Composite Samples of ]\iilk. 167 



and has been generally adopted in dairy regions in this 

 country and abrcad. While not perfectly harmless, the 

 bi-chromate is not a violent poison like other chemicals 

 proposed for this purpose, and no accidents are liable 

 to result from its use. 



191. The quantity cf bi-chromate necessary for pre- 

 serving half a pint to a pint of milk for a period of 

 one or two weeks is abcut one-half gram (nearly 8 

 grains). 



According to Winton and Ogden, 1 a .22-inch pistol 

 cartridge shell % inch long, cr a .32-inch caliber shell 

 1/4 inch long, when loosely filled, will hold enough pow- 

 dered bi-chromate to preserve y 2 pint, and a .32-inch 

 caliber shell % inch long will hold enough to preserve 

 one pint. These shells may be conveniently handled 

 by soldering to them a piece of stiff wire which serves 

 as a handle. The amount of bi-chromate placed in 

 each composite sample jar would fill about half the 

 space representing one per cent, in the neck of a Bab- 

 cock milk test bottle. 



192. The first portions of milk added to the com- 

 posite sample jars containing the specified amount of 

 bi-chromate will be colored almost red, but as more 

 milk is added day by day, its color will become lighter 

 yellow. The complete sample should have a light straw 

 color; such samples are most easily mixed with acid 

 when tested. If more bi-chromate is used, the solution 

 of the casein in the acid is rendered difficult and re- 

 quires persistent shaking. Bi-chromnte can be bought 



1 Connecticut experiment station, report for 1884, p. W2. 



