l66 COMPOSITION OF THE BODY 



treatment with this fluid they may be dissolved in dilute alcohol. 

 The principal examples of this class are gliadin and zein. 



Material which has been extracted with salt solution, should be 

 washed with water to remove the salt, and then 80 per-cent. al- 

 cohol added, which with the water in the material will make 

 about a 75 per-cent. solution. This extraction should be made at 

 a temperature of 40 C. to 50 C. The solvent is drawn off from 

 time to time and fresh alcohol of proper strength added until no 

 more proteid can be obtained. The extracts are filtered and the 

 filtrate evaporated or distilled while the proteid separates from the 

 solution. The precipitate should be purified by treating with abso- 

 lute alcohol, absolute alcohol and ether, and finally pure ether. 

 The portion rendered insoluble in alcohol by this process may 

 be separated by suspending the proteid in 75 per-cent. alcohol until 

 the soluble part is all dissolved, and filtering. The proteid remain- 

 ing in the filtrate may be separated by pouring the alcohol into 

 water, and filtering out the precipitated proteid. 



234. Proteids Soluble in Dilute Acid and Alkali, After the treat- 

 ment of material with the solvents as above described, there may 

 still remain a considerable amount of proteid undissolved, which 

 may be removed by the action of dilute acids and alkalies. By 

 the use of comparatively dilute solutions of acids or alkalies the 

 residual proteid becomes albuminate. It is possible to extract 

 the proteids unchanged in some instances however, if it is done 

 in the cold with very dilute alkali. 



The material from which other proteids have been removed by 

 methods already described is covered with twice or thrice its vol- 

 ume of i per-cent. potassium hydrate. This is allowed to stand 

 for some time at room temperature. The extract is then drawn 

 off and a fresh solution is added. This is repeated at least three 

 times and the extract filtered. The filtrates are neutralized with 

 acetic acid and the resulting precipitate washed with water, alco- 

 hol, and ether and, dried to constant weight. 



These methods will be found sufficient for the separation of the 

 more important proteids. If other and more detailed methods 



