THE BABCOCK TEST 69 



through the milk when poured into the test-bottle, 

 (6) interrupting the mixing of the milk and acid af- 

 ter beginning and before completion. Black particles 

 can usually be prevented by mixing 2 cc. of diluted 

 glycerine (80 cc. of glycerine and 20 cc. of water) 

 with the milk before adding the acid. The difficulty 

 may also be often overcome by using a mixture of 

 equal parts of water and sulphuric acid to fill the bottle 

 after the first whirling. 



(b) White particles of undissolved casein below or 

 above or in the fat-column, or a cloudy appearance of 

 the fat, are due to one or more of the following causes : 

 (i) Too weak acid (below 1.82 specific gravity), (2) 

 insufficient amount of acid (less than 17 cc.), (3) too 

 low temperature of milk or acid (below 60 F.), (4) 

 incomplete mixing of milk and acid, (5) insufficient 

 speed of tester. 



Sometimes when the fat is not clear, good results 

 may be obtained by allowing the bottles to cool enough 

 for the fat to harden some, and then warming in wa- 

 ter at 140 F. before reading. 



(c) Bubbles of gas, appearing as foam on the top 

 of the fat-column, are generally due to the use in the 

 test-bottle of hard water containing carbonates. This 

 condition may be prevented by adding to the water, 

 previous to use, a few drops of sulphuric acid. When 

 the foam appears and interferes with the reading, a 

 few drops of alcohol are put on the top of the fat-col- 

 umn and the reading is at once made. The alcohol 

 .causes the bubbles to disappear and produces a sharp 

 line of division between the fat and alcohol. If the 

 alcohol is allowed to be in contact with the fat for 



