THE VOLATILE PART OF PLANTS. 95 



Gluten- Casein. That part of the gluten of wheat 

 which is insoluble in cold alcohol is digested in a highly 

 dilute solution of potash, and the clear liquid is made 

 faintly acid by acetic acid. The curdy white precipitate 

 thus obtained, after washing with water, alcohol and 

 ether, and dried, is the gluten-casein of Ritthausen. It 

 is insoluble in water, and in solutions of common salt, 

 easily soluble in weak alkalies and coagulated by acids. 

 Eitthausen obtained this body from wheat, rye, barley; 

 and buckwheat. 



Legumin is the name that has been applied to the chief 

 albuminoid of oats, peas, beans, lupins, vetches, and other 

 legumes. It is extracted from the pulverized seeds by 

 dilute alkalies, and is thrown down from these solutions 

 by acids. From some leguminous seeds it may be partially 

 extracted by pure water, probably because of the presence 

 of alkali-phosphates which serve to dissolve it. It is 

 generally mixed with conglutin, from which it may be 

 separated by soaking in weak brine (a 5 per cent solution 

 of common salt). Thus obtained, it is insoluble in pure 

 water and in brine, but soluble in dilute alkalies, and has 

 a decided acid reaction. Legumin, as existing in the 

 horse-bean ( Viciafaba), is soluble in brine, but after solu- 

 tion in alkali and precipitation with acids, is insoluble 

 in salt solution. The casein, animal or vegetable, that 

 is thrown down from salt-solution by acids is evidently a 

 chemical compound of the original proteid with the acid 

 (acid-proteid). 



EXP. 52. Prepare a solution of vegetable casein from crushed peas, 

 almonds, or pea-mils, by soaking them for some hours in warm water, 

 1o which a few drops of dilute ammonia-water or potash-lye has been 

 added, and allowing the liquid to settle clear. Precipitate the casein 

 by addition of an acid to the solution. 



The Chinese are said to prepare a vegetable cheese by 

 boiling peas to a pap, straining the liquor, adding gypsum 

 until coagulation occurs, and treating the curd thus ob- 

 tained in the same manner as practiced with milk-cheese, 



