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 100 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: 
1. Provisional Method for the Determination of 
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 2500 parts of milk and keepin acool place. 10 
grams of the sample are diluted with about 90 c.c. 
of water at between 40° and 42°, 1.5 cc. 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 
