56 CANADIAN DA 1R YING. 



Sour milk which has thickened may be rendered 

 liquid by adding an alkali, such as concentrated lye, 

 in small quantities, and mixing them until the curd 

 is dissolved. 



THEORY OF THE BABCOCK TEST. 



A 17.6 c.c. pipette delivers about 17.5 c.c. of milk 

 into a Babcock bottle. This quantity of milk will 

 weigh about 18 grams (17.5 x 1.032 the av. sp. gr. of 

 milk). The volume of the graduated neck of the 

 bottle is 2 c.c. The average specific gravity of milk 

 fat is about .9, therefore 2 c.c. fat will weigh 1.8 grams 

 (2 x .9= 1.8). A sample of milk which contains suffi- 

 cient fat to fill the graduated neck of the bottle from 

 o to 10 is read as 10 per cent, fat, because 1.8, the 

 weight of the fat, is 10 per cent, of 18, the weight of 

 milk used in making the test. If the volume of fat 

 fills five spaces on the neck of the bottle, it is read as 

 five per cent, because its weight is about .9 of a gram, 

 which is 5 per cent, of 1 8 (5/100 of 1 8 = .9), and so for 

 all the readings. The Babcock test is based on aver- 

 age weights of milk and fat. The milk and fat are 

 not weighed, but measured, because 'it is more con- 

 venient to measure than to weigh. Any errors arising 

 from a difference in the specific gravity of milk are so 

 slight as not to materially affect the test, if care be 

 taken to do the work properly. 



WATERING AND SKIMMING MILK. 



By the use of the lactometer and the Babcock 

 tester, a skilful person can detect samples which have 



