356 



HEPORT — 1887. 



ture, as is well shown by the observations of Deville and Victor Meyer and Langer 

 that the decomposition of carbon dioxide takes place in porcelain at a temperature 

 several hundred degrees below that at which it occurs in platinum vessels. More- 

 over, there are not wanting chemists who assert that complication, not simplifica- 

 tion,' is the usual antecedent of chemical interchange.' No less an authority than 

 Kekule advocates this view, and I have recently had occasion to discuss its applica- 

 tion in explanation of the laws of substitution in the case of carbon compounds. I do 

 not mean for one moment to assert that anything which we know of the conditions 

 on which chemical change depends negatives beyond question the dissociation 

 hypothesis, but merely that it is possible, apparently, to explain the facts by means 

 of a molecular hypothesis. 



7. It appears to me that an almost conclusive argument in my favour may be 

 based on the results of Lenz's determinations of electric conductivity and diffusivity 

 embodied in the following table, where v is the volume percentage of alcohol, d the 

 diffusivity, and L the conductivity ; the values for an aqueous solution containing 

 half a gram-formula-weight of potassium iodide being put = 100 : — 



It will be observed that the numbers run strictly parallel, except in the case of 

 the cadmium salt ; and here the exception proves the rule, as it is established, 

 beyond doubt, by a variety of consistent observations that the cadmium salts are of 

 exceptionally complicated molecular composition. I entu'ely fail to see how we 

 are to explain liquid diffusion by means of the atomic dissociation hypothesis. But 

 if we assume that the water molecules are in motion, and that having an attraction 

 for the molecules of the dissolved body they necessarily tend to drag them forward, 

 the phenomena are of the same order as those of conduction on my hypothesis. 

 The diminution in conductivity and also in diffiisivity as the amount of alcohol is 

 increased is most striking. If the solvent be neutral the substitution of alcohol for 

 water should have little influence ; but if, as I suppose, the solvent be active, 

 alcohol beino- far less active than water, the effect to be expected is precisely of the 

 nature of that observed. 



8. AVith regard to Professor Lodge's remark, ' It is not easy to imagine why his 

 molecules should be travelling past each other in the fluid,' it is admitted by the 

 orthodox that the E.M.F. gives direction to the atoms. A\Tiy, then, should it not 

 also give direction to the moving molecules if these are still possessed of ' residual 

 affinity ' — i.e., if some portion of the original charge of tlie atom be stiU unueutral- 

 ised ? He then adds, ' nor why, even if they did, this fact should assist their pre- 

 viously incompetent forces to disrupt each other.' Let me put a case. Imagine a 



• This is in harmony with the 'third view ' of electrolysis set forth in my paper 

 (foot of p. 352).- O.L. 



