TESTING CREAM BY THE BABCOCK TEST 89 



VARIATIONS IN DETAILS OF TEST 



In carrying out the details of the Babcock test with 

 cream, some of the details require modification in com- 

 parison with the test as applied to milk. The points 

 to which we will call special attention in this connec- 

 tion are the following: (i) Amount of acid used, (2) 

 addition of water, and (3) control of meniscus. 



Amount of acid. The amount of sulphuric acid 

 (p. 43) that is needed to give good results varies some- 

 what (i) with the percentage of fat in the cream, or, 

 stated in another way, with the percentage of solids 

 not fat, and (2) with the temperature of cream and 

 acid. In illustration of the first point, Hunziker gives 

 the following results at about 70 F. : 



Per cent of fat Cream Amount of acid used, 



in Cream. Used for test. Largest Smallest. 



50 18 grams 13 cc. 8 cc. 



50 9 " 7.5 cc. 4.5 cc. 



28 18 " 15 cc. 11 cc. 



28 9 " 8 cc. 5 cc. 



It is seen that for any one sample the amount of acid 

 used can be varied considerably without affecting the 

 results of the test. The safest guide to follow in de- 

 ciding how much acid to use is the color of the cream 

 and acid after they are mixed. The mixture of cream 

 and acid is generally lighter in color at first than in 

 case of milk, because the sugar and casein are less. 

 Acid can be added until the mixture, after being agi- 

 tated, has a brownish color," similar to that produced by 

 mixing coffee and cream. It is usually well to let the 

 bottle stand after mixing the cream and acid until the 

 mixture turns dark, before whirling. Less acid can 



