dealing with the Phenomena of " Clot " Formations. 369 



salt solution a third phase is introduced, so that the total effect of erosive 

 salt action must be studied in a triphasic system. 



The cholate phase of the gel consists apparently of heavily hydrated 

 aggregates of cholate salt which may vary (a) in composition (nature of 

 cholate salt, degree of hydration, etc.), (b) in state of aggregation. It is 

 assumed that it is upon these two factors the stability of the gel structure 

 will mainly depend, and it remains to be considered how they may be 

 affected by the salts in the triphasic system in which the erosion is studied. 

 The possible actions of the salts are considered under six headings. 



I. The Influence of the Salts on the Cholate Component in the Cholate Phase. 

 — In the ordinary method of the formation of the gel, there is a reaction 

 between calcium chloride and sodium cholate. The nature of this reaction 

 is not, so far, clear. It is not an ordinary double decomposition, with the 

 formation of calcium cholate as an insoluble gel-like substance. Such a 

 method of gel-formation has been discovered in another system under 

 investigation by one of the authors of this paper (S. B. S.), who has found 

 that when calcium chloride is added to a solution of the sodium salt of 

 plant pectin (which is an acid) a gel is produced immediately by precipita- 

 tion. The cholate gel, on the other hand, forms only slowly at ordinary 

 temperatures. It is not possible to state at the present what proportions 

 of the cholate are present in the cholate phase as calcium and sodium 

 salts. Probably the reaction between calcium chloride and sodium 

 cholate may be represented in the form of a reversible reaction. 



2C 2 4H 39 5 Na + CaCl 2 ^ (CwHaAOaCa + 2NaCl. 



The addition of sodium chloride in excess, or of other chlorides, would, if 

 this equation truly represents the facts, influence the composition of the 

 cholates formed. Further work is necessary to determine the com- 

 position of the phases produced in the process of gel-formation. 



II. Influence of Salts on the Composition of the Two Phases of the Gel Result- 

 ing from the Establishment of Osmotic Equilibrium between these Phases. — The 

 cholate gel is an example of the special case in which the action of a non- 

 diffusible ion (cholate) holds electrostatically a diffusible one (the metallic 

 ion Ca, K, Na, etc.). The distribution of the components between the two 

 gel phases to establish osmotic equilibrium would probably proceed in 

 accordance with the hypothesis of Donnan, elaborated in the course of his 

 investigations of membrane equilibria and potentials in the presence of non- 

 dialysable electrolytes.* 



III. Influence of the Salts on the Electric Charge on the Particles of the 



* Donnan, 'Zeitsch. f. Elektrockemie,' vol. 17, p. 572 (1911). 



