Chemical Analysis of Milk and Its Products. 221 



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

 Weight of tube+beaker 24.1772 grains. 



Milk weighed out 5.1232 grams. 



Weight of tube+beaker+milk.... 29.3004 grams. 

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



Weight of water 4.3747 grams. 



I'or- cent, of \Yater in milk='' •''*''--■'- '*'=S.".:;9 per cent. 



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 oiit which this differ- 

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

 solids thus is 24.9257— 24.1772=.74S5 gram, and the 

 per cent, of total solids in the milk=]4.61 per cent. 



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

 on a weighed flat porcel.Tin dish (50-60 mm. in di.nmetpr; porce- 

 lain ('oxprs will auswcr the purpose ivoll if the liiindlo be broken 

 off cir giiiund off lovol on an emery wheel) ; this is wei};hed rap- 

 idly: two or three drops of 30 per cent.ncotic acid are ailded, 

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

 loss in Wright occnvs. After cooling in a desiccator, the weight 

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

 \>cv 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 npright 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- 



