Cream Testing. 



85 



-d, 



a milk test bottle, and two pipettefuls of water are added. In 

 this way all the cream in the pipette is easily rinsed into the 

 test bottle. The readings multiplied by ^=3.6 will give the 

 per cent, of fat in the cream. If the specific gravity of the 

 cream tested varies appreciably from 1, corrections should be 

 made accordingly; e. g., if the specific gravity is 1.02, the fac- 

 tor should read .^ 3.53; if .95, -Ji^. =3.79, etc. 



95. Proper readings of cream tests. The accom- 

 panying illustration (fig. 36), shows the proper method 

 of reading the fat column in cream 

 tests; readings are taken from a to c, 

 not to & or to d, when readings are 

 made at 140 P. 1 



No special precautions other than 

 those required in testing milk have been 

 found necessary in testing cream, ex- 

 cept that it is sometimes advisable not 

 to whirl the test bottles in the centri- 

 fuge at once after mixing, but to let the 

 cream-acid mixture stand for a while, 

 until it turns dark colored. At first, 

 the mixture of cream and acid is much 

 lighter colored than that of milk and 

 acid, owing to the smaller proportion of 



FIG. 36. Measur- 



n solids not fat contained in the cream. 



The liquid beneath the fat in a com- 

 pleted test of cream is sometimes milky 

 and the fat appears white and cloudy, making an exact 



in s the 6 



cream bottle. Read- 

 ing should be made 

 from a to c, not to b 

 or to d. 



1 The size of the meniscus is magnified in this cut. A study of the 

 meniscus formed in bottles with narrow or wide necks, and its bearing 

 on the results of cream tests is given in bulletin 58, Bur. An. Ind., 

 U. S. Dept. of Agriculture, where a discussion of the influence of dif- 

 ferent temperatures on readings of cream tests will also be found 

 (see 96). 



