2-87 52 9 3 23 55 9 3 61 58-9 4 02 619 4 46 64 9 4 93 52 50 0 2-88 53 0 3 25 56 0 3 63 59 0 4 03 62 0 4 47 65 0 4-95 54 50-1 2-90 531 3 26 56 1 3 64 59-1 4 04 62 1 4-48 651 4 97 35 50-2 291 53 2 3 27 56-2 3 65 59 2 4-06 62 2 4 50 65 2 4-98 56 50-3 2-92 53 3 3-28 56-3 3 67 59 3 4 07 62 3 4 52 65 3 5 00 57 50-4 2-93 53-4 3-29 56 4 3-68 59 4 4 09 62-4 4-53 65 4 5 02 58 50-5 2-94 53-5 3-30 56-5 3 69 59-5 411 62 5 4 55 65 5 5 04 60 50 6 2 96 53 6 3 31 56 6 371 59-6 412 62-6 4 56 65 6 5-05 (31 50-7 2-97 53-7 3 33 56-7 3 72 59 7 4-14 62 7 4-58 65-7 5 07 62 50-8 2-98 53 -8 3 34 56-8 3 73 59-8 415 62-8 4 59 65-8 5 09 63 50 9 2-99 53-9 3 35 56 9 3-74 59 9 1 4-16 62-9 4 61 1 65 9 66 0 511 5 12 TABLE LXXIX.— Specific Gka of Ethereal Solution of Fat and Corresponding Percentage of Fat at 17-5° C. (Soxhlet's Areometric itetlujd.) as Fat. Pit it. l.laV Fat. Perct. ££ Fat. Per ct 0-55 30 0 Fat. Perct. 0-33 Spec. F Grav. Pe t. Spec. F Grav. Pe 36 0 1 it. '(7 Spec. F '.rav. Pe (t. Sprc. Grav. Fat. Per ct. 1-97 & Fat. Perct. 2 '30 Grav. 48 0 Fat. Per ct. Spec. Fat. Per ct. ae Fat. Perct. ri'-iv 57 0 Fat. Per ct. lll.iv'. Fat. Pel el 63 0 Fat. Per ct. 240 0-28 27 0 330 1 10 39 0 1 67 42 0 45 0 2-64 510 3 00 540 3 37 3-75 60 0 418 4-63 211 o-oo 24'1 0-29 27-1 0'56 30-1 0 84 33 1 1 11 361 1 is 391 1 68 42-1 1-98 45-1 2-31 48-1 2-66 51 '1 3 01 541 3-38 57-1 3-76 601 419 031 4-64 21-2 001 24-2 0'30 27 '2 0'57 30-2 0-85 33 2 1 12 36-2 1 ::i 39-2 1 69 42-2 1-99 45 2 2-32 48-2 2-67 51-2 3-03 54-2 3-39 57-2 3-78 60-2 4-20 632 4-66 21-3 002 24-3 0 30 27-3 0'58 30 '3 0-86 33-3 1 13 36 3 1 40 39-3 1 70 42-3 2-00 45 3 2-33 48-3 2-68 513 3 04 54-3 3-40 57 3 '3-80 60-3 4-21 i;-;-:; 4 67 21-4 003 24-4 0-31 27-4 11-59 30-4 0-87 33 4 1 14 36-4 1 41 39-4 1 71 42-4 2 01 45 4 2-34 48-4 2-70 51-4 3-05 54-4 3-41 57-4 3-81 69-4 4-23 63-4 4-69 21 5 0 04 24-5 0'32 27 5 0-60 30 5 0 88 33o 1 15 36 5 1 42. 39-5 1 72 42-5 2 02 45-5 2 35 48-5 2-71 51-5 3 06 54'5 3 43 57-5 3-82 60-5 4-24 635 4-70 21-6 0-05 24-6 0 33 27 6 0 60 30-6 0 88 33 6 1 15 36-6 1 43 39 6 1 73 42-6 2 03 45-6 2-30 48-6 2-72 51-6 3 08 54-6 3-45 57-6 3-84 60-6 4-26 63-6 471 21-7 0-06 24-7 0 34 27-7 0 61 307 6-S9 33 7 1 16 36-7 1 44 39 7 1 74 42-7 2 04 45-7 2-37 487 2-73 51-7 3-09 547 3-46 57-7 3-85 60 7 4-27 637 4-73 21 '8 0-07 24 '8 0 35 27-8 0-62 30-8 0-90 33'8 1 17 36-8 1 45 398 1 75 42-8 2-05 45-8 2-38 48-8 2-74 51-8 310 54-8 3-47 57'8 3-87 60 8 .4-29 63 8 4-75 21-9 0-08 24-9 0-36 27-9 0-63 30 '9 091 33 9 1 18 36 9 1 11' 39-9 1 76 42-9 2-06 45-9 2-39 48-9 2-75 51-9 311 54-9 3 48 57-9 3-88 60-9 4-30 03-9 477 22 0 0-119 25 0 0 37 28 0 0 64 310 0-92 340 1 l'.l 37 0 1 17 40 0 1 77 43 0 2 '07 46 0 2 40 49 0 276 52 0 312 55 0 3-49 58 0 3-90 610 4-32 64 0 4-79 22-1 010 25 1 0 38 28 i 0 65 311 0-93 341 1 2(1 37 1 1 IS 40-1 1 7* 431 2-08 40 1 2 42 49-1 2-77 521 3 14 55-1 3-51 58-1 3-91 611 4-33 641 4-80 22-2 011 25-2 0-39 28-2 0 66 31-2 0 94 34-2 1 21 37 2 1 49 40 2 1 79 43 2 2 '09 40-2 2 43 49-2 2-78 52-2 315 55-2 3-52 58-2 3-92 61-2 4-35 64-2 4-82 22-3 0-12 25 3 0-40 28 3 0 67 31-3 0 95 34 3 1 22 37-3 1 50 40 3 1 Ml 43-3 2-10 46 3 2-44 49-3 2-79 52-3 3 16 55-3 3-53 58 3 3-93 613 4-36 64 3 4-84 22-4 013 25 4 0 40 28-4 0-68 31 '4 0-95 34-4 1 23 37 4 1 51 404 1 sl 43-4 211 46-4 2 45 49-4 2-80 52-4 3-17 55-4 3 55 58-4 395 614 4-37 64-4 4-85 22-5 0-14 25-5 0-41 28-5 0-69 31-5 0-96 34-5 1 24 37 5 1 52 40-5 1 S2 43-5 212 46-5 2-40 49-5 2-81 52-5 3-18 55-5 3-56 58-5 3-96 61-5 4-39 64 5 4 87 22 '6 015 25-6 0-42 28-6 0'70 31-6 0-97 34-6 1 24 37-6 1 53 40 6 1 s:t 43-6 213 46'6 2-47 49-6 2-83 52-6 3-20 55-6 3-57 58-6 3-98 61-6 4-40 64-6 4-88 22-7 016 25 7 0-43 287 071 31-7 0-98 34-7 1 25 37 7 1 -,) 40 7 1 S4 43 7 2-14 46'7 2-49 49-7 2-84 52-7 3-21 557 3-59 587 3 99 61-7 4-42 64-7 4-90 228 017 25-8 0-44 28 '8 0 72 31-8 0-99 34-8 1 26 37'8 1 55 ' 40-8 1 85 43-8 216 46-8 2-50 498 2-80 52-8 3-22 55-8 3 60 58-8 4 01 61'8 4.44 64-8 4-92 22-9 018 25-9 045 28-9 0-73 319 100 34-9 1 27 37'9 1 56 40 9 1 86 43 9 217 40 9 2-51 49-9 2-87 52-9 3-23 55-9 3-61 58-9 4-02 619 4-40 64-9 4-93 23 0 019 26 0 0-46 29 0 0 74 32 0 1-01 35 0 1 28 38 0 1 57 410 1 87 440 2-18 47 0 2-52 50 0 2-88 53 0 3-25 66 0 3-63 59 0 4 03 62 0 4-47 65 0 4-95 231 0-20 26 1 0-47 29-1 U 75 321 1-02 351 1 29 3S1 1 58 41 1 1 88 44-1 219 47 1 2-54 50-1 2-90 531 3-26 56 1 3-64 591 4 04 62 1 4'48 651 4-97 23 2 0'21 26 2 0 48 29-2 076 32-2 103 35 2 1 30 38 2 1 59 41-2 1 89 44-2 2-20 47'2 2-55 50-2 2-91 53-2 3-27 56 2 3-65 59-2 4'06 62-2 4-50 65 2 4-98 23 3 022 211 -3 0-49 29-3 0-77 32-3 104 35-3 1 31 38-3 1 60 413 1 90 44-3 2-22 47-3 2 50 50 3 2-92 53-3 3-28 56-3 3-67 59-3 4 07 62-3 4-52 65-3 5-00 23'4 0 23 26-4 050 29-4 078 32-4 105 35-4 1 32 38-4 1 61 414 1 HI 44-4 2-23 47-4 2-57 50-4 2-93 53 -i 3-29 56-4 3-68 59-4 4 09 62-4 4-53 65-4 5 02 23-5 "•24 26-5 0 50 29-5 079 32-5 105 355 1 33 38 5 1 02 41-5 1 92 44-5 2-24 47-5 2-58 50-5 2-94 BBS 3-30 56-5 3 69 59-5 411 62-5 4-55 65-5 5 04 23 0 0-25 20-6 0'51 29-6 0-80 32-6 106 35-6 1 33 38-6 1 63 416 1 93 44-6 2-25 47 6 2-60 50-6 2-96 53 6 3-31 56 6 3-71 59-6 4-12 62-6 4-56 65 6 5 05 23-7 0-25 26-7 0-52 29'7 0-80 32-7 1-07 35 7 1 34 38 7 1 64 41 7 1 III 44-7 2-26 477 201 50-7 2-97 53-7 3-33 567 372 59 7 414 62-7 4-58 65-7 5-07 23-8 0-26 26 S 0 53 29-8 0-81 32-8 1-08 35'8 1 35 38-8 1 65 41-8 1 95 44'8 2 '27 47 '8 2-62 50-8 2-98 53-8 3-34 56-8 373 59-8 415 62-8 4-59 65-8 5 09 23 9 0-27 26-9 0-54 29 9 0-82 32-9 109 35-9 1 36 38-9 1 66 41-9 1 96 44-9 2-28 47-9 2-63 50-9 2-99 53-9 3-35 56-9 3-74 59-9 416 02-9 4-61 65-9 66 0 511 5U2 354 APPENDIX C. TABLE LXXXI. — Weights and Measures. Linear Measure. 1 inch = "0254 metre. 1 foot = 12 inches = -3048 1 yard = 3 feet = 36 inches = 9144 1 metre = 10 decimetres = 100 centimetres = 1000 millimetres. 1 metre = 39371 inches = 3281 feet - 1094 yards. Square Measure. 1 square inch .......= '000645 sq. metre. 1 square foot = 144 square inches . . — '0929 ,, 1 square yard = 9 square feet = 1296 sq. inches = -8361 ,, 1 sq. metre = 100 sq. decimetres = 10,000 scj. centimetres = 1,000,000 sq. millimetres. 1 sq. metre = 1550'6 sq. inches = 10764 sq. feet = 1 '196 sq. yards. Cubic Measure. 1 cubic inch .......= 00001639 cub. metre. 1 cubic foot = 1728 cubic inches . . . = -0283 ,, 1 cubic yard = 27 cubic ft. = 46,656 cubic ins. = "7645 ,, 1 cubic metre = 1000 cubic decimetres = 1,000,000 cubic centimetres = 1 ,000,000,000 cubic millimetres. 1 cubic metre — 61,027 cubic ins. = 35 317 cubic ft. = 1'308 cubic yds. Measures of Capacity. 1 gill = -1420 litre. 1 pint = 4 gills = '5679 ,, 1 quart = 8 gills = 2 pints = 11359 litres. 1 gallon = 32 gills = 8 pints = 4 quarts . = 4 '5435 ,, *1 barn gallon = 68 gills = 17 pints = 8^ quarts . = 96548 ,, 1 litre = 1000 cubic centimetres — 1,000,000 cubic millimetres. 1 litre = 7 045 gills = T7608 pints = -8804 quart = '2201 gallon = -1036 barn gallon.* Avoirdupois Weight. 1 drachm = 1 '77 18 grammes. 1 ounce = 16 drachms . . . . = 28 349 ,, 1 pound = 256 drachms = 16 ounces . . = 463 '69 1 quarter = 7168 drachms = 448 ounces = 28 lbs. = 12700'.") 1 hundredweight = 28,672 drachms = 1792 ozs. = 112 lbs. =4 quarters = 50,802 1 ton = 573,440 drachms = 35,840 ozs. = 2240 lbs. = 80 qrs. = 20 cwt = 1,016,047 ,, 1 metrio ton — 1000 kilogrammes. 1 kilogramme = 1000 grammes. 1 gramme = 10 decigrammes 100 centigramme 1000 milligrammes. 1 gramme = '6644 drachm -03627 o*. = -0022051b. = -00001968 cwt. = -000000984 ton "The barn gallon Is nol a Legal measure j all oontraots made In bam gallons ar< null and void. It is, QOWeveT, muofa used. USEFUL TABLES. 355 Useful Data. The gallon weighs 10 lbs. (of distilled water at 62° F. ). The litre weighs 1000 grammes (of distilled water at 0° C. ). 1 gallon = i\ litres approximately. 1 barn gallon =10 ,, ,, 1 kilogramme = 2J lbs. approximately. 1 hundredweight = 50 kilogrammes approximately. Note. — The metre and litre compared with the standard English measures are those denned by the Act of 1878, and are not the true metre and litre. The difference is due to the fact that the English measures refer to a temperature of 62° F. , and the metric measures to a temperature of 0° C. In the Weights and Measures Act of 1878 the difference of temperature has not been allowed for. The following table shows the comparison between the two systems : — Metre. Litre. Kilogramme. True values at 62° F., . Adopted in Act, Inches. 39-38203 39-37079 Gallon. •22018 •2200967 Lbs. 2-20462 2-20462 TABLE LXXXII. — Barn Gallons and Imperial Gallons. For the Conversion of Bam Gallons into Imperial Gallons. Barn Gallons. Imperial Gallons. Gallons. Pints. 1 2-125 2 1 2 4 25 4 2 3 6-375 6 3 4 8-5 8 4 5 10 625 10 5 6 1275 12 6 7 14-875 14 7 8 17-0 17 0 9 19-125 19 1 10 21 -25 21 2 For the Conversion of Imperial Gallons into Bam Gallons. Imperial Gallons. Barn Gallons. Imperial Gallons. Barn Gallons. 1 •47 10 4-70 2 •94 11 517 3 1-41 12 5-64 4 ]-88 13 612 5 2 35 14 6 59 6 2-82 15 7-06 7 3 29 16 7 53 8 3 76 17 8-00 9 4-23 356 APPENDIX C. TABLE LXXXIIL— Table of Weights of Dairy Products. Milk at Farm. Milk at Dairy. Skim Milk. ButterCreara. Thick Cream Lbs. Ozs. Lbs. Ozs. Lbs. Ozs. Lbs. Ozs. Lbs. Ozs. 1 pint, 1 quart, 1 gallon, 1 2 10 4i 9" 4 1 2 10 4§ n 5 1 2 10 4| 9k 6 1 2 10 4 8 0 1 o 9 3* 7 12 2 gallons 20 8 20 10 20 12 20 0 19 8 3 „ 30 12 30 15 31 2 30 0 29 4 1 4 „ 41 0 41 4 41 8 40 0 39 0 5 ,, 51 4 51 9 51 14 50 0 48 12 6 „ 61 8 61 14 62 4 60 0 58 8 7 „ 71 12 72 3 72 10 70 0 68 4 8 ,, 82 0 82 8 83 0 80 0 78 0 9 „ 92 4 92 13 93 6 90 0 87 12 10 „ 102 8 103 2 103 12 100 0 97 8 11 „ 112 12 113 7 114 2 110 0 107 4 12 „ 123 0 123 12 124 8 120 0 117 0 13 „ 133 4 134 1 134 14 130 0 126 12 U „ 143 8 144 6 145 4 140 0 136 8 15 „ 153 12 154 11 155 10 150 0 146 4 16 „ 164 0 165 0 166 0 160 0 156 0 17 „ 174 4 175 5 176 6 170 0 165 12 18 „ 184 8 185 10 186 12 180 0 175 8 19 „ 194 12 195 15 197 2 190 0 185 4 20 „ 205 0 206 4 207 8 200 0 195 0 Differ ENCB ' r.\BLE Lbs. Ozs. I Lbs. Ozs. 1,1.3. Ozs. Lbs. Ozs. Lbs. Ozs. 1 pint, 1 quart, 3 pints, 2 quarts, 1 2 3 5 4£ 9 13* 2 1 o 3 5 4g 2* 1 2 3 5 4| 9.V 14| 3 1 2 3 5 4 8 12 0 1 2 3 4 34 7 10i 14 5 pints, 3 i|iiarts, 7 pints, 6 7 8 6£ 11 15i 6 7 9 7i 112 03 6 7 9 n 12i H 6 7 8 4 8 12 6 7 8 5 8i Xoi< . — The milk at farm is assumed to be warm and freshly milked. The milk at dairy is assumed to be at the average temperature (60° F.) and a few hours old. Skim milk is assumed to be at the average temperature (60° F.). Butter cream ii assumed to be at the average temperature (60°F.) and to contain 80 per cent. fat. Tliil> per cent. fat. he Weight of Butter in Quarts of Cream Churned. 40 50 60 70 80 I 17 4 218 26-1 30 5 34-8 ) 18 6 23 3 26-9 31-6 37 2 1 19-8 24-8 29-8 34-7 39-7 ] 21-0 26 3 31-6 36-8 42-1 J 22 3 27 9 33 4 39 0 44 6 5 23 5 29 4 35-2 41-1 47-0 "i 24 6 30 -8 37 0 43 1 49 3 I 25-8 32 3 3S-7 45 2 51-6 J 27 0 33-8 40-5 47 3 54 0 I 28-2 35 2 42 2 49 3 56 3 ) 29 3 36 7 44 0 51-3 58-6 > 30o 38-1 45 7 53 3 61-0 J 316 39 6 47-5 55 4 63 3 3 32-8 41 0 49-1 57 3 65 5 I 33 9 42 4 50 9 59 4 67-8 i 351 43 8 52-6 614 70-2 I 36 2 45 3 54 3 63-4 72 4 ) 37 4 46 7 56 0 65 4 74-7 ) 38-5 48-1 577 67 3 77-0 J 39 6 49-6 59 5 69 4 79 3 i 40-8 51 0 61-1 713 81-5 1 418 52 3 62-8 73 2 83-7 2 43 0 53-7 64 4 75-2 85 9 "J 44 0 551 66 1 77-1 88-1 I 45 2 56 5 677 79 0 90 3 7 46 2 57-8 69 4 80-9 92-5 5 47 3 59 2 71-0 82-8 94 6 3 48-4 60-5 72 5 84-6 96 7 L 49 4 61-8 74 2 86-5 98-9 ) 50-5 63 1 75-7 88-3 101 0 f 516 64o 77-3 ' 90-2 103 1 > 52 6 65-8 78-9 921 105 2 2 53 6 67 0 80-4 93 S 107 2 ) 54 6 68-2 81-8 95-5 109-1 ) 55 5 69 4 83-2 97-1 1110 1 56 4 70-5 84-6 98-7 112-8 TABLE LXXXIV. — Foe the Calculation of the Weight of Butter in Pounds obtained by Churning Cream. Quarts of Cream Ci Peruenta of Fat in Cre 1 1 2 3 4 5 6 7 8 9 10 20 30 40 60 60 7C 80 90 100 110 120 130 140 150 | 160 170 180 190 1 1 200 15 ■44 •87 1-31 174 2-1B 2-61 3 05 3-48 3-92 4-35 87 131 17-4 21 S 26-1 30 5 34-8 39-2 43-5 47 9 52-2 56-6 60-9 65-3 69-6 74-0 7S-3 827 87 0 16 •47 ■93 1-40 1-86 2-33 2-69 316 372 419 4-65 9-3 140 18-6 23-3 26-9 31- 6 37 2 41-9 46-5 51-2 55-8 60-5 0.5-1 60S 73-4 78-1 837 SS:4 , 930 17 •50 •99 1-49 1-98 2-4S 2-98 3-47 3-97 4-46 4-96 9-9 14-9 19-8 24-8 29-8 34 7 39-7 441', 49-6 54'6 59-5 64.7 69-4 74-4 79-4 B4-3 89-3 94-2 99-2 18 •53 105 1-58 210 2-63 316 3 'OS 4-21 473 5-26 10-5 15-8 21-0 26-3 31-6 36 8 42-1 47'3 52-6 57'9 63 1 68-4 73-6 78-9 84-2 69-4 947 99-9 1115-2 19 •56 1-11 1-67 2-23 279 3-34 3-90 4-46 501 5-57 111 167 22-3 27 9 33-4 39 0 44-6 501 55-7 61-3 66-8 72-4 78 0 83-6 891 947 100-3 105-8 111 4 20 •59 1-17 176 2 35 2 94 3-52 411 470 5-28 5-87 11-7 17-6 23-5 ■29 -4 35-2 41 1 47-0 52 'S 587 64-6 70-4 76-3 S2-2 ss-i 93-9 99S 1057 111-5 117 4 21 ■62 1-23 1-85 2-46 3 OS 370 4-31 4-93 5 54 616 12-3 18 \> 24-6 30 S 37 0 43 1 49-3 55'4 61-6 67 8 73-9 80-1 86 -2 92-4 98-6 104 7 110-9 1170 1-23 2 22 ■65 1-29 1-94 2-5S 3-23 3-87 4-52 510 5-81 6-45 12 9 19-4 25-8 32-3 3S-7 45 2 51-6 581 64 '5 71 0 77 4 83-9 90-3 96-8 103-2 109-7 116-1 122-6 129-0 23 ■6S 1-35 2 03 270 3-38 4 05 473 5-40 6 08 675 13-5 20-3 27-0 33 8 40-5 47 3 54 0 lio-s 67-5 74 3 SI II 87-8 94-5 101-3 108 0 114-s! 121-5 128-3 135-0 24 •70 1-4,1 211 2-82 3-52 4 22 4-93 5-63 6-34 7114 141 21 1 28-2 35-2 42-2 49 3 56 3 63-4 70-4 774 S4-5 91-5 98 6 105-6 112-6 119 7 1-20 7 133 - 140 -. 25 •73 1-47 2-20 2-93 3-67 4-40 5-13 5-86 6-60 7-33 14-7 22 0 29-3 367 44-0 51 3 58-6 06 0 73-3 80-6 88 0 95-3 102 0 1100 117-3 124-6 ' 131-9 139-3 146-6 26 •76 1-52 2-29 3 05 381 4-57 5 33 610 6-»6 7-62 15-2 22-9 30-5 38-1 J.", -7 53 3 61-0 68 -6 76-2 83-8 91-4 991 1H6-7 114-3 121-9 129-5 137 2 144 S 152-4 27 ■79 1-58 2-37 3-16 3 96 475 5-54 6-33 7 12 7-91 15 S 237 31-6 39-6 47 5 55 4 63-3 71-2 79 1 87-0 94-9 102-8 1107 1187 126-6 134-5 1 142-4 150-3 158 -2 28 •82 1-64 2-46 3-28 4-10 4-91 573 6 55 7-37 819 10-4 24-6 32-8 41 0 49-1 57 3 63-5 737 81-9 901 98-3 106-5 1147 1229 1310 139-2 147-4 155-6 163 S 29 ■S3 1-70 2-54 3 39 4-24 5 09 5-94 6 78 7 63 8'48 17 0 25-4 33-9 42-4 50-9 59 4 67 -S 76-3 84-8 93-3 101-8 110-2 1187 127-2. 1357 144-2 162-6 1611 169-6 30 ■88 1-75 2-63 3-51 4-38 5 26 6-14 7 02 7-89 877 17 r. 26-3 351 43-8 52-6 61 4 70-2 78-9 877 96-5 105-2 1140 122-8 131 6 140-3 1491 1579 166-6 175-4 31 ■91 1-81 2-72 3-62 4-53 5-43 6 34 7-24 8 15 9 05 18-1 27-2 36-2 45-3 54-3 63 4 72-4 81-5 90 -5 99-6 10S-6 1177 12li 7 135-8 144 -S 153-9 1629 172 0 181-0 32 •93 1-87 2-80 374 4-67 5-60 6'54 7-47 8-41 9 34 187 28 0 37 4 467 56 0 I,;, 4 74-7 84-1 93-4 1027 1121 121-4 131 IS 1401 ' 149-4 158-8 168-1 177-5 186-8 33 ■96 1-92 2-89 3'85 4-81 5 77 673 770 8-66 9-62 19-2 28 -9 38-5 48 1 57-7 67 3 77-0 86-6 96'2 105-8 115-4 1251 1347 144 3 153 9 103 5 173-2 182-8 192-4 34 •99 1-98 2-97 3'96 4-96 5-95 6-94 7 93 8-92 9-91 19-S 29-7 39-6 49-6 59-5 69 4 79-3 89-2 991 109 0 118-9 128-8 1387 1487 158-6 168-5 178 4 1SS-3 198-2 35 102 2 04 3 06 4'08 510 611 713 8-15 9-17 10-19 20-4 30-6 40-8 51-0 611 71 3 81-5 917 101-9 1121 122 3 132-5 1427 152-9 ]!'■■■•■-" 173 2 183-4 193 6 203-8 36 1-05 2 09 3-14 418 5-23 6-28 7*2 8-37 9-41 10-46 20-9 31-4 41-8 52-3 62-8 73 2 S3 7 941 104 0 1151 125 5 136 0 146-4 1569 167 4 177-8 1S8-3 1987 209-2 37 1-07 2-15 3 22 4-30 5-37 6 44 7-52 8-59 9-67 1074 21-5 32-2 43 0 537 64-4 75 2 85-9 967 107 4 118-1 128-9 139-6 150-4 1611 171-8 1S2-6 193-3 204 1 214S 38 110 2-20 3-30 4-40 5-51 6-61 771 8-81 9-91 1101 22 0 33 0 44-0 55 i 66 1 77 1 881 99 1 1101 121-1 132 1 1431 154-1 165-2 176-2 1S7-2 1HV2 209-2 220-2 39 1-13 2-26 3 39 4-52 5-65 677 7 90 9 03 1016 11-29 22-6 33-9 45-2 56-5 677 79 0 90-3 101-6 112-9 124-2 135-5 146-8 15S-1 169 4 180-6 191-9 203-2 214-5 225 S 40 1-16 2-31 3-47 4-62 578 6-94 S-09 9 25 10-40 11-56 23 1 34-7 46-2 57-8 69-4 80 9 92-5 104-0 115-6 127-2 13S7 150-3 161-8 173-4 185 0 196-5 208 1 219 6 231 2 41 118 2-37 3-55 473 5-92 7-10 8 28 9-46 10-65 11-83 23-7 35-5 47-3 59 '2 71-0 82 8 94-6 106-5 118-3 1301 142 0 153 8 165-6 177-5 189-3 201 1 21-2-9 224-8 236 i, 42 1-21 2-42 3-63 4'84 6 05 7-25 8-46 9-67 10-88 12 09 24-2 36-3 4S-4 60-5 72-5 84 6 967 108-8 120'9 133 0 1451 157-2 169-3 181-4 193-4 205-5 217-6 2-211 7 241 S 43 1-24 2-47 3-71 4-94 618 7-42 8-65 9 89 1112 12-36 .247 371 49-4 61-8 74-2 86 5 98-9 111-2 123-6 136-0 14S-3 1607 173 0 185-4 197S 211)1 222.-. 2:14 -8 247-2 44 1-26 2-52 3-79 5-05 6-31 7-57 8-83 10-10 11-36 12 62 25-2 37-9 50-5 031 75 7 s.s 3 1010 1130 120-2 138-8 151-4 1641 1767 1S9-3 201-9 •214;. 227'2 239 S 252-4 45 1-29 2-58 3-87 516 0 45 7 73 9 02 1031 11-60 12-89 25-8 387 51-6 64-5 77-3 90 2 1031 116 0 128-9 141-8 1547 167-6 180-5 191-4 206-2 ■2191 232 0 244-9 257-8 46 1-32 2-63 3 95 5-26 6-58 7-89 9-21 10-52 11-84 1315 26-3 39-5 52-6 65-8 78-9 92 1 105-2 118-4 131 -5 1447 157-8 1710 184-1 197-3 210-4 223-6 2367 249 11 263 0 47 1-34 2-68 402 5-36 670 8 04 9-38 10-72 12-06 13-40 26-8 40-2 53-6 67 0 80-4 93 8 107-2 120-6 134 0 147-4 160 8 174-2 187-6 201 0 214-4 2-27 -S 241-2 254-6 268 0 48 1-36 2-73 4 09 5-46 6-82 818 9-55 10-91 12-28 13 04 27-3 40-9 54-6 68-2 81-8 95 5 109-1 122-8 136-4 150 0 1637 177-3 1910 204-6 218'2 2319 245-6 259 2 272S 49 1-39 2-77 4-16 5-55 6-94 8-32 971 1110 12-48 13-87 277 41 -a 55-5 69-4 83-2 97 1 1110 124-8 13S7 152-6 166-4 180-3 194-2 ■211.-. 1 221-9 235-8 24117 263 5 277-4 50 1-41 2-82 4-23 5-64 7-05 8-46 9-87 11-28 12-69 1410 28-2 42-3 56-4 70-5 84-6 98 7 112-8 126-9 141-0 1551 169-2 183-3 197-4 211-5 225-6 2397 253-8 267 9 ■2S2-0 357 APPENDIX D. LIST OF USEFUL BOOKS. {a) Chemistry. Roscoe and Schorlemmer. A Treatise on Chemistry. 1898. London. Beilstein. Handbuch der organischen Chemie. 1897. Hamburg and Leipsic. Watts' Dictionary of Chemistry (edited by Morley and Muir). 1896. London. (b) Analysis. Fresenius. Quantitative Analysis. (Translated by C. E. Groves.) 1895. London. Allen. Commercial Organic Analysis. 1898. London. (c) Milk. Wynter Blyth. Foods : their Composition and Analysis. 1898. London. Bell. Foods. 1883. London. Leffmarm and Beam. Analysis of Milk and Milk Products. 1897. Philadelphia. Pearmain and Moor. Analysis of Food and Drugs. Part I. 1897. London. Aikman. Milk, its Nature and Composition. 1899. London. Konig. Chemie der Menschlichen Nahrungs- und Genussmittel. 1893. Berlin. Duclaux. Le Lait. 1S94. Paris. (d) Butter. Zune. Traite" d'analyses des beurres. Paris. Besana. Sui metodi atti a distinguere il burro naturale dal burro artificiale e le loro miscegle. 1891. Lodi. Benedikt and Lewkowitsch. Analysis of Oils, Fats, and Waxes. 1895. London. Wright. Fixed Oils, Fats, Butters, and Candles. 1898. London. (e) Water Analysis. Leffmann. Water Analysis. 1895. Philadelphia. 358 APPENDIX D. {J ) Bacteriology. Crookshank. A Text-Book of Bacteriology. 1898. London. Pearmain and Moor. Applied Bacteriology. 1898. London. Lehmann and Neumann. Essentials of Bacteriology. 1897. London. Lafar and Salter. Technical Mycology. 1898. London. Frankland (P. and G.). Micro-organisms in Water. London. Slater and Spitta. An Atlas of Bacteriology. 1898. London. (g) Periodicals. The Analyst. The Experiment Station Record. Milch-Zeitung. Landvvirthschaftliche Versuchsstationen. The Journal of the Royal Agricultural Society. The Journal of the British Dairy Farmers' Association. Stazioni Sperimentali Agrarie Italiane. LTndustrie Laitiere. The Journal of the Chemical Society. The Journal of the Society of Chemical Industry. 359 INDEX. Abbe refractometer, 285, 287. Abnormal milks, 121, 122. Absorption — Bromine, 276. Iodine, 274. Potash, 266. Acetic acid and acetates, 7,41. Acetic acid, Solubility of butter fat in, 273. Acetyl - derivatives of milk-sugar, 17. Acid — Acetic, 7, 41. Acrylic, 41. Benzoic (as a preserva- tive), 139. Boric (as a preserva- tive), 75, 139. Boric, Detection of, 75, 140. Boric, Estimation of, 76. Boric, Estimation of, Thompson's method, 76. Butyric, 35, 43, 46, 47. Capric, 35, 45, 46, 47. Caproic, 35, 44, 46, 47. Caprylic,35,44,46,47. Citric, 7. Citric, Estimation of, 77. Elaidic, 48. Formic, 41, 69, 145. Galactinic, 16. Gluconic, 8. Glyceric, 40. Glycollic, 41. Glyoxylic, 41. Lactic (see also Lactic acid), 18-20. Acid — Lactic, Estimation of, 113, 115. Lacto-bionic, 8, 16. Laurie, 45, 46, 47. Linolenic, 48, 49. Linolic, 48, 49. Mucic, 16. Myristic, 35, 45, 46, 47. Nitric, Estimation of, 234. Oleic, 35, 47, 49. Oxalic, 41. Palmitic, 35, 45, 46,47. Pecto-galactinic, 16. Phosphoric, Estima- tion of, 74. Salicylic (as a preser- vative), 139, 144. Salicylic, Detection of, 141. Sarco-lactic, 19. Stearic, 35, 45, 46, 47, 49. Sulphuric, Estimation of, 74. Sulphuric, Estimation of strength of, 177. Tartronic, 41. Acidity— Determination of, 113. Development of, 8. due to lactic acid, 18. Estimation of, in com- mercial milk-sugar, 319. of sour milk, 114. Acids, Action of — on albuminoids, 21. on glycerol, 41. on milk-sugar, 8, 16. on oleic acid, 47. Acids, Fatty (see also Soluble and insoluble. fatty acids), 1, 43-49. Acids of series — CHo^+iCOOH, 43-46. C^Hsn-iCOOH, 47. CnH2n_3COOH, 48. C„H2„-5COOH, 48. Acids, volatile. Estima- tion of, 117. Acrolein, 40, 42. Action — General, of hydro- lysts, 32. of acids on — albuminoids, 21. glycerol, 41. milk-sugar, 8, 16. oleic acid, 48. of alkalies on — glycerol, 41. oleic acid, 48. of cold on milk, 154- 157. of enzymes on — albuminoids, 21. milk-sugar, 17. of heat on — albumin, 27. albuminoids, 21. fat, 37. lactic acid, 18. milk, 145-154. milk-sugar, 9, 15. of hydrolysis, 32. of micro-organisms on milk, 225. of micro-organisms on milk, Products formed by the, 227. of rennet, 23, 298. of rennet, Conditions influencing. 300. of rennet, Influence of temperature on , 300. of salt on butter, 248. Adulteration of — butter, 291. Detection of, 291. 360 Adulteration of — cheese, 317. by foreign fat, 317. by skimming, 317. commercial milk- sugar, 319. cream, 216, 224. milk, 136-143. by ammonium salts, ' 138. by brains and mam- mary tissue, 138. l>y cane-sugar, 137. by dextrin, 137. by glycerine, 137. 1>V mineral matter, 138. by preservatives, 139. by salt, 138. by starch, 137. Adulteration of milk, Detection of, 136-138, 140. Advice on the choice of separators, 211. Agar, Nutrient, 237. Albumin (see also Lact- aUntmin), 6, 23, 24, 'J 7, 28. as alkaline salt, 6, 24. Composition of, 28. Estimation of, 108- 112. Denaimetrio, 110. Polarimetric, 112. Heat of combustion of, 335. in colost i'u m, 130. in gamoose milk, 329. in sterilised milk, 160, 162-154. Preparation of, 28. Properties of, 27. Action of heat on, 14.',. 160, 164. Reaction- of, 24. 28. Albuminoid ammonia, 232. Albuminoids (see Pro teida), 1, 6, 7. 20-32. AlbumoM and peptone nitrogen, Estimation of, in cheese, 318. Albumoses, 21. in chi 1 1 . 800, 818. in colost rum, ISO. in milk, 24. Alcohol — Behaviour of butter with, 273. Estimation of, 117, 118. in milk, 34. Micro-organisms pro- ducing, 220. Use of, for preserving milk samples, 144. Alcoholic extract in cheese, Estimation of, 315. Alcoholic fermentation, 6. Alcoholic soda solution, 266. Aldehydes, 8, 12, 13. Aldehydrol,8,12,13, 17. Aldoses, 8, 15, 17. Alkali- Salts of, 7. Alcoholic, 266. Alkalies — Action of, on glycerol, 41. on oleic acid, 48. Estimation of, 74, 75. Alkaline salts, 7. Alkalinity, Estimation of, in soluble ash, 73. Alteration of specific gravity by change of temperature, 66, • ">T- Amidic nitrogen, Esti- mation of, in cheese, 312. Amido- compounds, 22, 32. in cheese, 306. 308, 312. Ammonia — Free and albuminoid, 232. -free water, 234. in cheese. Est i mat ion of, 312, 316. Ammonium — chloride solution, Standard, 233. molybdate solution, 236. salts. Adulteration of milk by, 138. Amphioteno rea< I ion, B. Amy] alcohol 1 solvent , 1 15. Amy! alcohol — for milk testing. 177, 185. Use of, in fat estima- tion, 115. Anabolic ratio, 335, 336. Analysis of — butter fat, 257-291. buttermilk, 119. cheese, 309-317. cream, 115, 179, 187, 189. condensed milk, 116. decomposed milk, 1 16. fermented milk, 117. kephir, 1 17. koumiss, 1 1 7. milk products, 1 15. samples, 163. old butter, 295. skim milk, 116, 177. water, 231-237. Interpretation of results of, 236. whey, 1 19. Proximate, of butter, 251-256. Proximate, of butter, Interpretation of results of, 255. Analytical — characteristics of ster- ilised milk, 150. problems. Solution of, 197. properties of butter, Influence of keeping on the. 292 295. Annat! Detection of, 139. Use of, for colouring milk. 139. Apparatus — Drying, 71. for eel imation of fat in milk, 99. 171.17b 181-184, 191, 192. for est i mat ton of heat evolved by thi tion of sulphuric aeid OH butter fat, 278 for est imation of vie- oosity, 290. for observing the be- haviour of butter mi melt ing, 291. for sampling, 160. INDEX. 361 Appeal to the cow, 136. Aqueous extract of cheese, Estimation of, 310. 315. Arachis oil, Density of, 284. Areometric method for the estimation of fat, 192. Argonin, 320. Artificial human milk, 336. Artificial thickening of cream, 224. Ass, Milk of, :<34. Composition of, 323, 334. Sugar of, 322, 334. Asymmetric carbon atoms, 13. Ash, 32. Composition of, 32. Density of, in milk, 65. Estimation of, 73. in commercial milk - sugar, 319. in cream, 115. in cream, Ratio be- tween water, solids not fat, and, 215. Insoluble, 33. Composition of, 33. Estimation of, 73. of cheese, Estimation of, 310, 311, 315. of cream, Composition of, 217. of human milk, Com- position of, 327. Ratio of milk-sugar, proteids, and, 121. Ratio uf milk-sugar, proteids, and, in cream, 216. Soluble, 33. Estimation of, 73. Variations of, in milk, 121. Attraction, Capillary (see Surface energy). Automatic burette, 175. Average composition of cow's milk, 120. Average composition of milk fat, 35. Average specific gravi- ties, Rules to, 64. Average specific gravity of milk, 55. Ayrshire cows, Composi- tion of milk of, 125, 126. B Bacilli, 225. Hay and potato, 227. Bacillvs syncyanus or cyanogenus, 228. lactis erythrogenes, 228. tuberculosis, 220, 229. Bacteria, 225. Bacteriological examina- tion of water, 237. Bases, 7. Basic nitrogenous sub- stances, 34. Bath, Water-, 72. Behaviour of butter on melting, 290. Behaviour of fat with solvents, 273. Behaviour of milk with ether, 1, 2, 3. Bellelay cheese, 307- Bichromate, potassium, Use of, for preserving milk samples, 144. Biological and sanitary matters, 225-244. Birotation, 9, 10, 18. Birotation ratio, Esti- mation of, 318. Bitch, milk of. Composi- tion of, 323. Bitter milk, 228. Bitter taste in milk, 227. Blood, cause of red milk, 228. Blue milk. 22S. Boiling points (see under names of substances) . of acids of series CnH2jl+iCOOH, 46. of water, 347. Bondon cheese. 303. Borax (as a preserva- tive). 139, 140. Borax, Estimation of, in butter, 254, 255. Boric acid — Adulteration of milk with, 139, 140. Boric acid — as a preservative, 140. Detection of, 75. Detection of, in but- ter, 254. Estimation of, 76. Estimation of, in but- ter. 254 Injurious effects of, 139. Bottles, Gerber, 184. Leffmann-Beam, 175. Standardisation of, 345. Brains, Adulteration of milk with, 13S. Brie cheese, 303, 307. Bromhydrins, 41. Bromineabsorption, 274, 270. Buffalo- Milk of (see also Gamooxt), 327. milk of, Composition of, 323, 327, 328. milk of. Fat of, 322, 328, 329. Burette, Automatic, 175. Burettes, Standardisa- tion of, 344. Butter, 245-297. Action of salt on, 248. adulteration with water, 255. Characteristics of dif- ferent classes of, 256. Condition of globules in, 249. Composition of, 245, 246. Constitution of, 2,245, 250. Definition of, 245. Detection of formalin in. 255. Detection of nitrates in, 255. Detection of preserva- tives in, 254, 255. Detection of sulphites in, 255. Difference between fresh and salt, 248, 256. Effect of keeping on water in, 248. 362 INDEX. Butter — Estimation of boric acid and borax in, 254 Estimation of curd in, 253. Estimation of fat in, 253. Estimation of preser- vatives in, 254, 255. Estimation of solids not fat in, 253. Estimation of solids not fat and salt in, 253. Estimation of total nitrogen in, 253. Estimation of water in, 252. Evidence of existence of mucoid mem- brane in, 2, 246. Fresh, 246, 24s, 256. Influence of tempera- ture on churning, 251. Influence of tempera- ture on proportion of wat er in, 251 , 255. Interpretation of re- sults of proximate analysis, 255. Pickled, 255. Preparation of samples of, tor analysis, 251, •-'oT. Preservatives in. 251. Proportion of water in, 247. Proximate anah -i- of, 251-257. Salt, 246, 248, 256. Standard for water in. •_'."■-"■. Testing of, 180, 188, is: i "Thick," 249. Variations of water in. 247, 248 Work in- Of, 249. Bnttei I Anal] -i- "t. _'">7 291 , Behaviour of, on melt- ing, Behaviour of, with soh 'nt -, 273. Di itj of, :■: 39,281- 285. Butter-fat — density of, Limits of, 284 Detection of adultera- tion of, 291. Detect ion < »f cocoa-nut oil in. 291. Detection of mar- garine in, 292. Difference between, and other fats, 257. Estimation of bromine and iodine absorp- tion of, 274. Estimation of heat evolved by sulphu- ric acid hydrolysis of, 277. Estimation of in- soluble fatty acids in, 268. Estimation of molecu- lar weight of. 267. Estimation of refrac- tive index of, 285. Estimation of saponi- fication equivalent of, 266. Estimation of soluble and insoluble fatty acids in, 26S. Estimation ofviscosity of. 2'. Mt Estimation of volatile fatty acids of. 258. Influence of keeping on analytical pro- perties of. 292. Microscopical exami- nation of, under polarised light, 279. Physical examination of, 279-291. Bolubility of. in acetic acid, 273. Specific tests for adul- terants of. 272. Buttermilk, 296 •-'■.17. Analysis of. I pi A si, of, 296. asb of. t omposit ion of, 296. ( lomposition of, 296. Definition of. 2H6. Mucoid proteid in, 29 Pi "pe| | |, | ,,|, -_".t7. ngof, 177, 185. Buttermilk — Variation of fat in, 296. Butyrates (see Butyric acii/). Butyric acid, 35, 43. Micro-organisms pro- ducing, 226, 227. Ratio of, to oaproic acid in butter-fat, 264. Butyrin, 35. Butyro-refractometer, 2s7. Byre test, 136. Cacio-cavallo (cheese), 302, 304, 306. Calcium, Estimation of, 73. ( ialculation of — added separated milk, 138. added water, 136. density of total solids, 62. ' fat. Formulae for, 58, 59, 60, 61. fat in cream from specific gravity. 2 17. percentage of steri- lised milk in fresh milk, 153. Camel, milk of. Compo- sition of. 323. ( lamembert cheese, 301, 303, 307. 314. Cane sugar — Addition of. to con- densed milk, 1 16. Adulteration of milk by, 137. 1 detection of, in milk, s'.t. E-t imation of, in milk, ^7 lie it of combustion of, 335. Sweet ne^s of, ll Cans, Sample. 162. Cantal cheese, 316, Cap i .it \ , Seal . "t appa- ratus, 278 Capillary attract ion (see Swjaa • if >;/,'/'■ | ( lapric aoii INDEX. 363 Caprin, 35. Caproic acid, 44. Ratio of, to butyric acid in butter-fat, 264. Caproin, 35. Caprylic acid, 44. Caprylin, 35. Carbon dioxide — Estimation of, 118. In milk, 34. Caraway cheese, 302. Casein, 6, 25. Action of rennet on, 25. as a salt, 24. 0, 29. Behaviour of, with lime salts, 25. Combination of, with phosphates, 6, 25. Composition of, 25, 26. Estimation of, 112. Estimation of, densi- metric, 110. Genuine, 26. Heat of combustion of, 335. in colostrum, 130. Modifications of, 26. of gamoose milk, 329. Preparation of, 27. Properties of, 25. Reactions of, 24. Rotatory power of, 26. State of, in milk, 6. Caseinoaren, 23. Cat, milk of. Composi- tion of, 323. Change — (chemical), Lawof, 10. in composition of col- ostrum, 131 in composition of milk on standing, 133. of rotatory power (see Birotntion : Multi- rotation). of r tatory power of mi Ik -sugar on heat- ing, 15, 150. of temperature, Alter- ation of specific gravity of milk by, 66 Characters of sterilised milk, Analytical, 150. Characteristics of skim- med and separated milk, 205. Cheddar cheese, 302, 304. Cheese — Adulteration of, 317. Analysis of, 309-317. Classification of, 301- 302. Composition of, 302- 308, 314. Difference between various kinds of, 301,302. Estimation of amido- nitrogen in, 312. Estimation of ammo- nia in, 312. Estimation of albu- mose and peptone nitrogen in, 313. Estimation of alco- holicextractin,315. Estimation of aqueous extract in, 315. Estimation of ash in, 309, 311, 315. Estimation of digesti- ble proteids in, 31 3. Estimation of fat in, 309, 311, 315. Estimation of indiges- tible proteids, 312, 313. Estimation of nitro- gen in, 311. Estimation of primary products of ripening in, 310, 315. Estimation of proteids in, 310, 313, 315. Estimation of pro- ducts of ripening in, 310, 315. Estimation of salt in, 310, 311, 315 Estimation of secon- dary products of ripening in, 310, 312, 316. Estimation of soluble extract, 310. Estimation of volatile acids, 316. Estimation of water, 309, 311, 315, 317. Hard, 302, 304. Cheese — Heavy metals in, 30S. Insoluble fatty adds of cream-, 303. Moulds in, 229. Preparation uf, 298. Preparation of fat of, for analysis, 317. Proteids of, 305-307. Qualitative test for peptones in, 313. Rennet, 301, 302. Ripening of, 308. Soft, 301, 303. Sour milk, 302. Testing of, 180, 18S, 189. Chemical anatysis of water, 231-237. Chemical change, Law of, 10. Chemical control of churning, 297. Chemical control of the dairy, 158-224. Chemist, dairy, Duties of, 158. Cheshire cheese, 302, 304. Chlorhydrin, 41. Chlorides, 7. Estimation of, 75, 253. EstimatioTi of, in water, 232. Chloroform, Use of, for preserving milk sam- ples, 144. Choice of separators. Advice on, 211-214. Cholera, 230. Cholesterol, 42. in colostrum, 130. Chromogenic organisms, 228. Chrysotile — Use of, for total solids estimation, 70. Use of, for fat estima- tion, 101. Churning — Chemical control of, 297. Influence of tempera- ture on, 251. of butter, 249. Theories of, 249. Chymase (see Rennet). Chynio-caseoses, 21, 30. 36-4 INDEX. Citric acid and citrates, 7. Citric acid — Estimation of, 77. in human milk. .'>_'7. in gamoose milk, 330. in sterilised milk, 150. Inversion of cane sugar by, 88. Cladothrix, 225. Classification of — cheese, 301. micro-organisms, 225. milks, 321. schizomveetes, 225. Clotted cream, 219. Composition of, 219. Ratio of solids not fat to water in, 220. Testing of. ISO, 188, 189. Coagulation of albumin by heat. »>. 27. Coagulation by salts of mercury, •">. Cocoa, Milk, 320. Cocoa-nut oil, 25S, 267, 272, 28*. Detect ioi i of . i 1 1 butter, 291. Cold, Action of, on milk, 154. Cold storage for preserv- ing milk samples, 145. Colloids. 7. Colostrum. 129. Colour ol milk, 7. Colour of water, 231. Colour test s, Specific, for adulterants of butter, 272. Coloured-substances — Micro-organisms pro- ducing 226, 228. Colouring-matter <>f fat, 19. Colouring matter of milk, 34. Colouring of milk, Arti- 6cial, 139. Combust ion, Heal of (see //, ni of com ''Uttion i. ( 'oiniiieiri.il milk Bugar, 318. Composil ion Chemical, oi milk, 120. < leneral, of milk, 1. Composition of — albumin, 28. albuminoids, 20. asli of milk, 32. butter, 245, 246. butter, Influence oi keeping on the, 292- 296. buttermilk, 296. buttermilk, ash of, 296. casein, 25, 26. cheese, 302-308. clotted cream, 219. colostrum, 130. colostrum, human, 324. condensed milk, 146. cream, 215, 216. cream, ash of, 217. cream, froth of, 219. curd, 298. diabetic milk, 337. fat of milk. 35 frozen milk, 155, 156, 157. human milk, 323, 324, 325. human milk, ash of, 327. insoluble ash, 33 kephir, 243. koumiss. 241-243. mazoum, 244. milk, 120. milk. Change of, on Btanding, 133. milk-cocoa, 320. milk of different ani- mals, 323. milk of different breedsofcattle, 123. 124, 125, 126. milk of the ass, 323, 334. milk of the buffalo, 323. 327. milk of the ewe, 323, 331. milk of the gamoose, :;-.'s. milk of the gamoose, t ,t of, 329. milk of t lie goat , 323, 332. milk of the marc. 323, 333. milk-powders, 119. Composition of — mucoid proteid, 28. peptonised milk, 337. products of hydrolysis of casein. 2'.'. salts of milk, 33. separator slime, 210. separator .-dime, ash of, 211. skim milk, 209, 216. solids not fat. 121. sour milk whey, 299. whey, 298, 299. Compounds, Amido-,32. Condensed mare's milk, 333. ( londensed milk, 146. Analysis of, 1 1(5. Testing of, 187. Condition, Milk out of, 22S. Condition of fat in but- ter, 250. Conditions influencing action of rennet, 300. Conditions of develop- ment of micro-organ- isms, 226. Configuration of — glucose and galactose, is. lactic acid. 19. milk-sugar. 12. Constituents — Mineral, 32. of milk, 1. of solids not fat, Den- sit v of, 66. Other, 34. Constitution of — albuminoids, 20. butter, '-'. 245, 250. cream. 3, 215 fat of milk. 34. glucose and galactose, lactic acid, 18. milk sugar, 12. oleic and elaidic acids, lv ( iontamination of milk, 230. I .ml pol, ( 'hemic. il. of - churning, '-"■'7. the daii \ . 169, milk during delivery, 196. separators, 209. INDEX. :>•;:> Conveyance of — disease by milk, '229. disease by milkers, 230. disease by water, 230. Cooling milk, Practice of, in Denmark. 4 Copper solutions, Re- duction of, 15, 82. Copper-zinc couple, 234. Corps granuleux, 130. Correction of specific gravity for change of temperature 66. Cottonseed oil — Density of, 28-4. Test for, 272. Cow — Appeal to the, 136. Milk of, 1, 120, 321- 323. milk of, Composition of, 120, 323. Cow's milk koumiss, 241- 243. Cream — Analysis of, 115 Artificial of, 224. Ash of, -J16, 217. -cheese, 302, 303. Clotted (see Clotted cream ) . Composition of, 214- 216. Constitution of, 3. Definition of, 214. Density of, 217-218. Estimation of fat by measurement of, 102. Estimation of fat from total solids, 220. Evidence of existence of mucoid mem- brane in, 3. Formation of, 7. Froth of, 219. Phvsical state of fat in, 218, 338. Preservatives in, 140. Proportion of milk- sugar in. 3, 216. Proportion of proteids in, 216. Ratio of solids not fat to water in, 215, 220. Cream — Relation between fat and specific gravity in, 217. Relation between fat and total solids in, •220. Relation between milk - sugar, pro- teids, and a-h in, 216 Rising of, 133, 151, 195. rising of, Change of composition on, 134, 135. rising of, Explanation of, 206, 208. Rising of, in sterilised milk, 150, 151. rising of, Precautions to prevent, 135. Standard for, 216. Testing of, 178, 187, 189. Thickness of (see Thickness of cream). thickening Creamometer, Use of, in detecting sterilised milk, 152. Crescenza cheese, 307. Critical temperature of butter fat, 273. Crystallised milk-sugar, 9. Crystalloids. 7. Curd, 246, 298. Composition of, 298. Estimation of, in butter, 253. Curdled milk — Ash of. 33. Determination of cause of, 203. Curdling — by acidity, 7. by heat, 7. by rennet, 298, 300. milk, Micro - organ- isms, 226, 227. Dairy — Chemical control of, 158-224. chemist, Duties of, 158. Dairy — shorthorns, Composi- tion of milk of. 123- 125. Decision of Court of Queen's Bench that milk must be sold in its natural state. 135. Decision of Justices at Pontypridd that boric acid is an adulterant of butter 140. Decomposed milk, Ana- lysis of, 1 16. Decomposition of fat, 49, 292-296 Decomposition of milk. 225-22S Decomposition products of fat, 49. Definition of — butter, 245. buttermilk, 296. cream, 214. Dehydrolactic acid, 18, 19. Denmark. Practice of cooling milk in, 4. Densimetric method of fat estimation, 103. | Density (see also Specific gravity). Alteration of, by change of tempera- ture, 66. Definition of, 51. Determination of, 53, 164, 2S3. Modes of expression of, 51. of acids of series C„H,„+iCOOH, 46. of ash in milk, 65. of butter fat, 2S 1-285. of butter fat, Estima- tion of, 83. of cream, 21 7-2 IS. of fat of milk, 37-39. of fat and solids not fat in milk, 62. of glycerol, 40. of lactic acid, 19. of liquid portion of fat, 37. of milk-sugar, 9, 11. of milk-sugar in milk, 65. , of proteids in milk, 65. 366 INDEX. Density — of separated milk,338. of total solids of milk. 63. of water at different temperatures, 51. of watered milks, 196- 199. Relation between fat, solids not fat and, in milk, 56-63. Derby cheese, 302. Detection of — added water, 132,136, 196-199. adulteration of butter, 255, 291, 292. adulteration of cheese, 317. adulteration of com- mercial milk-sugar, 319. boric acid, 75. cane-sugar in milk, 89. ■cocoa-nut oil in butter, 291. colouring-matter, 139. fluorine compounds, 141. formaldehyde, 142. gelatine in cream, 224. nitric acid, 234, 2"> 4. nitrites, 234. phosphates, 235. preservatives,] 40-143, 254. salicylic acid, 141. > parated milk in milk, 132, 135. starch, 89, 137. starch in cream, 224. sterilised or diluted condensed milk in milk, 152. Determination (se«- Esti- mation)— of cause of big] fie gravity, 199. of cause of low specific ity, L97. rase "t poor milk. 27. Emulsion, Milk regarded as an, 4. Endosmose and exos- mose, 2. Energy, Surf ace.of small particles, 4. Enzymi — Action of, on milk- sugar, 17. Hydrolysis of albu- minoids by, 21, 29. in cheese, 298, 308. in human milk, 327- in milk, 6, 24. 34,298 Ripening of cheese by, 308. Secret ii >n of, by micro- organisms, 227. Equivalent, Saponifica- tion, 266. Estimation of— iity, 113. acidity of commercial milk -SUgai . 319. albumin. Ids 112,152. albuminoid ammonia, 232. albumose in ol 313. alcohol, 1 17. INDEX. 367 Estimation of — alcoholic extract in cheese, 315. alkalies, 75. alkalinity of soluble ash, 73. araidic nitrogen in cheese, 312. ammonia in cheese, 312, 316. aqueous extract in cheese, 315. ash, 73. ash of cheese, 309. 311, 315. ash in commercial milk-sugar, 319. bi rotation ratio, 318. boric acid, 76. bromine absorption, 276. calcium, 73. cane - sugar in milk, 87. carbonic acid, 118. casein, 108-113. chlorides, 73, 75, 253. chlorine in water, 232. citric acid, 77. curd in butter, 253. density of butter fat, 283. digestible proteids in cheese, 313. fat, Areometric, 192. fat, by measurement of cream, 102. fat, Centifrugal, 170- 192. fat, Densimetric, 103. fat, Gravimetric, 90- 102. fat in butter, 180, 188, 189, 253. fat in cheese, 180, 18S, 1S9, 309, 311, 315. fat in cream, 115, 172, 178, 187, 189. fat in cream from specific gravity,217. fat in cream from total solids, 220. fat, Indirect, 102-104. fat, Optical, 103. fat, Volumetric, 102, 170-192. free ammonia, 232. Estimation of — heat evolved by the action of sulphuric acid on butter fat, 277. indigestible nitrogen- ous substance, 312. insoluble ash, 73. insoluble fatty acids, 268-272. iodine absorption, 274. lactic acid, 113, 115. loss on ignition, 232. magnesium, 74. milk-sugar by alcohol, 77. milk-sugar by Fehl- ing's solution, 82-86. milk-sugar by Pavy's solution, 86. milk-sugar by polari- scope, 78-82. milk-sugar in commer- cial samples, 318. molecular weight of insoluble fatty acids, 271. nitric acid, 234. nitrogen, 105. nitrogen in butter, 253. nitrogen in cheese, 311. nitrogen incream, 116. oxygen absorbed from permanganate, 235. peptones in cheese, 313. phosphoric acid, 74. potassium, 75. primary products of ripening in cheese, 310. products of ripening in cheese, 310, 312, 315. proteid nitrogen in cheese, 311. proteids, 105-113. proteids in cheese, 310, 313, 315. refractive index, 285- 290. salt in butter, 253. salt in cheese, 310, 311, 315. saponification equi- valent, 266. Estimation of — secondary products of ripening in cheese, 31U. sodium, 75. solids not fat, 95, 100, 115. solids not fat i i i 1 mtter, 253. solubility of butter fat in acetic acid, 273. solubility of butter fat in alcohol, 273. solubility of commer- cial milk-sugar, 318. soluble ash, 73. soluble fatty acids, 270, 271. starch in milk, 89. strength of sulphuric- acid, 177. sulphuric acid, 74. total solids, 68-70. total solids in water, 232. total soluble extract in cheese, 310, 315. viscosity of butter fat, 290. viscosity of cream, 222. volatile fatty acids, 258-266. volatile fatty acids in cheese, 316. water in butter, 252. water in cheese, 309, 311, 315, 317. water in milk, 70. Ether- Behaviour of milk with, J , 2, 3. Emulsification of mu- coid by, 2. Preparation of, for fat estimation, 94. Use of, for preserving milk samples, 144. Ethoxide, Sodium — Action of, on fat, 36. Formation of, during saponification, 36. Eucasin, 320. Evening milk, morning and, Variation of, 127. Evidence for and against existence of membrane round fat globules, 1-6. 368 Ewe, Milk of, 323, 331. Examination Bacteriological, of water, 237. Microscopical, under polarised light, 279- 281. of commercial milk- sugar, 318. Physical, of batter Eat, 279-291. Expansion of — ■ cream, 338. fat of milk, 281, 339. milk, 06. separated milk, (ill, 338. Explanation of rising of— cream, 206. fat globules, 205. Extract — Alcoholic, of cheese, 315. Aqueous, of cheese, 310, 315. Soluble, of cheese, 310. Extractor — Soxhlet's, 93, 94, 97, 98. Siin-t ham's, 100. FAT(seeal80 /In/fur faf), 1-6, 34-50,321,326, 329. Adult era tini 1 1 if cheese u it h Foreign, 317. Change of percentage of, on standing, 133- 1 35. Composition of, of milk, 35. Density of,in milk, 65. Difference bel ween bul t e r t at and other, 257. [•'at , Kl im.it ion nf Areometric, 192. by measuremenl of mi. 102. Centrifugal, 170 192. Den 1 1 1 1. 1 1 [i . 103, Gravimetric, 90 102. in butter, 180, 188, 189, 258 l-'.it , Estimation of — in cheese, 180, 188, 189, 309, 311, 315. in cream, 115, 172, 178, 187, 189. in cream from specific gravity, 217. in cream from total solids, 220. Indirect, 102-104. Optical, 103. Volumetric, 102, 170- 19-2. Fat in separated milk, Percentage of, 209, •224. Fat, Limits for, 120, 123, 135. Fat of milk, 34-50. Action of heat on, 37. Composition of. 35. Density of, 37-39. Expansion of, 39. 339. Heat of combustion of. 39, 335. of different animals, 321, 322. Refract ive index of, 39. Separation of, on solidification, 37. Solubilities of, 37. Fat, Physical state of, in butter, cream, and milk. 2, 5, 250, 338. Fat, Preparation of, of cheese for analysis, 317. Fat, Relation between — and specific gravity in cream, 217. and bhiokness of cream, 221. total solidsand specific gravity, 56-63. Fat, Size oi globules of, 34, 321, 323, 332. Fa1 , Variat ions of — Daily. 127. in differenl churns, 126. in milk, 120, 123. 1 25. iii single i •"« b, 123. Monthly, 127. on partial milking. 12S. 9< i onal, 126. Fat, Variations of — with solids not fat, 129. Fatty acids, 1, 43-49. Fehling's solution, 82. Estimation of milk- sugar by, M2-86. test, 82. Fermentation — Alcoholic, 6. '227. Butyric, 227. Lactic, is, -226. of milk-sugar, 17. Fermented milk, Analy- sis of, 117. Flasks, Standardisation of, 345. Fluoborates as preserva- tives, 139. Detection of, 141. Fluoboric aeid, Dse of, for preserving milk samples, 144. Fluorescence, 7. Fluorides as preserva- tives, 139. Detection of, 141. Fluosilicates as preser vatives, 139. Detection of, 141. Food, Milk as a, and a medicine, 334-337. Fool and mouth disease, 229. Fore milk, 129. Formaldehyde as a pi e servative, 139 Detection of, 1 42. Detection of, in but- ter, 255. Injurious effects of, 140. Formalin (Formine, Fot mal. orFormol 1. 142. in butter, 254. I'sc of, for presen Log milk samples, 1 I I. Formic acid, 41 , 69. produoed on beating milk, 1 15. Formula for calculating fat in cream from specific kvity. 217. calculating fat from cream solids, '-'20. calculating fat in milk, 56 65, INDEX. 3U9 Formula for — calculating fat in separated milk, 207. calculating proteids, 111, 112. calculating thickness of cream, 223. heat equivalent of apparatus, 27S rate of distillation, 263. relative molecular Maumene figure, 278. Free ammonia, 232. Fresh butter, 246, 247, 256. Difference between, and salt butter, 248, 256. Froth of cream, Com- position of, 219. Frozen milk, Composi- tion of, 155-157. G G.ALACTIN, 24. Galactinic acid, 16. Galactose, 17. Birotation of, IS. Constitution of, 18. Rotatory power of, IS. Galacto-zymase, 24. Gamoose, Milk of (see also Bufalo), 328- 331. Composition of, 328. Fat of, 329. Proteids of, 329. Sugar of, 330. Gelatine — Detection of, in cream, 224. Nutrient, 237. General — action of hydrolysts, 32. composition, 1. properties of acids of series CH^+iCOOH, 46. Genuine casein, 26. Genuine, Method of judging whether milk is, 133, 135, 136. German cows, Composi- tion of milk of, 125. Gervais cheese, 301, 303, 314. Glamer cheese, 302, 307. Globules of fat, 1-6. in butter, 249. in condensed milk , 147. in milk, 34. Microscopical appear- ance of, 2. Size of, 34, 321, 323, 332. Surface energy of, 4. Globules of water in butter, 250. Globulin, 23, 28. in colostrum, 130. Gloucester cheese, 302, 305. Gluconic acid, 8. Glucose, 17. Addition of, to con- densed milk, 146 Birotation of, 18. Constitution of, 18. Rotatory power of, 18. Glucosone, 8. Glyceric acid, 40. Glyeerides, 1, 34. Glycerine, Adulteration of milk by, 137. Glycerol, 34, 40-42. Action of acids on, 41. Action of alkalies on, 41. Action of heat on, 40. Density of, 40. Oxidation of, 40 Properties of, 40. Refractive index of, 40. Solubility of, 42. Glyceroxide, Formation of, during saponifica- tion, 36. Glyceroxides, 36, 4!. Glycollic acid, 41. Glyoxylic acid, 41. Goat, Milk of, 323, 332. Cheese from, 302. Composition of, 323, 332. Gorgonzola cheese, 302, 306, 307. Grana cheese, 305, 3U6, 307. Gravimetric methods for estimation of — bromine absorption, 276. fat, 90-102. milk-sugar, S2-85. Green milk, 228. G tuyere cheese, 302, 304, 306, 307. Guernsey cows, Com- position of milk of, 125, 126. H Heat, Action of (see Action of hi U). capacity of apparatus, 278. evolved by the action of bromine on fat, 276. evolved by the action of sulphuric acid on fat, 277. Heat of combustion of — fat, 39, 3:^5. proteid, 335. sugar, 335. Heavy metals in cheese, 308. High specific gravity, Determination of cause of, 199. Holstein cows, Composi- tion of milk of, 12-"). Human colostrum, 324. Human milk, 323-327. Artificial, 336. Ash of, 327. Citric acid in, 327. Composition of, 324. Enzymes in. 327. Fat of, 322, 326. Fat globules of, 321. Proteids of, 327. Reaction of, 323. Sugar of, 326. Taste of, 323. Variations of, 324-326. Humanised milk, 336. Hydrocarbon in fat of milk, 35. Hydrofluoric acid, Use of, for preserving milk samples, 144. Hydrolo-albumoses, 21. 24 370 INDEX. Hydrolo-caseone, 21. Bydrolo-caseoses, 21, 30. Hydrolysis — Action of, 32. of albuminoids, 21, 22. of fat by alkalies, 35. of fat by sulphuric- acid, '262. of fat by sulphuric acid, Heat evolved by, '-'IT. of milk-sugar, 8. Products of, of albu- minoids, 21, 29, 30. Products of, of fat, 40-49. Hydrolyst, 22. Hydrolyte, 22. Hyphomycetes, 225. Hypozanthine, 34. I IGNITION, Loss on, 232. Index of refraction (see Refractivt index). Indigestible nitrogenous substance in cheese, Estimation of, 312. Indirect methods for the estimation of fat, 102- 104. Influence of — keeping on butter, _MS, -292-296. temperature on churn- ing, 251 . temperature on water in butter, 249, 256. temperature, f fat in separated milk. 207. Injurious effects of — boric acid, 139. formaldehyde, 139. I » r ■ ■ ■ .it ives, 139. salicylic acid, [39. Lised milk, 1 16. Insoluble ash of milk, :;::. 73. Insoluble fatty acids, Estimation of, 268- 272. Linn! of, -272. of cream cheese, 303. Insoluble fatty acids- Relation between, and critical temperature, 273. Inspection of source of water supply, 231. Interpretation of results of— bacteriological exam- ination, 238. proximate analysis of butter, 255. water analysis, 236. Invertase, 17. Estimation of cane- sugar by, 88. Investigation of water supply, 230-239. Iodine absorption, 274. Iodine solution, Hiibl's, 274. Jersey cows, Composi- tion of milk of, 123- 126. Junkets, 32(1. K Keeping, Effect of — on butter fat, 292-296. on water in butter, 248. Kephir, 243. Analysis of, 117. ( lompositioD of, 243. Kerry cows. Composi- tion of milk of, 123- L26. Ketoses, 15. Koumiss, 241-243. Analysis of, 1 17. on '- milk, CompOSJ Hon of. 241-243. man's milk, Com- position of, 24 1 . Lai talbi Mi-- (set also Albumin), 6,22,27. I 1 ... 1 1 . . r 1 of, ins 112. Lactase, 17. Lactation — Variations of human milk with, 324. Variations of cow's milk with, 124, 131. Lactic acid, 18-20. Estimation of, 1 13. Lactic fermentation, 18, 226. Lactide, 18, 19. Lactobionic acid. 8. Lacto-caramel, 9, 15. Lactoform, 320. Lacto-globulin (see also Globulin), 23, 28. Lactometers. 54, 164- 167. Determination of spei Lfic gravity by, 165-167. Faults of, 54. Galaine's, 165. Quevenne's, 104. Soxhlet's, 164, 165. Standardisation of, 346. Thermo-, 165. Vieth's, H'4. Lacto-protein, 23. Estimation of, 109. Lactoscope, 103. Lactose (see Milk-sugar). Lacto-somatose, 321 I. Laurie acid, 35, 4.">, 46. Laurin, 35. Law of chemical change, Harcourt's, 10. Law of distribution of a substance between two solvents, 4. Layf, Evidence of exist- ence of a, round fat globules, 1-3. Lecithin, 19. in colostrum, 130. Leicester chet se, 302. Leucine, 20, 22, 32. Leuconostoo, 225. Limburg cheese, :>I7. Lime (see ( 'alcium). Lime-water a- a Stan- dard solution, 1 Hi. Limits for — ash, 133. chlorine, 133. density of butter fat, 38, 284. INDEX. 371 Limits for — fat, 120, 132, 135. potash absorption, 267. Reichert process, 259, 260, 262. refractive index, 2S9. solids not fat, 120, 132, 133. soluble and insoluble fatty acids, 272. total nitrogen, 133. V'alenta figures, 274. Limits of composition of human milk, 325. Limits, Societvof Public Analysts', 132. Linolenic acid, 48. Linolic acid, 48. Liquid portion of fat — Composition of, 37. Specific gravity of, 37. Llama, Composition of milk of, 323. Loss on ignition, 232. Lowspecific gravity, De- termination of cause of, 197. M Magnesium, Estimation of. 74. Majorcan cheese, 306. Mammals — marine, Milk of, 1, 322, 323. Milk of, 1. other than the cow, Milk of, 321-334. Mammary tissue. Adul- teration of milk by, I3S. Mannitol, 17. Mare, Milk of, 333. Composition of, 323, 333. Sugar of, 6, 322, 334. Mare's milk koumiss, 241. Margarine — Detection of, 292. Properties of, 282, 290. .Mazoum, 244. Organism from, 227, 244. Medicine, Milk as a food and a, 334-337. Melting — Behaviour of butter on, 290. point of acids of series CnH8„nCOOH,46. point of fat, 37. 291. Membran-slim, 2. Composition of, 3. Properties of, 29. Membrane — Mucoid, 2, 3. round fat globules, 1-6. Mercury salts — Coagulation of pro- teids by, 5. Use of, for preserving milk samples, 144. Metabolic ratio, 335. Metals, Heavy, in cheese, 308. Meta - phenylene - dia- mine, 152, 234. Meta - phosphoric acid, precipitant for pro- teids, 82. Method for analysis of cheese — Duclaux, 315, 316. Richmond, 309, 311. Stutzer, 311-315. Method for detection of— added water, 133, 197. cane-sugar in milk, 137. Cotton, 89. separated milk, 133- 135. sterilised milk, 152. Method for dilution of cream to standard thickness, 222. Method for estimation of— acidity, 113. acidity in commercial milk-sugar, 3 1 9. albumin, 108-112, 152. albuminoid ammonia, 232. albumose, 313. alcohol, 117. alcoholic extract of cheese, 315. Method for estimation of— amidic nitrogen, 312. ammonia, 312, 316. aqueous extract of cheese, 310, 315. ash, 73. ash in cheese, 309, 31 1, 315. ash in commercial milk-sugar, 319. birotation ratio, 318. boric acid, Thompson, 76. bromine absorption, 276. Hehner, 276. Hehner & Mitchell, 276. calcium, 74. cane-sugar by inver- tase, 88. Muter, 87. Stokes and Bodmer, 88. carbonic acid, 118. casein — Densimetric, 110. Duclaux, 110. Frenzel and Weyl, 108. Hoppe-Seyler, 108. Lehmann, 112. Maissen and Musso, 109. Richmond, 113. Ritthausen, 10S. Schlossman, 113. Sebelein, 109. Van Slyke, 108. chlorides, 75. chlorine in water, 232. citric acid, 77. curd in butter, 253 density, 53, 54, 165- 167.' density of butter fat, 281, 2S3. digestible proteid, 313. extract in cheese, 310, 315. fat. Centrifugal — Babcock, 170-173. Gerber, ISO- 190. Leffmann and Beam, 174-180. Stokes, 191, 192. 372 INDEX. Method for estimation of— fat, Densimetric, 103. in cream, 217. - chlet, 192-195. fat, Gravimetric — Adams, 91-94. Babcock, 100. Bell (Somerset House), 94-96. Macfarlane, 101. Ritthausen, 101. Soxhlet, 98. Storch, 9 i. '.IT. Wanklyn, 101. Werner-Schmid,98- 100. fat in butter, 180, 188, 189, 253. fat in cheese, 188, 189, 309, 311, 31.-i. fat in cream, 1 15, 17—, 17*, 187, 189. fat, Indirect, 102-1U4. fat. Volumetric, 102, 170-192. fat, Volumetric, Soxhlet's, 192-195. free ammonia, 232. heat evolved by buI- phuric acid — Maumene, 277. Richmond, 278. Thompson & Ballan- tyne, 277. indigesl Lble nit rogen- ■ hi-- substa ace, 31 '-'. insoluble ash, 73. insoluble tatty acids Am* rican Associa- tion <>f Official A g ricull u r a 1 Chemists, 269 iTleischmann and Vieth, 269. FTehner and Angell, iodine absorption, 27 1. lad i' ■ • i ■ 1 . 1 13. I gnil ion, 232. magnesium, 74. milk sugar, I mel pic O'SuIlivai Wein, B4. milk -sugar iri commer cial imple . 31 8. Method for estimation of— milk - sugar, Polari- metric — Deniges, B2. Richmond and Boselcv, 81. Vieth, 80. Wiley and Ewell, 78. milk - Bugar, Volume- tric— Fehling, So. I'avy, 86. molecular weight of insoluble fatty acids, 271. nitric acid. 23.4. 255. nitrogen, Kjeldahl's, in.-., oxygen absorbed from permanganate, 235. peptones, 313. phosphoric arid, 74. potassium, 75. products of ripening in cheese, 310. proteid nil rogen, 313. proteids, 105-108. Deniges, 107. Ritthausen, 106. refractive index, 2S.V- 290. salt in butter, 253. salt in cheese, 310, 311. 315. saponification equi- valent, 266, 267. sodium, 7"'. solids lint tat, 95, Kin, 115. solid- lint fat in 1 Hit - ter, 253. soluble ash, 73. Boluble fatty acids, 268 272. solubility of butter fit in acetic acid, Cli.it taway. Pear- m, mi. and Moor, 271. jolubilil j "i butter t.it in alcohol, 273 Bolubility of commer- cial milk iigai ,.".l 8. stanh, 89. Btrentrth oi Bulphuric rengtfa ol ,-i acid, 1 77. Method for estimation of- Bulphuric acid, 74. total solids — Adams, 70. Babcock, 69. Duclaux, 7". Uanntner, 7". Gerber and Raden- hausen. 7. ( )w propionic acid (see Uact\C mil/). Palmitic acid, 35, 45, 46, 47. Palmitin, 35. Palm-nut oil, 267, 272, 284. Para - phenylene - dia - mine. Use of, for detecting sterilised milk, 145, 152. Parmesan cheese, 302, 305, 307. Partial milking, Varia- tion of fat by, 128. Pasteurised milk, 146, 149. Pathogenic organisms. 226, 229. Pecto-galactinicacid. 1 6. Pedigree shorthorns. Composition of milk of, 123-125. Penicillium glaucum, 229. Pepsin, 21, 23. Pepto-albumoses, 21. Pepto-caseone, 21. Pepto-caseoses, 21, 23. 1'cptones, 21. in cheese, 306, 309. 313. in colostrum, 1 3D. Test for. 313. Peptonised milk, 337. Peptonising organisms, 22li, 227 Permanganate, potas- sium, Standard solu- tion of, 235. Phenylgalacto8azone,18. Phenylgluoosaeone, Is-. Phenylhydrazine, 8, 16, is.' Phenyllactosazone, 8, 16. Phosphates, 33. ( !ombination of, with casein, 6, 2.".. 26. Detection of, 235. Phj deal — examination of butter fat, 279-290. Btate of casein in milk, li. 22. 2/.. atateof fat in milk.2 6. State ot tat in cream, 338 341 Pickled butter, 265, 256. INDEX. 375 Picro-carmine, Staining of membrane by, 2. Pipettes, Standardisa- tion of, 345. Placentine cheese, 306. Pleuro-pneumonia, 229. Polarised light, Micro- scopical examination of butter under, 279- 281. Pont l'Ev^que cheese, 301. Poor milk, Determina- tion of cause of, 200. Porpoise, Milk of, 323. Port du Salut cheese, 302, 307. Potash absorption, 266. Potassium — bichromate, Use of, for preserving milk samples, 144. Estimation of, 75. nitrate as a preserva- tive, 139, 254. nitrate, Standard solu- tion of, 234. permanganate, Stan- dard solution of, 235. Powders, Milk, 149. Practice of cooling milk in Denmark, 4. Precautions — against conveyance of disease, 23t>. Sanitary, 239. to prevent rising of cream, 135. Preparation of — albuminoids, 20. butter fat for analysis, 257. casein, 27. cheese, 298. condensed milk, 146. copper - zinc couple, 234. fat of cheese for analy- sis, 317. humanised milk, 336. lactalbumin, 2S. milk-sugar, 17. nutrient media, 237. rennet, 300. samples of butter for analysis, 251. sterilised milk, 149. Preservation of milk samples, 144. Preservatives, 139-145, 254. Adulteration of milk by, 139. Advantages of, 140. Detection of, 140-143. Estimation of, 75, 76, 255. in butter, 140, 254. in cream, 140. Injurious effects of, 139-140. Objections to, 139. Principle — Colouring, 7, 34, 49. Odoriferous, 7, 34, 49. Problems, Solution of analytical, 197-205. Process, Reichert (see also Method), 258- 262. Theory of, 263-266. Products — derived from milk- sugar, 18-20. formed from milk by the action of micro- organisms, 240-244. of decomposition of fat, 49, 50. of hydrolysis of fat, 35, 36, 40-49. of hydrolysis of pro- teids, 21. of ripening of cheese, 305, 310, 312, 315, 316. Other, derived from milk, 318-320. Properties — analytical, of butter, Influence of keeping on, 292-296. General, of acids of the series CnH.^rCOOH, 46- 47. General, of linolenic acid, 48, 49. General, of linolic acid, 48, 49. fjreneral, of oleic acid, 47, 49. of albuminoids, 20. of buttermilk, 296. Properties — of butyric and allied acids, 43-47. of casein, 25, 26. of glucose and galac- tose. 18. of glycerol, 40-42. of milk fat, 37-40, '257. of milk-sugar, 15-17. Proportion of — milk -sugar in cream, 3, 215, 216. proteids in cream, 2, 215-216. solids not fat to water in butter, 246. volatile acids to fat in cheese, 316. water in butter, 246- 248, 256. Proteid — nitrogen, Estimation of, 105, 313. -compounds, 320. Mucoid, 2, 24, 28. Mucoid, in butter, 2, 246. Proteids, 1, 6, 7,20-32. Coagulation of, by nitrate of mercury, 5, 78, 83. Composition of, 20, 25, 26, 28. 329. Density of, in milk, 65. Estimation of, 105- 11 3. Heat of combustion of, 335. Hydrolysis of, 21, 22. in butter, 2. Micro-organisms act- ing on, 226, 227. of cheese, 298, 305. of colostrum, 130. of human milk, 327. of milk, 6, 7, 20-32. of milk of different mammals, 322. of whey, 30, 299. Proportion of, 2. Proportion of, in cream, 2, 215, 216. Ratio between, milk- sugar, and ash, 121. Ratio between, milk- sugar, and ash, in cream, 216. Reactions of, 20, 26, 27, 28. 376 INDEX. Proteids — Removal of, in estima- tion of milk-sugar, 78, 83. Yield of urea £rom,335. Proto-albumoses, 21. Proto-caseoses, 21, 29, 30, 31. Composition of, 29, 30. Reactions of, 31. Proximate analysis of 1 .utter, 251-255. Proximate analysis of butter, Interpretation of results of, 255. Pseudo-solution, 7. R Rabbit, Milk of, 323. Rancidity, 49, 50. Rate of — change in percentage of fat on standing, 133-135. distillation of acids of the series C„H,,1+,COOH, 46. distillation of volatile tat t \ acids, 263. flow, Influence of, on percentage of fat in separated milk. 207. Ratio — Anabolic and meta- bolic, 335. 336. bel ween milk-sugar, proteids, and ash in milk. 121. between milk-sugar, proteids, and ash in cream. 216. bel ween Reicherl and Reicherl Wbllny figures, 262, bel ween solids nut tat and water in bul ter, 246, 256 bel ween Bolide i and water in dotted cream, 220. between water, solids nut t.it . and Bah in cream, 21 5. Read ion of human milk, 823. milk, B. Reaction of — milk of different mam- mals, 322. ion, Specific tem- perature, 277 Reactions of — albuminoids, 20, 26, 27, 28. caseones, 31. caseoses, 30, 31. cholesterol, 42, 43. deutero caseoses, 31. dys-caseoses, 30, 31. milk-sugar, 6, 15-17. proto-caseoses, 31. Recknagel's phenome- non, 67, 68. Red polled cows, Milk of, 123-125. Reduction of copper solutions, 15, 82. Refractive index — Estimation of, 285, 290. of fat of milk, 39. of glycerol, 40. Relation between, and Reichert figure, 287, 289. Relation between, and scale divisions of But vro-refracto- meter, 288. Refractometer Abbe, 285, 287. Butvro , 287-290. Oleo-, 285-287. Regulations against con- veyance of disease, 230. Reichert — figure, Limits for, 259, 260, 262. figure. Relation be- tween, and i> tive index, 287,289. process, 258 263. process, Theory of, 263 266. Wollny figure, 260. Wuiinv figure, Rela tion between, and critical tempera Mire, 273. Relation bet ween critical temperature and insoluble fattj . 273. Relation between — critical temperature and Reichert - W o 1 In v figure, 273. density, fat and solids not fat, 56-66. density, fat and Bolids not fat, Formula? for, 60. fat and specific grav- ity of cream, 217. fat and Bolids not fat, 129. fat and total solids of cream, 220. milk-sugar, proteids, and ash, 121, 216. potash absorption. and saponification equi- valent, 267. refractive index and Reichert figure, 287, 289. temperature, rate of flow, speed, thick- ness of cream and fat in separated milk, 207. thickness of cream and percentage of tat. 221. volatile acids and fat Of cheese. 316. water and solids not tat in e 1 o t t e d cream, 219. water and solids not fat in cream, 215. Relative molecular Mau- mene figure, 27s. Remedy for conveyam e Of disease. 230. Removal of proteids in estimation of milk- sugar, 7s, S3. Rennet, 21. 23, 298 301. Action of, on casein, 25. 298. Action of. on milk, 23. cheese, 301, 302. Conditions influenc- ing act ion of, 300, .-.in Influent e of tempera- ture Upon action ot. 300, -".id. INDEX. 377 Rennet — Optimum tempera- ture of, 300. Preparation of, 300. Secretion by micro- organisms of an enzyme resembling, 227'. Testing of, 301. Results of — bacteriological exa- mination, Interpre- tation of, 238. proximate analysis of butter, Interpreta- tion of, 255. water analysis, Inter- pretation of, 236. Ripening of clieese, 308. bv micro - organisms, v308. by enzymes, 308. Products of, 305, 310, 312, 315. 316. Rise of specific gravity of milk on standing, 67. 68. Rising of cream — Change of composi- tion on, 133-135. Explanation of, 208. in sterilised milk, 145, 150. Precautions against, 1 35. Romadur cheese, 317. Ropy milk, 228. Roquefort cheese, 305, 308. Rotatory power, 14. of casein, 26. of glucose and galac- tose, 18. of milk-sugar, 10, 11. Rule— for averaging specific gravities, 64. of use in chemical control of milk dur- ing delivery, 197. to prevent conveyance of disease, 230. Sacchakomyces cere- visise, 227. Saccharomycetes, 225. Salers cheese, 316. Salicylic acid — as a preservative, 139. Detection of, 141. Use of, for preserving milk samples, 144. I Salt- Action of, on butter, 248. Adulteration of milk by, 138. butter, 246-248, 256. butter, Difference be- tween fresh and, 248, 256. Estimation of, in butter, 253. Estimation of, in cheese, 310,31 1,315. Existence of lactic acid as a, 20. Salts — Alkaline, 7. of calcium, 7. of casein, 6, 7, 24, 25,26. of fatty acids, 44, 45, 46, 48. of magnesium, 7. of milk, 7, 33. of milk, Probable composition of, 33. of potassium, 7. of sodium, 7. Sample cans, 162. Samples — of butter, 2ft 1. of butter, Preparation of, for analysis, 25 1 , 257. of water, 23 1 . of water for bacterio- logical examination , 237. Preservation of, 144. Taking of, 159, 160. Sampling of — butter, 251. milk, 159, 160. water, 231, 237. Sanitary matters, 229, 230, 239. Sanitary precautions. Summary of, 239. Sanose, 320. Saponification, 35. equivalent, Estima- tion of, 266 Explanation of, 36. Sarcina, 225. rosea, 228. Sarcolactic acid, 19. Scale for correction of specific gravity of milk for temperature, 67. Scale, Milk, 61. Scarlatina, 229. Scarlet fever. 230. Schizomycetes, --'>. Secretion, Normal, of mammals, 1 . Sediment, Determina- tion of cause of. 204. Separated milk, 205-209. Adulteration of milk with, 136. Characteristics of, 205. Detection of, in milk, 135. Influence of tempera- ture, rate of flow, speed, and thickness of cream on fat in, 207. Testing of, 173, 177, 185. Separation of fat on solidification, 37. Separators, 209-214. Advice on the choice of, 211-214. Control of, 209. Separator-slime, 210. Ash of, 211. Sesame oil — Density of, 284. Test for, 272. Sheep, Milk of (see also Ehoe), 323, 331. j Sheep, milk of, Cheese from, 302. Shorthorns. Milk of, 123- 126. Size of globules. 34, 321 . 323, 332. Skim milk (see also Separated milk), 205-209. Adulteration of milk by, 136. Analvsis of, 116. cheese. 302-305. Detection of, 135. Globules of fat in, 208. Testing of, 173, 177, 185. 378 INDEX. Skimmed milk, Charac- teristics of, 205. Slim-membran, 2. Slime, Separator, 210. Smell of water, 231. Smell, unusual. Deter- mination of cause of, 201. Soapj- milk, 228. Society of Public Analysts' — limits, 132. method for total solid estimation, 68. Sodium, Estimation of, 75. Sodium thiosulphate, Standard solution of, 235, 275. Solid portion of fat, Composition of, 38. Solidification, Separa- tion of fat on, 37. Solidifying points (see under names of sub- stances . Solids not fat — Composition of, 121. Constituents of, 65, 121. constituents of, Den- si tv of, ()."). Density of, (JO, 62. Estimation of, in butter, 253. estimation of, Somer- set Utilise method for, 95. Limits of, 120, 132, 133. Ratio between water and, iii butter, 246. Ratio between water and. in cream, 215. Kal in liet ween water, ami clotted cream, 21! I. Variations of, a ing in season, L26. Vai iai ions of, in milk, 120 122. 12 1 128. Vai iai inn- ut, iii milk , 124. Solid-, Total (see Total aolida). 8olubility oi batter fal in aoetic e I' I. 273 Solubility of — butter fat in alcohol, 273. calcium salts of acids of series C„H.;„+1COOH, 44, 45, 46. fat, 37, 39. fatty acids in alcohol, 45, 46, 47. fatty acids in water, 43, 44, 45, 47. glycerol, 42. lactic acid, 20. milk-sugar, 9, 12, 15. milk - sugar, Estima- tion of, 318. Soluble- extract of cheese, Esti- mation of, 310, 315. fatty acids, 35, 43, 44, 46, 47. fatty acids, Estima- tion of, 26S-271. fattv acids, Limits of , 272. Solution — Fehling's, 82-86. Nessler, 233. of anal v t i cal problems, 197-205. of milk sugar, 9, 318. Pavys, INDEX. Thermolactometer, 164, 165. Thermometers, Stand- ardisation of, 346. Thermometric method for the estimation of bromine absorption, 276. Thick butter, 21'.>. Thick, Determination of reason for milk being, 204. Thickening of cream, Artificial, 224. Thickness — Method for diluting cream t > standard, 222. of cream, 221. of cnam, Influence of, on percentage of fat in separated milk, 207. Tl i i< >sulphate solution, 235, 27.-) Thymol, Use of, for pre- serving milk sam- ples, 144. Total nil rogen in cheese, Kstimat ion of, 31 1. Total Solids Density of, 63 Kstimat on of. (iS-71, K,7 I To. Estimation of, in cream, 1 15. Estimation of, in water. 232. Kstimat ionoffatfrom, in cream, 220. Total soluble exl ra< I ol cheese. 310, 315. Trypsin, 21. Trypto-albumoses,21,30. Trypto-caseone, 21 . 30. Tr\ | » t 0 21, 30. Tuberculosis, 229. Typhoid, 230 Tyrosine 22. 32 in colostrum, 130. Tyrot lirix. 308. U U NSW I, ill -.Mi eon densed milk, 14(», 147. Unsweetened condensed milk — Detection of, in milk, 152. Unusual taste or smell, Determination of cause of, 201. Urea, 7. 34. in colostrum, 130. Heat of combustion of, 335. Yield of, from pro t ids, 335. Variation' of — analytical properties of butter on keep- ing, 292-296. ash, 121. composition of human milk, 324. composition <>f human milk with lactation, 324. density of butter fat with temperature, 282. fat, 120, 123. fat and solids not fat, according to season, 126. fat and solids not fat, Daily, 127. fat and solids not fat in buttermilk, 296. fat and solids not fat in different churns, 126. fat and solids nol fal in milk, 120. fat and solids > in milk of gamoose, 328. tat and Solidfi not tat in milk of Bingle cow. 123, 124. fat and Bolids tlOl t.it in whey, 2'.''.l fal and solids not tal on partial milking, 128. fat with BOlidfl not 129. morning and e\ ening milk, 128. Variation of — potash absorbed, 267. Reichert figures. 269, 260, 262. refractive index. 287, 289. refractive index with temperature. 289. solids not fat, 120, 122, 124. soluble and insoluble fatty acids, 272. water in butter, 247. water in butter <>n keeping, 248. Vegetable oils, Test for, 272 Violet milk, 22S. Viscogen, 224. Viscosity of — acids of the series C„H,.„+iC<><)H. 47. hotter fat. 290. cream. 221 -223. milk. S Volatile acids in cheese, 316. Volatile acids in kou- miss, Estimation of, 117. Volatile fatty acids, Estimation of, 258 263. Volatility of lactic acid, 19. Volumetric method for t he estimation of milk- sugar, 85, s ». Volumetric method for the estimation of milk tat, 102, 17" 192 W \V Mil; Adulteration of butter with. 255. Ammonia free, 234. analysis, 231 235 .i n.i 1\ -a-, hit' Hon of result 286. baths, 72. 168 Boiling points at, 347. i on\ i-\ an. <■ of disease by, 230. INDEX TO PROPER NAMES. 381 Water — Conveyance of disease by, Precautions a- gainst, 230. Density of, 51. Detection of added, 133, 197. Detection of added, Method for, 197. Estimation of, in but- ter, 252. Estimation of, in milk, 70. in butter, Effect of keeping on propor- tion of, 248. in butter, Influence of temperature on pro- portion, 249, 25(5. in butter, Proportion and variations of, 246, 247. in butter. Standard for, 255. Water- in cheese, Estimation of. 309, 311, 315, 317. Lime-, as a standard solution. 113. oven, 71, 72 Ratio between, and solids not fat in butter, 246 Ratio between, and solids not fat in clotted cream, 219. Ration between, and solids not fat in cream. 217, 220. supply, 230. supply, Investigation of, 230. Weights, Standardisa- of, 342. Welsh cows, Milk of, 125, 126. Wensleydale cheese,. 302. Westphal balance, 54. Whale, Milk of, 323. Whey, 298-300. Analysis of, 119. Composition of, 299. Proteids of. 30, 299. Sour milk. 299 Testing of, 177, 185. Variations of fat in, 299. Wine, Milk, 320. Woman's milk (see Human milk). Working of butter, 250. Yk ast, Pink, 228. Yeasts, 225. Yellow milk, 228. YYirk cheese, 305. INDEX TO PROPER NAMES. Ai;i;k, 285, 287. Abraham, 93. Adams, 70, 71, 90, 91, 93, 96, 98, 99, 100, 101, 102, 169, 345. Aikman (see Cameron). Allen, 38, 87, 99, 44, 25S, 259, 262, 267, 274, 282, 322. Allen and Chattaway, 91. Allen and Cox, 308. Allen and Homfray, 36. Allen and Moor, 293. Amagat and Jean, 285. Ambuhl, 259. American Association of Official Agricultural Chemists, 69, 100,269. Angell (see Hehner). Aschmann, 147. Ashworth(see»S'wi€//ir7 (see also Allen). ' (hat taw ay, Pcarmain, and Moor, 274. Chittenden and Painter, 23, 26, 29. Clauznitzer and Mayer, 60. Clayton, 294. Coignet, 237. Cornwall, 272. Cornwall and Wallace, 259. Cotton, 89. i | Cripps, 139. ( Irismer, 273. Cnun, 255. I).\i>iii (see Spampani). Danilewaky (Bee Radt »• h< i a si a i. Deniges, 82, 83, H»7. I >i\ aula, .".17. Donne", ISO. Dragendorff, 12. Dronot, 291. Duclaux, 22, 23, 70, 102, 110, 162, 263, 264, 303, 304, 306, 807, 308, 315, 816, 334. Duffy, 36. Dumas, 106. Dyer, 128. Dyer and Roberts, 99. Dyke v. Gower, 135. IGooch, 75, S3, 84, 85, 107, 109, 110, 310. < lower (see Dyke). Griffin, 71. ( rrunzweig, 43. Embket, 170. Emery (see Schw initz). Estcourt, 282. Eugling, 130, 132. Ewell (sef Wiley). Fabek. 91, 103,247,272. de Fabris (see Villa- vecchia). Farrington, 67, 141. Fehling, 15, 28, 82, 83, 84, 85, 86, S7, 88, 137, 326. Fernandez-Krug and Harnpe, 102. Fischer, 8, IS. Fleischmann, 34, 38, 59, 60, 61, 125, 130, 147, 210, 217, 249, 296, 299, 300, 303. 304, 327, 331, 332, 333 Fleischmann and Mor- gen, 60. Fleischinann and Vieth, 269. Fox (see WanMyn). Frenzel and Weyl, 10S. Freudenreich, :08, 309. Froidevaux, 102. G < ; \ 11:1 m;k and Hugers 1h.I1. isi, 183, 184. Galaine, l(i.">. Ganntner, 7i». 102. < rarelli and ( larcano, 40. Gerber, 180, 181, L86, 188, 317. Gerber ami Raden liansin. 7", 170. 1 lei rana 1 see ( loMni). GlynBky, 01 < Inidmann. 281. H If wrnoN (seeCazt m uvt ). Hsentsch (see Schmidt). Eager, 260, 269. Halliburton, 23. Hammarsten, 22, 23, 26, 30. Hampe (see Fernanda 1- Krug). Hansenn, ^60. Sarcourt, 10. Harrington and Kinni- cutt, 327. Hart, 230. Hazen, 253. Heaton, 12s. Hehner, 40. (in, 76, 117, 118, 139, 142,143. 144, 258, 201.272.274.270, 2!)4. Hehner and Angell, 258, 259, 268. Hehner and Mitchell, 45, 40. 276, 277. Hehner and Richmond, 00, 01. Hint/.. 45. Henkel, 7- Henle, 130. Henniger, 40. Henry, 19. Hera, 228 Hewlett, 23. Hill. 99. Homfray (see . I VU n). Boppe Seyler, 20, 102, 1 i»s. 152, Houdet, 120. 131, 132. von HUbl, is. 268, 274. Hueppe, 227. ■ I QfM /■' //< r). Hunt. 27t. J] \s, 202, 2m. .1 magat). INDEX TO PROPER NAMES. 383 Johanssen, 324. Johnstone, 43, 69, 93, 271. Jones, 39, 274. K Kahlbaum, 43. Kennepohl (see Weiske). Killing, 290. Kinnicutt (see Harring- ton). Kjeldahl, 105, 106, 108, 109, 110,113,116,253, 311, 313. Koch, 2S1. Koefoed, 44. Koettstorfer, 266, 267. Konig, 299, 303, 304, 305, 332. Kreis, 262. Kiilm, 132. Landowsky, 332. Lassaigne, 129. Laurent, 81. Levels, 324, 325, 326. Leffmann, 145. Leffmann and Beam, 1 10, 117,139,163,170,174, 175, 178,180,181,262, 303, 304, 305, 345. Leonard, 142 (see also Smith). Lieben and Rossi, 43. Liebermann, 92, 102. Liebig, 237. Lindenmeyer, 42. Linder (see Picton). Lindt and Mtiller. 307. Ling and Richmond,330. Linnemann, 43. List (see Wohl). Lister, Lord, 20. Lister, R. A., & Co., 184. Liverseege, 125. Livett, 246. Lloyd, 122, 30S, 309. Longi, 262. Lowe, 122. Luck, 44. Luff, 324. M Macfarlane, 70, 101. Maissen and Musso, 109. Maissen and Rossi, 262. Mannheim, 62. Mansfeld, 261, 262,289. Marehand, 181. Marpmann, 102. Maumene, 277, 278, 279. Mayer, 262, 284 (see also Clauznitzer). Medicus and Scherer, 258. Meissl, 259, 260. Menozzi, 272 (see also Mu&to). Merckling, 259. Merkel (see Weigh). Millon, 28. Mitchell (see Hehner). Mitscherlich, 80. Molinari, 99. Moor (see Allen, Chatta- way, and Pearmain). Moore, 258. Morgen (see Behrend and Fleischmann). Morse and Burton, 271. Morne, Pigott, and Bur- ton, 102. Moser and Soxhlet, 332. Miiller, 285 (see also Lindt). Munier, 259. Musso and Menozzi, 23. Musso, Menozzi, and Bignamini, 306. Musso (see also Maissen). Muter, 3S. 87, 269, 282, 287, 289, 303, 304, 305. N Nessler, 138, 232, 233. Nicol, 279, 280, 2S1. Nilson, 259. Nitsche, 40. 0 O'Shaughnessy, 246. O'Sullivan, 83. Overend, 337. Painter (see Chitten- den). Palm, 24. Pappel and Richmond, 6, 322, 328. Parker, 93. Pasteur, 149, 240. Paterson, 180. Pavy, 86, 87, 88. Pearmain and Moor, 147, 303, 304, 305. Pearmain (see also Chat- taway). Perkins, 258. Pfeiffer. 324, 325. Piccardi, 331. Pickering {seeU.Broum). Picton and Linder, 6. Pigott (see Morse). Pizzi, 37, 39, 130, 279, 280, 321, 323, 327, 328, 331, 332, 334. Pohl, 20. Purdie, 18. Q QUEVEXNE, 164. Radenhausen and Uan- ilewsky, 23. Radenhausen (see also Gerber). Raoult, 40. Recknagel, 67, 68. Regnault, 347. Reichardt, 259, 272. Reichert, 258, 259, 260, 262,263,261,200,271, 273,287,289,291,292, 294, 295, 296, 32S. Ringer, 337. Ritthausen. 26, 101,102, 105,106,108,109,116, 119,320. Roberts (see Dyer). Rosier (sec Boseley). Rossi (see Lieben and Maissen). Rubners, 148. Russell (see Babcork). 384 INDEX TO l'KOl'ER NAMES. Salkowsky, 42. Sai tori, 262, 304, 306. Scheele, 4U. Scherer (Bee Medicus). Schiff, 142, 143. Schleicher and Schiill, 92, 93, 97, 310. Schlossmann, 1 i3. Schmid, Werner (see Werru r-Schmid). Schmidt and Hsensch, 78, 80. Schmitt, 259. Schmoeger, 10, 11, 12. Schnepel, 246. Schulze and Benecke, 307. Schweinitz and Emery, 39 Sebelein, 23,27,28, 109, 152. Sindtner, '260. Shenstone, 86. Short, 310. Skalweit, 281, 283, 285. Smetham, 68, 100, 133, 299, 303, 304. Smetham and Ash worth, 114. Smith and Leonard. 3, 1 42. Sociel V of Public Ana- lysts. 61, 68, 01, in), 132. Soldner, 7. 27, 33. Soxhlet, 27, 87, 91, 92, 93, 94, 07. 0s, loo. I or,. [13, 164, 165, 170, 192, L93, '-'to. 310 set also : ' Spallanzani, 202. Spampani and Daddi, 272. Spies and de Bl 3< o. SprengeL 53, •"■ i. Steiben, 308. Stein, 202. Stewart, I •">.'!. Stoddart, 308. Stohmann, 26, 39. Stokes, 98, 99, 170, 191, ■224. Stokes and Bodmer, 87, 88. Stoivh, 2, 3. 4,6.24,28, 29, 91, 96, 98, 102, 113, 2ln, 215, 245, 240, 250, 296. Strohmer, 327, 328, 335. Struve, 20. 244 Stutzer, 303, 304, 311, 312, 314, 315. Sykes, 62. Szombathy, 98. Tanbbt, 12. Tarnier, 334. Taylor, 279. Thompson, R. T., 76, 254. Thompson and Ballan- tyne, "277. Thompson, W., 91. Tichborne, 170. Turner, 268. Vaubnta, 273, 202. Van Slyke, 108. Varrentrap and Will, Hid. Vaudin, 131. Ventzke, 81. Vieth, 65, 06, 67. 60, 72, mi. si. 01. 93, on. I U.S. 121, 122, 12S, 125, 120, 132, 156, L64, lo;.. 102. 2 is. 221. 241, 2 10. 250, 202. 293, 20t. 295, 200, 299, 300, :;"■"•■ 305, 331, 333, 337, l-o /■'/< iachmann). Vigna, 262. Vifiavecchia and de Fabris, 272. Voelcker, 331. W WAUiACE(see< ornwall). Waller, 02. Wanklyn, 68, 101, 120. Wanklyn and Fox. 36, 250. ' Warrington, 20. WeigleandMerkel.140. Weigmann, 22s. Wcm. 84, 85, 89, 90. Weiske and Kennepohl, 332. Wellman, 272,201. Wender, 200. Werner-Schmid, 91, on. 99, 116, 117, 310. Westphal, 53, 54, 283. Weyl i see Fn nzel). Wiley, 78, 93, 224, 243. Wiley and Ewell, 7s, 70,' SO. Wilkinson, 171. Will (see Varn ntrcvp). Wislicenus, 10. Wold and List, is. Woll. 171, 20. Wollny, 2:.!'. 260, 261, 202.' 263, 20 1. 200. 27::. 291, 202. 204. 20.-,. 328. Wiirtz, 232, 276. Y Yoi no. 253. X win i;. 1.".. 1 I Zeiss, 287. BILL AM' li.UN, liUUTBV, lin - . $ • -AGRICULTURE - FORESTRY - UBRARY Ijfgjg@ft < FORESTRY AGRICULTURE LIBRARY