4 PHYSIOLOGICAL AND PATHOLOGICAL CHEMISTRY. 



casein and fat put the casein containing the fat into a dry 

 flask with about 100 cc. of ether, shake thoroughly, allow to 

 stand twenty-four hours, and then filter. 



The casein remaining on the filter (C) is washed once more 

 with ether, then pressed between filter-paper, and ground in 

 a mortar until the casein, still containing some fat, forms a 

 white dry powder. 



The ethereal solution (D) is poured into the evaporating- 

 dish in which the alcohol extract was. evaporated and the 

 solution allowed to evaporate spontaneously, taking care that 

 the ether vapor does not come into contact with a flame. 

 Finally it is separated from a small residue of water, alcohol, 

 and ether by evaporating on the water-bath. Thus we ob- 

 tain the butter -fat. 



The fluid (B) separated from the casein is filtered through 

 paper and then evaporated about one-half at the boiling- 

 point in a tinned vessel or in an enamelled-iron dish. The 

 albumin (E) precipitates in coarse white flakes ; it is filtered 

 off and washed a few times with hot water. The filtrate from 

 the albumin is evaporated further over a free flame until it 

 begins to bump. The bumping is due to the separation of 

 calcium phosphate (F). Filter once more and evaporate on 

 the water-bath; the sirupy solution yields an abundant crop 

 of milk-sugar crystals when allowed to stand till next day. 



PROPERTIES AND REACTIONS OF THE CONSTITUENTS OF MILK. 

 i. Coagulated Albumin (E). 



GENERAL REACTIONS OF THE COAGULATED ALBUMINS. 



1. Xanthoproteic Reaction. A portion of the substance 

 the size of a pea is heated in a test-tube with concentrated 

 nitric acid (sp. gr. 1.2). The albumin turns yellow and at the 

 same time a yellow solution is formed. When perfectly cold 

 supersaturate with caustic soda solution. The color turns to 



