I02 MILK PRODUCTS 



on which is placed a mixture containing equal 

 parts of anhydrous copper sulfate and pure dry 

 sand to the depth of about s cm., packed loosely, 

 and the upper surface covered with a film of 

 asbestos. On this are placed from 2 to 5 grams 

 of the sample, the mass extracted for five hours 

 with anhydrous ether, then removed and ground 

 to fine powder with pure sand in a mortar. The 

 mixture is replaced in the extraction tube, the 

 mortar washed free from all matters with ether, 

 the washings being added to the tube, and the 

 extraction is continued for ten hours. The fat so 

 obtained is dried at 100° to constant weight. 



Here, as in most extractions, carbon tetra- 

 chlorid can be substituted for ether, but the 

 results obtained are not necessarily equivalent, 

 and in official analyses the official method must 

 be used. 



Total Nitrogen. — This is determined by the 

 Kjeldahl-Gunning method, using 2 grams of the 

 sample. The percentage, multiplied by 6.38, 

 gives the nitrogen compounds. 



Ash. — The dry residue from the water de- 

 termination may be taken for the ash. If the 

 cheese is rich, the asbestos will be saturated there- 

 with. This mass may be ignited carefully, and 

 the fat allowed to burn off, the asbestos acting as 

 a wick. No extra heating should be applied 

 during the operation, as there is danger of spurt- 



