204 BACTERIOLOGICAL AND ENZYME CHEMISTRY 



sufficiently well known to permit of a strict ctemical classifica- 

 tion according to their decomposition products. An attempt 

 has, however, been made by Kossel, who divides albumins into 

 four classes, according to their yield of the so-called hexone 

 bases akeady referred to, viz., lysin, arginin, and histidin. 

 Kossel's classification was as foUows : — 



1. Protamins — All rich in arginin, but differing in the 

 amounts of other bases and of mono-amino acids. 



2. Histories — Eelatively high in arginin. 



3. Vegetable albumins. — Poor in arginin and no lysin. 



4. All others containing all three hexone bases and most 

 amino acids. 



The Separation and Extraction of Albumins.— It has 



already been seen when studying the properties of ordinary 

 egg-albumin that it was possible to separate it, e.g., from the 

 associated substance globuhn, by the insolubihty of the latter 

 in water. Further, it was found that whereas albumoses 

 were precipitated by both alcohol and ammonium sulphate, 

 peptones were precipitated by alcohol, and not by ammonium 

 sulphate. The method of precipitation by suitable salts and 

 other substances, if carried out with care, can be used for 

 separating the various albumins one from another. Such a 

 process is known as salting out. 



The salts chiefly used for separation of the albumins are 

 as follows, beginning with the least effective : — 



Class I. Sodium chloride ; 



Sodium sulphate ; 



Sodium acetate ; 



Sodium nitrate ; 



Magnesium sulphate. 

 Class II. Potassium acetate. 

 Class III. Ammonium sulphate ; 



Zinc sulphate. 



