158 Testing Milk and Its Products. 



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 unnecessary the addition of any 

 special coloring matter. 



None of the substances mentioned are as cheap as bi- 

 chromate or more effective for factory purposes when 

 the milk is to be kept not to exceed two or 

 three weeks. The compounds containing corrosive 

 sublimate are violent poisons and must always be handled 

 with the greatest care, lest they get into the hands of 

 children or persons unfamiliar with their poisonous 

 properties; they will preserve the milk longer than bi- 

 chromate when applied in sufficient quantities, but for 

 factory use the latter is amply effective and has, as 

 already stated, the advantage in several respects. 



192. Care of composite samples. The composite sam- 

 ple jars should be kept covered to prevent loss by 

 evaporation, and in a cool, dark place, or at least out of 

 direct sunlight; the chromic acid formed by the reducing 

 influence of light on chrornate solutions produces a leath- 

 ery cream which is very difficultly dissolved in sulfuric 

 acid. 



A coating of white shellac has been suggested to pro- 

 tect the labels of the composite sample jars. The shellac 

 is applied after the names of the patrons have been 

 written on the labels, and when these have been put on 

 the jars. Gummed labels, lx2J inches, answer this pur- 

 pose well. 



In keeping the milk from day to day, care should be 

 taken that the cream forming on the milk does not stick 



