184 CARE OF COMPOSITE MILK SAMPLES 



used. One tenth of a gram, or an amount of the preserva- 

 tive that could be piled on an area one-fourth inch square, 

 is sufficient to preserve a pint of milk in good condition for 

 testing for a period of from two to three weeks. The color 

 of the milk is changed by this chemical to a reddish yellow. 

 Potassium Bichromate is inexpensive and, like formalin, 

 may be purchased of the local druggist. 



CORROSIVE SUBLIMATE TABLETS. 



Tablets composed of Corrosive Sublimate combined with 

 coloring matter for preserving samples of milk to be tested 

 have recently been placed on the market by some of the 

 dairy supply houses, and when used according to the accom- 

 panying directions produce satisfactory results. Undoubt- 

 e«ily a preservative in tablet form possesses a distinct advan- 

 tage over others for general purposes, as the proper amount 

 of preservative can always be had without measuring. 



In using preservatives, the entire amount should be added 

 to the first lot of milk placed in the sample jar. 



The preservative should be completely dissolved at once 

 and thoroughly mixed with the milk. 



Every time a new lot of milk is added to the sample the 

 same should be thoroughly mixed with the older milk. Bot- 

 tles and contents should also be shaken often enough to 

 prevent the fat in the milk rising and forming a thick, 

 tough layer of cream on the surface. 



