VISCOSITY 



199 



influence on the viscosity of solutions of crystalline egg albumin 

 between pH 4.6 and pH 1.0. With a further lowering of pH the 

 viscosity suddenly rises, a fact to which we shall return later. 



The method of the experiments was as follows: 50-c.c. samples 

 of a 6 per cent solution of isoelectric crystalline egg albumin were 

 mixed with 50 c.c. of HC1 solutions of different concentrations 

 and the pH measured. The solutions were rapidly brought to a 

 temperature of 24C. and the viscosity was measured immediately 

 at that temperature. 



pH 0.8 1.0 .12 1.4 16 l& 2.0 23. 24 26 28 3.0 3.2 3.4 36 3.8 4.0 42 44 



FIG. 49. Showing that solutions of crystalline egg albumin have a low vis- 

 cosity in comparison with gelatin solutions, and that the pH has little influence 

 on the viscosity of solutions of crystalline egg albumin at pH over 1.0 and at 

 ordinary temperature. 



The question then arises, Why do amino-acids and at least one 

 protein, namely crystalline egg albumin, behave so differently 

 from gelatin in regard to the influence of the pH on the viscosity 

 of their solutions? As long as we assume that the influence of 

 the hydrogen ion concentration on the viscosity of gelatin-acid 

 salt solution is due to the hydration of the individual protein 

 ions this difference is incomprehensible, since the amino-acids 

 as well as crystalline egg albumin should in this case show the 

 same influence of ionization on viscosity as the gelatin. 



The puzzle becomes still greater if we take into consideration 

 the fact that the osmotic pressure of solutions of crystalline egg 

 albumin is affected in the same way by the hydrogen ion con- 

 centration as is the osmotic pressure of gelatin solutions (Chap. 

 V). Why then do these two proteins behave so differently as 

 regards the influence of the pH on their viscosity? 



We get an answer to this question by comparing the order of 

 magnitude of the viscosity of solutions of crystalline egg albumin 

 and of gelatin. The viscosity of solutions of crystalline egg 



