208 Testing Milk and Its Products. 



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



Weight of tube-fbeaker 24.1772 " 



Milk weighed out 5.1232 grams. 



Weight of tube+beaker+milk 29.3004 grams. 



Weight of tube-j-beaker-j-milk, dry 24.9257 " 



Weight of water 4.3747 grains. 



Per cent of water in milk=^^^:=85.39 per cent. 



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

 instead of that of water; this may be readily obtained 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 difference makes. In 

 the above example, the weight of milk solids thus is 

 24.9257 24.1772:=. 7485 grams, and the per cent, of 

 total solids in the milk = 14. 61 per cent. 



251. Alternate method. Five cc. of milk are measured out on 

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

 crucible covers will answer the purpose better than any other 

 vessel on the market, provided the handle be broken off or 

 ground off level on an emery wheel); this is weighed rapidly; 

 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 is obtained. After cooling in 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. 



252. c. Fat. The dried tubes from the water determi- 

 nation are placed in Caldwell extractors and connected 

 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 dissolved; 4-5 hours' ex- 

 traction is sufficient; in case of samples of skim milk it 



