168 Testing Milk and Its Products. 



at drug stores or from dairy supply dealers at about 30 

 cents a pound. Powdered bi-chromate of potash should 

 be ordered, and not crystals, as the latter dissolve only 

 slowly in the milk. Bi-chromate tablets contain the 

 correct quantity of preservative for a quart sample, and 

 will be found convenient. 



193. Other preservatives for composite samples. 

 Among other substances recommended for use in butter 

 or cheese factories as milk preservatives for composite 

 samples are formalin, boracic-acid compounds, chloro- 

 form, carbon bi-sulfid, 1 copper ammonium sulfate, so- 

 dium fluorid, ammonia glycerin (sp. gr., 1.031), and 

 mixtures containing mercuric chlorid (corrosive sub- 

 limate) with anilin color (rosanilin). 2 The coloring 

 matter in the latter compounds is added to give a rose 

 color to the sample preserved, thus showing that the 

 milk is not fit for consumption; the bi-chromate giving 

 naturally a yellow color to the milk, renders unneces- 

 sary the addition of any special coloring matter. 



The compounds containing corrosive sublimate are 

 violent poise ns and must always be handled with the 

 greatest care, lest they get into the hands of children or 

 persons not familiar with their poisonous properties; 

 they will preserve the milk longer than bi-chromate 

 when applied in sufficient quantities. During late years 

 corrosive sublimate tablets have come into general use 

 in factories. 



1 Delaware experiment station, eight li report, IS<M>, which also sec for 

 trials with a lar^e number of dilTerent preservat i\ >. 



2 Iowa experiment station, bulletins ( ., 11, iW. 



