60 3nn' and Its Products. 



it will frequently be noticed that the cream is not 

 thoroughly broken up. Under such conditions, extra 

 precautions must be taken to secure perfect sam- 

 pling. 



Composite sampling. — In testing milk at factories, 

 it is more convenient to take a sample every day, 

 and make one test of the mixed samples at the end 

 of a week, ten days or two weeks. In order to do 

 this, it is necessary to provide a suitable receptacle 

 for the milk of each patron. ( Pint lightning -top 

 fruit jars or milk bottles, or glass -stoppered sample 

 bottles, are most convenient. ) To these bottles is 

 added each daj^ a small portion of each patron's 

 milk, together with some preservative for preventing 

 the milk from souring. The preservatives in com- 

 mon use are bichromate of potash, corrosive subli- 

 mate, and milk preservaline. Caustic potash and 

 soda may also be used. Neumann* claims to have 

 had as good results with sodium nitrate as with 

 bichromate of potash. Most of these substances are 

 poisons, and render the milk unfit for use ; the jar 

 should, therefore, be plainly labeled. For many 

 reasons the bichromate of potash is to be preferred. 

 It gives a distinct color to the milk, and only a 

 small ciuantity of it is necessary to prevent the milk 

 from souring. Whatever preservative is emploj'ed 

 should only be used in quantity sufficient to keep 

 the milk from thickening. Of the bichromate of 

 potash, an amount sufficient to color the milk a bright 

 lemon yellow is all that is necessar3\ In taking 



♦Milch Zeitung, vol. xxii. p. 526. 



