Chemical Analysis of Milk and Its Products. 229 



inches long, closed at the bottom by a layer of stringy 

 asbestos, and filled two-thirds full of asbestos prepared 

 as for milk analysis (252). The tubes are dried at 

 100 C. in a water oven, until no further loss in weight 

 takes place, and are then cooled and weighed. The loss 

 in weight shows the per cent, of water present. 



267. b. Fat. The tubes are placed in Caldwell ex- 

 tractors and extracted for four hours with anhydrous 

 ether ; the ether is then distilled off, and the flasks dried 

 in the steam bath and weighed,, the increase in weight 

 giving the fat in the samples of butter weighed out. 



268. c. Casein. 10 grams of butter are weighed into 

 a small beaker provided with a lip, and treated twice 

 with about 50 cc. of gasoline each time; the solution is 

 filtered off, and the residue transferred to a filter and 

 dried; its nitrogen content is then determined by the 

 Kjeldahl method (255). The nitrogen in the filter and 

 the chemicals used is determined by blank trials and 

 deducted. The nitrogen multiplied by 6.25 gives the 

 casein in the butter. 



269. d. Ash. (1) 10 grams of butter are weighed 

 into a porcelain dish and treated twice with gasoline, as 

 in the preceding determination; the solution is filtered 

 through an ash-free (quantitative) filter, and the filter 

 when dry is transferred to the dish. The dish is heated 

 in an air-bath for half an hour and then placed in a 

 muffle oven, where the contents are burnt to a light 

 grayish ash; the dish is now cooled in a desiccator and 

 weighed. The difference between this weight and that 

 of the empty dish gives the amount of ash in the butter 

 weighed out. 



