240 Testing Milk and Its Products. 



then placed in ice water, and the milk (or water) stirred 

 until the temperature falls sufficiently for the fat to 

 congeal. If oleomargarine, the fat can now be easily 

 collected into one lump by means of the stick, while if 

 genuine or renovated butter, the fat will granulate and 

 can not be so collected. 1 



D. CHEESE. 



For method of sampling, see p. 104. 



285. a. Water. Five grams of cheese cut into very 

 thin slices are weighed into a smdll porcelain dish filled 

 about one-third full with freshly-ignited stringy asbes- 

 tos ; the dish is placed in a water oven and heated for ten 

 hours. The loss in weight is taken to represent water. 

 (See also Dean's method for determining water in but- 

 ter, curd and cheese, p. 234). 



286. b. Fat. About 5 grams of cheese are ground 

 finely in a small porcelain mortar with about twice its 

 weight of anhydrous copper sulf ate, until the mixture is 

 of a uniform light blue color and the cheese evenly dis- 

 tributed throughout the mass. The mixture is trans- 

 ferred to a glass tube of the kind used in butter analysis 

 (263), only a larger size; a little copper sulf ate is placed 

 at the bottom of the tube, then the mixture containing 

 the cheese, and on top of it a little extracted absorbent 

 cotton or ignited stringy asbestos; the tube is placed in 

 an extraction apparatus and extracted with anhydrous 

 ether for fifteen hours. The ether is then distilled off, 

 the flasks dried in a water oven at 100 C. to constant 

 weight, cooled and weighed. The method is apt to 



i For tests for artificial coloring mattepin oleomargarine, see Olrc. 

 629, Oom. of Internal Rev., Treasury Dept. 



