ON ELECTROLTSIS IN ITS PHYSICAL AND CHEMICAL BEAHINGS. 343 



conducts, the slower usually does its conductivity increase with temperature ; 

 in other words : ' the differences of conductivity of different substances usually 

 diminish at hi<?her temperatures.' 1 Tlie supposition expressed by Arrbenius, that 

 at high temperatures dilute solutions conduct equally well, does not lie beyond the 

 bounds of possibility, but is at present only a hypothesis. 



For common temperatures the law which I derived from Hittorf 's numbers for 

 migration of ions in connection with my observations in conducti\ity, which were 

 independent of this migi-ation, appears to me to contain a simple and natural 

 hypothesis which has proved true for substances with monobasic acids. One must be 

 blind to explain as an accident the systematic ordering of things under this view. 



Now, just a remark concerning some things by Arrhenius, who through the 

 introduction and consequent treatment of the conception of 'activity 'in connection 

 with Clausius's theory, has given us so important a point of view that his meaning 

 must be carefully considered ; especially do I regard as a decided advance the light 

 which has been thrown by his and Ostwald's memoirs upon a hitherto theoretically 

 dark group of bodies, viz., the bodies called by me, ' conductors of the lower order.' 



1 should, however, raise several objections to Arrhenius's radical meaning, that 

 the theory which accepts a connection between internal friction and electrical con- 

 ductivity ought to be rejected.'^ It appears to be a postulate a priori that besides 

 activity some kind of friction must necessarily be accepted ; through the work of 

 Wiedemann and others, it has long been known that usually a lesser conductivity- 

 is connected with a greater internal friction. One cannot deny the nearly quanti- 

 tative connection between the influence of temperature upon the so-called ' fluidity,' 

 and upon conductivity, as shown by Grotrian. The proof which I gave,^ that the 

 supposition of a mechanical and electrolytic frictional resistance of about equal 

 amount, allows the finding of an absolute size of molecules, which approaches the 

 sizes found, by other methods, by Maxwell, Sir W. Thomson, van der AVaals and 

 others, seems to me of no little interest. In fact, the surprising phenomena in gela- 

 tinous substances * and ' solid ' electrolytes must be supplemented by an accurate 

 definition of the idea 'internal friction ' before one can come to the conclusion that 

 electrical resistance and internal friction are totally distinct. 



Since, however, M. Arrhenius tells me that he intends to explain his remarks 

 for himself,^ I shall not enter into detail. 



But I must draw your attention to something else. The supposition which 

 Arrhenius makes in reference to the dissociation of solutions of MgSO^ and related 

 substances,^ is really one special case of the possibility, expressed by me, that water, 

 in extreme dilutions, can take part in the conduction. I have expressly left it an 

 open question whether such a co-operation should consist in the formation of a hy- 

 drate. The hypothesis of Arrhenius is such a possible case. Should this be true, 

 the possibility would thereby be strengthened that the rapid rise of the molecular 

 conductivity of many salts, in extreme dilution, may be referred to a sort of second- 

 ary cause ; MgS04 in solution conducts so much worse than H3SO4, and possibly also 

 than MgOjH.j, that a dissociation of the salt into these substances, even when only 

 a small quantity of the decomposed substance is found, may cause the conductivity 

 to increase considerably. 



M. Bouty's fear ' that by this means ' the calculated numbers on which the 

 discussion hinges would in that case lose all definite meaning,' is a little strained. 

 To my idea such an influence of the water, if it exists, comes only noticeably 

 into consideration in extremely dilute solutions, and in this case perhaps also only 

 in a limited group of compounds. 



I conclude this letter assuring you of my real satisfaction that you, my dear 

 colleague, have given the impulse to collect the newer results on electrolysis. My 

 own conclusions, drawn from phenomena made known to me, did not dare to 

 wander far from matters of fact, knowing myself to be not sufficiently weE 



1 Wiedemann, Ann. VI. 196. 1879. * p. 387. 



2 pp.344 and 348. " p. 311. 

 ' Wiedema7in, Ann. VI. p. 207. 1879. ' p. 340. 

 * p. 347. 



