SVANTE AREHENIUS — WALKER 727 



minute quantity of a dissolved electrolyte is dissociated, and that 

 all other physicists and chemists had followed him; but the only 

 reason for this assumption, as far as I can understand, is a strong 

 feeling of aversion to a dissociation at so low a temperature, without 

 any actual facts against it being brought forward. In my paper 

 on the conductivity of electrolytes I was led to the conclusion that 

 at the most extreme dilutions all salts would consist of simple con- 

 ducting molecules. But the conducting molecules are, according to 

 the hypothesis of Clausius and Williamson, dissociated; hence at 

 extreme dilutions all salt molecules are completely dissociated. The 

 degree of dissociation can be simply found on this assumption by 

 taking the ratio of the molecular conductivity of the solution in 

 question to the molecular conductivity at the most extreme dilution." 

 These two short excerpts give the gist of the complete theory. 



Van 't Hoff and Arrhenius now made their ideas available to a 

 wider public by publishing them in the first volume of the Zeitschrift 

 fiir physikalische Chemie in the latter half of 1887. Van 't Hoff 

 accepts Arrhenius's theory for electrolytes and adds finally 

 Avogadro's Law to those of Boyle and Charles as being applicable 

 to dilute solutions. Arrhenius gives the relationship between van 't 

 Hoff's constant i and the degree of dissociation a in the form 

 /=1+ {k — l)a. where k is the number of ions into which the molecule 

 of the electrolyte dissociates, e. g., 2 for KCl, 3 for K2SO4. He com- 

 pares the values of i calculated from Raoult's freezing-point data 

 on the one hand, and from the molecular conductivity on the other, 

 for some 80 different substances, and finds a very satisfactory accord- 

 ance. In the second part of his paper he discusses the properties of 

 electrolytes in aqueous solutions from the point of view of their 

 additive character, which he attributes to the independence of 

 their ions. 



The theories of osmotic pressure and of electrolytic dissociation 

 were now fairly launched, and, propelled by the driving power of 

 Ostwald through the waters of scientific opinion, they soon attained 

 a world-wide recognition, though often meeting very heavy weather. 

 That their reception was so favorable is indeed somewhat surprising, 

 for it must be remembered that in those days the marvels of X rays, 

 of radioactivity, of wireless transmission, had not prepared the way 

 for that loosening and abandonment of fixed physical ideas to which 

 we are to-day accustomed, if not altogether reconciled. Their gen- 

 eral acceptance was largely due to their comparative simplicity. 

 They could be easily tested practically, and little mathematics was 

 required in their development, so that experimental work, centered 

 originally in Ostwald's laboratory but gradually spreading to others 

 in Germany and abroad, was in the next decade assiduously carried 

 out by a new generation of physical chemists. Their application by 



