254 PHYSIOLOGICAL CHEMISTRY 



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 : 



(3) Test for loosely combined sulphur. The result should be 

 positive. 



(2) Add a small amount of 0.4% hydrochloric acid. The 

 precipitate dissolves. Neutralize carefully with sodium carbon- 

 ate. The metaprotein is precipitated. 



(3) Add a small amount of 0.4% NaOH. The metaprotein 

 dissolves. Neutralize with 0.4% HC1. It precipitates. 



(4) 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. 



(5) 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. 



(6) Dissolve the remainder of the acid albuminate in 0.4% 

 HC1. Apply (i) the biuret and Millon tests. Results should be 

 positive, (ii) Try precipitation 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. 



ii. 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- 

 pared in the same manner as acid metaproteins, using 0.4% 

 sodium hydroxide in place of the acid. Its properties are similar 

 to those of acid metaprotein, with the exception that it gives a 

 less definite neutral sulphur test, as a portion of the sulphur is 

 split off in its manufacture. 



'(c) Coagulated Proteins. These protein derivatives are pro- 



