Composite Samples of Milk. 157 



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 the Bab- 

 cock milk test bottle. 



190. The first portions of milk added to the composite 

 sample jars containing the specified amount of bi-chro- 

 mate 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 requires more 

 persistent shaking. Bi-chromate can be bought at drug 

 stores or from dairy supply dealers at about 30 cents a 

 pound and will cost about 25 cents a pound at wholesale. 

 Powdered bi-chromate of potash should be ordered, and 

 not crystals, as the latter dissolve only slowly in the milk. 

 Farrington's bi-chromate tablets contain the correct 

 quantity of preservative for a quart sample, and will be 

 found convenient. 



191. 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, chloroform, carbon 

 bi-sulfid, 1 copper ammonium sulfate, sodium fluorid, 

 ammonia glycerin (sp. gr., 1.031) and mixtures contain- 

 ing mercuric chlorid (corrosive sublimate) with anilin 

 color (rosanilin). 2 The coloring matter in the latter 



1 Delaware experiment station, eighth report, 1896, which also see for 

 trials with a large number of different preservatives. 



2 Iowa experiment station, bulletins 9, 11, 32. 



