CHEESE 69 



with asbestos, and on this place a mixture containing equal 

 parts of anhydrous copper sulfate and pure dry sand to the 

 depth of about 5 cm., packing loosely, and cover the upper 

 surface with a film of asbestos. On this are placed from 2 to 5 

 grams of the sample, the mass extracted for 5 hours with anhy- 

 drous ether, then removed and ground to fine powder with pure 

 sand in a mortar. The mixture is placed in the extraction 

 tube, the mortar washed free from all matters with ether, the 

 washings being added to the tube, and the extraction is con- 

 tinued for 10 hours. The fat so obtained is dried at 100 to 

 constant weight. 



Here, as in most extractions, carbon tetrachlorid can be 

 substituted for ether, but the results obtained are not neces- 

 sarily equivalent. 



Total Nitrogen. This is determined by the Kjeldahl- Gun- 

 ning method, using 2 grams of the sample. The percentage, 

 multiplied by 6.38, gives the nitrogen compounds. 



Ash. The dry residue from the water determination may 

 be taken for the ash. If the cheese be rich, the asbestos will 

 be saturated therewith. 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 spurting. When the flame has died out, 

 the burning may be completed in a muffle at low redness. 

 When desired, the salt may be determined in the ash by titra- 

 tion with silver nitrate and potassium chromate. 



Provisional Method for the Determination of the Acidity in 

 Cheese. Water at a temperature of 40 is added to 10 grams 

 of finely divided cheese until the volume equals 105 c.c., agitated 

 vigorously, and filtered. Portions of 25 c.c. of the filtrate 

 corresponding to 2.5 grams of the cheese are titrated with deci- 

 normal solution of sodium hydroxid, using phenol-phthalein 

 as indicator. The amount of acid is expressed as lactic acid. 



The above processes may be advantageously modified in 



