THE PRESENT POSITION OF THE 

 HYDRATE THEORY OF SOLUTIONS 



By T. MARTIN LOWRY, D.Sc. 

 Lecturer in Physical Chemistry and Crystallography at the Central Technical College 



PART II.-APPLICATION OF THE HYDRATE THEORY 



TO ELECTROLYTES 



In the previous communication an account has been given of 

 the transformation which Mendeleef's theory of solutions under- 

 went by the introduction into it of the ideas of mass-action and 

 reversibility. This transformation was essential in order to 

 bring the theory into accord with modern conceptions, and has 

 imparted to it a noteworthy increase of vitality. In the present 

 section it is proposed to describe the changes which have taken 

 place in the rival theory of Arrhenius, as a result, mainly, of 

 an increasing recognition of the importance of the solvent in 

 ionisation. These changes, no less than those described in the 

 preceding section, formed an essential stage in the process of 

 reconciling and harmonising the two opposing conceptions of 

 the nature of solutions. 



Arrhenius's Theory of Electrolysis 



In discussing the relationship between ionisation and 

 hydration, it is important to note that the essential feature of 

 Arrhenius's theory of electrolysis is the existence in the con- 

 ducting solution of two types of material, one active in electro- 

 lysis and the other inactive. This view was enunciated and 

 fully discussed in a Swedish memoir as early as 1883 — f° ur 

 years prior to the appearance of the German paper (Zcitschr. 

 phys. Chetn. 1887, i. 631), in which the conclusion was reached 

 that the " active " part of the solute was dissociated into ions, 

 whilst the part which was not thus dissociated was inactive and 

 played no direct part in the transmission of the current. That 

 Arrhenius was not, in the first place, committed to this particular 

 interpretation of his theory is clearly shown by the following 



quotations : 



202 



