SVANTE ARRHENIUS WALKER 719 



ideas which Arrhenius developed in the second part. Instigated and 

 encouraged by Otto Pettersson, then professor of chemistry in 

 Stockhohn, Arrhenius greatly expanded this theoretical section, which 

 contains the germ of the ^ater theory of electrolytic dissociation. 

 He bases his theoretical treatment on the hypothesis of Williamson 

 and Clausius. How this hypothesis presented itself to a clear 

 and critical contemporary mind, unacquainted with the work of 

 Arrhenius, may best be gathered from the admirable report on 

 electrolysis presented by Oliver Lodge to the British Association in 

 1885. 



Lodge writes : " No polarization exists inside a homogeneous 

 electrolyte; there is no chemical cling of the atoms there, but only a 

 frictional rub. Such a fact as this, if well established, renders neces- 

 sary some form of dissociation hypothesis. The form of dissociation 

 hypothesis suggested by Clausius and Wi^iamson is well known. It 

 supposes that the vast majority of molecules in an electrolyte are 

 quite insusceptible to the influence of electrodes, but that a few of 

 them (the number being increased by complexity of composition and 

 rise of temperature) are, by collision or otherwise, dissociated and 

 exist in the free atomic state, each atom with its appropriate charge. 

 These alone feel the influence of the electrodes. . . . Individual 

 atoms, although permitted to combine as soon as they like, on this 

 theory, are commonly thought of as existing in the dissociated state 

 for a finite time. If there are chemical or other objections to such 

 a view, it need not be held; all that the facts of electrolysis require 

 is the most momentary dissolution of partnership — temporary but 

 quite perfect freedom. . , Provided a sufficient supply of such 

 temporary severances occurs throughout the liquid, no individual 

 atom need remain uncombined for a thousandth of a second, so far as 

 the phenomena of electrolysis are concerned." 



Arrhenius derives from the hypothesis the notion of closed circu- 

 lar currents in the electrolytic solution in its normal state (i. e., when 

 not undergoing electrolysis) which are due to the separation of the 

 ions and their recombination with other than their original partners. 

 This notion he uses in dealing with the equilibrium between elec- 

 trolytes in aqueous solutions. But by far the most important original 

 idea, on which he bases his further treatment, is that of the distinc- 

 tion of the dissolved molecules into active and inactive. He arrives 

 at it in the following way. A solution of ammonia exhibits a 

 feeble molecular conductivity which increases with dilution. This 

 Arrhenius attributes to the progressive conversion of the non- 

 electrolytic NH3 into the electrolytic NH^OH as dilution is increased. 

 He proceeds : " It has been shown that pure anhydrous hydrochloric 

 acid is a nonconductor, that is, a nonelectrojyte. If water is added 

 ,to it, it is converted into an electrolyte, naturally in a progressive 



