DAIRY LABORATORY 
 GUIDE 
 
 H.E. ROSS 
 
Class r SFZf^ 
 
 Book Eh 
 
 GopgtitN?- 
 
 
 COPYRIGHT DEPOSIT. 
 
A DAIRY 
 
 LABORATORY 
 
 GUIDE 
 
 
 ROSS 
 
 ll 
 Assistant Professor of Dairy Industry 
 
 New York State College of Agriculture at Cornell University 
 
 NEW YORK 
 
 ORANGE JUDD COMPANY 
 
 1914 
 
SFZ53 
 
 Copyright, 1910-1914, by 
 
 ORANGE JUDD COMPANY 
 
 All Rights Reserved 
 
 APR 29 1914 
 
 Printed in the U. S. A. 
 
 ©CI.A369907 
 
PREFACE 
 
 In the study of any science the student should, 
 so far as possible, work out his own problems. Yet 
 the beginner may be saved much useless time and 
 labor by helpful suggestions at the proper time. 
 This Manual is designed as a guide to students in 
 dairy laboratory work, with just enough explana- 
 tion given to supplement the exercises which are 
 outlined in the Manual. It is not intended for a 
 text book and should not be used in the place of 
 one. 
 
 The author's thanks are due Prof. W. A. Stock- 
 ing, Jr., for many helpful suggestions in the ar- 
 rangement and preparation of this book. 
 
 The author recognizes that a book of this kind 
 needs frequent revision, and an eflfort will be made 
 to keep this Manual up to date. 
 
 H. E. Ross. 
 Dairy Laboratories^ 
 New York State College of Agriculture^ 
 at Cornell University, 
 
 August 31, 1910 
 
 m 
 
TABLE OF CONTENTS 
 
 I 
 
 The Composition of Alilk i 
 
 II 
 Explanation. The Babcock Test 5 
 
 III 
 
 Explanation of Boiled 2^1 ilk Test and Formalde- 
 hyde Test 18 
 
 IV 
 
 Explanation. Mixing Samples of Butter Be- 
 fore Testing for Fat and Moisture 19 
 
 V 
 
 Explanation. The C. U. Butter IMoisture Test 23 
 
 VI 
 
 Explanation. The Specific Gravity of i\Iilk and 
 the Lactometer 
 
 -/ 
 
 VII 
 Explanation. The Board of Health Lactometer 37 
 
vi DAIRY LABORATORY GUIDE 
 
 VIII 
 
 Explanation. Use of the Hand Machine in 
 
 Babcock Test 38 
 
 IX 
 Explanation. The Acidity of Milk 43 
 
 X 
 
 Explanation. The Effect of Speed of Machine 
 
 on the Babcock Test 51 
 
 XI 
 Explanation. Commercial Rennet and Its Use. 69 
 
A Dairy Laboratory Guide 
 
 THE COMPOSITION OF MILK 
 
 Milk is composed of a great many f"bstances 
 but ■ so far as the dairyman is concerned, there are 
 only six constituents which are of pnme impor- 
 tance The following table gives the constituents 
 of milk, together with the per cent of each, ob- 
 tained by a large number of analyses: 
 
 Water 87.opercent 
 
 Fat 4.0 per cent 
 
 Casein 2.6 per cent 
 
 Sugar S.opercent 
 
 Albumen 0.7 per cent 
 
 Ash o.7percent 
 
 Although in the above table the different con- 
 stituents are given definite per cents, yet the com- 
 nosition of normal milk is very variable. Ihe 
 Sineeds no discussion, as it is just like the water 
 found anywhere else m nature. , . ^ , 
 
 Fat is present in milk in the form of minute drop- 
 lets or globules. These globules are distributed 
 throughout the milk and are not in solution but 
 in fine suspension. This state is called an muteo». 
 It was disputed for a long time as to whether or not 
 the fat globule had a membrane around it. It is 
 now believed by the best authorities that the at 
 <rIobule has no membrane, but that the droplet 
 
2. A DAIRY LABORATORY GUIDE 
 
 keeps its circular form because of its power of con- 
 densing upon its surface the serum of the milk. 
 The size of the fat globules differ in milk from 
 different breeds of cows, and it is supposed that the 
 larger the fat globules the more easily they rise to 
 the surface when the milk is left standing in a 
 vessel. 
 
 Butter is composed largely of fat, so we speak of 
 the fat of milk as butter fat. 
 
 Fat is the most important constituent of the 
 milk, because milk which contains a fair amount of 
 butter fat is more valuable as a food than a milk 
 Avhich is poor in fat. The other food constituents 
 of the milk usually increase or decrease as the fat 
 increases or decreases. This is true, however, only 
 within certain limits. 
 
 Fat is an important constituent of nearly all of 
 the products of milk, so that in most cases a milk 
 rich in fat is more valuable for manufacturing pur- 
 poses than a milk poor in fat. 
 
 On account of the importance of the fat, it is 
 made oftentimes a basis of payment for milk. 
 
 Butter fat is composed mainly of nine different 
 fats. There are a few fats which are present in 
 such minute quantities that they are of no prac- 
 tical importance. All of the fats have the same 
 basis, namel}'', glycerin, and the fat is made by the 
 chemical union of glycerin "and the corresponding 
 fatty acid. For example, the fat butyrin is made 
 of glycerin and butyric acid. The fat stearin is 
 made of stearic acid and glycerin. While the com- 
 position of the different butter fats are knowm. yet 
 the chemist is unable to make them in the labora- 
 tory. 
 
 The fats of butter fat are divided into two main 
 groups, the volatile and nonvolatile, and are so 
 
A DAIRY LABORATORY GUIDE 3 
 
 named because they are made respectively from 
 volatile and nonvolatile fatty acids. 
 
 The fats under each class are as follows : 
 
 VOLATILE NONVOLATILE 
 
 Butyrin Olein 
 
 Caprin Myristin 
 
 Caproin Palmatin 
 
 Caprillin Stearin 
 Laurin 
 
 There is some dispute as to whether laurin is a 
 volatile or nonvolatile fat, but it is usually consid- 
 ered volatile. The volatile fats compose about 8 
 per cent and the nonvolatile about 92 per cent of 
 butter fat. The fats of butter fat have dififerent 
 characteristics and properties, and one chief dif- 
 ference of fats is their melting point. For example 
 the melting point of stearin is about 143° F., and 
 the melting point of olein is about 40° F. A varia- 
 tion in the amount of either of these two fats would 
 necessarily cause the melting point of butter fat to 
 vary. The melting point of butter fat is usually 
 between 92° F. and 96° F. 
 
 Casein is the chief proteid compound of milk, and 
 forms about 20 per cent to 23 per cent of the milk 
 solids. It exists in milk in very fine suspension, 
 and is held in suspension by the salts of calcium. 
 It is, therefore, sometimes called calcium casein. 
 The casein is in such a fine state of suspension that 
 it cannot be filtered out of the milk by any ordinary 
 means. This fine state of suspension is called the 
 colloidal state. When milk sours naturall}^ and 
 enough acid is found to unite with the lime salts 
 of the milk, the casein is precipitated. Casein is 
 also precipitated by any acid and rennet or pepsin. 
 Casein is A^aluable as food both in raw milk and in 
 
4 A DAIRY LABORATORY GUIDE 
 
 the products of milk, such as the various kinds of 
 cheese. It is also used commercially in many 
 ways, some of them being as a substitute for cel- 
 luloid in the manufacture of buttons and toilet 
 articles. It is also used in cold water paints. By 
 a new process it is said that casein is now being 
 made into a substitute for ivory, making excellent 
 table tops, mantels, etc. 
 
 Sugar forms about 37 per cent to 39 per cent of 
 the milk solids. The chief value of milk sugar is- 
 its food value in milk. It is also used in pharmacy 
 in mixing powders, coating pills, etc. Milk sugar 
 is not used very extensively commercially because 
 of the expensive cost of manufacture. It is not 
 as sweet as cane sugar, because it is not as soluble. 
 It has the same chemical formula (C12H22O11) 
 as cane sugar. Acid is produced naturally in milk- 
 by the action of bacteria upon the milk sugar. 
 
 The albumen in milk is in solution. It is valu- 
 able chiefly as a food in milk. It has one commer- 
 cial use in the manufacture of Italian cheese. This 
 cheese is made where large quantities of whey are 
 produced. The whey is heated nearly to the boil- 
 ing point, and this heat precipitates the albumen. 
 The/whey is then drawn off and the albumen is 
 dipped into molds. The cheese made from albumen 
 forms a very good, nutritious food. 
 
 The ash is the part of milk left after burning, and 
 it is the most constant constituent of the milk. 
 It very rarely goes below .68 per cent or above .J2 
 per cent. It consists chiefly of the phosphates of 
 calcium and the chlorides of sodium, potassium, 
 iron and magnesia. 
 
 Ash is important as a food in furnishing the- 
 mineral constituents for the body. 
 
A DAIRY LABORATORY GUIDE 5 
 
 THE BABCOCK TEST 
 
 The Babcock test is a test for the per cent of fat 
 in milk and its products. It was invented by Dr. 
 S. M. Babcock, chief chemist for the experiment sta- 
 tion at Wisconsin, and a description of the test was 
 published in a report of 1890 from that station. 
 The instrument used to measure the milk is called 
 a pipette and holds up to its graduated mark 17.6 
 cc. Since milk is somewhat viscous, the pipette 
 will deliver on an average 17.44 cc, which is for 
 all practical purposes 18 grams. In using the 
 pipette the milk is drawn above the 17.6 cc. mark 
 and the soft part of the index finger placed quickly 
 over the pipette. The column of milk can be 
 easily controlled and allowed to flow out until it is 
 on a level with the 17.6 cc. mark. The pipette 
 should always be held so that the 17.6 cc. mark is 
 on a level with the eye. The sample to be tested 
 is measured into a special bottle with a graduated 
 neck, holding a column of melted fat which is a 
 definite per cent by weight of the 18 grams of milk 
 taken. In adding the milk to the bottle the latter 
 should be held in a slanting position, so that the 
 milk will run down the lower inside of the bottle 
 neck and will not be forced out by the outcoming 
 air. 
 
 After measuring the milk into the bottle, 17.5 
 cc. of sulphuric acid (H2SO4) of a specific gravity 
 of 1.82 to 1.83 is added and the milk and acid at 
 once thoroughly mixed. The acid burns up (by 
 moist combustion) everything in the milk except- 
 ing the fat. The same precautions should be ob- 
 served in adding the acid as in adding the milk, 
 namely, to slant the bottle, and the bottle should be 
 revolved as the acid is poured in, so that all of 
 
6 A DAIRY LABORATORY CUIDE 
 
 the milk adhering to the neck of the bottle 
 will be washed down. The vessel contain- 
 ing the acid should be kept corked in order 
 to prevent the acid taking up moisture from the air 
 and becoming too weak for use. If the acid is too 
 weak more than 17.5 cc. are used, and if too strong 
 less than 17.5 cc. are used. Good acid is colorless, 
 although it may be quite dark and at the same time 
 be useful for the Babcock test. It must, in any 
 case, be free from undissolved foreign particles. 
 
 After adding the acid to the milk the bottles are 
 placed in a centrifugal machine and whirled. Care 
 should be taken to have the machine balanced, i. c, 
 for every bottle on one side of the machine there 
 should be a corresponding bottle on the opposite 
 side of the machine. The bottles are centrifugalized 
 for five minutes and then filled with hot water up 
 to the base of the neck. Centrifugalizing is then 
 continued for two minutes more and hot water is 
 added to bring the fat into the graduated neck. The 
 centrifuge is then run for one minute. 
 
 The bottles are then ready to read, and in case 
 of whole milk one should read between the extreme 
 points of the fat column. This method of reading, 
 by comparison with the chemical method, has been 
 found to make up for the fat which remains in 
 the bottom of the bottle and cannot be removed by 
 centrifugalizing. The bottles should be read at a tem- 
 perature of 120° F. It is no trouble to obtain this 
 temperature if centrifuging has been done with a 
 steam machine. Where the machine is filled with 
 steam the bottles should stand for from thirty 
 seconds to one minute in a room at ordinary tem- 
 perature to allow excess of heat to pass ofif before 
 reading. If a hand machine is used the tester must 
 have hot water placed in it to obtain the required 
 
A DAIRY LABORATORY GUIDE 7 
 
 temperature. This is especially necessary if the 
 testing is being done in a cold room. 
 
 The machine should always be kept well oiled 
 and securely fastened to the support on which it is 
 being operated. Skimmed milk contains such a 
 small amount of fat that the fat column could not be 
 read in an ordinary whole milk bottle. A bottle is, 
 therefore, used which has a neck with a small bore. 
 This neck is so small that the milk and acid could 
 not 'be poured through it, so a funnel tube is pro- 
 vided for this purpose. The skimmed milk bottle 
 should be placed in the machine in such a position 
 that the funnel tube will be on the outside. This 
 w^ill prevent fat lodging in the space between the 
 tube and the wall of the bottle. 
 
 The sulphuric acid is added to the milk to 
 destroy all of the milk solids except the fat, and the 
 chief solid to be destroyed is the casein. Skimmed 
 milk contains proportionately more casein than 
 does whole milk and, therefore, in making a Bab- 
 cock test of skimmed milk 2 cc. extra of sulphuric 
 acid should be used. The fat globules in skimmed 
 milk are small in size and correspondingly hard to 
 remove. A Babcock sample of skimmed milk 
 should, therefore, be whirled ten minutes, two 
 minutes and one minute. 
 
 Cream is so viscous that it cannot be measured 
 accurately into a test bottle by means of a pipette. 
 It should always be weighed. The New York state 
 dairy laws now consider it a misdemeanor to meas- 
 ure cream for testing where the tests are used as a 
 basis of payment for butter fat. 
 
 Because the cream is sometimes too rich in butter 
 fat to be tested in an ordinary cream bottle, 9 
 grams are tested in an 18-gram bottle and the result 
 multiplied by two. Nine-gram cream bottles are 
 
8 A DAIRY LABORATORY GUIDE 
 
 also coming into common use. These bottles give 
 the reading direct without any computation. In 
 testing 9 grams one would naturally use one-half 
 the usual amount of sulphuric acid. On account, 
 however, of the large proportion of fat present, the 
 acid is liable to char the fat ; and for this reason it 
 is better to add approximately 9 grams of water 
 and then add a little less than the usual amount of 
 acid. 
 
 The fat column in the neck of a cream bottle is so 
 large that its volume is affected by temperature. It 
 is necessary to read the bottles at some constant tem- 
 perature and the most accurate readings are ob- 
 tained at temperatures from 130° F. to 140° F. In 
 order to obtain the proper temperature the bottle 
 should be allowed to stand for at least three minutes 
 in a water bath, care being taken to have the water 
 in the bath as high as the fat column in the bottle 
 neck. 
 
 The meniscus on the fat column of a cream bottle 
 is large and is not constant so that no rule for in- 
 cluding it in the reading can be formulated. The 
 practice is, therefore, followed of removing the 
 meniscus by adding a few drops of glymol (white 
 mineral oil) to the top of the fat column after the 
 test is completed. This flattens the top of the fat 
 column and gives the best results of any method 
 yet devised. The glymol is easier to use if colored 
 pink with alkana root. 
 
 Butter is tested in the cream bottles, from 3 to 4 
 grams being used for the test. Enough warm 
 water is added to bring the sample up to approx- 
 imately 18 grams, and from 10 to 12 cc. of the sul- 
 phuric acid are used. 
 
 Cheese is also tested in the cream bottle, 4 to 5 
 grams being used. The cheese must first be minced 
 
A DAIRY LABORATORY GUIDE 9 
 
 with a knife as fine as possible in order to make it 
 possible for the acid to dissolve all of the casein. 
 After the cheese is weighed into the bottle, about 
 5 cc. of hot water are added and the mixture shaken 
 vigorously for two or three minutes. This softens 
 the casein. Enough warm water is then added to 
 bring the sample to approximately i8 grams. The 
 sample is again shaken for two or three minutes, 
 and the ordinary amount of H2SO4 is then added. 
 If the cheese is old and dry, 2 or 3 cc. of H2SO4 in 
 excess of the usual amount are sometimes necessary 
 to dissolve the casein. In mincing the cheese the 
 sample should not be allowed to dry out any more 
 than is absolutely necessary. 
 
 In the cases of both the butter and the cheese, 
 the results obtained must be reduced to an 18-gram 
 basis, when an 18-gram bottle is used. This can be 
 done by dividing the per cent obtained by the num- 
 ber of grams used and multiply the quotient by 18. 
 
 Whey is usually tested in whole milk bottles, 
 although it is best to test it in skimmed milk bot- 
 tles when possible. The right bottle to use can 
 only be determined by actual experiment. Whey 
 requires less acid than whole milk, usually about 
 12 cc. 
 
EXERCISES 
 
12 A DAIRY LABORATORY GUIDE 
 
 EXERCISE I 
 THE BABCOCK TEST 
 
 1. Draw the milk above the mark on the pipette 
 
 and allow the milk to settle just to the mark. 
 Repeat this until some proficiency in the use of 
 
 the pipette is obtained. 
 What two special precautions are to be observed 
 
 in handling the pipette? 
 
 2. Test by the Babcock method a sample of whole 
 
 milk. Perform this test before doing either 
 3 or 4. 
 
 3. Measure out into your white cup 50 cc. of the 
 
 same sample of milk used in experiment 2. 
 Add to this 15 cc. of water. Mix thoroughly 
 and test in duplicate by the Babcock method. 
 
 4. Using milk from the same sample as used in 
 
 experiment 2, measure out 50 cc. of milk and 
 add to it 15 cc. of skimmed milk. Mix thor- 
 oughly and test in duplicate by the Babcock 
 method. 
 Did you obtain the most fat in experiment 3 or 
 experiment 4? Include in your notes a brief 
 description of the Babcock test. 
 
A DAIRY LABORATORY GUIDE 13 
 
 STUDENT'S NOTES AND REPORT 
 
14 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 1 5 
 
 EXERCISE II 
 
 BABCOCK TEST 
 
 Test by the Babcock method a sample of whole 
 milk, skimmed milk and cream. 
 
 Weigh into some convenient dish i8 grams of 
 cream just tested. Add to it 20 grams of the 
 whole milk just tested. Compute the per 
 cent of fat in the mixture and verify your 
 computation by testing the mixture by the 
 Babcock method. 
 
 Test by the Babcock method a sample of butter- 
 milk. 
 
 STUDENTS NOTES AND REPORT 
 
1 6 A DAIRY LABORATORY GUIDE 
 
 EXERCISE III 
 BABCOCK TEST 
 
 1. Test in duplicate a sample of whole milk, 
 
 skimmed milk and cream. Test the skimmed 
 milk in the same way that the whole milk is 
 tested. 
 
 Why is cream taken by weight instead of by 
 volume? 
 
 Why are 9 grams used instead of 18 grams? 
 
 When 9 grams of cream are tested in an 18- 
 gram bottle, what correction has to be made 
 in the result and why? 
 
 2. Retest the cream and skimmed milk. Add acid 
 
 to the skimmed milk about one-fourth of an 
 inch above the mark on the acid measure and 
 whirl ten minutes the first time, two minutes 
 the second time and one minute the third 
 time. 
 
 In retesting the cream do not add water, and 
 use one-half the usual amount of acid. 
 
 In order to save time the cream and skimmed 
 milk may be whirled together. 
 
 Explain fully the object of using extra acid and 
 whirling an extra length of time in testing 
 skimmed milk. 
 
 Record carefully any difference in the appear- 
 ance of the fat column of the cream in ex- 
 periments I and 2. 
 
 What should be the appearance of an ideal fat 
 column in a completed Babcock test? 
 
A DAIRY LABORATORY GUIDE I? 
 
 STUDENT'S NOTES AND REPORT 
 
l8 A DAIRY LABORATORY GUIDE 
 
 EXPLANATION OF BOILED MILK TEST 
 AND FORMALDEHYDE TEST 
 
 There are two principal tests for boiled milk. 
 One test makes use of three chemicals — hydrogen 
 peroxide, potassium iodide and starch. In the 
 second test two reagents are employed — hydrogen 
 peroxide and paraphenylenediaminehydrochloride. 
 In both cases a blue color results if the milk has 
 not been boiled. If the milk has been boiled no 
 blue color will result. The last named test acts 
 more rapidly than the first one and also gives a 
 more intense color. Any double oxide may be sub- 
 stituted in place of the hydrogen peroxide. Such a 
 double oxide would be calcium peroxide. There is 
 in milk an enzyme galactase which is destro^^ed by 
 heat. When the milk has not been heated this 
 enzyme sets free the oxygen from the oxidizing 
 agent, and in case of the first test, the free oxygen 
 splits up the potassium iodide and liberates free 
 iodine. The starch in the presence of free iodine 
 turns blue. In case of the second test the oxygen 
 liberated by the galactase acts directly on the 
 paraphen3denediaminehydrochloride and turns the 
 solution blue. Hydrogen peroxide often contains 
 sulphuric acid. AMien this is the case, the reagent 
 is useless for the test with starch, as the free acid 
 would break up the potassium iodide. If this hap- 
 pened a blue color would result whether the milk 
 had been heated or not. 
 
 The test for formaldehyde is a delicate one and 
 is easy to perform, inasmuch as it may be done in 
 connection with the Babcock test. The regular 
 amount of milk is measured with the 17.6 cc. pipette 
 into a Babcock test bottle and a few drops of ferric 
 chloride added. The regular amount of sulphuric 
 
A DAIRY LABORATORY GUIDE 1 9 
 
 acid is next added, and if formaldehyde is present 
 a lavender-colored ring will appear between the 
 javer of acid and the layer of milk. If the contents 
 of the bottle are slowly mixed the dissolving casein 
 will take on a lavender color. The test w^ill not 
 w^ork if the milk is too old or if too much of the 
 formaldehyde has been added to the milk. 
 
 Sometimes sulphuric acid contains ferric salts as 
 an impurity; and when such is the case, the acid 
 w^ill give the test for formaldehyde without the use 
 of ferric chloride. It is best however, to always 
 add the ferric chloride to make sure there is a ferric 
 salt present. 
 
 EXPLANATION. MIXING SAMPLES OF 
 
 BUTTER BEFORE TESTING FOR FAT 
 
 OR MOISTURE 
 
 Before testing a sample of butter for either 
 moisture or fat the sample should be thoroughly 
 mixed. Fat and water do not readily mix, and 
 special precautions must be taken to make the 
 sample uniform throughout. The butter should be 
 heated and stirred until it is about the consistency 
 of thick cream. Do not heat the butter too much, 
 ?^ tne w^ater and fat will entirelv separate and it is 
 difficult to remix them. The sample should 
 then be cooled and stirred thoroughly while 
 cooling, else the fat will cool rapidly on the 
 outside and force all of the water towards 
 the middle of the sample. The cooling process 
 should be kept up until the sample is quite firm. 
 The heating and cooling may be accomplished by 
 placing the butter in any convenient vessel, such 
 as a glass-stoppered sample jar. The jar may then 
 be held under a water faucet or set in a dish of 
 water. 
 
20 A DAIRY LABORATORY GUIDE 
 
 EXERCISE IV 
 BABCOCK TEST 
 
 1. Test by the Babcock method a sample of whole 
 
 milk, skimmed milk and butter. 
 ]\Iix the butter properly before weighing it out 
 for the test. 
 
 2. Measure out about 36 grams of skimmed milk 
 
 (Babcock pipette twice full to the mark). 
 Divide approximately into four parts. Test 
 two of these parts for boiling by two dif- 
 ferent methods. Boil the remaining 18 
 grams, divide approximately into two parts 
 and test for boiling by two different methods. 
 Give the chemicals used in each case. Do 
 not add the chemicals to the milk while the 
 milk is hot. 
 
 3. Measure out in duplicate a sample of skimmea 
 
 milk as for the Babcock test. Before adding 
 the sulphuric acid dip your stirring rod into 
 the formaldehyde and rinse it off in one of 
 the samples. Then add to both samples the 
 ferric chloride and sulphuric acid and note 
 the difference in color due to formaldehyde. 
 
 4. Test for formaldehyde any four of the samples 
 
 furnished. Report the results by number. 
 Sometimes sulphuric acid will alone give the 
 
 color test for formaldehyde. Why is this? 
 Why is it best to always add the ferric chloride 
 
 when making the formaldehyde test? 
 
A DAIRY LABORATORY GUIDE 21 
 
 STUDENT'S NOTES AND REPORT 
 
^^ A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 23 
 
 THE CORNELL BUTTER MOISTURE TEST 
 
 When butter is heated over a flame, the casein 
 forms a snow-white blanket over the surface of the 
 butter. By a comparison with the chemical method 
 it has been found that when the butter loses its 
 snow-white color and turns a dirty brown color the 
 sample has given up its moisture. When this 
 brown color has appeared it is time to remove the 
 sample from the flame. Heating butter in a direct 
 flame is liable to volatilize some of the butter, even 
 before all of the water has been given off. In order 
 to do away with this danger a sheet of asbestos is 
 placed between the flame and the container ot the 
 sample. The asbestos so tempers the flame that 
 while a high heat is produced, the danger of sud- 
 denly volatilizing the butter is largely done away 
 with. 
 
 The scales used are made especially for use in 
 butter-moisture work. They are so constructed 
 that after the moisture is driven off, each notch 
 the large weight is reversed equals i per cent of 
 moisture driven off, and each notch that the small 
 weight is reversed equals .i per cent of moisture 
 driven off. Alwavs allow the sample to cool be- 
 fore weighing. While the sample is cooling it Is 
 well to cover it with something Ta sheet of paper 
 will do), ^o that the sample will not take water 
 from the air. 
 
24 A DAIRY LABORATORY GUIDE 
 
 EXERCISE V 
 
 BABCOCK TEST AND BUTTER MOISTURE 
 TEST 
 
 I. Prepare a sample of butter for the moisture test 
 and test by the Cornell method. 
 
 2. Test a sample of milk in the ordinary way. 
 Retest the same sample in duplicate, using only 
 
 9 grams of the sample. (It must be weighed 
 out.) Make the sample up to i8 grams by 
 adding water. Add the usual amount of 
 acid. 
 
 3. Test a sample of cream in the ordinary way. 
 Retest the cream in the whole milk bottle, divid- 
 ing 18 grams between four bottles (4^^ 
 grams by weight in each bottle). 
 
 In each case add enough water to bring the 
 sample up to 18 grams and then add the 
 proper amount of acid as indicated by the 
 appearance of the sample. Add the acid 
 slowly, a little at a time, and shake thor- 
 oughly. 
 
A DAIRY LABORATORY GUIDE 25 
 
 STUDENT'S NOTES AND REPORT 
 
26 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE IJ 
 
 THE SPECIFIC GRAVITY OF MILK AND 
 THE LACTOMETER 
 
 The specific gravity or density of a substance is 
 a ratio between the weight of a given volume of 
 the substance and the weight of a given volume of 
 some other substance taken as a standard. The 
 standard for liquids is water and its specific gravity 
 is taken as one. Milk is slightly heavier than water, 
 and the specific gravity of normal milk av^erages 
 1.032, and the specific varies from 1.029 to 1.035- 
 If we add water to milk the specific gravity is 
 lowered, because water is lighter than milk ; and if 
 we skim milk we take away fat which is lighter 
 than milk and the specific gravity is increased. 
 When the water is added to milk the effect is the 
 same as it would be if the solids were actually re- 
 moved from the milk. This is true because the 
 solids which were distributed throughout a given 
 volume on the addition of water, have to 
 distribute themselves throughout the increased 
 volume of the liquid. For this reason we say 
 that the addition of water to milk " decreases " 
 the total solids, and it is a fact that when water is 
 added to milk all of the solids are decreased in the 
 same proportion. It is important to remember 
 this fact when one is figuring out the per cent of 
 adulteration of milk. 
 
 The Lactometer. — The instrument used to 
 measure the specific gravity of a liquid is called a 
 hydrometer, and there are many kinds of specialized 
 hydrometers. The hydrometer used to test the 
 density of milk is called a lactometer, and, for the 
 most part, only two kinds are used. One is the 
 Quevenne (called Q. for abbreviation) and the other 
 is called the Ordinary, or Nezv York State Board of 
 
28 A DAIRY LABORATORY GUIDE 
 
 Health (commonly called the B. of H. lactometer). 
 
 The Quevenne lactometer has a long, narrow 
 stem which is extended into a hollow glass tube of 
 much larger diameter than the stem itself. At the 
 lower end of the instrument is a bulb of mercury 
 which causes the lactometer to sink in the liquid 
 to its proper level. The upper part of the stem 
 contains a thermometer scale, as it is important to 
 know the temperature of the milk when the lac- 
 tometer reading is taken. This scale does not re- 
 cord high temperature, and, therefore, the instru- 
 ment should never be placed in hot liquids. In 
 order to clean the lactometer wash in cool water 
 and wipe with a dry cloth. Immediately below the 
 thermometer scale is a lactometer scale with num- 
 bers ranging from 15 to 45, the lowest readings 
 being at the upper end of the scale. One may ob- 
 tain the specific gravity reading by prefixing i.o 
 before the lactometer reading. Thus, if the in- 
 strument gives a reading of 33, the specific gravity 
 would be 1.033. The fact that the Quevenne lac- 
 tometer gives specific gravity readings directly is 
 one of its chief advantages. 
 
 Temperature afifects the density of liquids. The 
 colder the milk the more dense it is, and the warmer 
 the milk the less dense it is. For this reason lac- 
 tometers are standardized to give readings at a 
 temperature of 60° F. When milk is warmer or 
 colder than 60° F. a correction must be made, and 
 this correction for the Quevenne is .1 of a lactometer 
 degree for every degree in temperature that the 
 sample is above or below the standard temperature. 
 When we cool the milk down we add ; when we 
 warm the milk we subtract. For example, if a 
 lactometer gave a reading of 32 at a temperature 
 of 66° F., we would add .6 (.1X6) to the lactometer 
 
A DAIRY LABORATORY GUIDE 29 
 
 reading, making the corrected or true reading 32.6. 
 In this case the specific gravity would be 1.0326. 
 
 Familiarity with the action of the lactometer may 
 be obtained by working theoretical problems, of 
 which the following is an illustration: If the 
 lactometer reading of a sample of milk is 31.5 at 
 62° F., what would be the reading at 57° F.? In 
 this case 57° F. becomes our standard, because it is 
 the temperature to which we are going to lower the 
 sample. Since the sample is 5 degrees too warm, 
 •5 (-iXS) of a lactometer degree must be added to 
 the lactometer reading, making the true or cor- 
 rected lactometer reading 32. 
 
 When used in connection with theBabcock test the 
 lactometer reading is important in obtaining the total 
 solids and solids not fat of milk. There are several 
 of these formulae in use, and while they do not give 
 quite as accurate results as the chemical method, 
 they give results which are accurate enough for all 
 practical purposes. They are as follows : 
 
 1. '-i^=S. N. F. Babcock's formulae. 
 
 2. ^=S. N. F. Troy's formulae. 
 
 3. ^ L+.2f+.i4=S. N. F. Babcock's modi- 
 
 fied formula. 
 
 Generally speaking, the first formula gives the 
 highest results, the second next highest and the 
 third the lowest results. One can find the total 
 solids by adding the fat reading to the solids not 
 fat. In these formulae L stands for the lactometer 
 reading and F for the fat reading. 
 
 In using these formulae, the following precautions 
 must be especially noted : Board of health readings 
 can never be used in these formulae, consequently 
 B. of H. readings must be changed to Q. ; specific 
 gravity readings cannot be used ; the per cent of 
 fat expressed in hundredths cannot be used. 
 
30 A DAIRY LABORATORY GUIDE 
 
 An illustrative example will show how these 
 formulae operate. Suppose the Q. lactometer read- 
 ing of a sample of milk was 32.5 at 60° F. and the 
 fat reading was 4.2 per cent, what are the solids 
 not fat ? 
 
 Formula= 
 
 I. W-'=S. N. F. .7X4.2=2.94 
 2.94+32.5=35.44 
 
 3544-^3-8=9-32+ 
 Formulating the above calculation: 
 
 2^^5^^1=9.32% S. N. F. _ 
 
 9.32+4.2'=i3.52 total solids. 
 Using formula 2 : 
 
 ^=S. N. F. 
 
 32.5+4.2=36.7 
 
 36.7--4=9.i7+% S. N. F. 
 Formulating the above calculation: 
 
 2M±^=9.i7 S. N. F. 
 
 9.17+4.2=13.37 T. S. 
 Using formula 3 : 
 
 i4L+.2f+.i4=S. N. F. 
 
 32.5-^4=8.12 
 
 .2X4-2=.84 
 
 8.12+.84+. 14=9.10 S. N. F. 
 
 9.10+4.2=13.30 T. S. 
 By modifying Babcock's third formula the total 
 solids may be obtained directly. It is as follows: 
 
 M L+i.2f+.i4=T. S. 
 Using the above lactometer and fat readings as 
 an illustration, the formula would give the following 
 results : 
 
 32.5-^4=8.12 
 
 i.2X4-2=504 
 
 8.12+5.04+. 14=13.30% T. S. 
 
A DAIRY LABORATORY GUIDE 3 1 
 
 The following- example will illustrate how a 
 knowledge of the per cent of S. N. F. of a sample 
 of milk is utilized in figuring adulteration per cents: 
 
 Before adulteration a sample of milk had 4.2 per 
 cent of fat and 9.0 per cent of S. N. F. After adul- 
 teration the sample contained 3.1 per cent fat and 
 7.5 per cent of S. N. F. The following questions 
 can be answered from calculations with the above 
 data: 
 
 1. What per cent of water w^as added to the 
 
 milk? 
 
 2. At what rate per cent was the water added ? 
 
 3. What per cent of the fat was adulterated 
 
 by skimming? 
 
 4. What per cent of the fat was adulterated 
 
 by watering? 
 (i) Since there were 9 parts of S. N. F. before 
 adulteration and 7.5 parts of S. N. F. after adultera- 
 tion, 1.5 must have been removed by adulteration. 
 
 9— 7-5=1 -5 
 
 1.5-^9=16.66% of S. N. F. removed by adding 
 the water. 
 
 Since 16.66 per cent of S. N. F. was removed, 
 water is the only thing that could have taken its 
 place; therefore 16.66 per cent of water was added 
 to the milk. 
 
 (2) For every 7.5 parts of S. X. F. in the milk 
 1.5 parts were removed, or in other words water 
 was added at the rate of 1.5 parts of water to every 
 7.5 of S. N. F. 
 
 The rate per cent at which water was added 
 would be i.5-f-7.5=2o%. 
 
 Before adulteration the sample had 4.2 parts fat 
 and after adulteration 3.1 parts fat, i.i parts of fat 
 were removed, which equals 26.19 P^^ cent. 
 1. 1-^4. 2=^26.19%. 
 
7^2 A DAIRY LABORATORY GUIDE 
 
 When milk is watered all of the solids are re- 
 duced in the same proportion. It has been found that 
 16.66 per cent of the S. N, F. was removed by water- 
 ing; therefore, according to the above rule 16.66 per 
 cent of the fat must have been removed by water- 
 ing. But 26.19 per cent of the fat was removed; 
 therefore the difference between 26.19 per cent and 
 16.66 per cent will show what is removed by skim- 
 ming; 26.19 — 16.66=9.53% removed by skimming. 
 
A DAIRY LABORATORY GUIDE 33 
 
 EXERCISE VI 
 
 BABCOCK TEST AND QUEVENNE 
 LACTOMETER 
 
 1. Test in duplicate by the Babcock method a 
 
 sample of whole milk as follows : 
 
 (a) Use ordinary amount of acid. 
 
 (b) One-half usual amount of acid. 
 
 (c) Fill the bottle up to the base of the 
 
 neck with acid. 
 
 (d) Use the regular amount of acid, but 
 
 warm the acid and milk before mix- 
 ing until they feel warm to the hand. 
 Add the acid slowly to the sample. 
 Observe and record all results care- 
 fully. 
 Test for fat a sample of butter. Why is it ad- 
 visable to add the acid slowly in (d) ques- 
 tion I? 
 
 2. (a) Take a Ouevenne lactometer reading of a 
 
 sample of whole milk and skimmed 
 milk, making corrections for tempera- 
 ture. 
 Explain fully the effect of temperature on 
 the lactometer readings. 
 (b) Starting with the first reading in 2 (a), 
 what would have been the reading if 
 the temperature had been 54° F., 62° 
 F., ys° F., 81° F.? 
 
 3. Add one-half an acid measure of water to the 
 
 skimmed milk sample and take the Ouevenne 
 
34 A DAIRY LABORATORY GUIDE 
 
 reading-. Note any change in the lactometer 
 reading, and explain the reasons for this 
 change. 
 4. Take the Qiievenne reading of a sample of 
 skimmed milk. 
 
 Compute what the reading would be if the tem- 
 perature were four degrees higher. Verify 
 your results by warming the sample and tak- 
 ing the reading. Be sure to mix the sample 
 thoroughly after warming it. Have the tem- 
 perature of the milk low enough so that rais- 
 ing the ternperature four degrees will not 
 bring the sample above 70° F. Why should 
 not the temperature be above 70° F.? 
 
 What is the chief advantage of the Quevenne 
 lactometer over other kinds? 
 
A DAIRY LABORATORY GUIDE 35 
 
 STUDENT'S NOTES AND REPORT 
 
3^ A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 37 
 
 EXPLANATION. BOARD OF HEALTH 
 LACTOMETER 
 
 The Board of Health lactometer (commonly called 
 E. of H. lactometer) is an instrument giving ar- 
 bitrary readings and it must be changed to equiv- 
 alent "^Ouevenne readings in order to obtain the 
 specific'^ gravity. It is of the same general shape 
 as the Quevenne, except that the thermometer 
 scale is usually on the opposite side of the stem 
 from the lactometer scale. The instrument is 
 graduated from o to 120, and one degree Board of 
 Health equals .29 of one degree Quevenne. In 
 order, therefore, to change from Board of 
 Health to Quevenne, the Board of Health 
 reading is multiplied by .29. Vice versa to 
 change from Quevenne to Board of Health reading, 
 the Ouevenne reading is divided by .29. Like the 
 Oue\'^enne, the Board of Health lactometer is gradu- 
 ated to be read at a temperature of 60° F., and if 
 the temperature is above or below the standard, 
 the correction factor is .3 of one lactometer degree 
 for every degree that the sample is above or below 
 the standard. The following example will illustrate 
 how correction is made: B. of H. reading 110.5 at 
 65° F., what would be the reading at 60° F.? The 
 sample must be cooled down 5 degrees ; therefore, 
 Ave would add 1.5 (5X.3) to the reading (110.5), 
 making a corrected reading of 1 12.0. One of the 
 chief advantages of the B. of H. lactometer is that 
 a small adulteration of the milk will make a notice- 
 able change in the lactometer reading. This is be- 
 cause the instrument has so large a scale. Also, 
 when milk is watered, the number of lactometer 
 degrees recorded below 100 indicates roughly the 
 per cent of adulteration. 
 
38 A DAIRY LABORATORY GUIDE 
 
 EXPLANATION. USE OF HAND MACHINE 
 IN BABCOCK TEST 
 
 It is a popular notion that milk cannot be tested 
 accurately in a hand machine. This is a mistaken 
 idea, as a hand machine should do as good work as 
 any other machine. One of the chief reasons for 
 inaccuracy in using a hand machine is the inatten- 
 tion paid to the temperature. It is necessary to 
 have the proper degree of heat in order to properly 
 perform the Babcock test. To provide the proper 
 temperature the hand machine should be filled with 
 hot water up to the bottle cups if the room is at all 
 cold. The small two-bottle and four-bottle hand 
 testers have no frame, and so the bottle cups are 
 made large in order that they may be filled with 
 hot water if necessary. While it is not absolutely 
 necessary to use hot water at all times, its use is 
 always advisable. By its use the danger of test- 
 ing milk at too cold a temperature is largely done 
 away with. The operator should be careful to keep 
 the machine to its proper speed during the entire 
 run. 
 
A DAIRY LABORATORY GUIDE 39 
 
 EXERCISE VII 
 
 BABCOCK TEST AND B. OF H. 
 LACTOMETER 
 
 I Take the B. of H. lactometer reading and 
 make a Babcock test of a sample of whole milk. Re- 
 move the lactometer, and allow the milk to stand m 
 vour lactometer cylinder while you do No. 2. i hen 
 draw off from the top of the sample all the cream 
 the pipette will hold. Then add to the sample 17.6 
 cc of water and mix thoroughly. Again take a lacto- 
 meter reading and make a Babcock test and hgure 
 out the per cent of fat removed by skimmmg and 
 the per cent of fat removed by watermg; make 
 the test in the whole milk bottles. After drawmg 
 off cream and adding water be sure to mix the sam- 
 ple thoroughly. Upon what rule does your ability 
 to do the above computation depend? Better results 
 will be obtained if the milk is warmed to about «5 
 F and allowed to stand as long as possible. In re- 
 moving the cream keep the point ot the pipette as 
 near as possible to the surface of the liquid. ^ 
 
 2 Test in the steam machine whole milk, skim- 
 med milk and butter. Run the skimmed milk ten 
 minutes, two minutes and one minute, and use acid 
 one-quarter inch above the mark on the acid meas- 
 ure Retest the whole milk in the hand machine 
 and compare the results with those obtained m the 
 steam machine. 
 
 3 (a) Take the B. of H. lactometer reading 
 of a sample of skimmed milk. See how much water 
 it will take to lower the lactometer reading one 
 degree. Great care must be taken to mix the water 
 with the milk as the former is poured in. This is 
 
40 A DAIRY LABORATORY GUIDE 
 
 best done by pouring the milk from one vessel to 
 another. 
 
 (b) S^e if one-half gram of salt will bring the 
 reading back to where it was originally. 
 
A DAIRY LABORATORY GUIDE 4I 
 
 STUDENT'S NOTES AND REPORT 
 
i2 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 43 
 
 EXPLANATION. ACIDITY OF MILK 
 
 The acidity of milk is of two kinds — apparent 
 and real acidity. The apparent acidity is due to 
 the acid reaction of the acid phosphates and casein. 
 The real acidity is due to the presence of lactic 
 acid (C3H6O3), which is produced by the action of 
 bacteria upon the sugar of the milk. The follow- 
 ing reaction is supposed to be the one which takes 
 place: 
 
 Ci2H220ii + H20=-4C3H603 
 
 The apparent acidity, according to Van Slyke, 
 does not go above .08 per cent to .1 per cent, and is 
 of minor importance so far as dairy work is con- 
 cerned. In determining the acidity of milk it is as- 
 sumed that all of the acidity is due to the presence 
 of lactic acid. 
 
 The real acidity will ordinarily go as high as I 
 per cent, and in some cases, higher. Usually, how- 
 ever, when from .8 per cent to i per cent acidity 
 is reached the lactic acid organisms will cease 
 working. If a part of the acid is neutralized the 
 organisms will again commence the production of 
 acid. 
 
 Lactic acid is important in the manufacture of 
 dairy products. For example, butter is churned 
 from cream which is soured or " ripened " by lactic 
 acid. The presence and amount of lactic acid is 
 very important all through the process of cheese 
 making. In many cases the nature of the product* 
 depends on the amount of acid present during the 
 successive steps of manufacture. 
 
 For these reasons it is necessary to have soine 
 means of finding the amount of acid in the milk. 
 The process by which this is done is called titration. 
 
44 A DAIRY LABORATORY GUIDE 
 
 It is a principle of chemistry that an alkali will 
 neutralize an acid. In order, therefore, to find the 
 acid in the milk we take a known quantity of the 
 milk and measure into it an alkali whose strength 
 we know. The instrument used to measure the 
 amount of alkali used is called a burette, and the unit 
 of measure is the cubic centimeter. It is commonly 
 graduated as fine as tenths of a cubic cen- 
 timeter. One can tell when all of the acid is neu- 
 tralized by means of an indicator. The indicator 
 used most in dairy work is phenolphthalein, which is 
 colorless in acid and pink in alkali. If two or three 
 drops of the indicator are put in milk the color will 
 not change, because the milk is acid in reaction. 
 The instant that just enough alkali is added to the 
 milk to neutralize all of the acid the solution will 
 turn pink. 
 
 It is a chemical fact that equal volumes of acids 
 and alkalies of the same chemical strength will ex- 
 actly neutralize one another. In i cc. of a normal 
 solution of lactic acid there are .09 grams of lactic 
 acid. According to the above rule i cc. of any 
 normal alkali solution would just neutralize .09 
 grams of lactic acid. 
 
 In actual practice a solution weaker than a normal 
 solution is usually employed, because a normal solu- 
 tion is so strong that any small variation in the 
 amount used makes a big variation in results. A 
 com.mon solution used is j/io normal (expressed 
 n/io). One cc. of an n/io alkali solution would 
 neutralize .009 grams of lactic acid. An example 
 will illustrate how the per .cent of acid in milk is 
 calculated. Suppose it took 6 cc. of n/io alkali 
 solution to neutralize the acid in 20 grams of milk. 
 What is the per cent of acid? One cc. of n/io alkali 
 will neutralize .009 grams of lactic acid. Six cc. will 
 
A DAIRY LABORATORY GUIDE 45 
 
 neutralize 6X.009=-054 grams of acid. .054-^20= 
 .0027. .0027X100^.27% acid in the milk. Formu- 
 lated, the above example is expressed as follows : 
 
 :0^6^IOO=.27% 
 
 If the milk for the acid test is measured in cubic 
 centimeters it should be reduced to grams by mul- 
 tiplying by the specific gravity of milk. The acid 
 is obtained in terms of grams and we cannot divide 
 grams by cc. and obtain per cent. 
 
 Professor Farrington has devised some alkali 
 tablets, each one of which will neutralize .03492 
 grams of lactic acid. These tablets are dissolved 
 in water and an alkali solution made. The strength 
 of the solution per cc. will vary according to the 
 number of tablets used and the number of cc. of 
 water in which they are dissolved. The indicator 
 IS added to the tablets when they are manufactured. 
 Consequently, when using an alkali tablet solution 
 no phenolphtholein is needed. A concrete example 
 will show how these tablets are used. 
 
 Suppose that it required 15 cc. of an alkali tablet 
 solution to neutralize the acid in 20 grams of milk. 
 The tablet solution was made by dissolving five 
 tablets in too cc. of water. What is the per cent 
 of acid in the milk? 
 
 .03492=grams of lactic acid one tablet will neu- 
 tralize. .03492X5=- 1 746 grams of lactic acid five 
 tablets will neutralize. Since the five tablets are 
 dissolved in too cc. of wnter .1746 is the amount of 
 lactic acid too cc. of the solution will neutralize. 
 Then . 1746-^100=. 00 1746, the strength of i cc. of 
 the solution ; in other words, the number of grams 
 of lactic acid i cc. of the solution will neutralize. 
 
 .ooi746Xi5=-026i90 
 
 .026I90-^2o=.ooI3095XIOO=.I3095% 
 
46 A DAIRY LABORATORY GUIDE 
 
 If five of the alkali tablets are dissolved in 97 cc. 
 of water each cubic centimeter of the solution will 
 neutralize .01 per cent of acid when 18 grams of 
 milk are used. This solution is often used by 
 creamerymen, as the per cent of acid may then be 
 read directly from the burette. Many devices for 
 testing the acidity of ^ilk are on the market, all 
 tending to do away with computation and giving 
 the percentage of acid directly. One of these is 
 Publow's acidimeter. In this apparatus an n/io 
 alkali solution is used and 9 grams of milk are 
 tested. Each cc. on the burette equals .1 per cent 
 of acid and each i/io of a cc. equals .01 per cent 
 acid. In testing for acid one should always try 
 and obtain the same degree of color each time. 
 This color" should be permanent for at least one 
 minute. Great care should be taken not to run in 
 an excess of alkali. It will be much easier to detect 
 the color change if some ^vater is added to the 
 sample after it is measured out before the alkali 
 is added. 
 
A DAIRY LABORATORY GUIDE 47 
 
 EXERCISE VIII 
 BABCOCK TEST AND AClD TEST 
 
 I (a) Test by the Babcock method, butter, cream 
 and whole milk. Compute the weight of 
 the fat column in the cream test. 
 (b) Retest the whole milk, putting 9 grams in 
 one bottle and 5 grams in the other. Re- 
 duce each reading to a basis of 18 grams. 
 
 2. (a) Test the skimmed milk for per cent of acid, 
 using n/io alkali solution, and using 
 17.6 cc. of milk. Do not add water to the 
 sample. 
 
 (b) Retest the skimmed milk, using 25 cc. of 
 
 milk and compare with first test. 
 
 (c) Measure out 18 grams of skimmed milk and 
 
 add to this 17.6 cc. of water. Test for 
 acid and compare with the first test. 
 
 (d) Measure out 20 cc. of skimmed milk from 
 
 same sample as used in above experi- 
 ments and add to it 3 cc. of buttermilk 
 or starter and test for acid. What is 
 the object of using different amounts in 
 (a) and (b)? What is the object of 
 adding water to (c) ? 
 
 3. Take the B. of H. lactometer reading of the 
 
 whole milk and compute per cent of T.S. 
 and S. N. F. 
 
 4. Take a B. of H. lactometer reading of skimmed 
 
 milk. Cool the milk as low as possible 
 and compute what the reading would be 
 at this temperature. Then compare your 
 computation with the actual reading. 
 
48 A DAIRY LABORATORY GUIDE 
 
 Perform the same experiment, heating the milk 
 to 95° F. The object of this experiment is 
 to show the incorrectness of a correction 
 factor when used at a temperature of more 
 than 10° F., either above or below 60° F. 
 
I 
 
 A DAIRY LABORATORY GUIDE 49 
 
 STUDENT'S NOTES AND REPORT 
 
50 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 51 
 
 EXPLANATION. EFFECT OF SPEED OF 
 MACHINE ON BABCOCK TEST 
 
 The following exercise illustrates the influence of 
 the speed of the machine on the amount of fat 
 broug-ht to the surface. The speed of the machine 
 is important, because the greater the speed the more 
 force exerted. One should always run a Babcock 
 tester up to the speed indicated in the directions for 
 running the machine. Sometimes one will make as 
 good a test when running a machine slow as when 
 running faster. This, however, is not always the 
 case, and in operating the tester one must be sure 
 that the machine is run fast enough to bring all of 
 the fat into the neck of the bottle. 
 
S2 A DAIRY LABORATORY GUIDE 
 
 EXERCISE IX 
 BABCOCK TEST AND LACTOMETER 
 
 1. (a) Test by the Babcock method a sample of 
 
 whole milk, skimmed milk and butter. 
 
 (b) Retest the butter in the hand machine. 
 
 (c) Retest the whole milk in tjie steam ma- 
 
 chine, but do not let the speed of the 
 machine exceed 250 revolutions per 
 minute. 
 In performing- the above experiment it is 
 best to experiment with the machine 
 before putting- in your samples. Other- 
 wise, you will be liable to run the ma- 
 chine too fast. 
 
 2. (a) Take a lactometer reading of the whole 
 
 milk and figure out the S. N. F. and 
 T. S. 
 (b) Take a lactometer reading of the skimmed 
 milk and figure out the S. N. F. and T. S. 
 
 3. (a) Test the skimmed milk for acid with n/io 
 
 alkali solution and the alkali tablet solu- 
 tion. The alkali tablet solution was 
 made by dissolving eight tablets in 95 cc. 
 of water. 
 (b) Test for acid 18 grams of tap water. Add 
 to 18 grams of tap water 3 cc. of starter 
 or buttermilk, again test for acid. Use 
 n/io alkali solution. 
 
A DAIRY LABORATORY GUIDE 53 
 
 STUDENT'S NOTES AND REPORT 
 
54 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 55 
 
 EXERCISE X 
 
 BABCOCK TEST. LACTOMETER READING 
 AND ACID TEST 
 
 1 Make a Babcock test of cheese, whole milk and 
 
 skimmed milk. Add acid to the skimmed 
 milk about one-quarter of an inch above the 
 usual mark, and run ten minutes, two mm- 
 utes and one minute. 
 Run the whole milk the usual time at the usual 
 speed Be sure to cut the cheese fine before 
 putting into the test bottle. 
 
 2 (a) Retest the whole milk, running the machine 
 
 one minute, one minute, one mmute. Be 
 careful to run the machine at the same 
 speed at which it was run the first time. 
 Do you get any different results either m 
 the amount or the appearance of fat? It 
 so give the reasons. 
 (b) Retest the whole milk, running the machine 
 fifteen minutes, five minutes and three 
 minutes. Do you get any more fat than 
 when the machine is run the usual length 
 of time' Be careful to run the machine 
 at the same speed at which it was run 
 the first time. 
 Oil the machine well before each run. 
 7 Take the B. of H. lactometer reading of skimmed 
 ^- milk and whole milk. Make corrections for 
 
 temperature and figure out the S N. F. and 
 T. S. for whole milk, using three formulae. 
 
56 A DAIRY LABORATORY GUIDE 
 
 4. Test the whole milk for acid, using 18 grams. 
 Use both n/io and alkali tablet solution. 
 Test the skimmed milk for acid, with the iVio 
 solution. Use only 5 cc. of the milk. Do this 
 twice, so that one result will be a check on 
 the other. Again test the skimmed milk, 
 using a 50-cc. sample. Do this twice. See 
 if you get the more uniform results with the 
 large sample. 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE S7 
 
 STUDENT'S NOTES AND REPORT 
 
58 A DAIRY LABORATORY GUIDE 
 
 EXPLANATION OF EXERCISE XI 
 
 In testing butter by the Babcock method, the 
 practice is sometimes followed of melting the 
 butter and then putting it into the test bottle 
 by means of the pipette. It is posssible to do 
 this sometimes and get accurate results, but 
 the tendency for fat and water to separate 
 makes it difficult to get accurate tests. 
 
 Division b of experiment 2 illustrates how 
 readily the fat and water separate. In draw- 
 ing off the fat for this experiment, keep the 
 point of the pipette at the surface of the fat. 
 
 Carbon dioxide acts toward an alkali like an 
 acid. We are told that some of the acidity 
 of the milk is due to the presence of CO2. 
 In experiment 4, pouring the milk back and 
 forth from one vessel to another tends to mix 
 the CO2 of the air with the milk. Heat will 
 expel the CO2, and so after boiling the milk 
 the acid test would be lower than it would 
 be before boiling. This experiment also 
 shows that milk will take up gases. 
 
 In the same way that acids and alkalies form 
 reactions so do solutions of certain salts form 
 reactions. When salts do react they follow 
 the same rule as acids and alkalies, namely, 
 that equal volumes of salts of the same chem- 
 ical strength will just neutralize one another. 
 This fact is made use of in determining, 
 quantitatively, the amount of salt (sodium 
 chloride) in butter. The salt used to neutral- 
 ize the sodium chloride is silver nitrate (Ag 
 N03) and the indicator used to tell when 
 enough silver nitrate has been added is a solu- 
 
A DAIRY LABORATORY GUIDE 59 
 
 tion of potassium chromate (K2Cr O4). This 
 indicator added to sodium chloride solution 
 produces a lemon yellow color. When enough 
 silver nitrate has been added to just neutral- 
 ize all of the sodium chloride the solution 
 turns a light brown color. No more silver 
 nitrate should be added when a permanent 
 light brown color is obtained. 
 
 The chemical reaction which takes place is as 
 follows : 
 
 Nacl+Ag No3=Na Nog+Agcl 
 
 One cc. of n/jo silver nitrate solution will neu- 
 tralize .00585 grams of sodium chloride. Since 
 the butter is in solid form, it is necessary to 
 dissolve the sodium chloride and this is done 
 by washing the butter in a definite amount 
 of warm water, and titrating the water. 
 
 Suppose 10 grams of butter are washed in 200 
 cc. of warm water and it takes 6 cc. of silver 
 nitrate solution to neutralize the salt in 50 cc. 
 of the wash water. It would then require 24 
 cc. of silver nitrate solution to neutralize the 
 salt in 200 cc. of wash water. Since i cc. of 
 silver nitrate will neutralize .00585 grams of 
 salt (sodium chloride) 24 cc, will neutralize 
 .1404 grams of salt (24x.oo585=.i404). 
 
 This salt was obtained from 10 grams of butter 
 so .1404 grams of salt divided by 10 grams of 
 butter, and the quotient multiplied by 100 
 will give 1.404 the per cent of salt in the but- 
 ter. 
 
6o A DAIRY LABORATORY GUIDE 
 
 EXERCISE XI 
 BABCOCK TEST AND ACID TEST 
 
 1. ]\Iake up an alkali tablet solution as directed. 
 
 Shake frequently, and set aside for use later 
 in the exercise. 
 
 2. (a) Test by the Babcock method a sample of 
 
 whole milk and a sample of butter. 
 (b) Place a piece o*f butter in your acid measure 
 and allow it to stand in a cup of hot 
 water for about fifteen minutes. Then 
 with a pipette draw the fat from the sur- 
 face of the liquid. Weigh out the proper 
 amount and test by the Babcock method. 
 What conclusions do you draw from this 
 experiment ? 
 
 3. Test for acid a sample of starter, using the 
 
 alkali tablet solution furnished and n'lo 
 alkali solution. Use 3 cc. of starter. 
 
 4. Pour back and forth from one vessel to another 
 
 about 100 cc. of skimmed milk. Do this for 
 about three minutes. Test 25 cc. of it for 
 acid, using the alkali tablet solution which 
 you made up at the beginning of the exer- 
 cise. Then boil about 35 cc. of the milk for 
 about one minute ; cool ; keep covered while 
 cooling, and retest 25 cc. for acid. Compare 
 with first test and see if you get lower re- 
 sults. 
 
 Explain fully why lower results may be ex- 
 pected with boiled milk. 
 
 The alkali tablet solution was made by dissolv- 
 ing 10 alkali tablets in 115 cc. of water. 
 
A DAIRY LABORATORY GUIDE 6t 
 
 STUDENT'S NOTES AND REPORT 
 
6^ A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 63 
 
 EXERCISE XII 
 
 BABCOCK TEST AND BUTTER MOISTURE 
 TEST 
 
 1. Test a sample of cheese, whole milk and 
 
 skimmed milk for butter fat. In testing the 
 skimmed milk, run extra time and use extra 
 acid as previously directed. 
 
 2. Test cheese for acid, using n/io alkali solution. 
 
 In order to test cheese for acid, weigh out 3 
 grams. Place in a white cup and add 17.6 cc. 
 of warm water. Then with a stirring rod 
 grind the cheese up as fine as possible. This 
 will take at least five minutes. Then test 
 the solution as usual, and calculate the per 
 cent of acid. 
 
 3. Test a sample of butter for moisture by the 
 
 Cornell method. 
 
 4. Test for salt a sample of butter, using an n/io 
 
 silver nitrate solution. Use 10 grams of but- 
 ter and 250 cc. of water. Titrate at least three 
 50 cc. portions of water and check results 
 carefully. 
 
 Note. — To what is the high acid content of cheese 
 due? 
 
64 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 65 
 
 STUDENT'S NOTES AND REPORT 
 
66 A DAIRY LABORATORY GUIDE 
 
 EXERCISE XIII 
 
 BABCOCK TEST, LACTOMETER AND ACID 
 
 TEST 
 
 1. Test by the Babcock method a sample of whole 
 
 milk, cottage cheese and buttermilk. Fill 
 your lightning top sample jar about one-third 
 full of whole milk, add a preservative tablet 
 and shake at intervals until tablet is dis- 
 solved. Set the sample away in your desk 
 and test at the next exercise. 
 Use 9 grams of cottage cheese, and add 9 grams 
 of water. Test in whole milk bottle. Shake 
 well after adding acid. 
 
 2. To about 54 grams of skimmed milk add 2 cc. 
 
 of light machine oil, shake thoroughly. Using 
 the whole milk test bottle, test the sample 
 in duplicate by the Babcock method. Com- 
 pare the appearance of the fat column with 
 that obtained with ordinary butter. 
 
 3. Test with the alkali tablet solution the acid in 
 
 the whole milk and buttermilk. 
 
 4. Take a lactometer reading of the whole milk. 
 
 Add some water (about 25 cc.) to the 
 sample. Again take a lactometer reading 
 and make a Babcock test. Figure out T. S. 
 and S. N. F. and the per cent of the water 
 added. 
 
 5. Test for salt a sample of butter using 10 grams 
 
 of butter and 300 cc. of water. Titrate sev- 
 eral 17.5 cc. portions of the water and check 
 results carefullv. 
 
A DAIRY LABORATORY GUIDE 6/ 
 
 STUDENTS NOTES AND REPORT 
 
68 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRV LABORATORY GUIDE 69 
 
 EXPLANATION. COMMERCIAL RENNET 
 AND ITS USE 
 
 Commercial rennet is a liquid prepared by soak- 
 ing: in brine the fourth stomach of the calf. It has 
 under certain conditions the power of precipitating 
 the casein from milk. It is so desirable for this 
 purpose that rennet is used almost exclusively in 
 the manufacture of cheese. One peculiar character- 
 istic of rennet is the fact that it is not destroyed 
 by its use in precipitating casein. If it could be 
 extracted the same rennet could be used over and 
 over again for precipitating the casein in different 
 lots of milk. 
 
 Temperature has a decided effect upon the action 
 of rennet. The colder milk is, the less rapid the 
 rennet action. This is very noticeable at tempera- 
 tures below 80° F. The rennet acts most rapidly 
 at temperatures from ioo° F. to 120° F. At 130° 
 F. the action of the rennet is less active and its 
 action is entirely destroyed somewhere between 
 140° F. and 150° F. The high temperature destroys 
 the rennin, which is the active principle of the 
 rennet. The action of rennet increases as the acid 
 in the milk increases. The action of rennet seems 
 to depend to a great degree upon the solubility of 
 the lime salts of the milk. If an insoluble lime 
 salt is added to the milk, the action of the rennet 
 is retarded, and if a soluble lime salt is added to 
 milk the action of rennet is hastened. If milk is 
 heated to a high temperature the lime salts are 
 supposed to be rendered insoluble and the rennet 
 has no effect on the casein. Freezing does not seem 
 to injure rennet. When it is again melted and 
 given the proper temperature it will act as though 
 it had never been frozen. 
 
70 A DAIRY LABORATORY GUIDE 
 
 EXERCISE XIV 
 
 BABCOCK TEST, MICROSCOPIC APPEAR- 
 ANCE OF MILK, USE OF RENNET 
 
 1. Test the composite sample preserved at the last 
 
 exercise. 
 
 2. Examine under the high-power microscope 
 
 cream, whole milk and skimmed milk. Make 
 a drawing of each field. Describe fully the 
 difiference in the appearance of the fat 
 globules in each of the three fields. 
 
 3. Heat 18 grams of skimmed milk to about 100° 
 
 F. and add four drops of rennet ; shake thor- 
 oughly and let stand. Note the length of 
 time it takes the milk to curdle. 
 
 4. To one-half a teacup of water add six drops of 
 
 sulphuric acid. Add three drops of this solu- 
 tion to 18 grams of milk. Heat to about 
 100° F. and add four drops of rennet and 
 note the time it takes for milk to coagulate. 
 Compare length of time with that required 
 in No. 3. 
 
 5. To about 20 grams of skimmed milk add six 
 
 drops of sulphuric acid and shake thoroughly. 
 Note time it takes the milk to coagulate and 
 compare the coagulum with that obtained 
 when rennet is used. 
 
 6. Measure out two 25 cc. samples of skimmed 
 
 milk. Warm to 80° F. To one sample add 
 five drops of rennet ; to the other add five 
 drops of sulphuric acid. Note and compare 
 the length of time it takes each to coagulate. 
 What two things hasten the action of rennet 
 in milk? 
 
A DAIRY LABORATORY GUIDE 7! 
 
 STUDENT'S NOTES AND REPORT 
 
72 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 73 
 
 EXERCISE XV 
 BABCOCK TEST AND USE OF RENNET 
 
 1. Test by the Babcock method a sample of butter- 
 
 milk and a sample of skimmed milk cheese 
 and whole milk cheese. Compare the results 
 of the cheese tests. 
 
 2. Boil a sample of milk for about two minutes 
 
 and then cool. Add some rennet and see if 
 the milk will coagulate. State the amount of 
 milk and rennet used. 
 
 3. Boil 25 cc. of milk for about two minutes and 
 
 then cool. Add one-half cc. of sulphuric acid 
 and see if the milk will coagulate. 
 
 4. Add to 25 cc. of milk six drops of rennet. Have 
 
 the temperature of the milk at ioo° F. Note 
 the time it takes the milk to coagulate. Test 
 25 cc. of the same lot of milk for acid. Com- 
 pute the amount of n/io alkali necessary to 
 neutralize the acid in 50 grams of the milk. 
 Add this alkali to the 50 grams of milk. 
 Divide the milk into two portions of 25 cc. 
 each and bring the temperature of each to 
 100° F. and add to each six drops of rennet. 
 Note the tim^e it takes the samples to co- 
 agulate. Compare with the length of time 
 required to coagulate the milk before the 
 alkali was added. 
 
 ; 
 
^74 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 75 
 
 STUDENT'S NOTES AND REPORT 
 
76 A DAIRY LABORATORY GUIDE 
 
 EXERCISE XVI 
 
 BABCOCK TEST AND LACTOMETER 
 READING 
 
 Take a lactometer reading and make a Babcock 
 test of a sample of whole milk. Compute the 
 T. S. and the S. N. F. Allow the sample to 
 stand in the lactometer cylinder while you 
 do No. 2. Then remove all of the cream pos- 
 sible and add 25 cc. of water. Ag"ain make 
 a Babcock test, and take a lactometer read- 
 ing. Compute the per cent of water added, 
 the rate per cent at which water was added, 
 the per cent of fat removed by skimming, 
 the per cent of fat removed by watering and 
 the rate per cent at which the fat was re- 
 moved. 
 
 Test in the steam machine a sample of whole 
 milk, and a sample of butter. Retest a 
 sample from the same lot of milk in 
 the hand machine and fill the machine 
 with water at 60° F. Note the result 
 of the low temperature upon the fat column. 
 Run the same bottles which were tested in 
 the hand machine in the steam machine for 
 a period of three minutes and then read the 
 fat column. N^ote if there is any increase 
 in the fat column. 
 
A DAIRY LABORATORY GUIDE 77 
 
 STUDENT'S NOTES AND REPORT 
 
^S A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY T.ADORATORV GUIDE 79 
 
 EXERCISE XVII 
 
 USE OF RENNET. PRECIPITATION OF 
 
 ALBUMEN 
 
 1. Take i8 grams of milk in a white cup and cool to 
 
 50° F. Add four drops of rennet and note 
 time it takes the milk to coagulate. Com- 
 pare this with the same amount of milk 
 warmed to 85° F., to which four drops of 
 rennet have been added. 
 
 2. Boil some whey and note the albumen which is 
 
 thrown down in a white flocculent pre- 
 cipitate. Fill your lightning top sample jar 
 about one-half full of skimmed milk at about 
 100° F. Add I cc. of rennet. Set aside to 
 coagulate. Then strain ofif the whey and 
 precipitate the albumen in the whey by boil- 
 ing. 
 
 In both cases the boiling should be done in a 
 test tube. It may at first be difficult to see 
 albumen, as it is in very fine particles. The 
 albumen may be distinguished more readily 
 by holding the test tube between the eye and 
 the window. 
 
 Turn in desk, key and locker. See that all glass- 
 ware is clean before turning in the desk. 
 
80 A DAIRY LABORATORY GUIDE 
 
 STUDENT'S NOTES AND REPORT 
 
A DAIRY LABORATORY GUIDE 8 1 
 
 STUDENT'S NOTES AND REPORT 
 
INDEX 
 
 PAGE 
 
 Aci<l: 
 
 Lactic ^"^ 
 
 Measure '^ 
 
 In Milk 4;^ 
 
 Sulphuric ^ 
 
 Acidity : 
 
 Apparent and real *^ 
 
 As effected by CO. ^■• 
 
 Alkali Tablet Solution 45 
 
 Babcock Test ^^ 
 
 Boiled Milk Test 1^ 
 
 Burette ^^ 
 
 Butter Fat I 
 
 Melting point ^ 
 
 Moisture in }^ 
 
 Preparation for fat test l^ 
 
 Preparation for moisture test 23 
 
 Casein 
 
 Amount in milk ^ 
 
 Characteristics of ;^; 
 
 Commercial uses of ^* 
 
 Collodial state ^ 
 
 Cornell Moisture Test 23 
 
 Cream 
 
 Viscosity of ^ 
 
 Weighing for testing ' 
 
 Fat I 
 
 Composition of 
 
 Formaldehyde Test 1^ 
 
 Galactase ^^ 
 
 Indicator '^^ 
 
 Lactometer ;^ 
 
 Board of Health ^ ' 
 
 Quevenne ^^ 
 
 Uses of ~" 
 
 Machines ^\ 
 
 Hand • ;^ 
 
 Effect of speed on test -^^ 
 
 Melting Point of Butter Fat -^ 
 
 83 
 
84 DAIRY LABORATORY GUIDE 
 
 PAGE 
 
 Milk 1 
 
 Adulteration 31 
 
 Albumen in 4 
 
 Ash in 4 
 
 Composition of 1 
 
 Casein in 3 
 
 Fat in 2 
 
 Sugar in 4 
 
 Water in 1 
 
 Phenolphthalein 44 
 
 Pipette 5 
 
 Reading Fat Colun.ii 6 
 
 Rennet 09 
 
 Effect of acid on action (il) 
 
 Effect of temperature on action 69 
 
 Salt, test for 59 
 
 Solids Not Fat 29 
 
 Formulae for finding 29 
 
 Specific Gravity 27 
 
 Of milk 27 
 
 Testing : 
 
 Butter 8 
 
 Cheese 8 
 
 Cream "^ 
 
 Skimmed w.'u'k 7 
 
 Whey 9 
 
 Whole milk 5 
 
 Temperature : 
 
 Effect on lactometer reading 28 
 
 Effect on fat column 6 
 
 Effect on rennet action 69 
 
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 First Principles of Soil Fertility 
 
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The Cereals in America 
 
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 The Forage and Fiber Crops in America 
 
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Feeding Farm Animals 
 
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 Practical Dairy Bacteriology 
 
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