290 PHYSIOLOGICAL CHEMISTRY 



the solution vigorously. This will coagulate any unchanged 

 albumin. The metaprotein is not coagulated by boiling in acid 

 solution. Filter if necessary. 



Exactly neutralize the solution of acid albuminate with 0.4% 

 sodium hydrate. A white precipitate should form. This will 

 redissolve in a slight excess of alkali, so that the process of 

 neutralization must be carried on with great care. Filter off 

 the precipitate and wash it once with distilled water. Suspend 

 the precipitate in a small amount of distilled water, and with 

 small portions make the following tests : 



64. Test for loosely combined sulphur. 



65. Add a small amount of 0.4% hydrochloric acid. The 

 precipitate dissolves. Neutralize carefully with sodium carbon- 

 ate. The metaprotein is precipitated. 



66. Add a small amount of 0.4% NaOH. The metaprotein 

 dissolves. Neutralize with 0.4% HC1. It precipitates. 



67. Metaprotein may be distinguished from globulins by the 

 fact that it is insoluble in ammonium sulphate of any concentra- 

 tion, whereas globulins dissolve in ammonium sulphate of con- 

 centrations less than half saturation, and are precipitated only 

 at this latter concentration. 



68. Boil a small portion of the neutral suspension. Cool and 

 add 0.4% HC1. The metaprotein no longer dissolves in dilute 

 acid, it has been coagulated by boiling in neutral solution. Re- 

 call that it is not coagulated by boiling in acid or alkaline solu- 

 tion. 



69. Dissolve the remainder of the acid albuminate in 0.4% 

 HC1. Apply (i) the biuret and Millon tests, (ii) Try precipi- 

 tation with mercuric chloride. Acid metaprotein made from 

 meat is known as syntonin. 



Acid metaprotein is especially interesting from the fact that 

 it is the first product formed in the digestion of proteins in the 

 stomach by the acid gastric juice. 



70. Alkali metaprotein. Although differing in some important 

 respects, many of the properties of alkali metaprotein are similar 

 to those of acid metaproteins. If time permits, it may be pre- 



