22 



Completing the test. -Instead of adding a measured 

 quantity of sulphuric acid to the cream in the test bottle, 

 as is done with milk, the best way is to add the acid until 

 the mixture assumes the color of coffee to which cream has 

 been added. 1 The quantity of acid required to produce 

 this color varies with the percentage of fat in the cream. 

 If the cream and acid when mixed are about 70 F., about 

 one-quarter or one-half the regular quantity (4 to 8 cubic 

 centimeters) of acid (specific gravity 1.82 to 1.83), depend- 

 ing upon the percentage of fat, will be required for a 9- 

 gram charge. After adding the acid to the cream, the 



FIG. 19. Type of balance for several bottles. 



procedure up to the reading of the percentage is exactly 

 the same as in the milk test. After the final whirling, the 

 test bottles are submerged to a point above the fat column 

 in water at 135 to 140 F. in a suitable tank. After re- 

 maining in this tank for about 15 minutes they are re- 

 moved and the readings quickly made. The important 

 difference between reading the cream test and the milk 

 test is that in the cream test the fat column included is 

 from the bottom of the lower meniscus to the bottom, not 

 the top, of the upper meniscus. (See fig. 20.) 



i O. F. Hunziker and H. C. Mills, Testing Cream for Butter Fat, Indi- 

 ana Agricultural Experiment Station, Bui. 145. June, 1910, 



