THE MANUFACTUKE OF FOODS 



361 



acid to run to the bottom of the bottle, 

 milk until the other bottle is prepared. 



Do not shake the acid and 

 Measure another 17.5 c.c. 



cc Pipette 



toy. Milk Bottle 



FIG. 250. 



17. y cc Graduate for 

 sulphuric acid 



portion of the acid and pour it into the second bottle of measured 

 milk. (4) Now carefully shake the bottles containing the milk and 

 acid so as to mix thoroughly. Do not try to mix the liquids by 

 placing the finger over the mouth of 

 the test bottle or the finger will be 

 burned. In shaking, be careful that 

 the curd does not become lodged in 

 the neck of the bottle. The mix- 

 ture becomes very hot and it is to be 

 kept hot during the entire test from 

 this point on. The acid has now dis- 

 solved all of the constituents in the 

 milk except the fat. The fat is now 

 to be separated by use of the ma- 

 chine. (5) Have about a pint of 

 water heating so it will be ready 

 for use later on. (6) Place the test 

 bottles at opposite points in the centrifuge machine (Fig. 251; and 

 place bottles filled with water in the other holders so as to balance 

 the machine. Turn the handle of the machine at the rate of 

 about 70 revolutions per minute for five minutes. Remove the test 



FIG. 251. The centrifuge machine. 



