1903.] 



and the Median leal Friction of the Solvent. 



347 



conductivity, so that it may be supposed that the 19 per cent, solution 

 would reach a relatively negligible value at a much higher tempera- 

 ture than the stronger solutions, if it were possible to follow it. 



Mr. Kunz adopts the view that the electrical resistance is clue to 

 friction. It is his opinion, indeed, that the conductivity would disap- 

 pear only at the absolute zero of temperature ; this conclusion can 

 hardly be supported by his observations, as his lowest temperatures 

 are still +200° absolute. 



(8.) The Temperature Coefficients of the Single Ions. — For these* I have 

 recently published values. It is of importance to us that the tempera- 

 ture coefficients of univalent monatomic ions appear to be functions of 

 mobility, decreasing as the mobility increases. Complex and multi- 

 valent ions as groups deviate from this series, so that in this relation- 

 ship we have a new criterion for univalent elemental ions. The largest 

 temperature coefficients of the ions approach that of water. 



(9.) The Electrolytic Resistance Considered as Friction of the Solvent. — 

 In the common view concerning the motion of the ions, an assumption 

 is tacitly made which in other cases we do not consider justifiable. In 

 the relative motions of adjacent particles we assume a discontinuity 

 only in the case of friction between two rigid bodies where this by 

 definition must occur. Even here it is impossible to deny that on the 

 actual surfaces of contact there may be connected with the motion a 

 rubbing away of particles which produces a continuous variation of 

 velocity from one to the other. 



When a fluid is in question, whether in contact with another fluid 

 or with a solid, we concede no finite variation of velocity in two 

 points at an infinitesimal distance from each other. The primitive 

 assumption, until recently held to be correct, in the case of mercury 

 on glass, that the fluid in actual contact with the solid moved with a 

 finite velocity, would demand that the external friction be infinitesimal 

 in comparison with the internal. This is now, to the best of my 

 knowledge, entirely given up.f The idea of discontinuity, however, 

 we employ in regard to the ions when we think of them as moving- 

 through the solvent without connection with it. 



In addition to the objection of discontinuity there exist also the 

 following difficulties in this assumption. In the first place, it is diffi- 

 cult to see how the electrical energy passes into the solvent in the 

 form of heat, unless the latter takes part in the motion of translation. 

 Further, it seems probable, from the fact of the ionisation of the salts, 



* 'Sitz. Ber. d. Berlin. Akademie,' 1902, p. 572. The values here given are 

 strengthened by the fact that a linear connection between a and & {cf. 3) appears 

 a priori in the case of the single ions as well as in the case of electrolytes. 



f Comp. Warburg, 'Pogg. Ann.,' vol. 140, 1870, p. 379. The "slipping" of 

 rarefied gases on solid surfaces, established by Xundt and Warburg, being a 

 separate phenomenon, need not be considered here. 



VOL. LXXI. 2 C 



