Laboratory Exercises 367 
the percentage of fat contained in the sample, the former method 
is the more accurate. 
30. Bascock Test or WHOLE MILK usinG DIFFERENT AMOUNTS 
oF AcID 
Object. To show the effect of different amounts of acid upon 
the sample in performing the Babcock test. 
Materials. Same as previously given for testing whole milk. 
Directions. Test a sample of milk in the ordinary way. Re- 
test the same as follows: after measuring 17.8 cubic centimeters 
of milk into the test bottle, add sulfuric acid up to the base of 
the bottle neck. Run the sample seven minutes and then add 
enough water to bring the fat into the graduated neck,’ and then 
run the sample one minute. Then read the per cent of fat and note 
the effect of the extra acid upon the fat column. 
31. Errecr or Dirt in THE KrEpInc QuaLities or MILK 
Object. To show the relation of dirt and dust to the keeping 
quality of milk. 
Materials. Some fresh milk, glass bottles or test tubes. 
Directions. Mix the milk thoroughly and divide into several 
lots and treat as follows: (1) Set aside at room temperature ; 
(2) add a few hairs taken from the body of a cow; (8) add a piece 
of cobweb carrying dirt; (4) add some hay dust; (5) expose for 
a few minutes in an open pail to the dust of the room after sweep- 
ing; (6) add two or three small pieces of hay. 
Shake the samples to incorporate the dirt in the milk and set 
aside at room temperature and note time of curdling and odor and 
appearance of curd. Do any show bubbles of gas due to the gas- 
producing bacteria? Compare with the untreated sample. Any 
changes in the milk are due to the bacteria carried on the added 
dirt. 
