THE CHEMISTRY OF ALBUMINS 205 



The members of each class are more or less equivalent in 

 precipitating power, but whereas, e.g., sodium chloride will 

 not precipitate egg-albumin, ammonium sulphate will not 

 only precipitate egg-albumin, but also its primary disintegra- 

 tion products, viz., albumoses. 



In making salting- out experiments it is important that the 

 concentration of the albumin solution shall not be altered. 

 Thus, for example, to study the effect of various concentra- 

 tions of any salt on an albumin solution, a number of test- 

 tubes, each containing 2 c.c. of the albumin solution, may be 

 taken, and 8 c.c. of a mixture, in varying proportions, of 

 distilled water and a saturated solution of the salt under 

 observation. 



By experiments of this sort it has been found that the 

 operation of salting out is subject to the following well-defined 

 laws: — 



1. The degree of concentration of any salt necessary for 

 the precipitation of any particular albumin is character- 

 istic for that body. If, for example, a serum solution is 

 precipitated with ammonium sulphate, it has been found 

 that the globuhn begins to come down when ammonium 

 sulphate is present to the extent of 24-29 per cent, of 

 complete saturation. The albumin does not begin to be 

 precipitated until the degree of saturation reaches about 

 64 per cent. 



2. If one albumin is precipitated by a lower degree of 

 concentration than others of any given salt, a propor- 

 tionally lower concentration will also be efEective with other 

 salts. 



Thus, in the example just given, if zinc sulphate were used 

 instead of ammonium sulphate, less of it would be required 

 to precipitate the globuhn than the albumin. 



3. The limits between which precipitation commences 

 and finishes on addition of a salt to a solution are numbers 

 characteristic for each albumin. Thus the precipitation of 



