90 THE THEORY OF IONS 



sodium salts decrease in precipitating power from 

 sulphate to sulphocyanate in the order given. It 

 is therefore the metallic ion which precipitates, while 

 the anion inhibits or prevents that action, the ions 

 being antagonistic. Sodium acetate will precipitate 

 protein because the Na ion is too powerful to be 

 inhibited by the acid ion ; but ammonium acetate 

 will not precipitate because the acid ion is more 

 powerful than the metallic ion. 



The effect of the salt is therefore made up of two 

 parts, a cation and an anion effect, and the result 

 is the algebraical sum of the effect of the ions. 

 While bringing about a physical change in the state 

 of the colloid the ions antagonise one another ; one 

 ion has a precipitant, the other a solvent effect, and 

 according as one or the other predominates the 

 colloid is either precipitated or dissolved (or remains 

 in solution) ; and this is called an additive ion-effect.* 

 It is the protein constituent of protoplasm which 

 constitutes the chief point of attack, or which is 

 most readily affected by ions in the organism. It 

 is well known that, in a living organism, the salts 

 are held fast and with great force ; and this affinity 

 is an analogue of the affinity exhibited between the 

 salts and the proteins. There can be little doubt 

 that ion-protein compounds are ever present in the 

 animal organism ; in fact, Pauli states that there is 

 reason to believe that all the protein constituents of 

 the protoplasm enter into the composition of this 

 substance only in combination with ions.f The 

 additive ion effects of the salts show a dependence 

 upon certain quantitative relations. This may be 



* Loc. cit t Ibid -> P- 14 - 



