370 Mr. S. B. Schryver and Miss M. Hewlett. Investigations 



Cholate Phase of the Gel. — It is a well-established fact that the state of 

 aggregation of a colloid is subject to the influence of the charge it carries, 

 and that this charge can be affected by the presence of salt ions. The action 

 of these , is a function of their nature and valency, the multivalent ions 

 exerting the greatest amount of influence. The suspensoid (lyophobe) 

 colloids are more especially sensitive to this particular action of salt ions, 

 but it has been shown by Mines* that the hydrated (emulsoid or lyophil) 

 colloids are by no means insensitive. Preliminary experiments indicate that 

 the cholate gel is affected by the valency of the anions, but experiments 

 dealing with this possible factor are not yet complete. 



IV. The Influence of Salts on the Distribution of Water between the Two 

 Phases of the Gel. — As an extreme instance of the action of salts on the 

 distribution of water between two phases, the salt precipitation of proteins 

 may be quoted. This action is ascribed to the withdrawal of water from the 

 protein phasef and the efficiency of salts in producing such an action is, most 

 probably, a function of their state of hydration in solution. It is conceivable 

 that in a two-phased gel system salts may exert an analogous action (by 

 withdrawing water from the phase containing the larger amount of the 

 substance to which gel formation is clue, in the special case under considera- 

 tion the cholate phase), although the effects may not be so readily 

 demonstrable as in the case of proteins and only be revealed by a detailed 

 analysis of the separate phases. 



V. Influence of Salts due to their Effect on the Surface Tension of Water. — 

 It has been shown that the greater the lowering of the surface tension of 

 water produced by dissolving a given salt, the greater is the disaggregating 

 action of the solution.^ It has already been pointed out that the rate of 

 formation of the cholate gel by different calcium salts is partly a function of 

 the surface tensions of their solutions ; the lower the surface tension of the 

 calcium salt solution, the more slowly does gel-formation take place. In the 

 case of certain calcium salts, gel-formation can be inhibited entirely when 

 the concentration of the calcium salts is sufficiently great. § Some experi- 

 ments on the reversal of the gel by salts, which are not given in detail in 

 this paper, indicate that, at any rate in the second phase of the erosion curve, 

 the action of the salts which markedly lower the surface tension of water is 

 on the whole greater than those which produce aqueous solutions of higher 



* ' Kolloidchemische Beihefte,' vol. 3, p. 191 (1911-12). 



+ See especially Harriette Chick and C. J. Martin, ' Biochem. Jour.,' vol. 7, p. 380 

 (1913). 



| For examples see Schryver, ' Roy. Soc. Proc.,' B, vol. 83, p. 96 (1910). 

 § Schryver, ' Roy. Soc. Proc.,' B, vol. 87, p. 366 (1914). 



