68 



COLLOIDS IN BIOLOGY AND MEDICINE 



extraordinary degree. This, however, does not depend only upon 

 the electrolytic dissociation of various acids and the concentration of 

 H or OH ions. In the case of strong acids it reaches a maximum 

 at a certain concentration and then decreases. Thus MARTIN H. 

 FISCHER found that fibrin, which swelled to 8 mm. in water, in 

 0.02 normal HC1 reached the maximum swelling of 48 mm. ; whereas 

 in 0.1 normal HC1 the swelling reached only 21 mm. In the case of 

 H 2 SO4 the maximum swelling was only 11 mm. in 0.024 normal acid. 

 Purified glutin (according to the experiments of R. CHIARI in PAULI'S 



FIG. 7. The swelling of fibrin in solutions of various sodium salts 

 (& molecular). (From M. H. Fischer.) 



laboratory) is so sensitive to acids that it swells less in distilled 

 water than an Vienna Hochquellwasser, because of the CC>2 contained 

 in the latter. Furthermore, distilled water may even be distin- 

 guished from conductivity water by swelling experiments with 

 glutin. The swelling in alkalis is still greater; in 0.02 normal NaOH 

 it reached 77 mm. M. H. FISCHER believes that the swelling in 

 acids is dependent upon the concentration of the H ions minus the 

 effect of the anions of the acid under consideration. In this case, 

 there probably exists an antagonism between cation and anion, such 

 as may be demonstrated in the case of neutral salts. A similar rule 

 probably obtains for alkalis. 



