70 



Testing Milk and Its Products. 



it, is generally caused by the action of the acid on the 

 carbonates in hard water. The carbonic acid gas liber- 

 ated from hard water by the sulfuric acid is more or less 

 held 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 driven out of it. 

 By simply boiling, many hard waters will be rendered 

 soft and adapted to use in the Babcock test, as most of 

 the carbonates which cause this foaming are thereby 

 precipitated. 



W 



FIG. 25. The Russian test. 



If the test has been completed, and 

 a layer of foam appears over the fat, 

 it may be destroyed by adding a drop 

 or two of alcohol. If this is done, 

 the fat column should be read at once 



FIG. 26. Pipette used in 



after the alcohol is added, as the tne Russian test. 

 latter will soon unite with the fat and increase its vol- 

 ume. 



