THE ALCOHOL TEST IIST RELATION TO MILK. 25 



We can not see that the alcohol test is of any particular value in 

 the control of a market milk supply except as a means of evidence 

 that milk from a particular source is abnormal in some way and 

 should be examined by other tests. It might be of value at a re- 

 ceiving station as a means of detecting sour milk, but the test would 

 be expensive compared with the use of alkaline tablets for the rapid 

 determination of acidity as described by Farrington and Woll (9). 



THE TITRATION METHOD OF APPLYING THE ALCOHOL TEST. 



From the simple alcohol test in which a definite volume of a definite- 

 percentage alcohol is added to an equal volume of milk there has 

 developed a method in which a definite volume of milk is titrated 

 with certain percentages of alcohol until a coagulation of the milk is 

 produced. 



Lohnis (16) has found this titration method to be of value as a test 

 for the quality of market milk. He found that there was quite a 

 definite relation between the titration with 80 per cent alcohol and 

 the bacterial content of market milk. He titrated 2 c. c. of milk in a 

 beaker against a black background with 90, 80, and 70 per cent alco- 

 hols, the titration being made at a temperature of from 15° to 20° C. 

 The first appearance of flakes was considered the end point. 



We have used this method in the titration of 116 samples of market 

 milk furnished with bacterial counts by Dr. Kinyoun and Dr. Dieter, 

 of the Health Department of the District of Columbia. In our 

 titrations of 92 samples of raw and 24 samples of pasteurized milk we 

 have not found any definite relation between the titration with 90 

 per cent and 80 per cent alcohols and the bacterial count. In Table 

 20 is shown the acidity, bacterial counts, and alcohol titration of 92 

 samples of raw milk, and in Table 21 the results of an examination 

 of 24 samples of pasteurized milk. The bacterial counts of the raw 

 milk ranged from 2,100 to 20,600,000 per cubic centimeter, and the 

 pasteurized milk from 1,200 to 3,100,000 bacteria per cubic centimeter. 

 Consequently we were able to titrate samples having a great variation 

 in their bacterial content. If a study is made of the bacterial counts 

 and the alcohol titrations shown in Tables 20 and 21 it will be seen 

 that there is no definite relation between them. In order to bring 

 this point out more clearly the titrations of samples containing more 

 than 500,000 and less than 500,000 bacteria per cubic centimeter 

 have been averaged, as shown in Table 22. The average titration 

 with 90 per cent alcohol of 46 samples of raw milk containing more 

 than 500,000 bacteria per cubic centimeter was 1.95 c. c, while the 

 average titration of 46 samples containing less than 500,000 per cubic 

 centimeter was 2.39 c. c. The average titration of 46 samples with 

 80 per cent alcohol was 4.61 c. c. when the bacterial count was more 



