728 ANNUAL EEPORT SMITHSONIAN INSTITUTION, 192 8 



Nernst (1889) to electromotive force was an advance of the first 

 order. Arrhenius himself played a principal part in the develop- 

 ment. Amongst his important contributions to the subject published 

 in Ostwald's Zeitschrift may be mentioned the theory of isohydric 

 solutions (1888), the heat of dissociation of electrolytes and the influ- 

 ence of temperature on the degree of dissociation (1889), the condi- 

 tions of equilibrium between electrolytes (1890), the determination of 

 electrolytic dissociation of salts from solubility experiments (1893), 

 the hydrolysis of salts of weak acids and weak bases (1894), 

 the alteration of the strength of weak bases by the addition of 

 salts (1899). 



At this point it may be well to refer to Arrhenius's position with 

 regard to the problem of the abnormality of strong electrolytes, 

 which, unlike the weak electrolytes, do not conform to Ostwald's 

 dilution law. Naturally this puzzling exception to the theory he 

 had put forward constantly claimed his attention. Although he 

 did not succeed in accounting for it, he had arrived at a clear con- 

 ception of the lines along which a solution might be sought, as may 

 be seen from his book. Theories of Solution, published in 1912 from 

 the Silliman lectures delivered at Yale in 1911. He groups the 

 theories which might be brought forward to explain the anomaly 

 under four headings : 



1. Change of ionic friction with dilution. 



2. Electric attraction of the charges of the ions. 



3. Influence of foreign substances on the osmotic pressure (so- 

 called salt-action). 



4. Hydration of the ions. 



The second of these, with its effect on the first and third, is now 

 recognized as the chief cause of the abnormality. Arrhenius's origi- 

 nal theory is sometimes spoken of as entirely obsolete. But it is well 

 to remember that if the younger men of to-day see a little further into 

 the nature of electrolytic solutions than Arrhenius, they do so by 

 standing on Arrhenius's shoulders. 



During these years Arrhenius also worked on other physico-chemi- 

 cal subjects, for example, on viscosity of pure liquids and solutions, on 

 conduction in hot gases and flames, on diffusion in aqueous solution, 

 on the velocity of hydrolysis of ethyl acetate and on the inversion 

 of cane sugar in acid solutions. In a paper on the last .subject (1889) 

 Arrhenius makes another theoretical contribution of great significance. 

 He is discussing the effect of temperature on reaction velocity which 

 amounts at the ordinary temperature to an increase of 10 to 15 per 

 cent for 1° rise. This is much too great to be accounted for by in- 

 crease of molecular velocity or diminution of viscosity. Besides, the 

 nature of the increase is altogether different from that exhibited in 

 the temperature coefficient of ordinary physical properties. For 



