36 Svante Arrhenius on Electrolytic 



bability of electrolytic dissociation could be in any degree 

 lessened by the possibility of the phenomena which it explains 

 being in the future deducible from other data (e. g. the exist- 

 ence of known hydrates). If this were actually to occur, then, 

 conversely, the existence of the hydrates could be deduced from 

 these phenomena, and thus indirectly from the theory of dis- 

 sociation, so that new territory would be added to the exten- 

 sive domain already commanded by this hypothesis. 



A striking example of this is found in the hypothesis itself. 

 From his powerful generalization of Avogadro's law, van't 

 Hoff had deduced the conditions of equilibrium for several 

 electrolytes in one solvent, and I had done the same from a 

 consideration of the electric conductivity by means of a hypo- 

 thesis which may be characterized as the imperfectly developed 

 dissociation hypothesis. Immediately after the appearance of 

 this paper by van't Hoff the fusion of the two partially over- 

 lapping theories took place, and it cannot be denied that the 

 fruitful period of both was reached only after their union, and 

 was conditioned by this. Although, therefore, the supporters 

 of the dissociation hypothesis cannot homologate the mode of 

 deduction of the views of the great Russian chemist, they 

 have every reason to wish him the best success in his efforts to 

 explain the above-mentioned phenomena. 

 Leipzig, May 25, 1889. 



Note. — In the last numbers of the - Chemical News,' and 

 of the ' Abstracts of the Proceedings of the Chemical Society,' 

 are reports of a paper by Mr. S. U. Pickering which confirms 

 in the most decisive manner the views I have expressed above. 

 Mr. Pickering (Chemical News, May 27, 1889, p. 278) says 

 that " on plotting out the first differential of his density- 

 results, he was surprised to find that it formed an irregularly 

 curved figure, and not the rectilineal figure given by Men- 

 delejeff ; and he was still more surprised that, on plotting out 

 the values used by Mendelejeff himself, the figure obtained was 

 curvilinear like his own, and not rectilinear like Mendele- 



jefFs Mendelejeff's statement, therefore, that he had 



proved the hydrate theory by showing that the densities dif- 

 ferentiated into straight lines meeting at points corresponding 

 to definite hydrates is erroneous." He then proceeded to a 

 second differentiation, but " owing to the magnitude of the 

 experimental error " did not take the values of ds/dp obtained 

 directly from his observed results, but instead took " the 

 smoothed first differential curve " as his point of departure 

 (Proc. Chem. Soc. May 16, 1889, p. 89). 



In this way Mr. Pickering found that the second derived 



