ON ELECTEOLTSIS. 351 



electrical resistances there may be a certain relation ; though the numbers, as may- 

 be expected, show considerable differences (if we put these constants for HCl 

 equal to 100, they are for some other acids 65-1 and 73-4, 79-9 and 91 74-6 

 and 104). 



It seems to be very difficult, even if possible, to study both conditions which 

 determine the velocity of the formation of compounds separately, and then compare 

 only the resistance to their formation with the resistance opposed to their ions 

 during the passage of the current. 



So we see that a great deal of work has yet to be done in electrolysis, and I 

 hope that the impulse given by the Committee of the British Association will 

 mightily contribute to advance our knowledge in this most complicated and 

 difficult problem. 



Comparison between the Views of Dr. Arrhenius and Professor Armstrong 

 on Electrolysis. By Oliver Lodge, F.B.8. 



It may be convenient to summarise the main views of Professor Armstrong con- 

 cerning electrolytic conduction, as expressed in his Royal Society Memoir (Proc. 

 Royal Society, No. 243, 1886). He discards the view of exact equivalence between 

 the positive and negative atoms of a compound, considering that no ordinary mole- 

 cule is really saturated, but that its electro-negative element has an unsatisfied or 

 residual affinity, with which it is ready to cling on to fresh atoms or to other 

 molecules. By means of these residual affinities of unsatisfied atoms he imagines 

 molecular aggregates to be built up. And he considers a concentrated substance 

 in the liquid state to be largely or wholly composed of these complex molecular 

 aggregates, each in a nearly or quite saturated, and therefore inert, condition. The 

 effect of dilution, however, is to break up these aggregates into simpler molecules 

 until, in an extremely dilute solution, the molecules may be as separated and as 

 simple as they are in the gaseous state. 



So far the views of Arrhenius ' somewhat correspond. Without any doctrine 

 of residual affinity as accounting for them Arrhenius also postulates the existence 

 of molecular aggregates, which he imagines to be broken up by dilution ; but he 

 goes further, and imagines a certain number of the molecules themselves broken 

 up by dilution into their constituent atoms, i.e., he postulates real dissociation after 

 the manner of Williamson and Clausius, a hypothesis for which Professor 

 Armstrong sees no necessity, and to which he apparently perceives some chemical 

 objection. 



The dissociated molecules are called by Arrhenius the * active part ' of the 

 liquid, and are believed to be the only ones which take part directly either in 

 chemical action or in electrolytic conduction. These are the molecules which are 

 constantly exchanging their atoms, either with each other or with foreign mole- 

 cules, and so give rise to double-decomposition and ordinary chemical action. All 

 other molecules, having their atoms firmly combined, are inert. Heating and 

 dilution increases the active portion, i.e., the proportion of dissociated molecules 

 and thus intensifies at the same time the chemical power and the electrolytic con- 

 ductivity of the compound. To every state of temperature or admixture, a certain 

 proportion exists between the active and inactive molecules of a given substance • 

 and thus its ' activity ' or * avidity ' in chemical reaction, as well as the current it 

 can convey under the influence of a given E.M.F., i.e., its conductivity, is re- 

 gulated and determined. The velocity of chemical action between the mixed 

 substances, i.e., the rate at which their molecules interchange atoms, can thus be 

 calculated in arbitrary time-units from a knowledge of the conductivity of the con- 

 stituent substances ; and the final state of equilibrium is obtained by putting this 

 rate equal to zero. 



The special point of Arrhenius 's paper is therefore not any peculiar view which 

 he holds regarding the nature of electrolysis, for his view is a perfectly orthodox 



' ' Recherches snr la Conductibilite galvanique des Electrolytes (152 pages) 

 par Svante Arrhenius. Mem. presente a, I'Acad. des Sciences de Suede le 6 Juin' 

 1883.' Abstract and semi-translation appear in last year's B A. Eeport. 



