30 MILK 



tion and the powdered salt added to saturation. 

 The mixture is washed into a graduated measure 

 with a small amount of the saturated solution, 

 made up to loo c.c. with the same solution, 

 mixed, and allowed to stand until the separation 

 takes place. As much as possible of the clear 

 portion is drawn off with a pipet and passed 

 through a dry filter. An aliquot portion of the 

 filtrate is taken, the albumin precipitated by a 

 solution of tannin, and the nitrogen in the 

 precipitate ascertained as above. 



The following are A. O. A. C. methods: 

 I . Provisional Method for the Determination oj 

 Casein in Cows' Milk. — The determination should 

 be made when the milk is fresh. When it is not 

 practicable to make the determination within 

 twenty-four hours, add one part of formaldehyd 

 to 2 500 parts of milk and keep in a cool place. 10 

 grams of the sample are diluted with about 90 c.c. 

 of water at between 40° and 42°, 1.5 c.c. of a 

 solution containing 10% of acetic acid by weight 

 added, allowed to stand for five minutes, washed 

 three times by decantation, pouring the washings 

 through a filter, and the precipitate transferred 

 completely to the filter. If the filtrate is not 

 clear at first, it will generally become so in two 

 or three filtrations, after which the washing can 

 be completed. The nitrogen in the washed 

 precipitate and filter is determined by the 



