14 VETEEINAEY TOXICOLOGY 



concentration and temperature there will be a given pro- 

 portionality between the four components of the system. 

 Hydrolytic dissociation of the type shown is indicated by 

 the marked acidity of the solution to litmus and other 

 indicators. 



The kinds of salt liable to suffer hydrolytic dissociation 

 are — (1) Salts of weak bases and strong acids showing acid 

 reaction — e.g., heavy metal chlorides, nitrates, and sul- 

 phates ; (2) salts of strong bases with weak acids, showing 

 alkaline reaction — e.g., carbonates of the alkali metals ; 

 (3) salts of weak bases with weak acids — e.g., the organic 

 acid salts of the heavy metals, such as zinc and lead acetates. 

 The reaction of such heavy metal acetates is feebly acid. 



It seems not unreasonable to associate irritant effect with 

 hydrolytic dissociation. A solution of zinc chloride contains 

 a fair proportion of free hydrochloric acid, and, similarly, 

 the sulphates contain free sulphuric acid. In support may 

 be adduced the well-known fact that the double alkali 

 chlorides and sulphates — e.g., potassium zinc sulphate, 

 potassium copper sulphate, potassium zinc chloride, are 

 less irritant and are also less hydrolysed than the normal 

 sulphates. On the other hand, mercuric salts are feebly 

 hydrolysed and also feebly ionised, yet they are irritant, or 

 even corrosive, a fact which well illustrates the danger of 

 ascribing to any one property an effect which is jointly 

 due to several factors, the chief of which, in the case of 

 mercury, appears to be the facility with which it forms 

 compounds with proteins. 



But considerations of this kind help us to understand 

 why the double salts — the salts of the weak organic acids 

 and the metal albuminates — are more or less devoid of 

 irritant properties. 



The formation of albuminates and their degree of solu- 

 bility in excess of protein, or in salt solution, are very 

 important factors as regulating the penetration of metals 

 into the cells and tissues, and the speed of their absorption 

 into the circulation. 



By whatever chemical and physical processes the libera- 



