244 Testing Milk and Its Products. 



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, par. 276.) 



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

 finely in a small porcelain mortar with about twice its 

 weight of anhydrous copper sulfate, 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 sulfate 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 give 

 too low results and, therefore, not to be preferred to 

 the Babcock test for cheese (105). 



287. c. Casein (total nitrogen X 6. 25). About 2 grams 

 of cheese are weighed out on a watch glass and trans- 

 ferred to a Jena nitrogen flask, and the nitrogen in the 

 sample determined according to the Kjeldahl method 

 (253) ; the percentage of nitrogen multiplied by 6.25 

 gives the total nitrogenous components of the cheese. 



288. d. Ash. The residue from the water determina- 

 tion is taken for the ash ; it is preferably set fire to, in 

 the same manner as explained under determination of 

 ash in butter (270), before it is placed in the muffle 

 oven and incinerated. The increase in the weight above 



