168 Testing Milk and Its Products. 



190. Bi-chromate of potash. This preservative is 

 preferred by many because it is relatively harmless, 

 cheap and efficient. The bi-chromate method for pre- 

 serving samples of milk was proposed by Mr. J. A. 

 Alen, city chemist of Gothenburg, Sweden, in 1892, 1 

 and has been generally adopted in dairy regions in this 

 country and abroad. 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 of bi-chromate necessary for pre- 

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

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

 grains), about one-half as much as can be placed on a 

 dime. 



According to Winton and Ogden, 2 a .22-inch pistol 

 cartridge shell y 2 inch long, or a .32-inch caliber shell 

 14 inch long, when loosely filled, will hold enough pow- 

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

 caliber shell y 2 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 



1 Biedermann's Centralblatt, 1892, p. 549. 



2 Connecticut experiment station, report for 1884, p. 222 



