The Babcock Test. 69 



ference of forty degrees will often have considerable 

 influence on the clearness of the fat separated, show- 

 ing white curdy substances and a light colored fat in 

 winter, or black flocculent specks, with a dark colored 

 column of fat in summer. Both these defects can be 

 avoided, when the acid is of the proper strength, by 

 bringing the temperature of the milk and the acid to 

 about 70 F. before the milk is tested. 



The operator should be particularly cautious against 

 over-heating either milk or acid, since the heat intensi- 

 fies the action of the acid and this may become so vio- 

 lent as to force the hot liquid out of the neck of the 

 test bottle when the acid is added to the milk, thus 

 spoiling the test and possibly causing an accident. 



4. WATER TO BE USED IN THE BABCOCK TEST. 



80. Rain water, condensed steam, or soft water should 

 be used for the purpose of bringing the fat into the 

 neck of the test bottles. The surface of the fat column 

 will then usually be clear and distinct. The foam or 

 bubbles that sometimes obscure the upper line (menis- 

 cus) of the fat, making indistinct the point from which 

 to measure it, is generally caused by the action of the 

 acid on the carbonates in hard water. The carbonic 

 acid gas liberated from such water by the sulfuric acid 

 is held more or less by the viscid fat and produces a 

 layer of foam on its surface. If clean soft water cannot 

 be obtained for this purpose, hard water may be used, by 

 adding a few drops of sulfuric acid to the water before 

 it is heated, thus causing the carbonic acid to be ex- 



