BOUGHT WITH THE INCOME FROM THE SAGE ENDOWMENT FUND THE GIFT OF Henrg W, Sage X891 Cornell University Library The original of tliis book is in tine Cornell University Library. There are no known copyright restrictions in the United States on the use of the text. http://www.archive.org/details/cu31924031490612 ANALYSIS OF MILK AND MILK PRODUCTS LEFFMANN AND BEAM. EXAMINATION OF WATER FOR SANITARY AND TECHNICAL PURPOSES. BY HENRY LEFFMANN. Third Edition. lamo. 154 pages. Illustrated. $1.25. A COMPEND OF CHEMISTRY, INORGANIC AND ORGANIC, INCLUDING URINARY ANALYSIS. by henry leffmann. Especially Adapted to Students in Medicine and Dentistry. Fourth Edition. Revised. Price $0.80. Interleaved for taking Notes, $1.25. Sanitary Relations of the Coal-Tar Colors. BY THEODORE WEYL. AUTHORIZED TRANSLATION BY HENRY LEFFMANN. i2mo. 154 pages. $1.25. Progressive Exercises in Practical Chemistry. A LABORATORY HANDBOOK. BY HENRY LEFFMANN. Illustrated. Second Edition. i2mo. Cloth, $1.00. P. BLAKISTON, SON & CO. ANALYSIS MILK AND MILK PRODUCTS HENRY LEFFMANN, M.A., M.D., WILLIAM BEAM, M.A., M.D. SECOND EDITION, REVISED AND ENLARGED, WITH ILL US TRA I IONS. PHILADELPHIA: BLAKISTON, SON & CO., !OI2 WALNUT ST'REET. 1896. Copyright, i8g6, by P. Blakiston, Son & Co. ^-^ PRESS OF WM. F. FFl.L & CO., 1220-24 8ANS0M STREET, PHILADELPHIA. PREFACE The first edition of this book was quite favorably received by competent critics, but it was noted that the analysis of butter and cheese was too briefly treated. It is hoped that this objection has been removed in the present edition. A large amount of matter has been added concerning those topics ; all the processes of analysis which have practical value in detecting butter adulteration have been given in delail, many from the latest publication of the A. O. A. C. A large addition has been made to the Chapter on Cheese, and a brief note on the fermented milk beverages. Other features have not been neglected. Considerable matter has been added in relation to the determination of lactose, among which may be mentioned Wiley and Ewell's recently described process of double dilution and polarization, and Allen's manipulation of Pavy's solution. The tables for determining total solids by Hehner and Richmond's formula have been recalculated according to Richmond's corrected formula. Concerning the rapid method of fat-extraction with which our names are connected, we desire to say that the taking out of a patent was rendered necessary by some business arrangements over which we had no control and which, at that time, seemed to require such action to pro- tect a reputable merchant from serious loss. The amount VI , PREFACE. paid was small and an offer has since been made to repur- chase the patent for the sum originally paid for it, the intention being to make its use free, but the negotiations failed. We also deem it proper to say that the originality of the discovery rests only on the chemicals employed in liberating the fat. The application of centrifugal machinery to the separation of liquids of different specific gravity dates from more than a generation ago and cannot be now allowed as an invention. We have regretted that a foreign chemist has appropriated, without acknowledgment, the special features of our method. As in the first edition, we have relied largely upon the contributions published in the " Proceedings of the Asso- ciation of Official Agricultural Chemists," and in The Analyst. H. L. W. B. 775 Walnut Street, Philadelphia, September, i8gb. CONTENTS. Nature and Composition of Milk. page Formation and Ingredients of Cow's Millt — Colos- trum — Milk of Various Animals — Properties and Decompositions of Milk — Skimmed Milk — Butter- milk — Whey, . . 9-17 Analytic Processes. Specific Gravity — Total Solids— Ash — Fat — Pro- teids — Sugar — Milk Adulterants, . . 18-52 Data for Milk Inspection. Variations in Composition — Sanitary Relations, 53~^3 Milk Products. Condensed Milk — Butter — Cheese — Fermented Products, . . . 64-106 Appendix. Table for Correcting Specific Gravity — Table for Calculating Total Solids — Table for Calculating Lactose — Supplementary Notes — Index, . . 107-120 NATURE AND COMPOSITION OF MILK. Milk, the nutritive secretion of nursing mammals, con- sists of water, fat, proteids, sugar, and mineral matters. Cow's milk, being of the greatest importance to the analyst, will receive the largest share of attention, and will be under- stood to be meant in all cases, unless otherwise stated. With rare exceptions, the secretion of milk takes place only as a result of pregnancy and delivery at term, and continues for a variable period. The chemistry of its formation is not entirely understood. The organic in- gredients do not exist in appreciable quantities in the blood, and must, therefore, be elaborated by specific secretory action. Fat. — This occurs in globules varying from .0015 mm. to .005 mm. in diameter, in a condition which prevents spontaneous coalescence. According to Gutzeit, the aver- age size of the globules is affected by many circumstances, such as change of weather, of food, or locality. During the whole time of lactation they regularly diminish in diameter. Among cows of the same breed their average size, extending over the whole lactiferous period, is fairly constant. The properties exhibited by the fat-globules have been regarded as indicating the existence of a mem- brane surrounding them, but they may be explained with- out such an assumption. If an envelope of any kind exists, it probably is merely a liquid one, such as the film of a soap-bubble. B 9 lO NATURE AND COMPOSITION OF MILK. The fat of milk consists of a mixture of the ethers of tritenyl (C3H5), but is peculiar among animal fats in con- taining a notable proportion of acid-radicles with a small number of carbon atoms. Thus, about gi per cent, con- sists of stearin, palmitin, and olein, and the remaining nine per cent, of butyrin and caproin along with minute amounts of caprin, myristin and caprylin, and some others. The exact arrangement of these constituents is not known, but the weight of opinion is that milk-fat is not a mixture of simple fats, but that several acid radicles are united to^ the same tritenyl molecule. The following results of the analysis of a sample of but- ter-fat are given by Dr. Bell : — Per cent. Butyric acid, 6.1 Caproic, caprylic, and capric acids, .... 2.1 Myristic, palmitic, and stearic acids, . . . 49.4 Oleic acid, 36.1 Glycerol (calculated), 12.5 According to Duclaux, the mean composition of butter- fat is probably : — ■ Per cent. Palmitin, stearin, olein, with traces of my- ristin and butin, 91.5 Butyrin, . 4.2 Capronin, 2.5 Caprylin, caprinin, laurin (traces), .... r.8 lOO.O Proteids. — The nature of the proteids of milk has been much discussed, but it is now generally conceded that there are at least three forms, casein, albumin, and globu- lin, the casein being present in by far the greater amount, and the globulin as traces only. Casein. — Casein is in large part, at least, in a gelatinous PROTEIDS. II (colloidal) form, probably in combination with calcium phosphate. It is precipitated from this condition by acids, rennet, magnesium sulfate, and other substances. Acids precipitate the casein by breaking up the combina- tion with calcium phosphate. The action of rennet is more complex. Hammersten has shown that it is depend- ent upon the presence of calcium salts; thus, if the curd precipitated by dilute acid be dissolved in dilute alkali and the solution neutralized, it is unaffected by rennet, but regains its coagulability by the addition of a solu- tion of a calcium salt or, what amounts to the same thing, a little of the whey from which the casein was precipitated. It appears that rennet splits the casein into two proteids, one of which is precipitated in the curd. Halliburton uses the term " caseinogen " to designate the form in which the casein exists when in solution or pre- cipitated by acids, and reserves the term casein for the curd produced by rennet. Films of proteid matter occur abundantly in milk, for which reason it is distinctly opaque, even when all but a trace of the fat has been removed by centrifugal action. The albumin of milk appears to be a distinct form, and is called lactalbumin. It is not precipitated by dilute acids, but is coagulated by heating to 7o°-7S° C. The proportion in cow's milk is usually from 0.35 to 0.50 per cent., but colostrum may contain much larger proportions. S^belien gives the composition of lactalbumin as fol- lows : — Carbon, 52.19 Hydrogen, 7.18 ' Nitrogen, i5-77 Oxygen, . . . . ■ 23 '3 Sulfur, 1-73 12 NATURE AND COMPOSITION OF MILK. Globulin is present only in minute amounts in normal milk, but colostrum may contain as much as eight per cent. It is coagulated on heating. Lactose. — This is the sugar of milk and is peculiar to it. Richmond discovered in the milk of the gamoose a sugar not identical with lactose; probably extended investiga- tion of the milk of various animals will show the existence of other forms of milk-sugar. Crystallized lactose has the composition CijHjjOu -(- HjO. By heating to 125° C. the water is expelled. It has a specific rotatory power of -[-52.5, which is independent of concentration. Freshly prepared solutions exhibit higher rotatory power, but after twenty-four hours standing, at ordinary temperatures, or immediately on boiling, the rotatory power is reduced to the figure given above. Alkaline solutions of copper salts are readily reduced by lactose at the boiling temperature. Richmond has shown that continued heating of a solution of milk-sugar causes caramelization and diminution of the rotatory power, but the reducing power to alkaline copper solution is not sensibly affected even after heating for two hours. In contact with yeast, lactose undergoes alcoholic fermentation, but with difficulty. It undergoes the lactic fermentation, however, very readily under the influence of certain microbes. When milk is evaporated rapidly to dryness, as in the determination of total solid residue, the milk-sugar is left in the anhydrous state. Citric acid is a normal constituent of the milk of various animals. In human milk, the quantity is about 0.5 gram to the liter, in cow's milk from i to 1.5 grams. It is not dependent on the citric acid present in the food. Minute amounts of nitrogenous bases and a starch- liquefying enzym also occur. COLOSTRUM. 13 K, Na, CI, CO, .113 per cent, (of milk) .0126 The ash of milk has the following composition : Ca, Mg, . Fe, . . . .0002 .146 .082 .263 traces . 169 .020 Colostrum. — This term is applied to the milk secreted in the early stages of lactation. It usually differs marked- ly from ordinary milk. It contains characteristic struc- tures known as colostrum corpuscles. These are ameboid bodies several times as large as the fat-globules. They are present for a variable period — three to fourteen days — but may persist much longer. Colostrum usually contains much less fat than fully developed milk, but a larger pro- portion of proteids, the increase being principally in the albumin, though Emmerling has found over 8 per cent, of globulin. The large proportion of albuminous matter causes colostrum to coagulate on boiling. Lactose is in small amount and is said to be largely replaced by another carbohydrate. The following analysis is the average of the colostrum of 22 cows. (Eugling.) Fat, . . Casein, . Albumin, Sugar, Ash, . . Total solids. Colostrum is usually acid to litmus. 4 IS 28 37 83 8S 48 78 31 14 NATURE AND COMPOSITION OF MILK. -asiOdHOH vO ro Tj- li-i tJ- 00 xo LO 10 ro d ro , 15.86 Pappel and Rich- mond. -aavx^ o^ LTi cr\ M ON MD 00 ro 4 ^ vd ^ d ^ . > -xMVHdan^ 00 CO w-i LO LO "I ■^ vO d I>- ro d -ooa r-- ro ro M *0 t^^ Cf- ro vd d d 2" W ° -M03 0\ i^ -o vo r^ ro tJ- N d d -Nvwnjj 00 M iJ^ N ro MD M d d II. 7 Lehmann and Ilempel. Specific Gravi- ty, ... Fat, . . Sugar, .... Casein , Albumin, Ash, Total Solids, . Analyst, . . . COLOSTRUM. 15 Normal milk is an opaque, white or yellowish-white fluid, with an odor recalling that of the animal, and a faint sweet taste. The opacity is due partly to the fat-globules, but when these are entirely removed the liquid does not become transparent. The reaction of freshly drawn milk is amphoteric to litmus, that is, it turns the red paper blue and blue paper red. The specific gravity varies between 1028 and 1035. It usually undergoes a gradual augmentation (sometimes termed Recknagel's phenomenon) for a con- siderable time after the sample has been drawn. The increase may amount to two units. The specific gravity becomes stationary in about five hours if the milk be maintained at a temperature below 15" C, but at a higher temperature it may require twenty-four hours to acquire constancy. The change is not dependent on the escape of gases, and is believed to be due to some molecular modifi- cation of the casein, possibly under the influence of an enzym. Unless collected with special care and under conditions of extreme cleanliness, milk always contains bacteria and animal matter of an offensive character, such as epithelium, blood and pus cells, particles of feces and soil. Many minute organisms, especially bacteria, propagate with great rapidity in milk and produce changes in its composition. Some specific organisms, such as the Spirillum cholera, multiply to only a limited extent in ordinary milk, being hampered by the bacteria normally present, but when introduced into sterilized milk increase with great rapidity. At ordinary temperature milk soon undergoes decompo- sition under the influence of the microbes present, by which the milk-sugar is converted principally into lactic acid, and the proteids partly decomposed and partly coag- 1 6 NATURE AND COMPOSITION OF MILK. ulated. The liquid becomes sour and the fat is enclosed in the coagulated casein. In the initial stages of decomposition the proteids fre- quently undergo transformations into substances which are the cause of the violent poisonous effects occasionally pro- duced by ice cream and other articles of food into the preparation of which milk enters. Boiling produces coagulation of the albumin, some caramelization of the sugar, and develops a greater facility of coalescence on the part of the fat globules. Enzyms and most microbes are destroyed. The skin which forms on the surface of boiling milk is composed largely of casein. It is due probably to the more rapid evaporation at the surface of the liquid. Partial freezing produces a concentration of the milk solids in the part remaining liquid, while the solid portion is deficient in them. The normal condition can, there- fore, be restored only by thawing the entire mass and mixing thoroughly. Richmond has published the following analyses as show- ing how great a difference may exist between the ice and liquid portion. The ice amounted to about lo percent.: — Ice. Liquid. Water, 96 23 86.62 Fat, 1.23 4.73 Sugar, 1.42 4.95 Proteids, 91 3.90 Ash, 21 .80 Specific gravity, . . 1009 io34-S When milk is allowed to stand, some of the fat rises gradually and forms a rich layer, constituting cream. The proportion of cream depends on several conditions. COLOSTRUM. 1 7 The amount formed in a given time cannot be taken as a measure of the richness of the milk. Water added to milk causes a more rapid separation of the cream. When milk is subjected to centrifugal action, a larger proportion of cream is quickly obtained, nearly all of the fat being removed. The following figures, given by D'Hout as aver- ages, show the effect of the centrifugal action : — Whole milk. Separated milk. Cream. Specific gravity, . 1032 Total solids, . .14.10 Sugar, 4.70 Casein, . . . 3.50 Ash, 0.79 Fat, 5.05 Buttermilk is the residue after removal of the butter by churning. Vieth gives the following figures : — Total solids. Fat. Solids not fat. Ash. g.03 0-63 8.40 0.70 8.02 0.65 7.37 1.29 10.70 0.54 10.16 0.82 The whey left after the precipitation of the curd by rennet or acid still contains a notable amount of proteids. The following analyses are by C. B. Cochran (/". A. C. S., 1893' P- 347): — 1034 1015 9.6 26.98 S-oS 3-32 3.62 2.02 0.78 058 0.20 21-95 M LK Whey. ?tal solids. Solids not fat. Total solids Proteids removed. 9.27 913 6.62 2.51 9.27 913 6.1 303 14.05 8-35 6.62 2-33 7.71 7.61 5-98 1.63 8.91 8.71 6.50 2.21 The whey of any given milk has the same composition, whether taken from the original milk, skimmed milk, or ANALYTIC PROCESSES. The specific gravity determination is to be made only after the spontaneous rise has ceased. This will require about five hours, after the milk is drawn, if it has been kept below 15° C, but at a higher temperature it will be neces- sary to allow at least twelve hours. For all other deter- minations the milk must be analyzed as soon as possible, as it decomposes very rapidly at ordinary temperatures. The following figures, published by Bevan, show that a con- siderable loss in total solids may occur in twenty-four hours : — Total solids. Loss. Evaporated immediately, . . .11.73 " after 24 hours, . . 10,79 °-94 " 48 " . . 10.38 1.35 " " 120 " . . 9.42 2.31 The decomposition is very irregular and it is not possible to determine, by estimation of the lactij: acid or other products, the original composition of the milk. The pipet used for taking a portion for analysis should have a wide opening, that no cream may be retained when the pipet is discharged. SPECIFIC GRAVITY. Air bubbles are held rather tenaciously by milk, and care must be taken in mixing, preparatory to taking the specific gravity, to avoid as far as possible the enclosure of 18 SPECIFIC GRAVITY. 1 9 air, and to allow sufficient time for the escape of any bubbles that may be present. Determinations of specific gravity of milk are understood to be taken at the tempera- ture of 60° F., and samples at temperatures materially different from this should be brought to it. If at a few degrees above or below 60°, it will suffice to take the gravity at once and obtain the correct figures by reference to Table A. The specific gravity of normal milk varies between 1028 and 1035. /^ince the specific gravity can be raised by the abstraction of fat (skimming) and restored by the addition of water, the figure taken alone cannot be relied upon as an index of the character of the sample, but in conjunction with the figure for fat or for total solids it is of great value, as a check on the results furnished by other determinations. The simplest method of determining specific gravity is by the lactodensimeter, a delicate and accurately graduated hydrometer. The instrument must be immersed carefully so as not to wet the stem above the point at which it will rest. The instrument should be tested by immersion in distilled water at 15° C. The indications furnished by the lactodensimeter are sufficiently accurate for most purposes, but its employment necessitates a considerable amount of the sample. More accurate determination can be made by the ]Vestphal balance. This is a delicate steelyard with a counterpoised plummet, displacing 5 c. c. The plummet being immersed in the milk, the equilibrium is restored by weights, the value of which can be directly expressed in figures for the specific gravity. The principle of the Westphal balance may be applied by means of an analytic balance and a plummet. The ANALYTIC PROCESSES. latter may conveniently consist of a short thermometer, or a thick glass rod, having a bulk of from 5 to 10 c. c. It is suspended from the hook of the balance by a fine platinum wire and its weight ascertained. It is then immersed in distilled water at 60° F. and the loss in weight noted. The figure so obtained is the weight of a bulk of water equal to that of the plummet. This having been determined, the specific gravity of a milk may be found by immersing the plummet in it and noting the loss in weight, which, divided by the loss in pure water, gives the specific gravity. The pyknometer or specific-gravity bottle furnishes a means of accurate determination and is especially appli- cable when only a small amount of liquid is available. It is a small flask furnished with a perforated glass stopper. It is provided with a counterpoise equal to the empty flask and the weight of water that it carries is indicated. These data may, of course, be easily verified, and any error noted. The milk should be first brought to the proper temperature, the bottle completely filled, the stopper inserted, and the excess which flows out through the perforation and around the sides of the stopper re- moved by bibulous paper. The weight of milk divided by that of the water which the flask will hold at the same temperature gives the specific gravity. TOTAL SOLIDS. 21 TOTAL SOLIDS. This determination is made by evaporation in a shallow, flat-bottomed dish, preferably of platinum, from 7 to 8 cm. in diameter. The milk must be spread evenly in a thin layer. If the ash is also to be determined, about 5 grams should be accurately weighed in the dish, evaporated rapidly to apparent dryness over the water-bath and the heating continued in the water-oven until the weight, be- comes practically constant, which will require about three hours. If the evaporation be slow, some decomposition occurs and the residue is brown, but if the larger portion of the water be evaporated quickly, a white residue is ob- tained. When the ash is not to be determined, it is more convenient to follow the method suggested by Richmond, using I to 2 grams, accurately weighed. The drying can be completed in about one and a half hours. When a higher degree of accuracy is desired, Babcock's method (A. O. A. C.) may be employed as follows : — Provide a hollow cylinder of perforated sheet metal 60 ram. long and 20 mm. in diameter, closed 5 mm. from one end by a disk of the same tpaterial. The perforations should be about 0.7 mm. in diameter and the same distance apart. Fill the cylinder loosely with from 1.5 to 2.5 grams of freshly ignited woolly asbestos free from fine or brittle material. Cool in a desiccator and weigh. Introduce a weighed quantity of milk (about 4 gm.) and dry at 100° C. to constant weight. The residue will serve for the determination of the fat. When rigid accuracy is not essential, it will suffice to measure the portion of milk taken for this and other deter- minations. Vieth uses a pipet graduated to deliver 5 2 2 ANALYTIC PROCESSES. grams and finds that, working with whole and skimmed milk, under the ordinary variations of temperature, the error will not exceed o. i on the total solids and is less on the fat. A good plan is to use a 5 c. c. pipet and to wash out that which adheres to the glass with a little water. The specific gravity of the milk being known, the amount taken can be calculated. The milk should be as near 60° F. as possible. ASH. The residue from the determination of total solids is heated cautiously over the Bunsen burner, until a white ash is left. The result obtained in this manner is apt to be slightly low from loss of sodium chlorid. This may be avoided by heating the residue sufficiently to char it, ex- tracting the soluble matter with a few c.c. of water, and filtering (using paper extracted with hydrofluoric acid). The filter is added to the residue, the whole ashed, the fil- trate then added, and the liquid evaporated carefully to dryness. The ash of normal milk is about 0.7 per cent, and faintly alkaline j if the milk be watered the ash will be less. The ash of milk' does not exactly represent the salts present in the milk. On ignition, the phosphorus of the casein is oxidized to phosphoric acid, which decom- poses the carbonates formed by the ignition of the organic salts of the milk, and liberates carbonic acid. A marked degree of alkalinity and effervescence with hydrochloric acid will suggest the addition of a carbonate. The method of the A. O. A. C. is as follows : In a weighed dish put 20 c.c. of milk from a weighing bottle, add 6 c.c. of nitric acid, evaporate to dryness, and burn at a low red heat until all form carbon. ^(£rtf-*/-«V^^^'^-«-y^'-«»-' — FAT. 23 FAT. The method introduced by Wanklyn for the determina- tion of fat by extracting it with ether from the total solid residue, has been found to give results 0.5 per cent, or more below the correct figure, and is therefore not described. Adams' Method. — This consists essentially in spread- ing the milk over absorbent paper, drying, and extracting the fat in a Soxhlet apparatus ; the milk is distributed in an extremely thin layer, and by a selective action of the paper the larger portion of the fat is left on the surface. It is essential that the paper contain no materials soluble in the liquid used for extraction. A paper, manufactured espec- ially for this purpose by Schleicher & Schuell, is obtain- able in strips of suitable size. Each of these yields to ether from .001 to .002 gram of extract, which may usually be disregarded. The procedure is as follows : Five c.c. of the milk are dis- charged into a beaker 5 cm high and 3.5 cm. in diameter. The charged beaker is weighed, and a strip of the paper, which has been railed into a coil, thrust into it. In a few minutes the paper will absorb nearly the whole of the milk. The coil is then carefully withdrawn, and stood dry end downward on a sheet of glass. With a little dexterity, all but the last fraction of a drop will be absorbed by the paper. The beaker is again weighed and the milk taken found by difference. It is of importance to take up the whole of the milk from the beaker, as the paper has a selective action, removing the watery constituents by preference over the fat. The charged paper is placed in the water-oven on a glass plate. 24 ANALYTIC PROCESSES. milk-end upward, and dried. Usually about one hour is sufficient. It is inserted in a Soxhlet continuous-extraction apparatus, the tared flask of which should have a capacity of about 150 c.c. and contain about 75 c. c. of anhydrous, alcohol-free ether, or petroleum spirit boiling at about 45° C. Heat is applied to the flask by means of a water bath, or by resting it on a piece of asbestos paper, which is heated by a small flame. After the coil has received at least ten or twelve wash- ings, the flask is detached, the ether removed by distillation, and the fat dried by heating in an air oven at about 105° C, and occasionally blowing air through the flask. After cooling, the flask is wiped with a piece of silk, allowed to stand ten minutes, and weighed. Richmond states that to perform a rigidly accurate determination attention to the follow- ing points is necessary : The ether must be anhydrous (drying over calcium chlorid and distilling is sufficient). Schleicher & Schuell's fat-free papers should be used and one should be extracted without any milk on it, as a tare for the others. Four or five hours' extraction is necessary, and the coils should be well dried before ex- traction is begun. Thimble-shaped cases made of fat-free paper are now obtainable and are convenient for holding the absorbent material on which the milk is spread. The fine texture prevents undissolved matter escaping. A case may be used repeatedly. Sour milk must be thinned with ammo- nium hydroxid before taking the portion for analysis. 25 When the Babcock method has been used for determining the total solids, the cylinder and contents maybe placed in the Soxhlet tube and extracted with ether in the usual way. In addition to weighing the fat, after evaporation of the ether, it may be determined by difference, by drying the extracted cylinder at ioo° C. and weighing. A still higher accuracy is secured by performing all the drying operations in an atmosphere of hydrogen. Werner-Schmid Method. — This is a very satisfac- tory and rapid method for the determination of fat and is especially suitable for sour milk. Ten c. c. of the milk are measured into a long test-tube of 50 c. c. capacity, graduated to tenths c. c, and 10 c. c. of strong hydro- chloric acid added, or the milk may be weighed in a sm^U beaker and washed into the tube with the acid. After mixing, the liquid is boiled one and a half minutes, or the tube may be corked and heated in the water bath from five to ten minutes, until the liquid turns dark brown. It must not be allowed to turn black. The tube and contents are cooled in water, 30 c. c. of well-washed ether added, shaken, and allowed to stand until the line of acid and ether is dis- tinct. The cork is taken out, and a double-tube arrangement, like that of the ordinary wash-bottle, inserted. The stopper of this should be of cork and not of rubber, since it is difficult to slide the glass tube in rubber, and c 26 ANALYTIC PROCESSES. there is a possibility, also, of the ether acting on the rubber and dissolving it. The lower end of the exit-tube is ad- justed so as to rest immediately above the junction of the two liquids. The ethereal solution of the fat is then blown out and received in a weighed flask. Two more portions of ether, lo c. c. each, are shaken with the acid liquid, blown out, and added to the first. The ether is then dis- tilled off, and the fat dried and weighed as above. Leffmann-Beam Method. — Among the processes for the rapid determination of fat those employing centrifugal machines have been most satisfactory. The following method can be applied very cheaply, both as regards the original cost of the apparatus and of the chemicals required for the test, the latter being usually no inconsiderable item when many tests are made. The manipulation is very simple. Machines arranged for either two, four, six, eight, or twelve bottles are manufactured. The process is covered by patent in the United States, which has been assigned to J. E. Lonergan, of Philadelphia. The test-bottles have a capacity of about 30 c. c, and are provided with a graduated neck, each division of which represents one-tenth per cent, by weight of butter-fat. Fifteen c. c. of the milk are measured into the bottle, 3 c. c. of a mixture of equal parts of amyl alcohol and strong hydrochloric acid added, mixed, the bottle filled nearly to the neck with concentrated sulfuric acid and the liquids mixed by holding the bottle by the neck and giving it a gyratory motion. The neck is now filled to about the zero point with a mixture of sulfuric acid and water pre- pared at the time. It is then placed in the centrifugal machine, which is so arranged that when at rest the bot- FAT. 2 7 ties are in a vertical position. If only one test is to be made, the equilibrium of the machine is maintained by means of a test-bottle, or bottles, filled with a mixture of equal parts of sulfuric acid and water. After rotation for from one to two minutes, the fat will collect in the neck of the bottle and the percentage may be read off. It is convenient to use a pair of dividers in making the read- ing. The legs of these are placed at the upper and lower limits respectively of the fat, allowance being made for the meniscus ; one leg is then placed at the zero point and the reading made with the other. Several years' experience by analysts in various parts of the world has shown that with properly graduated bottles the results are reliable. As a rule, they do not differ more than one-tenth of i per cent, from those obtained by the Adams process, and are generally even closer. Richmond, as the result of an exhaustive series of investigations, draws the following conclusions : — 1. As variations in the sulfuric acid and fusel- oil may slightly influence the result, it is well to obtain large quan- tities of these at a time, and by a few preliminary experi- ments fix the factor necessary to convert scale readings into percentages of fat. 2. It is advisable to use the same strength of acid (94 to 96 per cent. H2SO4 is convenient). This may be esti- mated either by converting a known quantity into ammo- nium sulfate, drying at 100° C, and weighing; titrating the acidity with decinormal barium h3droxid, using methyl-orange as indicator, and then igniting, and weigh- ing the non-volatile matter (correcting for the barium sul- fate formed); or deducing the strength from the density (hydrometers are rarely of sufficient accuracy, and a pyc- 28 ANALYTIC PROCESSES. noraeter should be used), and correcting by subtracting twice the weight of the non-volatile matter. 3. If it be necessary to perform the experiment when the atmospheric temperature is high, the milk and acid should be cooled beforehand, or if this is not practicable, the acid should be added in small portions (2 c. c.) at a time, and the botrle shaken between each addition, or a weaker acid may be used. 4. About half to three-quarters of a minute's revolution, at the rate of from 1200 to 1500 revolutions a minute, has been found the most convenient in practice. The machine has not been found dangerous at this speed ; but, if wished, a longer period of revolution at a slower speed is equally efficacious. For accurate work the factor for correcting the reading on each of the bottles should be determined by comparison with the figures obtained by the Adams or other standard process. Cream is to be diluted to exactly ten times its volume, the specific gravity taken, and the liquid treated as a milk. Since in the graduation of the test-bottles a specific gravity of 1030 is assumed, the reading must be increased in proportion. A more accurate result may be obtained by weighing in the test-bottle about 2 c. c. of the cream and diluting to about 15 c. c. The reading obtained is to be multi- plied by 15.45 and divided by the weight in grams of cream taken. The mixture of amyl alcohol and hydrochloric acid seems to become less satisfactory when long kept. It is best, therefore, not to make up large amounts at once. The mixture should be clear and not very dark in color. FAT. 29 Samples of amyl alcohol that produce a black solution with hydrochloric acid are unsuitable. (See Appendix.) Calculation Method. — Several investigators have proposed formulae by which when any two of the data, specific gravity, fat, and total solids are known, the third can be calculated. Since fairly accurate determinations of the fat and specific gravity can be made by rapid and sim- ple methods, the formulae become very serviceable and should always be used to check the results. That of Hehner and Richmond has been almost exclusively used. It is as follows : — F = .859 T — .2186 G in which F represent the fat, T the total solids, and G the specific gravity. This formula will suffice for ordinary milks, but for poor skim milks it has been found necessary to modify it as follows : — F=.8S9T — .2186G — .05 (^ — 2.5) This correction is to be applied only when G divided by T exceeds 2.5. In these formulee, G represents the last two units of the specific gravity and any decimal. Thus, if the observed specific gravity be 1029.5, G will be 29.5. A ready means of applying the formula is by the use of Richmond's slide-rule. This has three scales, two of which, for fat and total solids respectively, are marked on the body of the rule, while that for the specific gravity is placed on the sliding portion. The divisions are as follows : — ■ Total solids, i inch divided into tenths Fat, 1. 164 inches " " " Specific gravity, . . . 0.254 " " " halves 30 ANALYTIC PROCESSES. The rule is employed by adjusting the arrow point to the graduation corresponding to the fat found, when the figure for the total solids will coincide with that for the observed specific gravity. This instrument does not take into con- sideration the necessary correction for poor skim milks, but the error from this cause will in no case exceed .08 per cent, of fat and may usually be disregarded. It has been found that the fat calculated by the above formula is slightly higher than the actual amount. Re- cently, Richmond has proposed a new formula — G T = .2625 (1000 + G) -|- 1.2 F 1000 and finds the results obtained by it to agree much better with accurate analysis. The formula may be simplified as follows, T=^+'F+r.4 4 5 and the result will not differ in extreme cases more than .02 from those calculated from the more complex formula. Results calculated from this formula will be found in Table B. A milk-scale to express the same relation may be con- structed on which i per cent, total solids ^ i inch, 1 per cent, of fat ^ 1.2 inches, and i degree of gravity =r i^ inch ; if the zero on the fat scale be placed on a line with 5 per cent, on the total-solids scales, the arrow will be in its cor- rect position : 0.14 (^) inch below 20 degrees on the spe- cific gravity scale. By placing an arrow 0.14 inch below the present arrow, existing milk scales will give a near approximation. TOTAL PEOTEIDS. 3 1 TOTAL PROTEIDS. This determination is best made by calculation from the figure for total nitrogen obtained by Gunning's modifica- tion of Kjeldahl's process. The reagents and apparatus required are as follows: — Standard sulfuric acid. — This should be about deci- normal, the exact value being determined by precipitating a measured volume with barium chlorid, collecting and weighing the barium sulfate under the usual precautions. Standard barium hydroxid. — This should be aboi(t deci- normal. The volumetric relation between this solution and the standard sulfuric acid must be accurately determined, employing phenolphthalein as an indicator. Acid potassium sulfate mixture. — One part of pure potas- sium sulfate is heated with two parts of sulfuric acid (strictly C. P.) until the potassium sulfate is dissolved. The mixture is semi-solid when cold but may be readily liquefied by warming. Sodium hydroxid solution. — A saturated solution in water. A good quality of pulverized sodium hydroxid is now sold under various trade names, e.g., "Lewis' Lye," "Banner Lye," and these will be found satisfactory. Digestion and distillation flask. — This has a body capable of holding about 550 c. c, and a cylindrical neck about 18 cm. in length and 25 cm. in diameter. It is supported on wire-gauze or asbestos, and the mouth may be covered by a watch-glass or funnel during the digestion. For dis- tilling, a well-fitting rubber stopper with delivery tube should be attached. The tube should be of the same diameter as the condensing tube, and should have one or two bulbs, about 4 cm. in diameter, to prevent any solution 32 ANALYTIC PROCESSES. being carried over by spurting. It should project slightly below the stopper and be cut off obliquely. Condenser. — The condensing tube must be of block tin of an external diameter of about one centimeter. At least 30 centimeters of its length should be in contact with the cooling water. The junction of the glass and tin tube is made by a short, close-fitting rubber tube, and the tubes are so bent as to slope toward the distilling flask. The lower end of the tin tube is connected by a short rubber tube with a glass bulb-tube which dips below the surface of a measured volume (20 c. c.) of the standard sulfuric acid in an Erlenmeyer flask of about 300 c. c. capacity. Five c. c. of the milk are weighed or measured into the flask and evaporated to dryness over the water-bath ; 30 c.c. of the acid potassium sulfate mixture are added and heated over the Bunsen burner. At first, frothing occurs and white fumes escape, consisting chiefly of water-vapor. To prevent loss of acid, the neck of the flask is now fitted with a funnel which is covered with a watch glass. This will cause the acid to condense and run back into the flask. The operation is finished when the liquid is colorless, which generally requires about an hour. When cold, the contents of the flask are diluted with about 200 c. c. of water, several pieces of ignited pumice dropped in, and sufficient of the sodium hydroxid solution (about 50 c. c.) added to make the mixture strongly alkaline. It should be poured down the side of the flask so that it does not mix at once with the acid. The flask is now connected with the con- denser and the contents mixed by shaking. The liquid is now distilled until the whole of the ammonium hydroxid is collected, which will usually be the case when 150 c. c. have passed over. The receiver and short tube dipping in TOTAL PROTEIDS. 33 it are then detached and the distillate titrated to determine the amount of acid unneutralized. From this the amount of ammonium hydroxid can be calculated, and the nitrogen in this multiplied by 6.38 will give the figure for the total proteids. The A. O. A. C. recommends an indicator prepared as follows; Three grams of cochineal are digested for several days at room temperature in a mixture of 50 c. c. of strong alcohol and 200 c.c. of water. The filtered solution is used. The Ritthausen Method for Total Proteids. — This method depends on precipitation by copper sulfate and sodium hydroxid. It is applicable only to fully de- veloped milks ; the proteids of colostrum and whey are only partially precipitated. The reagents are : — Copper sulfate solution. — 34-639 grams of pure crystal- lized copper salfate are dissolved and made up to 500 c. c. Sodium hydroxid solution. — About 12 grams are dissolved in 500 c. c. of water. Ten grams of the milk are placed in a beaker, diluted with 100 c. c. of distilled water, 5 c. c. of copper sulfate solution added, and thoroughly mixed. The sodium hydroxid solution is then added drop by drop, with con- stant stirring, until the precipitate settles quickly and the liquid is neutral, or at most very feebly acid. An excess of alkali will prevent the precipitation of some of the proteids. The reaction should be tested on a drop of the clear liquid, withdrawing it by means of a rod, taking care not to include any solid particles. When the operation is correctly performed, the precipitate, which includes the fat, settles quickly, and carries down all of the copper. 34 ANALYTIC PROCESSES. It is washed by decantation with about loo c. c. of water, and collected on a filter (previously dried at 130° C. and weighed in a weighing bottle). The portions adhering to the sides of the beaker are dislodged with the aid of a rubber-tipped rod. The contents of the filter are washed with water until 250 c. c. are collected, which are mixed and reserved for the determination of the sugar as de- scribed below. The water in the precipitate is removed by washing once with strong alcohol, and the fat by six or eight washings with ether. The Soxhlet apparatus may be used for this purpose. The washings being received in a weighed flask, the determination of the fat may be made by evaporating the ether with the usual precau- tions. The residue on the filter, which consists of the pro- teids in association with copper hydroxid, is washed with absolute alcohol, which renders it more granular, and then dried at 130° C. in the air bath. It is weighed in a weigh- ing bottle, transferred to a porcelain crucible, incinerated, and the residue again weighed. The weight of the filter and contents, less that of the filter and residue after igni- tion, gives the weight of the proteids. The results by this method are slightly high, since copper hydroxid does not become completely converted into copper oxid at 130° C. Richmond and Boseley {^Analyst, 1893) modify this pro- cess by diluting the milk to 200 c. c, add.ing a little phenolphthalein, and neutralizing any acidity by the cautious addition of dilute sodium hydroxid solution, then adding from 2.0 to 2.5 c. c. of the copper sulfate solution. The precipitate is allowed to settle, washed, and estimated as above. CASEIN AND ALBUMIN. 35 CASEIN AND ALBUMIN. Twenty c. c. of the milk are mixed with 40 c. c. of a saturated solution of magnesium sulfate and powdered magnesium sulfate stirred in until no more will dissolve. The precipitate of casein and fat, including the trace of globulin, is allowed to settle, filtered, and washed several times with a saturated solution of magnesium sulfate. The filtrate and washings are saved for the determination of albumin. The filter and contents are transferred to a flask and the nitrogen determined by the method described above. The nitrogen so found multiplied by 6.38 gives the casein. The filtrate and washings from the determination of casein are mixed, the albumin precipitated by a solution of tan- nin, filtered, and the nitrogen in the precipitate determined as above. The same factor is used. On account of the difficulty of washing the precipitated casein, we prefer to proceed as follows : 20 c. c. of the milk are mixed with saturated magnesium sulfate solution and the powdered salt added to saturation. The mixture is washed into a graduated measure with a small amount of the saturated solution, mixed, the volume noted, and allowed to stand until the separation takes place. As much as possible of the clear portion is drawn off with a pipet and passed through a dry filter. An aliquot portion of the filtrate is taken, the albumin precipitated by a solution of tannin, and the nitrogen in the precipitate determined as above. The casein is found by subtracting the figure for albu- min from that for total proteids. For the separation of the proteids in milk, the methods of Hoppe-Seyler and Rittbausen have been much used. 36 ANALYTIC PROCESSES. The casein is precipitated by the addition of acetic acid to the diluted milk, the action being rendered complete, in the one case, by raising the temperature to 40° C, and in the other by passing a current of carbon dioxid through the mixture at ordinary temperatures. L. L. Van Slvke (_/ A. C. S., Vol. XV, p. 635), as the result of a series of investigations, finds these methods to give practically identical results and recommends the following procedure for the separation and estimation of the casein and albu- min : — Casein. — Weigh out about ten grams of milk, dilute in a beaker with about 90 c. c. of water at 40°— 42° C, and add at once 1.5 c. c. of a solution containing 10 per cent, of acetic acid by weight. Stir with a glass rod, let stand three to five minutes, decant on to a filter, wash two or three times with cold water by decantation, transfer the pre- cipitate completely to the filter, and wash it once or twice. The washed precipitate and filter paper are then treated bv the Kjeldahl-Gunning method for the determination of nitrogen, and the estimation made in the usual manner. To calculate the nitrogen into an equivalent amount of casein, multiply by the factor 6.38. Albumin. — The filtrate from the separated casein is heated in boiling water for ten or fifteen minutes. The coagulated albumin is collected in a filter, washed, and the filter and precipitate treated by the Kjeldahl-Gunning method. The amount of nitrogen multiplied by 6.38 gives the amount of albumin. Remaining tii/rogen compounds. — The remaining com- pound or compounds of nitrogen are determined by differ- ence, subtracting from the amount of total nitrogen com- pounds the sum of the casein and albumin. The albumin of condensed milk is partly coagulated by the heat employed in its manufacture. When magnesium sulfate is added, therefore, to precipitate the casein, the coagulated albumin will be carried down at the same time SUGAR. 37 and only the soluble albumin will be found in the filtrate. Faber {Analyst, 1889) has applied this fact to the detection of the previous heating of a sample of milk. Usually, only about one-third of the albumin is found uncoagulated in condensed milk. SUGAR. The following method, due to Soxhlet, employs a Feh- ling's solution, made as required, by mixing equal parts of the following solutions: — Copper sulfate solution. — 34,639 grams of pure crystal- lized copper sulfate are dissolved in distilled water and made up to 500 c. c. Alkaline tartrate solution.— One hundred and seventy- three grams of pure sodium potassium tartrate, and 51 grams of sodium hydroxid of good quality, are dissolved and made up to 500 c. c. One hundred c. c. of the mixed filtrate obtained as de- scribed on p. 33 are brought to boiling, 50 c. c. of boil- ing Fehling's solution added, and the boiling continued for six minutes. The precipitate is allowed to settle for a sliort time, and the supernatant liquid poured through a filter. About 50 c. c. of boiling water are added to the residue, and the heating continued for a minute or two. The precipitate is then conveyed to the filter, washed with boiling water, with alcohol, and finally with a small quan- tity of ether. The filter and contents are dried in the water oven, the precipitate removed to a tared porcelain crucible, the filter held over the crucible and burnt to ash, which is added to the precipitate, and the cuprous oxid converted into cupric oxid by strong ignition, for five or ten minutes, over the Bunsen burner. 38 ANALYTIC PROCESSES. The amount of copper reduced under the conditions de- tailed above is not directly proportional to the milk-sugar present. Table C shows the amounts of milk-sugar (C,2 H22 On -{- H2 O) equivalent to given weights of cupric oxid. The volumes of Fehling's solution and sugar solu- tion must conform strictly to the figures given above. Many of the English analysts prefer to make volumetric determinations by means of Pavy's modification of Feh- ling's solution, in which strong ammonium hydroxid is used to maintain the cuprous oxid in solution and thus permit nicer determination of the end-reaction. Allen has in- vestigated with great care the value of this method for determining the form of glucose that occurs in urine and finds that considerable variation may be made in the formula of Pavy's solution without the oxidizing ratio being appre- ciably affected, but it will be best to adhere closely to a particular formula in milk determinations. A description of the process is given in connection with analysis of con- densed milks. The determination of sugar may also be made by means of the polarimeter after removal of the fat and proteids. This may be effected by means of a nitric acid solution of mercuric nitrate as suggested by Wiley. The mercuric nitrate solution is prepared by dissolving mercury in twice its weight of nitric acid of 1.42 sp. gr. and adding to the solution five volumes of water. Sixty c. c. of the milk are placed in a 100 c. c. flask and 10 c. c. of the mercuric solution added. The flask is filled to the mark with water, well shaken, and the liquid filtered through a dry filter. The filtrate, which will be perfectly clear, may be examined at once in the polarimeter. Several readings should be made and the average taken. SUGAR. 39 It is to be noted that the actual volume of the sugar- containing solution is loo c. c, less the space occupied by the precipitated proteids and fat. The volume of fat is found by multiplying the weight in grams by 1.075 ^^'^ the proteids by multiplying the weight by 0.8. For example : — Sp. gr. of milk 1030, fat 4 per cent., proteids 4 per cent. Milk taken = 60 X 1.03 ^ 61.80 gms. The weight of fat = 4 per cent, of 61.80 = 2.47 gms. The weight of proteids = 4 per cent, of 61.80= 2.47 gms. The volume of fat = 2.47 X 1-075 ^= ^-^5 ^- ^■ The volume of proteids = 2.47 X .8 ^ 1.97 c. c. The bulk of the sugar containing liquid is therefore 100 — (2.65 + 1.97) = 95.38 c. c. In order to avoid the calculation involved in taking 60 c. c. of the milk as given above, an amount may be employed which is a simple multiple of the standard quan- tity to be used in the polarimeter at hand. Thus, for instruments adjusted so that 16.19 grams of sucrose (20.56 grams of milk-sugar) in 100 c. c. of the solution produce a rotation of 100 degrees on the percent, scale, 61.68 grams (20.56 X 3) may be weighed out directly for the purpose and made up to 100 c. c. plus the volume occupied by the fat and proteids, the latter being calculated as above. The sugar-containing liquid will then be exactly 100 c. c, and the reading on the polarimeter divided by three will give the percentage of hydrated milk-sugar direct if a 200 mm. tube be employed. With a 400 mm. tube or 500 mm. tube the reading is to be divided by 6 or 7.5 respectively. Polarimeters. — A discussion of the construction of the various forms of polarimeters and of the optical principles 40 ANALYTIC PROCESSES. involved, would be beyond the scope of this work. The most economic instruments are the so-called half-shadow instruments, using the sodium flame, and they are the most satisfactory. They are so arranged that the field is divided into semicircles which are equally illuminated when the instrument registers zero. On the introduction of the tube carrying the sugar solution, the illumination becomes unequal and the angular rotation of the analyzer, which is required to restore the original condition, measures the rotation which has been caused by the sugar. Most instru- ments are furnished with two scales, one showing the rota- tion in angular degrees and the other expressing per cent, directly. The latter reads to loo when a certain fixed quantity of the material has been dissolved in water and diluted to loo c. c. The specific rotatory power of a substance is the amount of rotation of the plane of polarized light, in angular degrees, produced by a solution containing one gram of the substance in I c. c, examined in a column i decimeter long. It is expressed by the following formula, in which 6^ is the specific rotatory power for light of wave length corresponding to the D line of the spectrum (sodium flame). a is the angular rotation observed, c is the concentration of the solution (weight in grams, in ICO c. c. of the liquid), and /is the length of the tube in decimeters. ^ loo a Calculation of the amount of sugar corresponding to the observed rotation may be made by substitution in the for- mula. SUGAR. 41 The specific rotatory power of milk-sugar is unaffected by the concentration within the limits encountered in ordi- nary milk-analysis. It is slightly affected by temperature, being decreased by about .075 angular degree for each successive rise of one degree Centigrade. The specific rotatory power at 20'' C. is 52.5" when observed by the sodium flame. The employment of an arbitrary factor for correcting for the volume of precipitate may be avoided by the so- called method of " double dilution," in which two solutions of different volume are compared. With the higher class of polarimeters, the determinations may be easily made within one-tenth per cent. The following is a summary of the method given by Wiley and Ewell (y. A. C. S., 1895, p. 428) who recommend it strongly. The instrument used was the new triple-field shadow polarimeter made by Schmidt and Haensch, which permits readings to be made within 0.05 per cent. 32.91 grams of lactose dissolved in 100 c. c. gave a reading of 100. The amount of milk taken was double this quantity, that is, 65.82 grams, which were placed in a 100 c.c. flask, loc.c. of the acid mercuric nitrate added, the flask filled to the mark, the contents well mixed, filtered, and polarized. A similar quantity of the milk was placed in a 200 c. c. flask and treated in the same way. The true polarization is obtained by dividing the product of the readings in the two flasks by their difference. Thus in the paper above noted the following experiments are recorded : — Heading in 200 Reading in 100 c. c. flask. Apparent per cent, lactose. True per cent. lactose. 10 15 20.84 5.21 4- 95 The polarimeter used had a tube 4 decimeters long. 42 ANALYTIC PROCESSES. The figure for apparent percentage is obtained by dividing tiie reading of the small flask by 4. The true percentage is obtained by multiplying 10.15 by 20.84, dividing by their difference (10.69), and taking one-fourth this quo- tient. Birotatioti. — When freshly dissolved in cold water, milk sugar shovsrs a higher rotation than that given above. By standing, or immediately on boiling, the rotatory power falls to the point mentioned. In preparing solutions from the solid milk-sugar, care must be taken to bring them to the boiling point previous to making up a definite volume. This precaution is unnecessary when operating upon milk. MILK ADULTERANTS. Water. — The addition of water to milk is usually de- tected by the diminution in the amount of solids. It was formerly supposed that normal milk does not contain ni- trates, and since these are almost universally present in surface and subsoil waters, it was suggested that the ap- plication of some of the delicate tests for nitrates would detect the addition of water, but Bevan has shown that pure milk may contain nitrates, and Richmond obtained a reaction for nitrates from the milk of a cow to which had been administered a very small quantity of niter. The addition of water decreases the specific gravity, while abstraction of fat increases it. It is possible, there- fore, by carrying out both methods of adulteration care- fully, to maintain the same gravity as in the original sam- ple, so that this datum alone will not suffice to detect adulteration. Taken in conjunction with either the figure for fat or for total solids, the specific gravity becomes' of MILK ADULTERANTS. 43 direct value, and furnishes a means for deternaining, by calculation, the remaining datum. Vieth has pointed out that in normal milks the following ratios obtain : Sugar : proteids : ash =13:9:2, and a determination of these ratios may aid in the attempt to distinguish genuine but abnormal milks from watered milks. In the case of a watered milk the proportion would remain unchanged, but in abnormal milk it has been found to vary. Richmond finds that " the most con- stant figure in normal milks is the proportion of ash to solids-not-fat, which averages 8.3 per cent, and very rarely passes outside of the limits of 8.0 per cent, and 8.5 per cent. In cases of low solids-not-fat this proportion has been disturbed, and the ash has had a higher ratio to the solids-not-fat. In no case has the percentage of ash in the milk fallen below 0.7 per cent., even in milks notably below the limit. In an adulterated milk containing, say, 8 per cent, of solids-not-fat, the ash would usually be lower than this — about 0.66 per cent.; this difference is small, but as the ash is capable of being estimated with great ac- curacy, it is significant. Other observers have found the same thing." For milk control in dairies, etc., it will suffice to take the specific gravity by the lactodensiraeter (see page 19) and the fat by the Leffmann-Beam method. From the figures thus obtained the total solids can be ascertained by Table B or Richmond's slide-rule. Various substances are added to milk to conceal adulter- ation or inferiority in quality. The most frequently em- ployed are coloring matters. Sugar, salt, and starch have been added to milk, but are of infrequent occurrence. It has been stated that chalk has been added, but this is ob- 44 ANALYTIC PROCESSES. viously unlikely. The coloring matters most frequently employed are annatto and certain coal-tar colors. Cara- mel, saffron, and carotin are occasionally used. Annatto is easily detected by rendering the sample slightly alkaline by the addition of sodium acid carbonate, immersing in it a slip of filter paper, and allowing it to remain over night. The presence of annatto will be indi- cated by a distinct reddish-yellow tinge to the paper. Coal-tar colors are detected by adding to the milk ammonium hydroxid and allowing a piece of white wool to remain in it over night. The dye is taken up by the wool, which acquires a yellow tinge. When milk contains Martins' yellow, ammonium hydroxid intensifies the color and hydrochloric acid bleaches it. Further information as to coloring matters will be found under the analysis of butter. Starch may be detected by the blue color developed on the addition of solution of iodin to the milk, which has previously been heated to the boiling temperature and then cooled. Starch is very often added to ice-cream and similar articles. Salt and cane sugar are occasionally added to milk that has been diluted with water. The former is easily detected by the taste, the increased proportion of ash and^^ of chlorin. Cane sugar may be detected, if in considera- ^^ ble quantity, by the taste. The quantitative determination is made by the methods described in connection with con- densed milk. Antiseptic substances are largely used, especially in the warmer season, as a substitute for refrigeration. Many of these are sold under proprietary names which give no indi- MILK ADULTERANTS. 45 cation of their composition. Preparations of boric acid and borax were at one time the most frequent in use, but lately, formalin, a 40 per cent, solution of formaldehyde (methyl aldehyde), has come into favor. Sodium benzoate is now in common use as a preservative for cider, fruit- jellies, and similar articles, and may, therefore, be found in milk. Salicylic acid is not so much employed as in former years. Sodium carbonate is occasionally used to prevent coagulation due to slight souring. R. T. Thomson ("Glasgow City Anal. Rep., 1895," quoted in Analyst, March, 1896) has studied the compara- tive value of milk preservatives. He finds that a mixture of boric acid and borax is more efficient than the acid alone. The quantity generally used is equivalent to about one-half gram of boric acid per liter. Formalin was shown to be by far the most efficient antiseptic. In the proportion of 0.125 g''a-ra to the liter, it kept milk sweet for eight days. Formaldehyde. — The presence of this body may sometimes be detected by its odor developed on warming the milk. Hehner's method, the most characteristic for its detection, depends upon the fact that when milk contain- ing it is mixed with sulfuric acid a blue color appears. Richmond and Bosely showed that the delicacy of the test is much increased by diluting the milk with an equal bulk of water and adding sulfuric acid of 90 to 94 per cent., so that it forms a layer underneath the milk. Under these conditions, milk, in the absence of formaldehyde, gives a slight greenish tinge at the junction of the two liquids, while a violet ring is formed when formaldehyde is present even in so small a quantity as one part in 200,000 of milk. The color is permanent for two or three days. In the ab- sence of formaldehyde, a brownish color is developed after 46 ANALYTIC PROCESSES. some hours, not at the junction of the two liquids but lower down in the acid. Another test is by the use of Schiff's reagent — a solution of magenta bleached by sulfurous acid. In presence of an aldehyde a pink color is developed. This test is usu- ally applied to the distillate from the milk, but Richmond and Bosely consider it safe to use the whey produced by adding dilute sulfuric acid to the milk. They point out further that great care must be exercised in applying the test. Excess of sulfurous acid must be carefully avoided in preparing the reagent, since the color is not developed in its presence. On the other hand, a red color is easily developed in the reagent by warming, blowing air through it, or even placing it in an uncorked bottle. Hehner has shown that when a small amount of the reagent, say two drops, is added to the distillate from the milk, a red color, due to the oxidation of the sulfurous acid by the oxygen of the water, is developed after some time, whereas no color appears if a larger amount — say ten drops — has been added. He recommends to add about five drops of the reagent to the distillate (amounting to about 25 c.c.) from 100 c.c. of milk, place the mixture in a stoppered cylinder, observe the color next morning, and then add a few drops of sul- furous acid solution. After a short time, any color which may be due to oxidation will have vanished, while that due to the presence of an aldehyde remains. There is a differ- ence in the tint produced by color oxidation, which re- sembles that of rosanilin, and that of the aldehyde com- pound, which is violet ; and with the small amounts that are often to be detected, only a comparison of the relative colors would allow of anything like a safe conclusion being drawn. Hehner also recommends the following as a sensi- MILK ADULTERANTS. 47 tive and characteristic test : To the distillate from the milk, add one drop of a dilute aqueous solution of phenol, pour the mixture upon strong sulfuric acid contained in a test- tube. A bright crimson zone appears at the line of contact. This color is readily seen with one part of formaldehyde in 200,000 of water. If there is more than one part in 100,000, there is seen above the red ring a white, milky zone, while in stronger solutions a copious white or slightly pink, curdy precipitate is obtained. This reaction has an advantage over the one above referred to, in that it is obtained with formaldehyde solution of all strengths, while the blue color with sulfuric acid is not obtained with milk containing much formaldehyde. Acetaldehyde also gives a coloration and a precipitate with phenol and sulfuric acid, but it is orange-yellow, not crimson. Many hydroxy-derivatives of benzene, such as salicylic acid, resorcinol, and pyrogallol, give the red color with formaldehyde. Hydroquinone does not give the red color but only an orange-yellow one. The reaction only succeeds when carried out as described above ; the phenol must first be mixed with the solution to be tested, and the mixture poured upon the sulfuric acid. Only a trace of phenol must be used. If the hydroxy- compound is first dissolved in the acid and the formal- dehyde solution then added, no color is obtained. The precipitate obtained by sulfuric acid, formaldehyde, and phenol is highly insoluble, and might be utilized for the determination of the strength of dilute formalin solutions. Benzoates. — Two hundred and fifty to five hundred c. c. of the sample are rendered alkaline by a few drops of calcium or barium hydroxid, evaporated to one-fourth bulk, 48 ANALYTIC PROCESSES. mixed with sufficient calcium sulfate, powdered pumice, or other inert material as an absorbent, to make a pasty mass, and dried on the water bath. When condensed milk is examined, loo io 150 grams should be mixed directly with sufficient absorbent material and a few drops of barium hydroxid. The dry mass is finely powdered, moistened with dilute sulfuric acid, and then exhausted three or four times with about twice its volume of cold (50 per cent.) alcohol, which dissolves benzoic acid freely, but only mere traces of the fat. The alcoholic liquid which, in addition to the benzoic acid, contains milk-sugar and mineral mat- ter, is mixed thoroughly, neutralized with barium hydroxid, and evaporated to small volume. The residue is acidified with weak sulfuric acid and extracted with successive small portions of ether. On evaporation, the ether leaves, almost pure, the benzoic acid, which may be recognized by its odor and volatility. Boric Acid. — When boric acid or borates are not pres- ent in quantities sufficient to appreciably increase the ash of the sample, the quantitative determination is difficult. The qualitative test is delicate. One hundred c. c. of the sample are rendered alkaline with calcium hydroxid, evaporated and ashed. Calcium hydroxid is preferred because the ashing takes place more rapidly. The ash is dissolved in the smallest possible quantity of strong hydro- chloric acid, the solution filtered, and evaporated to dryness. An appreciable loss of boric acid will not occur. The residue is moistened with very dilute hydrochloric acid, mixed with tincture of turmeric, and dried on the water bath. The smallest trace of boric acid gives to the residue a ver- milion or cherry-red tint. Concentrated hydrochloric acid gives, with tincture of MILK ADULTERANTS. 49 turmeric, a cherry-red color, which, however, disappears on addition of water, and also becomes brown on drying, while the boric acid color appears only on drying, and is not destroyed unless much water be added, or at the boiling point. The red color adheres strongly to the vessel, and may be removed by alcohol. The flame test may be applied to the residue, but it is not delicate. R. T. Thomson (^Analyst, March, 1896) gives the fol- lowing method for the estimation of boric acid. One hundred c. c. of milk are mixed with from one to two grams of sodium hydroxid, evaporated to dryness in a platinum dish, the residue thoroughly charred, heated with 20 c. c. of water, and hydrochloric acid added drop by drop until all but the carbon is dissolved. The bulk should not be allowed to exceed 60 c. c. The liquid is trans- ferred to a 100 c. c. flask, 0.5 gram of dry calcium chlorid, a few drops of phenolphthalein solution added, then a 10 per cent, solution of sodium hydroxid until a permanent pink color is produced, and then 25 c. c. of lime-water. All the phosphate will be thus precipitated as calcium phos- phate. The mixture is made up to 100 c. c, well mixed, and 50 c. c. collected through a dry filter. Normal sul- furic acid is added to this until the pink color is discharged, then methyl orange is added and the acid again dropped until the yellow tinge is just changed to pink. Fifth-nor- mal sodium hydroxid is added (with care to avoid ex- cess) until the liquid is yellow, At this stage all acids likely to be present exist as salts, neutral to phenolphtha- lein, except boric acid (which, being neutral to methyl orange, is in the free condition) and a small amount of carbonic acid that may be expelled by a few minutes' boil- ing. The solution is cooled, a little phenolphthalein added, 5° ANALYTIC -PROCESSES. and as much glycerol as will give at least 30 per cent, of that substance in the solution, and then titrated with fifth- normal sodium hydroxid until the pink color appears. Each c. c. of the alkaline solution equals 0.0124 of crys- tallized boric acid. The process is satisfactory with milks containing not over 0.2 per cent, of boric acid. The charring must be carried only so far as to obtain a residue which will give a clear solution with the hydrochloric acid. Boric acid may also be estimated by Gooch's method which is described in the analytic manuals. Hehner {Analyst, 1 891) has modified the method by substituting sodium phosphate for powdered lime. (See page 52.) Salicylic Acid. — Fifty c. c. of the sample are treated with acid mercuric nitrate for the removal of the fat and proteids, as described in connection with the determina- tion of milk sugar, and the liquid filtered. The filtrate is shaken violently with about one-half its volume of a mix- ture of equal parts of ether and petroleum ether. The ethereal liquid is evaporated and a drop of neutral solution of ferric chlorid added to the residue. If salicylic acid be present, a characteristic violet color is developed. The reaction is very delicate. Sodium Carbonate. — The following .method, due to E. Schmidt, is stated to be capable of detecting one-tenth of one per cent, of sodium carbonate, or of sodium acid carbonate. Ten c. c. of the milk are mixed with an equal volume of alcohol, and a few drops of a one per cent, solution of rosolic acid added. Pure milk shows merely a brownish- yellow color, but in the presence of sodium carbonate a MILK ADULTERANTS. 5 I more or less marked rose-red appears. The delicacy of the test is enhanced by making a comparison cylinder with the same amount of milk known to be pure. If the salt is present in considerable amount, it may be detected by the increase in the ash, its marked alkalinity and efferves- cence with acid. Preservation of jnilk samples. — For preserving milk sam- ples for future analysis or comparison, various substances have been suggested, among which are hydrofluoric acid, alcohol, chloroform, carbon disulfid and formaldehyde. Richmond reported {Analyst, 1889, p. 2) good results by the addition of 0.5 per cent, of commercial hydrofluoric acid. In a discussion at a meeting of the Society of Public Analysts, in October, 1894 {Analyst, 1894, p. 247), Allen stated that he had added to each sample twice its weight of alcohol, but was not satisfied with this method, although it had, in some instances, served a good purpose. Mr. Rich- mond stated that he had been using formalin for a year and a half; 0.05 per cent, will keep milk for a month and larger quantities for an indefinite period. Bevan has, however, noted the fact {Analyst, 1895, p. 152) that the total solids of milk containing formaldehyde are always higher, and that the increase is much greater than can be accounted for, even assuming that the whole of the formaldehyde remains in the residue, which is im- probable, since it is volatile. Experiments on pure solu- tions of albumin, milk-sugar, and cane-sugar showed in each case an increase in residue when evaporated with formaldehyde. He has suggested that a small part, at least, of the increase in weight observed, is due to the formation of a non-volatile polymer of formaldehyde, and 52 ANALYTIC PROCESSES. in the case of milk-residues the increase is largely due to the conversion of milk-sugar into galactose. Commercial solutions of formaldehyde, even after recent, re-distillation, leave considerable residue, — probably the polymer, paraformaldehyde, — when evaporated in a flat dish in the manner employed in determining milk-solids. Addendum to detection of boric acid. — E. A. Farrington {J. A. C. S., Sept., 1896) has found that " preservaline " (which contains boric acid) added to fresh milk, increases the acidity four times as much as when added to water in the same proportion. He considers, therefore, that a milk which exhibits an acidity equal to 0.36 per cent, of lactic acid (8 c. c. of decinormal alkali to 20 c. c. of milk), and does not smell nor taste sour, has been probably adulterated with boric acid, since that proportion of lactic acid would be distinctly evident to the senses. DATA FOR MILK INSPECTION. VARIATIONS IN COMPOSITION. Average Proportion of Solids in Milk. — The most extensive data on this point are those obtained by Vieth, a summary of whose results, covering a period of eleven years, was published in the Analyst of May, 1892. The total number of samples was 120,540, and although some changes had been made in the methods of analysis since the beginning of the work, the results were recalcu- lated so as to be strictly comparable. The averages of the entire series were as follows : — • Fat, 4.1 percent. Non-fatty Solids, 8.8 " Total Solids, 12.9 " Seasonal Variations in the Composition of Milk. — The diagrammatic synopsis of Vieth's results {Analyst, 1892) shows that a notable variation in the proportion of ingredients occurs during the year. The poorest .quality occurs during the first half of the year, especially in April. A low figure is also frequently noted about July. In autumn the quality rises, being highest in October and November. The figures show that the variations in the total solids are due mainly to the variations in fat, but not entirely, for an increase in the proportion of fat is usually attended by a slight increase in the non-fatty solids. 53 54 DATA FOR MILK INSPECTION. The earlier tendency was to assign too high a limit for the non-fatty solids, since this figure was obtained by methods which failed to extract all the fat. In applying, therefore, the more modern processes, normal milk will be found to yield a figure for the non-fatty solids decidedly below the extreme limit of 9.5 per cent. Even nine per cent, for the non-fatty solids is more than is usually present. While it may be permissible in special cases, such as the purchase of milk under contract, or in the operation of a large dairy, to reject samples which yield below nine per cent, of non-fatty solids, it is not just to exact such a standard for purposes of public inspection, and as a basis for penal proceedings. The standard of the Society of Public Analysts of England (8.5 per cent, of non-fatty solids) has been found satisfactory in the large experience of the members of that body, and Dr. Vieth has ex- pressed himself as follows concerning it : " My object is by no means to raise the cry that the standard adopted by the Society is too high ; on the con- trary, I 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 given their assent to it, and that they will at times produce milk below standard. A bad season for hay-making is, in my experience, almost invariably followed by a particularly low depression in the quality of milk, toward the end of winter. Should the winter be of unusual severity and length, the depression will be still more marked. Long spells of cold and wet, as well as of heat and drought, during the time when cows are kept on pasture, also unfavorably influence the quality and, I may add, quantity of milk." VARIATIONS IN COMPOSITION. 55 Deficient Solids. — The following are some instances of deficiency of solids in milk known to be genuine : — Sp. Gr. Fat S-N-F. Total Solids Analyst 1029.6 338 7-95 11-33 C. B. Cochran 1030.0 3.62 8.31 11-93 11 1029.3 363 8.02 11.65 it 3-99 8.36 I2-3S Lefifmann and Beam 3- 1 1 833 11.44 ) Monthly Averages 3 05 8.33 11.38 N. J. State Agric'l 3-23 8.44 11.67 Exp. Station The following analyses have been kindly furnished us by C. B. Cochran, in advance of publication by him. The samples were taken under precautions which ensured their genuineness. The data are all direct determinations. The total solids were obtained by drying in the usual manner, and the fat by the L-B. method. Low milks have been often noted in the vicinity of Philadelphia. Cow SJ>. Gr. Fat S-JVF. Total Solids Pansy, . . . 1026.6 2-35 6.78 9-13 Rosie, . . . 1028.8 2-95 7-56 10.51 Dubell, . . . 1028.8 2.40 756 9.96 Gussie, . • - i°33-5 2.90 8.68 11.58 R. Bodmer {Analyst, 1895) reported the analysis of a sample obtained from one cow (June 13, 1895) as follows: Sp. Gr. Fat Proteids Sugar Ash 1024.8 3.14 3-77 2.59 0.88 In a herd of 60 cows, Richmond found 19 per cent, of the samples to contain between 8.38 and 8.50 per cent, solids-not-fat. The following instances of unusually rich milk, were reported in the Analyst, January, 1893 : — S6 DATA FOR MILK INSPECTION. Sp. Gr. Total Solids Fat Ash Analyst 1026.6 19-50 11.06 ■53 Smetham 1027.8 16.06 7-37 .72 ti 1031S 14.98 3-92 — De Hailes Since a partial creaming takes place in the udder, the first milkings (fore-milk) are poorer, and the last milkings (strippings) richer in fat, than the average milk. To insure a proper sample, the entire milking must be taken. Babcock (Pfoc. 12th Annual Conv. A. O. A. C, p. 123) states that during the protracted drought of the summer of 1895, the average of nearly 100 determinations at the Uni- versity of Wisconsin creamery gave but a trifle over 8.5 per cent, solids-not-fat. The casein was low in this milk, while the sugar was about normal in amount. Similar con- ditions have been observed by Van Slyke at the New York Station. Variation According to Breed. — The following fig- ures, taken from Bulletin 77 (1890), New Jersey State Agricultural Experiment Station, show the average com- position of milk of various breeds of cattle : — AVERAGE COMPOSITION OF MILK FOR EIGHT MONTHS. Pekchntage Herd Specific Geavitv Water Total ■ Solids Fat Casein Sugar Ash Ayrshire, . . . 1034 I 87.30 12.70 3-68 3-48 4.84 0.69 Guernsey, .... 1035.0 85-. S 2 14.48 5.02! 3.92 4.80 0.75 Holstein-Friesian, 1032.8 87.88 12.12 3-51 3.28 4.6q 0.64 Jersey, . . 1035-3 85.66 14-34 4-78 3-q6 4.85 0.75 Short- Horn, . . I033-9 87-55 1 12-45 3-&5 3-27 4.80 0.73 VARIATIONS IN COMPOSITION. 57 Variations According to Season. — The following table is condensed from the above report : — Ayrshire holstkin- Friesian Jersey Guernsey Sh't-Horn Total Solids Fat Total Solids Fat Total Solids Fat Total Solids Fat Total Solids Fat March, . . 13.00 .vg.? 12.46 3-89 14.99 536 15.29 5-46 13-99 4.69 April, . . . 13.09 .3.i< <: o H pq <; iC x; ' o o o o s c s tt •a s -^ l-l < " - :; ' : C z ■rf < 'ri a B s. E3 H Q " 0) OJ Ph P^' O, (M IN u-i r^ ^ i>. 00 ^ E l-l IT) CO U-) O ^ 00 a\ PI VD o < pi " l-H >-i pi ^' ^ M pi HH M __^ _, , id Se K OJ dj lo in 'd- P) ro '5 'S c a c c '^ ON pi r-^ \o >:. >i « o o o O d fO pi CO M ^ ^ a c a c a 't ■^ Td- '=*- T|- (n 0\ CO M en M ^ a> o p^ 00 ^ g IN 00 00 N ro ^^ 00 •H vq O vo u 4 d ds pi ro pi d^ d t-i vd ^ w " S c tH 0-) cr. O j>- o ro 0^ u !>. W u-i ^ M o ■^ fO ■^ up ^ s d\ C^ 00 d d^ d 00 d^ d >. i-( M ^ rn „ y^ r^ •^ hH PO ^^ h lo o oo M ro CO LT) o 00 o ■* o d\ 00 C^ C^ r^ r^ On a\ M " tn P o u-i 'rS ■* ? p) -^ Tj- o o o CO r^ M q u^ IH 00 Pl 00 q OS bJ ^o m 00 rh 00 ^6 On 4 \n 00 6 < ro ro IN ro r^ I>. ^£) i>. r^ w-) i^ H O h c z in' < oT («■ w _ .2 '^^ in (U *^ 'U C/2 C % J3 6 ^ "rt a i^' .£ "2 ^ S O <1 S Q ,i4 s "13 O O BUTTER. 75 BUTTER. Butter, commercially, consists of a variable mixture of fat, water, and curd, obtained by churning cream from cow's milk. The water contains in solution milk-sugar and the salts of the milk. Common salt is usually present, being added after the churning. Artificial coloring is frequently used. The composition of commercial butter usually varies within the following limits : — Fat, 78 per cent, to 94 per cent. Curd, I << • • 19-756 . . 36.706 37-825 2-340 . . . 3.260 Total, .... . . . .99.887 Pure proteids, . Ammoniacal nitrogen, Amidic nitrogen, . . Reichert-WoUny figure f 34-125 0616 665 or fat, . . . 25.30 FERMENTED MILK PRODUCTS. I°S FERMENTED MILK PRODUCTS. The usual fermentation of milk is the conversion of the lactose into lactic acid, but by special methods other changes may be substituted. These modified fermenta- tions are of rather ancient origin, and being produced by mixture of organisms, the products are complex and ir- regular. The proteids are more or less changed into pro- teoses and peptones. With advances in mycology, it will be possible to carry out each fermentation by a pure cul- ture and thus obtain a product of any desired compo- sition. Kumiss is milk which has undergone alcoholic fermen- tation. The inhabitants of the steppes of Russia prepare it from mare's milk. When cow's milk is used, cane- sugar must be added. It is often made by adding cane- sugar and yeast to skim-milk. Vieth {Analyst, 1885 and 1886) gives the following analyses of kumiss : — ■ KUMISS FROM COW'S MILK Q . Q Ash. i-i s u .J < s in 1.6.S •z. u < z n < 0° 11 s < U 1 < At the End OF V s One dav, 1. 12 ».,is 2.06 ■30 • 32 .26 6.16 .16 .42 One week, . .q2 S.93 1.48 2.00 .22 • 56 ■97 3-14 .22 ■34 Three weeks, I.O^ 8.66 i,S8 1-93 .21 • 74 1-39 2.23 ■ 23 ■3S Three months I. 12 8.52 1-57 1.70 .09 •91 1.94 ^-73 •^5 ■33 The item " lactoproteid and peptone " refers to the sub- H I06 MILK PRODUCTS. Stances precipitated by tannin after removal of the casein and albumin. KUMISS FROM MARE'S MILK. At the Alcohol Fat Nitrogenous Lactic Sugar Ash end of Matters Acid I day, . 2.47 1.08 2.25 0.64 2.21 0.36 8 days, 2.70 1.13 2.00 1.16 0.69 0.37 22 " . . 2 84 1.27 1.97 1.26 0.51 0.36 Kefyr.^This is usually made from cow's milk. It has been used in the Caucasus for centuries. For its prepara- tion a peculiar ferment is used, which is contained in the kefyr grains. These are first soaked in water, by which they are caused to swell, and are rendered more active and then added to the milk. If taken out of the milk and dried, the grains may be used repeatedly. The following analysis is given by Hammarsten (quoted by Aikman, " Milk, Its Nature and Composition ") : — Alcohol, . 0.72 Fat, . .... . . . 3.08 Casein, . . 2.94 Albumin, . . 0.186 Peptones, 0.067 Lactose, .... . . . 2.685 Lactic Acid .727 Ash, . .708 According to Konig, good kefyr will not contain more than one per cent, of lactic acid. APPENDIX. VIETH'S TABLE FOR CORRECTING THE SPE- CIFIC GRAVITY OF MILK FOR TEM- PERATURE, EXTENDED BY COCHRAN. The figures for temperatures frotn 38° to 4^" inclusive, were determined by experiment by C. B. Cochran. DIRECTIONS FOR USE. Find the Temperature of the Milk in the uppermost horizontal line, and the Specific Gravity in the' first vertical column. In the same line with the latter, under the Temperature, is given the Corrected Specific Gravity. Fahrenheit Degrees. 38 39 40 41 42 43 44 45 1027 2S.2 25-3 253 25.4 25.S 2^.6 2S-7 25.8 28 26.1 26.2 26.2 26 3 26.4 26.^ 26.6 26.7 29 27.1 27.2 27.2 27 3 27.4 27.5 27.6 27.7 30 28.0 28.1 28.1 28 2 28.3 28.4 28. s 28.6 31 29.0 29.1 29.1 29 2 293 29.4 29s 29.5 32 29.9 30.0 30.0 30 I 30.1 30.2 30-3 304 33 30-7 30-7 3P-7 3° 9 31.0 311 31,2 31-3 34 3i-b 31-7 31-7 31 9 32.0 32.1 32.2 32.2 35 32.5 32.b 32.7 32 9 32.9 33-0 33- 330 36 33-5 33b 33-7 33 8 33-9 34- 340 340 37 34-5 34-6 34-7 34 8 34-9 35° 350 35-0 3« 35-4 35-5 35-b 35.7 3S.« 107 io8 APPENDIX. Sp. Gr. Fahrenheit Degrees. 46 47 48 49 50 51 52 53 54 55 I020 19.0 19. 1 19.1 19.2 19.2 19.3 19.4 19.4 195 19.6 21 20.0 20.0 20.1 20.2 20.2 20.3 20.3 20-4 20.5 20.6 22 21.0 21.0 21. 1 21.2 21.2 21.3 21.3 21.4 21.5 21.6 23 22.0 22.0 22.1 22.2 22.2 22.3 22.3 22.4 22.5 22.6 24 22. 9 23.0 23.1 23.2 23.2 23-3 23-3 23-4 23.5 23.6 25 23-9 24.0 24,0 24,1 24.1 24.2 24-3 24.4 24-5 24.6 26 24.9 24.9 25.0 25-1 25.1 25.2 25.2 25-3 25.4 25-5 27 25-9 25.9 26.0 26.1 26.1 26.2 26.2 26.3 26.4 26.5 28 26.8 26.8 26.9 27.0 27.0 27.1 27.2 27-3 27.4 27.5 29 27.8 27.8 27.9 28.0 28.0 28.1 28.2 28.3 28.4 28.5 30 28.7 28.7 28.8 28.9 29.0 29.1 29.1 29.2 29-3 29.4 31 29.6 29.6 29.7 29,8 29.9 30.0 30.1 30.2 30-3 30-4 32 30-5 30-5 30.6 30-7 30-9 31.0 311 31-2 31-3 31-4 33 31-4 31-4 31-5 31.6 31.8 31-9 32.0 32.1 32.3 32-4 34 32.3 32-3 32-4 32.5 32.7 32-9 33-0 331 33-2 33-3 35 33-1 33-2 33-4 33-5 33-6 33-8 33-9 34- 34-2 34-,3 TEMPERATURE CORRECTION. 109 Sp. Ge. Fahrenheit Degrees. 56 57 58 59 60 61 62 63 64 65 1020 19.7 19.8 19.9 19 9 20.0 20.1 20.2 20.2 20.3 20.4 21 20.7 20.8 20.9 20 9 21.0 21. 1 21.2 21.3 21.4 21-5 22 21.7 21.8 21.9 21 9 22.0 22.1 22.2 22.3 22.4 22.5 23 22.7 22.8 22.8 22 9 23.0 23.1 23.2 23-3 23-4 23-5 24 23.6 23-7 23.8 23 9 24.0 24.1 24.2 24-3 24.4 24.5 25 24.6 24.7 24.8 24 9 25.0 25-1 25.2 25-3 25-4 25-5 26 25.6 25-7 25.8 25 9 26.0 26.1 26.2 26.3 26.5 26.6 27 26.6 26.7 26.8 26 9 27.0 27.1 27-3 27.4 27-5 27.6 28 27.6 27.7 27.8 27 9 28.0 28,1 28.3 28.4 28.5 28.6 29 28.6 28.7 28.8 28 9 29.0 29.1 29-3 29.4 29.5 29.6 30 29.6 29.7 29.8 29 9 30.0 30.1 30-3 30-4 30.5 30-7 31 30-5 30.6 30.8 30 9 31.0 31.2 31-3 31-4 315 31-7 32 31-5 31.6 31-7 31 9 32.0 32.2 32-3 32.5 32.6 32-7 33 32.5 32.6 32-7 32 9 33- 33-2 33-3 33-5 33-6 33-8 34 33-5 33-6 33-7 33 9 34-0 34-2 34-3 34-5 34-6 34-8 35 34-5 34-6 34.-7 34 9 3S-0 35-2 35-3 35-5 35-6 35-8 APPENDIX. Sp. Ge. Fahkenhhit Degrees. 66 67 68 69 70 71 21. 1 72 73 74 75 I020 20.5 20.6 20.7 20. 9 21.0 21.2 21,3 21-5 21.6 21 21.6 21,7 21.8 22.0 22.1 22.2 22.3 22.4 22.5 22.6 22 22.6 22.7 22.8 23.0 23.1 23.2 23-3 23-4 23-5 23-7 23 23.6 23-7 23.8 24.0 24.1 24.2 24-3 24.4 24.6 24.7 24 24.6 24.7 24.9 25.-0 25-1 25.2 25-3 25-5 25.6 25.7 25 25.6 25-7 25-9 26.0 26.1 26.2 26.4 26.5 26.6 26.8 26 26.7 26.8 27.0 27.1 27.2 27-3 27.4 27-5 27.7 27.8 27 27.7 27.8 28.0 28.1 28.2 28.3 28.4 28.6 28.7 28.9 28 28,7 2$. 8 29.0 29.1 29.2 29.4 29.5 29.7 29.8 29.9 29 29.8 29.9 30.1 30,2 30-3 30-4 30-5 30.7 3°-9 31° 30 30.8 30-9 311 31-2 31-3 31-5 31.6 31.8 319 32.1 31 31.8 32.0 32.2 32.2 32-4 32-5 32.6 32.8 33-0 33- 1 32 32-9 33-0 33-2 33-3 33-4 33-6 33-7 33-9 34- 34-2 33 33-9 34.0 34-2 34-3 34-5 34-6 34-7 34-9 35-1 35-2 34 34-9 35-0 35-2 35-3 35-5 35-6 35-8 36,0 36.1 36.3 35 35-9 36.1 36.2 36-4 36.5 36.7 36.8 37-0 37-2 37-3 TOTAL SOLIDS CALCULATED. B TOTAL SOLIDS CALCULATED FROM FAT AND SPECIFIC GRAVITY. Foinnda of Hehner and Richmond, corrected by H. Droop Richmond. T. S. = 1 F + 0.14. Sp. Gr. Fat. 1 I.O 8.95 i.i 9.08 1.2 1-3 9-V- 1-4 1-5 1.6 1-7 1.8 1-9 1030-5 9.20 9-44 9-S6 9.68 9. So 9.92 10.04 31.0 9.09 9.21 9-33 9-45 9-57 9.68 9.80 9.92 10.04 10.16 ■5 9.21 9-33 9-45 9-57 9.69 9.81 9-93 10.05 10.17 10.29 32.0 9-34 9.46 9.58 9- 70 9.82 9-94 10.06 10,18 10.30 10.42 •5 9.46 9.58 9.70 9.82 9-94 10.06 10.18 10.30 10.42 10.54 33-0 9-59 9.71 9-^1 9-95 10.07 10.19 10.31 IO-43 10.55 10.67 •S 9.71 983 9-95 10.07 10.19 10.31 10.43 10.55 10.67 10.79 1034.0 9,84 9.96 10.08 10.20 10.32 10.44 10.56 10.68 10.80 10.92 APPENDIX. Sp. Gr. Fat 1 2.0 2.1 2.2 2.3 2.4 2-5 2.6 2.7 2.8 2.9 1026.0 9.04 9.16 9.28 9.40 9.52 9.64 9.76 9.88 lO.OO 10.12 ■5 9.17 9.29 9.41 9-53 9-65 9-77 9.89 10.01 10.13 10.25 27.0 9.29 9.41 9-53 9.65 9-77 9.89 10.01 10.13 10.25 10.37 •5 9.42 9-54 9.64 9.76 9.88 10.00 10.12 10.24 10.36 10.48 28.0 9-54 9.66 9.78 9.90 10.02 10.14 10.26 10.38 10.50 10.62 •5 9.67 9-79 9.91 10.03 10.15 10.27 10.39 10.51 10.63 10.75 29. 9-79 9.91 10.03 10.15 10.27 10.39 10.51 10.63 10.75 10.87 •5 9.92 10.04 10.16 10.28 10.40 10.52 10.64 10.76 10.88 11.00 30.0 10.04 10.16 10.28 10.40 10.52 10.64 10.76 10.88 11.00 11.12 ■5 10.17 10.29 10.41 IO-53 10.65 10.77 10.89 II. 01 II.I3 11.25 31.0 10.29 10.41 i°-S3 10.65 10.77 10.89 II. 01 11.13 11.25 11-37 •5 10.42 10.54 10.66 10.78 10.90 11.02 II. 14 11.26 11.38 11.50 32.0 10.54 10.66 10.78 10.90 11.02 II. 14 11.26 11.38 11.50 11.62 •5 10.67 10.79 10.91 11.03 11.15 11.27 11-39 11.51 11.63 11-75 33-0 10.80 10.92 11.04 II. 16 11.28 11.40 11.52 11.64 11.76 11.88 •5 10.92 11.04 II. i6 11.28 11.40 11.52 11.64 11.76 11.88 12.00 1034.0 11.04 II. 16 11.28 11.40 11.52 11. 64 11.76 11.88 12.00 12.12 TOTAL SOLIDS CALCULATED. "3 Sp. Gr. Fat. 30 31 3.2 3^3 3-4 3^5 3^6 3^7 3^8 3^9 1026.0 10.24 10.36 10.48 10.60 10.72 10.84 10.96 11.08 11.20 11.32 ■5 10.37 10.49 10.61 10.73 10.85 10.97 11.09 II. 21 "•33 11.45 27.0 10.49 10.61 10-73 10.85 10.97 11.09 II. 21 ^1-33 11.45 11.57 •5 10.62 10.74 10.86 10.98 II. 10 11.22 "•34 11.46 11.58 11. 70 28.0 10.74 10.86 10.98 1 1. 10 11.22 "•34 11. 46 11.58 11.70 11.82 •5 10.87 10.99 II. II 11.23 "•35 11.47 11.59 II. 71 11.83 "•95 29.0 10.99 II. II 11.23 "•35 11.47 "■59 11.71 11.83 11.95 12.07 •5 II. II 11.23 "•35 11.47 "■59 II. 71 11.83 "•95 12.07 12.19 30.0 11.24 11.36 11.48 11.60 11.72 11.84 11.96 12.08 12.20 12.32 ■5 "•37 11.49 II. 61 "•73 11.85 11.97 12.09 12.21 i2^33 12-45 31.0 11.49 II. 61 "•73 11.85 11.97 12.09 12.21 12.33 12^45 12.57 •S 11.62 "•73 11. 85 11.97 12.09 12.21 1233 12.45 12.57 12.69 32.0 11.74 11.86 11.98 12.10 12.22 12.34 12.46 12.58 12.70 12. S2 •5 11.87 11.99 12. II 12.23 1 2^35 12.47 12^59 12.71 12.83 12.95 33° 11.99 12. II 12.23 12.35 12.47 12.59 12.71 12.83 12.95 13-07 ■5 12.12 12.24 12.36 12.48 12.60 12.72 12.84 12.96 13.08 13.20 1034.0 12.24 12.36 12.48 12.60 12.72 12.84 12.96 13.08 13.20 13^32 114 APPENDIX. Sp. Ge. Fat. 4.0 4-1 4-2 4.3 4.4 4-5 4-6 4-7 4.8 4-9 1026.0 11.44 11.56 11.68 11.80 11.92 12.04 12.16 12.28 12.40 12.52 •5 11.57 11.69 II. 81 11-93 12.05 12.17 12.29 12.41 12.53 12,65 27.0 11.69 II. 81 11-93 12.05 12.17 12.29 12.41 12.53 12.65 12.77 ■5 11.82 11.94 12.06 12.18 12.30 12,42 12.54 12.66 12.78 12. go 28.0 11.94 12.06 12.18 12.30 12.42 12.54 12.66 12,78 12.90 13.02 •5 12.07 12.19 12.31 12.43 12.55 12.67 12.79 12.91 13-03 13-15 29.0 12.19 12.31 12.43 12.55 12.67 12.79 12.91 13-03 13-15 13-27 ■S 12.32 12.44 12.56 12,68 12.80 12.92 13-04 13.16 13.28 13-40 30.0 12.44 12.56 12.68 12.80 12.92 13-04 13.16 13.28 13-40 13-52 •5 12.57 12.69 12.81 12.93 13-05 13-17 13.29 13-41 .3.53 13-65 31.0 12,69 12.81 12.93 13-05 13-17 13-29 13-41 13-53 13-65 i3-77i ■5 12.82 12.94 13.06 13,18 13-30 13-42 13-54 13.66 13-78 13,90 32.0 12.94 13.06 13.18 13-30 13-42 13-54 13.66 13-78 13.90 14,02 ■5 1307 13-19 13-31 13-43 13-55 1367 13-79 13-91 14-03 14-15 33-0 13-19 13-31 13-43 13-55 13-67 13-79 13-91 14-03 14-15 14,27 •5 13-32 13-44 13-56 13.68 13.80 13.92 14.04 14.16 14.28 14,40 1034.0 13-44 13-56 13.68 13.80 13-92 14.04 14.16 14.28 14-40 14.52 TOTAL SOLIDS CALCULATFD. 115 Sp. Gr. Fat. 5-0 5-1 5-2 5-3 5-4 5-5 5-6 5-7 5-8 5-9 1026.0 12 64 12.76 12,88 13.00 13-12 13-24 13-36 13-48 13.60 13-72 ■5 12.77 12.89 13.01 13-13 13-25 13-37 13-49 13-61 13-73 13-85 27.0 12.89 13.01 13-13 13-25 13-37 13-49 13.61 13-73 13-85 13-97 •5 13.02 13-13 13-25 13-37 13-49 13.61 13-73 13-85 13-97 14.09 28.0 13-14 13.26 13-38 13-50 13-62 13-74 13.86 13-98 14,10 14,22 •5 13-27 13-39 13-51 13-63 13-75 13-87 13-99 14,11 14.23 14.35 29.0 13-39 13-51 13-63 13-75 13-87 13-99 14,11 1423 14.35 14.47 ■S 13-52 13-64 13.76 13-88 14.00 14.12 14-24 14-36 14. 48 14,60 30.0 13-64 13-76 13.88 14.00 14.12 14.24 14-36 14-48 14.60 14.72 ■5 13-77 13-89 14.01 14-13 14-25 14-37 14,49 14.61 14.73 14.85 31.0 13.89 14.01 14- 13 14-25 14-37 14,49 14.61 14.73 14.85 14.97 ■5 14.02 14.14 14.26 14-38 14.50 14.62 14-74 14.86 14.98 15.10 32.0 14.14 14.26 14-38 14.50 14.62 14.74 14,86 14.98 15.10 15.22 ■5 14.27 14-39 14-5' 14-63 14-75 14-87 14,99 15,11 15-23 15-35 33-° 14-39 14-51 14-63 14.75 14.S7 14-99 i5ii[i5-23 15-35 15-47 ■5 14.51 14-63 14-75 14-87 14-99 15. II 15-2315-35 15-47 15.59 1034.0 14.64 14-76 14.88 15.00 15,12 15-24 15,36 15,48 15.60 15.72 ii6 APPENDIX. WEIN'S TABLE FOR EQUIVALENTS OF LAC- TOSE, CALCULATED FOR USE IN SOXHLET'S METHOD. 0. O u s < X e U 3 s < 1 g U s H U 120 86.4 -73 215 158.2 .76 51° 232.2 .81 125 90.1 -73 220 161. 9 .76 31S 236.1 .81 130 93-8 -74 225 165.7 -76 320 240.0 .81 '35 97.6 -74 230 169.4 .76 325 243-9 .81 140 101.3 -74 235 173-1 .76 330 247.7 .82 145 105.1 -74 240 176.9 -76 335 251.6 .82 150 108.8 -74 245 180.8 -77 340 255-7 .82 155 112. 6 -75 250 184.8 -77 345 259-8 .82 160 116.4 -75 255 188.7 .78 350 263.9 .82 1 65 120.2 -75 260 192.5 .78 355 268.0 .82 170 123.9 -75 265 196,4 .78 360 272.1 .82 175 127.8 -75 270 200.3 -79. 365 276.2 .82 180 131.6 -75 275 204.3 .80 370 280,5 -85 18s 135-4 .76 280 208.3 .80 375 284,8 •85 190 139-3 .76 285 212.3 .80 380 289.1 -85 195 143- 1 ■76 290 216.3 .80 385 293-4 .85 200 146,9 .76 295 220.3 .80 390 297.7 .85 205 150.7 .76 300 224.4 ,81 395 302.0 -85 210 IS4-5 .76 305 228.3 .81 400 306,3 -85 LACTOSE TABLE. I 1 7 The weights of copper and lactose (CijHjjOn -\- H2O) are in milligrams. For amounts of copper intermediate be- tween those given in the table, the quantity of lactose is determined by the factor in the third column, which repre- sents the weight of copper corresponding to i milligram of lactose at that point. Thus, if 178 milligrams of cop- per are obtained, the calculation will be 178 — 175 =3 ; 3X -75 =2-25 additional milligrams of lactose; 175^ 127. 8. •. 178 = 130.00. The figure in the second decimal place in the product may be disregarded. The equivalent weights of copper and copper oxid are almost exactly in the ratio of 4 to 5, hence, if the weight _is in terms of copper oxid, it may be converted into copper by multiplying by o. 8. Addendum to page 2g. The mixture of amyl alcohol and hydrochloric must not be drawn into the measuring pipet by suction. It should be kept in a bottle provided with a pipet which can be filled to the mark by dipping, or the Greiner overflow-pipet may be used. Rigid accuracy in the measurement of the solu- tion is not needed. Addendum to page 46. N. Leonard {Analyst, June, 1896) finds that the addition of a trace of ferric chlorid to the sulfuric acid increases the delicacy of Hehner's test for formaldehyde. NDEX. A BNORMAL milks, 62 ■**■ Acetic acid test, 84 Acid mercuric iodid, 72 Adams' method, 23 Adulterants of milk, 42 Albumin, lo in condensed milk, 36 , determination of, 35, 36 Alumina cream, 72 Amido-compounds, 103 Ammonium compounds, 103 Analytic processes, 18 Annotto, 44, 62, 96 Antiseptics, 45, 77 Ash, 13, 22, 76 Average solids in milk, 53 TD ABCOCK'S method for solids, 21 "^^ Bacteria in milk, 15 Baking soda, 50 Benzoates, 47 Birotation, 42 '* Black pepsin," 75 Blue milk, 62 Borax, 45 Boric acid, 45, 48, 50, 52 Breed, influence of, 56 Butter, 75 , calorimetric test for, 95 , colors, 96 , ether test for, 95 , fat, 10 ■, melting point of, 94 , pan-test for, 95 , specific gravity of, 94 , yellow, 96 Buttermilk, 17 pALCULATION method, 29 ^ Cane-sugar, 44, 66, 70, 72 Caramel, 44 Carotin, 44 Casein, 10, 75-6 in butter, 75-6 Casein, determination of, 35, 36 Caseinogen, 11 Cheddar cheese, 98 Cheese, 97 , analyses of, gg, 100, 104 , cottage, 97 , Dutch, 97 , filled, 99 , green, 97 ■, proteid nitrogen in, 102 , ripening, 97 , skim-milk, gg , sour-milk, 97 , Swiss, 97 Chrome-yellow, 103 Citric acid, 12 Coloring matters, 44, 61 Colostrum, 11-12-13 corpuscle, 13 Condensed milk, 64, 65 , composition of, 64, 74 Copper hydroxid mixture, 103 Cream, 16 evaporated, 64 Curd of milk, 11, 17 ■r\ECOMPOSED milk, 18 *-^ Decomposition of milk, 15 Diseases due to milk, 5g Distillation method, 78, 8i " Double dilution " method forsugar,4i Drought, effect of, 56 E NZYMES in milk, 12-16 Evaporated cieam, 64 "C^AT,g, 23, 66 "*• in butter, 75-6 , extraction from cheese, 100, loi globules, g Kehling's solution, 37 Fermentation method, 73 Fermented milk product?, 105 Formaldehyde, 45-47, 51 118 INDEX. 119 Formalin, 45, 51 Formula, Hehner and Richmond, 29 , Richmond, 30 Fluidometer, 92 Freezing, effect of, 16 r^ERRARD-ALLEN method, 70 ^*^ Globulin, 12 Glycerol-soda, 78 tJEHNER'Stest, 47 ^■^ ' and Angell's method, i Hoppe-Seyler method, 35 Hiibl's method, 85 jaiTRATES inmUk, 42 QLEOMARGARIN, 76 ^^ Oleorefractometer, 94 PARAFORMALDEHYDE, 52 ■^ Pavy's solution, 38, 68 Poisonous effects, 16 Polarimeters, 39, 71 Polarimetry, 39 Preservaline, 52 Preservation of samples, 51 Preservatives, 45, 51 Protcitis, 10, 66 ■ , determination of, 31 Pyknometer, 20 tNSOLUBLE acids, 88 ■*■ Inversion of sucrose, 67 Invertase, 67 Invert-sugar, 72 lodin number, 85 T^EFYR, 106 •^^ Kjeldahl-Gunning method, 31 KoeLtstorfer number, 90 Kumiss, 105 T ACTALBUMIN, 10, 11 ■'■^ Lactodensimeter, 19 Lactometer, 19 Lactose, 12, 66 , table for, 117 Leffmann Beam method, 26, TWrARGARIN, 76 ■^'■^ Martius' yellow, 44, 61 Methyl aldehyde, 45 Microbes in milk, 15 Milk, abnormal, 55 adulterants, 42 , blue, 62 , composition of, 53 • inspection, 53 , nature of, 9 Milks of various animals, 14 Milk products, 64 , red, 62 , ropy, 62 • — ■ • scale, 30 standards, 54, 57-8 sugar, 12, 66 , variations in, 52 Mineral matters of milk, 13 "p ECKNAGEL'S phenomenon, 15, 18 ■*^ Red milk. 62 Refriictive index, 93 Reichert method, 78, 81 Rennet, 97 , action of, 11 Rennin, 97 Richmond's ratio, 43 Ritthausen method, 33-4, 35 Ropy milk, 62 C ALICYLIC acid, 45, 50 ^ Salt, 45, 75-6 Sanitary relations, 58 Saponification, 81 equivalent, 90 flasks, 81 Schiff's reagent, 46 Season, influence of, 57 Separator milk, 17, 59 Skim-milk, 59 Slide-rule, 29 Sodium benzoate, 45 acid carbonate, 50 carbonate, 45, 50 Solids, deficiency in, 55 , excess of, 55 Soluble acids, 88 Sour milk, analysis of, 25 Soxhlet's method for lactose, 37 Specific gravity, 19 , change in, 15, 18 Specific rotatory power, 40 Starch, 44 Sterilized milk, 15, 60 Sucrose, 66, 70, 72 Sugar of milk, determination of, 37 ■^ABLE for lactose, 116 for temperature, 107 for total solids, 111 120 INDEX. Temperature, correction for, 107 Thomson's method, 49 Total proteids, 31, 33 solids, 21 solids calculated, m solids, decrease of, 18 Tuberculosis, 59 VALENTA'S test, 84 Vieth's method for solids, 21 - ratio, 43 ViscDsimeter, gi Viscosity of butter, 91 WATER in butter, 75-76 in milk, 42 Werner-Schmid method, 25 Westphal balance, 19 Whey, 17 Wiley and Ewell's method for sugar^ 41 Wiley's method, 38 Catalogfue No. 8. February, 1898. CLASSIFIED SUBJECT CATALOGUE OF MEDICAL BOOKS AND Books on Medicine, Dentistry, Pliarmacy, Cliemistry, Hygiene, Etc., Etc., PUBLISHED BY P. Blakiston, Son & Co., Medical Publishers and Booksellers, 1012 WALNUT STREET, PHILADELPHIA. SPECIAL NOTE. — The prices given in this catalogue are absolutely net, no discount will be allowed retail purchasers under any consideration. This rule has been established in order that everyone will be treated alike, a general reduction in former prices having been made to meet previous retail dis- counts. 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