pets thet é 7 saiatet ey 3 5 : : Sset Sy 575 / i Pigs ts baste ‘ z : asi i Ped i Siebert sth 2 beech ibe boosie aris rest hess oeere ok : 2 4 ee ehtecs ay or s fe i serabe Gy real erttet tre Te sions Spear oe sea te tee Distr opie ae Copyright N° COPYRIGHT DEPOSIT: a 7 Pere BABORATORY EXERCISES ON TESTING AND COMPOSITION OF DAIRY PRODUCTS ¢ BY nie Cs TROY and T. J: MCINERNEY . Professor of Dairy Industry in Charge Assistant Professor of Dairy Industry, of Testing and Composition of Dairy City Milk Inspecter. Products, Consulting Chemist of New York State Department of Farms and Markets. New York State College of Agriculture at Cornell University FIRST EDITION ITHACA, NEW YORK ITHACA PUBLISHING COMPANY 117 South Tioga Street 1921 ALL RIGHTS RESERVED ight 1921 By H. C. TROY and T. J. McINERNEY Cop - Ot a627278 i TABEE OF CONTENTS PAGE eehheaGenera) | Composiiionvot Milka ssi Sees o ae ee 1 ime lbnecwmb ab cocks -Watahest2ee. {= hak 5S ee eee ee SW ol 5 Mitemnesino: Butters for Moisture >to a ee eee 37 IV. The Specific Gravity of Milk and the Use of Lactometers_--_----~__- 41 Ameer emer NC riitiyes Ot: PMI eae Se Se eS SE Ee ee a5) WiteeOheese: Moisture) Testo 2= = bee ee ste 62 WI0k Salli; fin IBiiere Bing IBimiere Selly AN 67 Nea Cows estinio. wAssociation Recordsi22= "= 222 n eee ee eee - 75 VIII. The Majonnier Test for Fat and Solids im Milk and Its Products-- 102 PART I EXERCISES 21 lteerlthembabcocks Nes, 222 2222 ae a ee ee Soe een ai 22 II. ‘Conformity of Babcock Glassware to Specifications_-__________-__- 25 iit. Accuracy of Calibrations and Speed of Centrifuge_____________-_- 28 ieee heciinomnskame Milk and, Cream. 2 os 2 ee 3l Radia toomles Tah ed MeL. ee eee NON ee Mya Be Se BA Virsebabcock Rest Butter Moisture Test. 2 -- = 2s ae ee 38 VII. Effect of Temperature and Different Amounts of Acid and Use of Onevennemaciometens =. ssa ats a eee ee es 45 VIII. Composition of Milk and Test for Boiled Milk_________________ 49 Xe apcock les ands Calculating. Adulierations’== 2" ===. e aes 52 Sx, iBeloeoelk West, Avene! ANesi; ginGl Ieee 58 XI. Cheese Moisture Test, Babcock Test, Acid Test and Lactometer____ 64 XII. Babcock Test, Use of Hand Machines, Acid Test, Butter Moisture EMG Salt PRESS eg ee al aE Bs 8 Oe ee ee 69 XIII. Microscopical Appearance of Milk, Use of Rennet, Salt Test, Bab- COC Kg Gs te tnt ere ens ele eer ee Se te ot ee 72 XIV. Babcock Test, Cow Testing Association Experiments ~------~~_-- 76 XV. Testing Sour Milk, Effect of Temperature, Use of Different Acids-_ 80 PART II EXERCISES 83 XVI. Variations in Composition of Milk, Acid Test, Adulteration__-_-- 84 XVII. Comparing Different Fat Tests, Effect of Temperature and Test- more Matos OW AGT = = ee ee eee ee Ee 88 xVM Nhe Babcock andy Shaw. butter Mat Westss= 92s eee 91 XIX. Comparison of the Babcock and Adams Tests for Fat in Milk____ 95 XX. ‘Composition of Butter by the Gravimetric and Kohlman Methods__ 99 XXI—XXII. The Majonnier Tests for Milk Fat and Solids____________ 103 VI PAGE XXIII—XXIV. Testing and Standardizing Before Condensing a batch for the Manufacture of Evaporated Milk_-_------__________ 106 XXV—XXVI. Testing and Standardizing Before Condensing a Batch for the Manufacture of Sweetened Condensed Milk___-___-_~_ 109 XXVII—XXVIII. Testing and Standardizing Ice Cream Mix_____-~-- 112 XXIX—XXX. Testing and Standardizing Ice Cream Mix (Con- tinued), ~-224525 13255225) Se es ee eee 115 XXXI—XXXII. Testing and Standardizing Ice Cream Mix (Continued) 118 XXXITI—XXXIV. Making and Checking Standard Acid and Alka- lie Solwtion. «22222 222) 5 S22 ee ee 121 XXXV—XXXVI: Milk Analysis and Modified Leffman-Beam Method for Fat/in. Molk and ,Créam 2-2-2222 ee 125 XXXVI. Hart and Walker Casein Tests, Gerber Fat Test--_--------- 129 XX VES, Determinine thes Solubility, (ot Casenme eee eee eee 132 XXXEX. Detectine Butter Substitutes’-2-=2 === see 136 XL—XLI. Reichert-Meiss] Number of Butter and Oleomargarine, Mak- img, Viseoven' 22 2. isa eee 2 Se 139 XLII—XLITI. Modifying Milk for Infants and Invalids-_--------- 143 XLIV—XLY. Testing Unsweetened Evaporated, Sweetened Condensed Milkcand, Teev@ream: = Se ase te eee 147 XLVI—XLVII. Test for Preservatives, Adulterants and Boiled Milk__ 154 ist of’ Bulletitisy 2s aoe See RE ee ee ee 166 Index 222 n= 2 See a ee ee ee ee ee 164 PREP OR NOM: This book is intended to provide an outline of exercises for students in dairy industry. It is not intended that it should serve as a text book. The exercises in Part I may be used in all schools and colleges as an introductory course on the testing and composition of dairy products. The exercises in Part II are intended to serve as an advanced course for those specializing in dairy work and food control work. Ithaca, N. Y., October 1st, 1921. iit IV Dairy Laboratory Exercises GENERAL COMPOSITION OF MILK The fluid normally secreted in the mammary gland of female mammalia is called milk. In defining the standards of purity for dairy products the Association of American Dairy, Food and Drug Officials adopted the following definition of milk on August 3rd, 1917 :— “*Milk is the whole, fresh, clean lacteal secretion obtained by the complete milking of one or more healthy cows, properly fed and kept, excluding that obtained within fifteen days before and five days after calving, or such longer period as may be necessary to render the milk practically colostrum-free.’’ The six main constituents of milk and their approximate percentage is shown in the following chart :— Water 87.42% Fat 3.80% Total Sharing puea LTD Solids Solids roteins | Casein BISON 3.45% | Albumin 60% eat Ash or mineral matter .70% Tora/ solids Totea/ V/, 57%, : SOAS /4.53 Gf, Water BE.434, Yoter 68.439, Water Water 82.47 ¢, 65.472, Evrrerqy urits 580 Lrergy uriits BOO Comporatire food valve Comporative Tood valve JO crs. per Gr. /#- CPS. PCL GT Fig. 57. COMPARISON OF AVERAGE COMPOSITION AND FOOD VALUE OF MILK CON- TAINING THREE AND FIVE PER CENT OF FAT 2 COMPOSITION OF MILK The difference in the food values of equal quantities of milk containing different percentages of fat is shown in figure 57. A 1-per-cent increase in the percentage of fat in normal milk indi- eates about a 20-per-cent increase in the food value. Thus when a quart of milk containing 3 per cent of fat is worth 10 cents, a quart containing 4 per cent is worth 12 cents, and a quart con- taining 5 per cent is worth 14 cents. These facts have not been generally understood in the past, and have not received sufficient attention in the retail marketing of milk. They point out the importance of the fat test. One hundred pounds of milk containing 3 per cent of fat will make about 3.6 pounds of butter, while the same weight of milk A B (Cc Fic. 58. AMOUNT OF BUTTER MADE FROM ONE HUNDRED POUNDS OF MILK CON- TAINING VARIOUS PERCENTAGES OF FAT A, one hundred pounds of milk containing 3 per cent of fat made 3.6 pounds of butter; B, one hundred pounds of milk containing 4 per cent of fat made 4.8 pounds of butter; C, one hundred pounds of milk containing 5 per cent of fat made 6.0 pounds of butter containing 5 per cent of fat will make 6 pounds of butter (fig. 58.) This shows the importance of testing milk when calculating its butter-making value. The increase in the number of pounds of butter over the number of pounds of fat in the milk or the cream COMPOSITION OF MILK ee is called the overrun and it is due to the water, the salt, and the casein that remain in the butter when the churning process is completed. One hundred pounds of butter of average compo- sition contains about 82 pounds of fat, 14.5 pounds of water, 2.5 pounds of salt, and 1 pound of casein. The percentage of fat in milk also indicates its cheese-making value. Thus while 100 pounds of milk containing 3 per cent of fat will make on an average about 8.3 pounds of cheese, the same amount of 4-per-cent milk will make 10.6 pounds, and a like amount of 5-per-cent-milk will make 12.9 pounds. Fat exists in milk in the form of very small globules. With the aid of a high-power microscope they may be seen floating in the liquid. Since the fat globules are lighter than the other milk constituents, most of them rise to the surface under the influence of the force of gravity. There, mixed with other milk substance, these globules form a layer of cream. When sulfuric acid of proper strength and temperature is added to milk, as in the Babcock fat test, the milk sugar, and the protein are decomposed, and the sticky quality of the milk is destroyed. The acid does not, however, decompose the fat, but leaves it free to come to the surface of the mixture under the influence of centrifugal force generated in the testing machine. FAT VARIATIONS IN MILK The fat in milk commonly varies between three and six per cent. These variations come from several causes. One of the most important is the breed of the cows; another is the difference between individuals of the same breed. The percentage of fat in the milk of an individual in extreme cases may average either one per cent above or one per cent below the breed average. Also, the percentage of fat is affected by the length of time since the cow has freshened. It is a well-known fact that toward the end of the lactation period, when the cow is being dried off, the milk contains a higher percentage of fat than it did earlier in the season. It is also fairly well established that, when the time elapsing between milkings is not of equal length, the milk drawn after the longer period contains the lower percentage of fat. There are also minor influences affecting the fat content, such as feverish condition of the animal, or overexcitement due to dog- 4 COMPOSITION OF MILK ging or other ill treatment that might cause the cow to hold up part of her milk, thus giving a larger portion of the milk that is first let down, which is not so rich in fats as the strippings. The character of the food of an animal has very little effect on the percentage of fat in the milk, altho it has a marked effect on the amount of milk and fat produced. FAT PERCENTAGE AND FOOD VALUE When measured by energy units, the fat supplies about one- half of the food value of average milk, and the solids not fat furnish the other half. The solids not fat are composed of milk sugar (lactose), casein, albumin, and mineral matter (ash). Recently it has been discovered that milk also contains two very important growth-promoting and health-regulating prin- ciples, known as vitamines. The principal proteins in fresh milk are calcium caseinate, lactalbumin and lacto-globulin. The casein is not in true solution but is evenly distributed throughout the mass of milk in minute gelatinous particles known as a colloidal condition. The casein assists in retarding the rise of fat globules and is largely account- able for the opaque, nearly white color of milk. In fresh milk it is not precipitated by boiling but is thrown down by dilute acids while strong mineral acids dissolve and decompose it. Milk © albumin is present in true solution. It is not precipitated by dilute acids but is thrown down by heating milk to a temperature of about 80° C. Lacto-globulin is present in milk only in traces. Milk sugar forms about 58 to 60 per cent of the solids not fat. It is valuable chiefly as a food, having the same energy and heat producing power as cane sugar but it is not so sweet. It is con- verted to lactic acid by bacterial action and its presence in the digestive tract is thought to assist digestion. The importance of milk sugar is also increased since lactic acid and its control plays an important part in the manufacture, quality and preser- vation of milk products. The ash is the substance derived from the mineral salts of milk that remain when dried milk is burned to a white ash at a low red heat. The mineral salts in milk consist chiefly of potas- sium, sodium, calcium and magnesium in the form of chlorides, phosphates and citrates. The high calcium content gives the mineral salts of milk special value as a food. THE BABCOCK FAT TEST 5 THE BABCOCK FAT TEST Previous to the year 1890 comparatively few people knew any- thing about the composition of milk or the percentage of fat it contained. Dairy products were bought and sold by weight or measure almost regardless of their composition or food value. In 1890 Dr. S. M. Babeock of the Wisconsin Agricultural Experi- ment Station invented the milk fat test that bears his name and published a report on it. By the application of this test, or. slight modifications of it, the approximate percentage of fat in nearly all dairy products many be determined. TESTING MILK Sampling the Milk. If the milk is fresh and no cream has risen on it, the sample shall be taken immediately after pouring the milk from one vessel to another three or four times. Where such milk cannot be poured, it should be thoroughly and vig- orously stirred for at least half a minute with some suitable instrument long enough to reach the bottom of the container. If the cream has risen on the milk, or if a layer of cream has formed, mixing must be continued until all cream is detached from the vessel and all particles of cream are broken up and evenly distributed throughout the mass and no longer are visible on close observation. In taking composite samples, a porportionate amount of each mass of milk sampled should be placed in the composite sample bottle. This can usually be done best by means of a sampling tube. At least ten cubie centimeters of milk should be taken from each mass of milk sampled. A composite sample, as referred to here, means a sample of milk made up of proportionate amounts of each dielivery from a single source, to be tested for fat content. A composite sample should not represent milk de- livered for a period of more than 16 days. A herd sample taken one day during the period cannot be considered a composite sample of such period. Care of the Milk Sample. Composite samples in order to give satisfactory results, should be kept in a shaded place in clean, air-tight jars and should contain a sufficient amount of preservative. Corrosive sublimate or potassium bichromate shall - be used as preservatives, care being taken not to use excessive 6 THE BABCOCK FAT TEST amounts. Care also should be taken to keep such samples in a cool place, but they should not be allowed to freeze. If transported by mail, express or otherwise, the sample bottle should be completely filled, tightly stopped and sealed. Immediately before testing, the sample must be mixed gently until it is homogeneous. Composite or other than fresh samples must be placed in water warm enough to soften all lumps of cream and cream attached to the inside of the jar. Then mix gently until the sample is homogeneous and pipette at once, using 18 grams of milk. Avoid incorporating air bubbles while mixing the sample. Curdy and churned samples are not de- pendable. Operation: Mix the milk by pouring, allow- ing it to flow down the side of the vessels to avoid incorporating air bubbles. Vigorous shak- ing should be avoided. See that all cream is removed from the sides of the sample bottle and that it is evenly distrib- uted thruout the milk. Then holding the pi- pette between the thumb and the second finger of the right hand, place its tip well under the surface and draw in the milk by suction with the lips on the upper end until it is filled well above the Fic. 61. CORRECT POSITION OF THE PIPETTE graduation. Quickly AND TEST BOTTLE WHILE TRANSFERRING THE place the fleshy pad of MILK the forefinger over the opening and at right angles to the pipette. By rolling the pipette a little between the thumb and the second finger sufficient air will enter to allow the milk to run out slowly until the upper surface THE BABCOCK FAT TEST 7 is exactly level with the graduation. The pipette should be held perpendicular, with the graduation on a level with the eye. Hold the milk test bottle in a slanting position and place the tip of the pipette into it about one-third of an inch and at a slight angle (fig. 61). Allow the milk to flow slowly down the side of the bottle neck, making certain that none is blown out by the escaping air. Blow the drop that remains at the tip of the pipette into the test bottle. Measure out another test sample in the same manner, as the test must be made in duplicate. Adding the Acid: Fill the measure to the mark with acid, . and then rotate the test bottle slowly while adding the acid so that it will rmse down any milk remaining in the neck. Imme- diately mix the acid and the milk thorcly by whirling the body of the bottle in a circle five or six inches in diameter (fig. 62), using care to keep the mixture out of the neck of the bottle. Shake the mixture vigorously for about one minute after all curd has disappeared, and shake it again Fig. 62. DIAGRAM SHOWING THE MO- just before centrifuging to in- TION AND POSITION OF A TEST Bor- Sure complete solution. Avoid a ee SNS poinhine thermeck of the bottle toward any person during the mixing operation and so prevent the possibility of having acid thrown into the eyes or on the clothing. The acid unites with all of the milk substances except the fat, thus generating much heat. The temperature of the mixture usually rises to 225° F. Centrifuging: Steam driven centrifuges will be warm enough. Hand or electrically driven centrifuges are heated either by placing on a stove or by adding a few quarts of boiling water. A corked opening in the bottom provides a means of removing the water. The disk of the machine must be balanced by placing test bottles in exactly opposite pockets. Cover the machines before starting. 8 THE BABCOCK FAT TEST Table showing the revolutions per minute the bottles should make while whirling in Babcock testers: TOtineh= igh... lccs 6 ss seta cs Noles steno 1,100 revolutions 2 ANChis Gish st fra csae sth seis leew viele he to eee 1,000 revolutions 4: amici <@iis ga 2-6) 4 seats eee Once eee 925 revolutions IG AMCHRAUSKSe = hk tise ola eee 850 revolutions lS eamehadisies:4 steak ee eek bye Ce ee eee 800 revolutions AOWINCHAGISTES!s 5 rsp . A “ ty rl if . a ae ee t itate hae re can ’ = { o s au <9 at 4 OEE ogee : ; o. a ye I etysirey edt ether ‘ ; 1c) maples tear 112 DAIRY LABORATORY EXERCISES EXERCISES XXVII—XXVIII TESTING AND STANDARDIZING ICE CREAM MIX 1. Make up a 1000 gram batch of ice cream mix so that the fat is about 0.8 per cent under, and milk solids not fat about 0.5 per cent over the desired standard. (See {8 for desired standard. ) 2. Determine by using the Mojonnier method the exact per- centages of fat and milk solids not fat in the mix. Also make these tests on the cream to be used in standardizing the mix. 3. Calculate the grams of cream, sugar and water that must be added to the mix in order to make it test 10% of fat, 11% of milk solids not fat and 13% of sugar. 4. Add the standardizing materials to the 1000 gram bateh, mix thoroughly and test by the Mojonnier method for fat and solids. Compare the percentages of fat and milk solids not fat obtained with those desired. {os Pa iebla ie ae “4 SR Nk , nN = ' DAIRY LABORATORY EXERCISES 115 EXERCISES XXIX—XXX TESTING AND STANDARDIZING ICE CREAM MIX (CONTINUED) 1. Make up a 1000 gram batch of ice cream mix so that the fat is about 0.5% over the percentage finally desired and the milk solids not fat about 0.3% under the percentage finally desired. 2. Determine by the Mojonnier method the exact percentages of fat and milk solids not fat in the mix. Also make these tests on the condensed skim-milk to be used in standardizing the mix. 3. Caleulate the grams of condensed skim-milk, sugar and water that must be added to the mix in order to make it test 10% of fat, 11% of milk solids not fat and 13% of sugar. 4. After adding the necessary standardizing materials mix the batch thoroughly and make certain that the sugars are in solu- tion. Again test the mix for its percentages of fat and milk solids not fat and compare the results with the composition desired. am a: a : 3 eg sagt chee See PRC . > 5 a ‘ 118 DAIRY LABORATORY EXERCISES EXERCISES XXXI—XXXII TESTING AND STANDARDIZING ICE CREAM MIX (CONTINUED) 1. Make up a 1000 gram batch of ice cream mix so that the percentages of fat and milk solids not fat present are both about .O per cent under that desired. 2. Test the batch for fat and milk solids not fat by the Mojonnier method. Also test the materials that are to be used in standardizing the batch. 3. Calculate the grams of each material to add to bring the fat and milk solids not fat up to the desired percentages. 4. Add the materials to the original mix and test the mix for fat and milk solids not fat by the Mojonnier method. Compare the percentages obtained with the percentages desired. DAIRY LABORATORY EXERCISES 121 EXERCISES XXXIII—XXXIV MAKING AND CHECKING STANDARD ACID AND ALKALI SOLUTIONS. 1. Make up an alkaline tablet solution by dissolving 26 Far- rington alkaline tablets in small amount of distilled water and make the solution up to 100 cc. Determine the strength of alka- line solution by titrating with a standard HCl solution. What weight in grams of NaOH does each tablet contain? How many grams of lactic acid does each tablet neutralize according to your results ? ; 2. Cork a clean dry test tube and weigh it accurately on a chemical balance. Working quickly, place in the weighed tube ~a stick of C. P. NaOH between two and three inches long. Cork the tube at once and reweigh. Determine the weight of caustic in the tube and dissolve it in distilled water at the rate of .416 erams for each 100 ce. of solution. Determine the strength of N/10 NaOH solution by titrating it against standard tenth normal hydrochloric acid and tenth normal oxalic acid solution. The standard HCl solution will be furnished. .To prepare tenth nor- mal oxalic acid (C,H,O, + 2H,O) dissolve in distilled water at the rate of .63 grams for each 100 ce. of solution. 3. Test a sample of skimmed milk for per cent of acid by using each alkaline solution. Save some of the milk to be tested for acid at the next laboratory period. 4. Test a sample of vinegar for per cent of acid by using each alkaline solution. Molecular formula for acetic acid = CH,COOH It will be necessary to determine the specific gravity of the vinegar. This may be done with a Quevenne lactometer. 5. Slake a few ounces of lime in a small amount of warm water. Add about 100 ec. of water to the slaked lime, and set aside until the next exercise. 6. Place 300 ce. of concentrated HCl in an evaporating dish. Add 200 ee. of water. Boil down to 200 ce. or % of the original volume. The specific gravity then equals 1.10. It contains 20.2% 122 DAIRY LABORATORY EXERCISES HCl. 18 grams of this solution diluted to 1000 ce. gives an N/10 solution of HCl. (18.0 « 20.2% = 3.636 gers.) Using the above method make up an N/10 solution of HCl. -Note: Aliquot portions of the above amount may be used. QUESTIONS What is the advantage in using Farrington alkaline tablets in making an alkali solution? Give the grams per ce. in tenth normal solutions of (a) three acid solutions; (b) three alkali soultions; (c) three salt solutions. How much NaOH by weight does each tablet contain? What is the legal requirement for vinegar in New York state? What is the normality of a limewater solution? If a N/10 KOH solution and a N/10 NaOH solution were mixed together, how would you use the resultant solution in determining the acidity in a sample of milk? How does the specific gravity of vinegar vary from that of milk? iW DAIRY LABORATORY EXERCISES 125 EXERCISES XXXV—XXXVI MILK ANALYSIS, AND MODIFIED LEEFMAN-BEAM METHOD FOR FAT IN MILK AND CREAM. 1. Milk analysis. Take the Sp.Gr. of a sample of milk with Quevenne lactometer, and measure three cc. of the milk into a weighed silica dish. Evaporate to a constant weight at the temperature of boiling water (100° C€.). Cool in a dessicator and weigh. Determine the per cent of fat by the Babcock method. Compare the per cent of solids obtained by the gravi- metric method, with the per cent of solids calculated by applying different formulas. 2. Heat the silica dish containing the residue from No. 1 in ‘the muffle to an ash: Cool in the dessicator, reweigh, and deter- mine the per cent of ash in the milk. What conclusions do you draw in No. I[? 1. Test in duplicate a sample of milk and cream for per cent of buter fat by the Babcock ‘method. If the fat column in the completed test is not a clear, straw color, with sharply defined lines, the test must be repeated. Compare the results of this method with the results you obtained by the following modifica- tion of the Leffman-Beam method. 2. MODIFIED LEFFMAN-BEAM METHOD: Test for per cent of fat in Milk: Prepare the sample of milk and measure the charge by following the Babcock method up to the point of adding sulphuric acid. Then proceed as follows: 1. Add 3 ee. of a mixture of Amy] alcohol and Hydrochloric acid (equal parts of Amyl alcohol and Hydrochloric acid). 2. ‘Add 12 ec. of Sulphuric acid cautiously, mix and let stand for 3 minutes or until all the protein is dissolved and fat has risen to the top. 3. Add to top of graduation on neck of bottle a mixture of hot and freshly made solution of equal parts of sulphuric acid and water. NOTE: In making the solution, add the acid to the ~yater. 4. Whirl in centrifuge at the usual speed of Babcock test for 5 minutes. 126 DAIRY LABORATORY EXERCISES Reading the Test: Make three readings of the fat column. 1. From bottom of fat column to bottom of top meniscus. 2. From bottom of fat column to middle of top meniscus. 3. From bottom of fat column to top of meniscus. | Record all results. Test for per cent of fat in Cream: Prepare the sample of cream same as for Babcock test, and weigh 9 grams of the sample into a 9-gram cream test bottle, adding 9 ce. of water. Complete the test by following the method given for milk with the exception of adding a little less sulphurie acid. Reading the Test: Temper the cream test in water bath at a temperature of 130°—140° F. for 3 to 5 minutes. Make the fol- lowing readings and record each: 1. Bottom of fat column to bottom of top meniscus. 2. Bottom of fat column to middle of top meniscus. Bottom of fat column to top of meniscus. as Add meniscus remover and read from bottom of fat column to the sharp line at the junction of meniscus remover and fat eclumn. ; The official chemical results of this experiment will be given out at the close of the laboratory period. Enumerate and deseribe the desirable and undesirable features of each method in this exercise. Include'a tabulated form of all results. QUESTIONS 1. How do the percentages of solids not fat and total solids of milk as determined by the chemical method compare with those obtained by the use of the different formulae? 2. Why should ash determinations be made in a muffle? 3. What is the purpose of adding the mixture of amyl] alcohol and hydrochloric acid in the Leffman-Beam method of testing milk for fat? 4. How does this test compare with the regular Babeock test? DAIRY LABORATORY EXERCISES 129 EXERCISE XXXVII HART AND WALKER CASEIN TESTS, GERBER FAT TEST, DETERMINING THE SOLUBILITY OF CASEIN. 1. Walker Casein Test. Titrate 9 ¢ ec. of sweet milk in a white cup for per cent of acid using N/10 alkali solution. Use 1 ce. e. of a 1% phenolphthalein solution as indicator. Stir con- stantly with a glass rod during the titration, and titrate to a fair- ly deep pink color. Then add 2 ¢. c. of neutral 40% formalde- hyde solution. Take the reading on the burette and again run in, with constant stirring, the alkaline solution until the same degree of pink color again developes. The number of ee. of tenth nor- mal solution used for the final titration multiplied by 1.63 gives the per cent of casein in the milk. Set aside some of the milk un- til the next exercise and again test it to determine if one may use this test for the per cent of casein in sour milk. 2. Test a sample of milk for fat by the Gerber method and compare the results with a test made by the Babcock method. 38. The Hart Casein Test: Place 2 ec ec. of chloroform in the casein test tube, add 20 ¢. ¢. of a 0.25% solution of acetic acid at a temperature of 65 to 75° F. (10 ee. of glacial acetic acid dilut- ed to 100 with water then diluting 25ce. of this solution to 1000ec.) 5 ec. of milk at a temperature of 65 to 75°F is then run in, the tube covered with the thumb and inverted and the mixture shaken vig- orously for exactly 20 seconds, centrifuge within 20 minutes at a speed of 2000 revolutions per minute. Allow to stand ten minutes before reading the per cent of casein. Check the results by the Walker method. 130 132 DAIRY LABORATORY EXERCISES EXERCISE XXXVIII 4. TESTING CASEIN FOR SOLUBILITY AND ADHESIVE PROPERTIES 4. Dahlberg Method: Place 50 grams of the powdered casein in a flask, beaker or dish, add ‘about 100 cc. of water, measuring the amount. Mix the water and casein thoroughly. In another vessel place 5 grams of borax and add 75 ee. of water to it. Heat the wat- er and mix until borax is dissolved. Pour the borax soultion on the casein mixture and add water to bring the volume of the mixture C. for quite a long time (30 to 60 minutes) with stirring until all casein is in complete solution. (Sometimes 2 ¢. ¢. of concentrated NH, are added to the mixture to assist solution but it is not usual- ly added.) Then take 100 grams of Kaolin, (china clay) add 60- 70 ce. ec. of water and work to a smooth heavy paste. To all of this Kaloin mixture add 30 gramd of the casein mixture (6 grams of the casein) and thoroughly mix by use of a large spoon or similar instrument in a 3 pint bowl until the paste is very smooth. May also use brush in mixing. Then by using the brush transfer some of the mixture to a piece of brass, spreading it along a straight edge. Then spread the mixture without delay evenly on paper by holding the brass in a slanting position and pressing the mix- ture into the paper. The brass should be drawn across the paper with a quick motion. To the portion of the Kaolin-casein-borax mixture that remains add 5 grams more of the casein-borax mix- ture, mix it thoroughly and spread on paper as before. Then make one more mixture by adding 5 more grams of the casein-borax-water solution and again spread on paper and let dry. Test each mixture for adhesive properties by heating the end of a rod of wax till soft, then sticking it on the paper. When cool pull the wax off. The mixture which gives the best results is the proportions that should be used in making the sizing. The best results are indicated by the amount of paper that sticks to the wax and fiber that is pulled up from the paper. The wax should be pulled off perpendicular to the paper. And the more shreds of paper and solid paper substanees that sticks to the wax the better the quality of the casein. DAIRY LABORATORY EXERCISES 133 QUESTIONS For Walker Casein Test, read article in Journal of Industrial & Engineering Chemistry, Feb. 1914, p. 151. Make a drawing of the Gerber milk test bottle. What is your opinion of Gerber method as compared with Babeoeck method? Explain why the per cent of fat may be read directly in the Gerber milk test bottle. What is the purpose of the different reagents used in the Hart Casein test? Why is borax used in the Casein Solubility test? : ad i - Sel 1 PEN, eat a ne 136 DAIRY. LABORATORY EXERCISES EXERCISE XXXIX DETECTING BUTTER SUBSTITUTES 1. Melt samples of the butter substitutes in large test tubes two-thirds full. Keep at a temperature of about 150°F, until well melted and most of the casein and water have separated. Note any differences in transparency of the melted fat, when compared with the melted fat from pure butter. 2. Over a flame about an inch high from an alcohol lamp, gas jet, or kerosene lamp, heat in a teaspoon a quantity of the sub- stance about the size of a chestnut. Heat slowly until melted, then rapidly until the water is nearly boiled off. Note any differ- ences in the amount of foam formed and the length of time elaps- ing before the bubbles of foam break, when compared with pure - butter heated in the same manner. 3. Filla pint tin cup half full of skimmed milk, and heat near- ly to boiling. Place a piece of the sample about the size of a butternut in the hot milk. Set the cup in a pan of ice water, and stir briskly by a rotary motion with a small wooden splinter a little longer than a match in diameter. When the fat begins to harden, it may readily be gathered into a mass at the center or in a lump on the end of the splinter if it is oleo. Butter fat or ren- ovated butter will not gather so readily, but will float on the surface spread out quite uniformly. 4. Halpen’s Test for Cotton-Seed Oil: To 3 ce. of the oil or melted and filtered fat in a small test tube, add 3 ¢. ¢. of amyl al- cohol and 3 ¢. ¢. of a one per cent solution of sulphur in carbon disulphide. Heat the test tube in a boiling salt saturated water solution for 10 or fifteen minutes. If cottonseed oil is present, the mixture turns red. 138, DAIRY LABORATORY EXERCISES 139 EXERCISES XL—XLI REICHERT-MEISSL NUMBER OF BUTTER AND OLEOMARGARINE, AND MAKING VISCOGEN 1. Melt about 30 grams of the substance in a test tube, at a temperature of about 140°F. and hold at this temperature until the water and casein have separated. Filter the liquid fat through a dry filter with funnel inserted into a convenient Hrlen- meyer flask; keep warm in the 100°C. oven to assist the filteration process. Measure 5.75 ec. ec. of the filtered fat into a weighed 300 e. c. Erlenmeyer flask that has been thoroly cleaned and dried in the water oven. Cool and weigh to get the amount of fat taken; saponify the fat adding 20 ¢. ec. of a soda glycerine solution (20 ¢. ec. of 50% solution of sodium hydroxide in 180 e. ¢. of glye- erine), heating the flask in the 100°C. oven, or over a bunsen flame. The solution is perfectly clear when saponification is com- plete. Then add 135 c. c. of water, drop by drop at first, to pre- vent foaming. A pinch of pumice stone powder is added, and 5 «¢. e. of dilute sulphuric acid solution (20 ¢.c. of Cone. H,SO, + 80 ¢.c. of distilled water.) Connect the flask to the condenser, using distilling connecting bulb, and distill over 110 ¢. e. of the volatile fatty acids. Mix the distillate, and if not perfectly clear, filter. Titrate 100 c.c. of the distillate with N/10 NaOH, using phenolphthalein as indicator, and increase the number of e. ¢. of N/10 NaOH required, by one-tenth to obtain the Reichert-Meissl number. 2. Viscogen: Slake one ounce (28.35 er.) of quick lime in sufficient hot water to nearly cover it, using a pint milk sample bottle. Mix during the slaking process. The substance should be in a pasty condition when slaked. Add 150 ¢. ¢. of cold water. Dissolve 3 oz. of sugar in 150 ec. of water, and mix it thoroughly with the slaked lime solution. Mix at intervals for a few hours. Let settle and use the clear solution at the next exercise. Note: Viseogen may be made in large quantities for com- mercial purposes by slaking 3 pounds of good quick lime in water. Make the volume up to 5 gallons by adding water. Dissolve 10 Ibs. of sugar in 5 gallons of water. Mix the two solutions and stir at intervals for 3 hours. Let settle and use the clear solution. 140 DAIRY LABORATORY EXERCISES 3. Determine the alkalinity of the viscogen made in 3. Make an acid test of a sample of cream and add a sufficient amount of viscogen to 25 ec. of the cream to just neutralize the acid. Determine the viscosity of the visco-cream and the original cream by comparing the distance that drops of equal size from each will flow on an inclined glass plate. QUESTIONS 1. Make a drawing of the distilling apparatus used in determ- ining the Reichert-Meiss] number. 2. Give the variations and average Reichert-Meiss] number and refractive index of butter and oleomargarine. 3. What is visecogen and for what is it used? DAIRY LABORATORY EXERCISES 143 EXERCISES XLI—XLIII MODIFYING MILK FOR INFANTS AND INVALIDS Cream, skim-milk, milk sugar and water are mixed to obtain the desired percentages. Factors used in formulas: A = the percentage of fat in the cream = the percentage of proteids in the skim-milk C = the ounces of cream required D = the ounees of sugar required E = the percentage of sugar in the cream F = the desired percentage af fat M = the ounees of skim-milk required N = the percentage of sugar in the skim-milk P = the desired percentage of proteids @ = the ounces of modified milk desired ‘R = the percentage of proteids in the cream S = the desired percentage of sugar W = the ounces of water required Problem: Make up 24 ounces of modified milk contain- ing 3.5% fat 1.25% proteids and 5.% milk sugar. Materials available for use: Cream containing 18% fat, 3.0% proteids, 4.0% sugar Skim-milk ”’ 3.5% PN SOG) ae Milk sugar, 100% lactose Calculating the ounces of cream required: (F x Q) ee Calculating the ounces of skim-milk required: (QE) = Ch) B Caleulating the ounces of milk sugar required: DS) ex ©) (MXN) Calculating the ounces of water required: Wie) Cp vn D) In addition to the problem given above another will be C ie 144 DAIRY LABORATORY EXERCISES given to each student. The mixtures are to be made up and test- ed for fat and total solids on the Mojonnier tester. QUESTIONS 1. What is modified milk and for what purpose is it generally used? 2. What are three general methods of modifying milk? 3. How is the percentage of each solid not fat in cream affect- ed by an increase in the percentage of fat? 4. Ifasample of whole milk contained 4% of fat and 3.7% of protein, what percentage of protein would be found in cream con- taining 40% of fat made by separating the milk? a _* N=) bo! Le] DAIRY LABORATORY EXERCISES 147 HXERCISHS XLIV—XLV METHOD OF TESTING UNSWEETENED EVAPORATED MILE: The sample is mixed by shaking, pouring and stirring. Exam- ine the surface closely and if fat particles are observed, warm the mixture to 100°F. and again mix. Fat Test: Weigh 9 grams of the sample mixed as above into a Babeock milk test bottle. Add 9 ¢.c. of water and shake to mix thoroughly. Add about 17.5 ¢. e. of sulphuric acid. Mix thor- oughly, then add about 2 ¢. ec. more of the acid, and shake vigor- ously for two or three minutes. Complete the test as for whole milk. The fat reading multiphed by 2 gives the per cent of fat. METHOD OF TESTING SWEETENED CONDENSED MILK FOR PER CHNT OF FAT. Mix thoroughly by transferring the contents of the can into a convenient dish and stirring until homogeneous. Weigh out 40 grams and wash it into a 100 ¢. ¢. flask and make up to the mark with water, or the 40 grams may be weighed directly into the flask before making up to the 100 ¢. ¢. mark. Place 15 ¢. ¢. of this 40% solution in a Babcock milk test bottle. Fill the bottle nearly to the neck with water, add 4 ec. ec. of Fehl- -ing’s solution, shake thoroughly and rapidly, centrifuge, pre- ferably in a cold machine. The casein and fat are thrown to the bottom. Withdraw the supernatant liquid by means of small- stemmed pipette with a wisp of wet absorbent cotton twisted over the tip to serve as a filter. Wipe off the cotton into the bottle on withdrawing the pipette. Give the precipitated proteids and fat two additional washings by shaking up with water, again centri- fuging and removing the water each time with the pipette. If the precipitate is caked hard after centrifuging, it must be broken up by using a fine wire stirrer. Finally, add water to an approxi- mate volume of 17.5 ce. and add 17.5 ec. of Babcock sulphurie acid and complete the test as for milk. The reading multiplied by 3 gives the per cent of fat in the sample. Note: Fehling’s copper solution — 34.639 grams of pure copper sulphate (CuSO4 . 5H,O) dissolved in water and diluted to exactly 500 c.e. 148 150 DAIRY LABORATORY EXERCISES TESTING ICE CREAM FOR BUTTER FAT: METHOD BY A. W. RUDNICK. Weigh out 9 grams of the freshly melted and mixed sample in a 9-gram, 6-inch, 50% cream test bottle. Add 9 ¢. ¢. of dilute sul- phurie acid (1 of acid to 3 of water) saturated with ammonium sulphate, and centrifuge for 5 minutes at a little higher speed than for ordinary testing. Pour off or draw off the liquid by means of a pipette. Add 9 ¢. c. of water and proceed as in the cream test. If nuts or fruit have been used, these should be ground very fine, preferably by means of a mortar and pestle, and the fat col- umn brought into the neck by using denatured alcohol instead of water. Read the fat column in this case from the extreme bottom to the extreme top. METHOD OF PROF. H. BE. ROSS FOR TESTING ICE CREAM Mix equal parts by weight of the melted ice cream and water. The water should: be at a temperature of about 100°F. and the mixing is best done by pouring the mixture from one vessel to an- other. Weigh into a cream bottle 9 grams of the mixture. A 9- gram cream bottle with a body the size of an 18-gram cream bottle is best, although a regular 18-gram cream bottle may be used. To the 9 grams of the mixture add 17.5 ¢. ¢. of the glacial acetie acid. Thoroughly mix the acid and cream by shaking the bottle from two to three minutes. Next add 15 ee. of sulphurie acid such as is commonly used for the Babcock test. Thoroughly mix the eon- tents of the bottle by shaking about a minute. Then proceed with the test in the ordinary way. If a 9-gram bottle is used, the result should be multiplied by 2 as the cream was diluted one-half. If an 18-gram cream bottle was used, the result should be multi- plied by four, as the cream was diluted one-half and one-half the regular amount was used for the test. METHOD OF J. P. DAWSON FOR TESTING ICE CREAM Weigh 18 grams of melted ice cream at a temperature of 70°F. into a 30%, 9-inch cream test bottle. Add 8 ¢. ¢. of glacial acetic acid, agitate gently for 2 minutes, and add 10 «. ¢. of sulphuric DAIRY: LABORATORY EXERCISES 151 acid. Shake thoroughly and centrifuge and complete the test in the usual manner for ordinary cream. Note: There appears to be no reason why the above described method would not work equally well using 9 grams of the ice cream and an 8-inch 50% 9-gram cream test bottle, and adding only one-half the volume of acids. 152 peed or rs DAIRY LABORATORY EXERCISES EXERCISES XLVI—XLVII TESTS FOR PRESERVATIVES AND ADULTERANTS, TESTS FOR BOILED MILK To 10 or 15 ce. of milk in a test tube or bottle add an amount of calcium peroxide the size of a kernel of wheat, shake and add the same amount of paraphenylenediamine-hydrochloride. Again shake the mixture and if the milk was not boiled or heated above 175°F. it will develop a blue color in a few minutes. SECOND TEST FOR BOILED MILK Add one ¢.c. of a slightly pasty starch solution that was made by boiling starch in water, to 10 or 15 ce. of milk in a test tube or bottle, next add 5 to 6 drops of a 10% solution of potassium iodide and finally a pinch of calcium peroxide the size of a kernel of wheat and shake. A blue color will develope in a few minutes if the milk has not been heated above 175°F, TEST FOR MYSTIN (A COMPOUND OR MIXTURE OF FORMALDE- HYDE AND A NITRITE.) -Five ce. of milk or cream are mixed with 5 ec. of water and to it are added 0.5 ee. of a 10% solution of urea, then 1 ee. of nor- mal (N/1) sulphuric acid and the mixture heated in boiling water for two minutes. Cool and add 2 or 3 drops of a 10% solution of ferric chloride. Then add 5 ce. H,SO,, Sp. Gr. 1.82. Do not mix. In the presence of formaldehyde a blue color will form where the acid comes in contact with the lower surface of the milk. TEST FOR SODIUM CARBONATE IN MILK OR CREAM To ten ce. of the milk or cream add 10 ee. of alcohol and a few drops of a 1% solution of rosolic acid. Carbonates are pres- ent if a rose red color appears. Pure milk may give a brownish yellow color. TEST FOR STARCH IN DAIRY PRODUCTS Add to a few cc. of the milk or other product in a test tube or vial a drop of iodine solution. ' Test for: isi---52 -=s2-842-202.4 ee eee 156 Albumin’ 3520228 eee ee ee re a Alkali Tablet Solution, Harmngton’s: 23222322 ——————EEEe 56 Analysis of Butter, Kohlman Method___--_____-_-_____=§_ === === 99 Ash). Of Milk. See ee ee et Se ee 4 Babcock;. DrSocMs! 2. =: =. eS ee 5 Babeock Glassware, Washing, Specifications for_-_____-___-_----.___-__ 13-15 Bath, for Cream Test Bottles, Samples) 225-*_2.-_-<.__ = eee AUT Board: of Health (hactometer: 2252 22 ee ee eee 41-42 Boiled); Milk) Test). 42-220 er Se ee 49-154 IBoraities! 2550. 0. ae eee ee oun) dee eo oe 155 Bulletins; Mist of £2.22 -425 (5 9 eee ee eee 160 ButteroPat Test, Shaw Method2==—) "2-322 91 Buttermilk, ‘Testing 2252-4 Se eh ee eee 11 Butter Moisture (Test..2- 22.25) 2.0. oe ek a eee 37 Butter, (Overrun) 2.32) ke ee ee eee 3 Butter; Saltvin, Salt Téstia22236. 2 2iog 2 ee eee ee 67, 68 Butter Yield) _Eifect’ of Pat Percentage on-2--2 =) ee 2 Casein” oo aS 2 BS ee ee ee 4 Cheese, Moisture’ Test Yield): 2.32 22.55 eee 3, 62 Chemicals) 22522 2.4 es te ha 2 eke ea ln =: eli Composite Samples, Definition, Care ....- 2 252. _- 22 ee 55, Li Condensed Milk, Sweetened, Test for ~.--2-=.2_ 2... 2 ae 147 Cow Testing Associa fiom’: Soe SS a oe eee oe 75 Cream, Reasons for Weighing for Fat Test._.-_2._..____2.-- =e 9 Cream ‘Samples 2 225-2 eee ee A ee ee 18 165 PAGE Creams Mestinions) in eChlONS ton mee aa see wee i oe 14, 19 Cra WesumB ones, Specitcailons: Lobes saan e ses ee aaa) ye! aoe 15 Cream Wesn, WWermnjocreine eracl level = 9 10 Wahilberos Method tor Casem ‘Solubility2===2222= 55 os Sees 132 ADD iacat Cl gs ae see are ee = era eae elena del eee ate Stee 17 INERcIses wantin bart lo. 25.2 eek we ee ae ele a2, 83 Error, Limit of APL SES ee eA aA al a 9 vaporateduu Vili. MMEStS. sho! vs. eee es ea et 147 Pei, lho Mb Wepeienmos unGl ORWIROS Oi oe eee 3 Hehlinews: Copper Solution) 222222322 s2s see nee as ee EAI Wary I eSenES em AChOSCOpPer Sane aes De ee ee Bee eee eee 88 MMonidest Mestsehorivcs2se. Oca Sean ere ese Lae LOS eee eet 156 Hiomumalld ely dew umesty seems Dat ee Mey ek ee le ee ae aol Bee a 49 Houmas mor Solid SNoty Malte sashes ee ee ee jiiae Gellentizinn, “Dexter: Selene: | cb 2 Pee SO VS alae racy paves ta Da he a 156 inlalljoem (ss Mes: tor (Conmmmseedl Oil oo oe 136 ISHS MRO ASIN west eile SR ee le A Ses eed 129 HilcenenusilOSCOMew= see ae es Se ed Be a eee Le a 88 Ebvdnomeber S222 eee s SSN De ee ce ake SLA al er dA Bee. \Ceceyen ial Ssh te ae TE po RD ee eee ae at ge ea 150 TE GUase oI i re ne SEE 2 Utes aa Bee Son VGA AU RTa GCN Oey i a mS nee capOrak Wan oeneees, lay WIE pe ano ae Mee EL REY ESO Kohiman Butter Hat, Method) 22222252525 005 tse I SNL UIT A Uta 99 ihactometer; Board ot Health, @uevenne) 2225255255 25 sees eee 42 IbuvstioseOpe, IESerS 22-62-5222 ooo ee ee 68 IVI e IanO SES 0.6 Gli Oke shee ee a a aE a Sl Ua 8 AGS UInT, CoM NCC Cl ppeeeeereenstloes eB Re SN ly I es aa Se ee a! a aia 17 SMUG SGLONSY Ee es ea Us aN eee NO ve NTCLAD Ics 11 IMLUNK, Comynosiimom, IDeximhmomn oS Lee 1 Milk, Specific Gravity of ___-____ ee EC Natasa al MeO Sam My ey ANU ay Toes sa gS cava ey a ee a a I TN SL) eR ks eg ALG poe 6 Millen ep ani Olson Mes (imi ite se ey le eo pe Nia ea Goal Milk; Restine Specifications) and Directions=-— 9-4-2522 7 2s 22 5, 14, 18 MiorscunenMests, butter. Cheesesoo2 ees See 2a eee ae 37, 62 Majonnier HYSYS ee I ea ie PAN Sa Wee ees Seal 102 IM breshamls ALIS gS Ou ee Se Ee ee Si So ee pie ST ER dO ee Te 154 Nomi Sollunbtonn, AD yeaa auherony Coie eae a ea 55 ONE UT ae eoeet eee mils ep eT Eh AAG Rast ee ll a CE ea 3 TE PYRG TAWC)I ol aN te ene CS sa AN ae LE Belen MOE DPS ec a5) 166 PAGE Proteins 22.22.22)... 25. 3325 oS Se 4 Quevenne Lactometer --22--2_5=~_ 5 See ee ee eee 42 Reading Wat. Tests ..--223-2 24-5220 2 =e ee eee Real: Aeidity 2.220 oe = ee ee ee ee 55 Reichart:Meissl Number 2222222... 2-253. = SS Ee 139 Salt in: Butter, Mest: 22222 "4.2 ee ee eee 67 Samples, Composite’ Care of £2. = 2. 28 eee eee Ey Sediment Test 2222222020). Se oS ee ee ee 95 Shaw, Method for Bat im (Butter 2222) 3). 223 Eee 91 Sodium ‘Carbonate, Tests for —222-==25-__- ===.) eee 154 Solids’ not Mat, Calculating ~----.-22__._--) == ee 4, 42 Specific Gravity, Sulphuric Acid, ‘Milk, Definition of _--_---_---_ 12, 13, 41 Skim-Milk. Test. Bottle: ...--.2-2..5--2.--2=2t22)-5- 12 Specifications, Vestine, Glassware =—-- == eee 14, 15 Starch, est) for ,-...2./<.l.-.22s 2 ee eee 154 Silicates,. Test for 222222. --22) 23-2) See 155 Sucrose, West, for) 2222. ee ee eee 155 Saccharate of Time .-22.2_..-2s-242- 282. 822 ee 155 Table: of" Contents, .2222 2.2.25 =e lee eee eee Vv Table, Speed, of Centrifuge 2.2224. -)- 222823 ee 8 Tablets, Barrington ’s; Alkaline >= 9. == eee 57 Temperature for Reading Tests 2.222225 =.= _ 3 9 Teniperine. ‘Tests, 2222s. 22. 222 = 10 Tester: s22-f25-- bess so oe ee eee av Tésts, Defective .-.52 22s Se es eee 19 Tests, Duplicate =2.. 2200 2-_=- 2S ee eee 20° VitaiMines =. 22 22 == Se ee ee 4 Viscose, 222. 8 ee ee ee Ae 139 Washing Babcock Glassware 25---*_.--./._..2----.4 ae 13 ‘Wialker ‘Casein: Dest) 223 ios ees es eee 129 Water Bath, for Cream Samples, Test Bottles ..._._..___> 33a 17 Weights. .22--W-2-2--2 322 Seo eke =e 7 Wizard’ Sediment Test, .-2--.2-.2 525-223) Joe eee 91 ie ee. fe ie LIBRARY OF CONGRESS UNI INVNI 00008956133