156 Testing Milk and Its Products. 



check or prevent the fermentation of the milk must be 

 added to it. A number of substances have been proposed 

 for this purpose. 



188. Bi-chromate of potash. This preservative is, in 

 the opinion of the authors, to be preferred, on account of 

 its relative harmlessness, its cheapness and efficiency. 

 The bi-chromate method for preserving samples of milk 

 was proposed by Mr. J. A. Alen, city chemist of Gothen- 

 burg, Sweden, in 1892, l 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; at least none 

 have been known to the writers to occur during the years 

 that it has been used in creameries or dairies as a pre- 

 serving agent. 



189. The quantity of bi-chromate necessary for preserv- 

 ing half a pint to a pint of milk for a period of one or 

 two weeks is about one-half-gram (nearly 8 grains). As 

 there are about 900 half-grams in a pound, this quantity 

 will suffice for nine weeks in a creamery having one 

 hundred patrons, if tests are made once a week, or for 

 three months (90 days) if tests are made every ten days. 



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

 cartridge shell cut to J inch long, or a .32-inch calibre 

 shell cut to J inch long, when loosely filled, will hold 

 enough powdered bi-chromate to preserve Jpint, and a 

 .32-inch calibre shell cut to \ inch long will hold enough 

 to preserve one pint. These shells may be conveniently 



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



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



