Chemical Analysis of Milk and Its Products. 221 



Example : Weight of tube-f beaker+milk 29.3004 grams. 



Weight of tube+beaker 24.1772 grams. 



Milk weighed out 5.1232 grams. 



Weight of tube+beaker-fmilk 29.3004 grams. 



Weight of tube+beaker+milk,dry 24.9257 grams. 



Weight of water 4.3747 grams. 



Per cent, of water in milk= 4 ; 3 ! 47 * 10 =85.39 per cent. 



5 . 12*32 



Note. The per cent, of total solids in milk is often 

 given, instead of that of water; this may be readily ob- 

 tained by subtracting the weight of the empty tube 

 from that of the tube filled with milk solids, and finding 

 the per cent, of the milk weighed out which this differ- 

 ence makes. In the above example, the weight of milk 

 solids thus is 24.9257 24.1772=.7485 gram, and the 

 per cent, of total solids in the milk=14.61 per cent. 



252. Alternate method. Five cc. of milk are measured out 

 on a weighed flat porcelain dish (50-60 mm. in diameter; porce- 

 lain covers will answer the purpose well if the handle be broken 

 off or ground off level on an emery wheel) ; this is weighed rap- 

 idly; two or three drops of 30 per cent.-acetic acid are added, 

 and the dish is dried in a steam oven at 100 C. until no further 

 loss in weight occurs. After cooling in a desiccator, the weight 

 of the milk solids is obtained, and by calculation as before, the 

 per cent, of water or total solids in the milk. 



253. c. Fat. The dried tubes from the water deter- 

 mination are placed in Caldwell extractors and con- 

 nected with weighed, numbered glass flasks (capacity, 

 2-3 oz.) ; the extractors are attached to upright Liebig 

 condensers and the tubes extracted with pure ether, 

 free from water, alcohol or acid, until all fat is dis- 

 solved; 4-5 hours' extraction is sufficient for whole 

 milk ; in case of samples of skim milk it is well to con- 



