274 
MR. J. LARMOR ON A DYNAMICAL THEORY OF 
seem impossible to imagine that its electrolysis, if it remains of normal type, is 
conducted through a mechanism like Grotthus’ chains ; the dissolved molecules are 
far out of each others range of influence, and the very first stage of the working of a 
Grotthus’ chain containing molecules of the solvent would produce that dissociation 
Vv'hich it is the object of the chain theory to evade. Similar considerations apply to 
the velocity of chemical reactions. When a solution of K.HO neutralizes one of 
HCl, the heat generated is mainly that of the union of H and HO to form H^O ; 
when the solutions are very dilute this should take a considerable time to develope, 
even allowing for intimate mixture by stirring, if each H had to find its HO partner 
directly. The immediate reaction must therefore be due to a mobile equilibrium of 
dissociation being disturbed by the mixing of the solutions, and then re-establishing 
itself.^' Thus in the progress of an ion H through the water under the electric force 
in electrolysis, it would not be the same H that is driven on, but that ion often gets 
fixed liberating another one in its place, so that it is the mean translation of a 
condition of matters in which there is a definite number of H ions in the element of 
volume that is given by Kohlrauscti’s law, not that of an individual ion. This 
accords with Whetham’s interpretation of his result, that in acetic acid solutions, in 
which the conductivity is abnormally low, the ionic velocity is abnormal to an 
equal extent.t 
59 . A principle quite analogous to the one on which van’t Hoff s law has here been 
based, has already been applied to a cognate phenomenon in authoritative investig¬ 
ations. The transpiration of two different gases into each other across a porous 
partition establishes a difference of pressure ; there is thus present a store of available 
energy, which would be run down in the mixing of the gases; its amount, as 
originally determined by Lord Kayleigh from the special properties of gases, is 
obtained by finding hoAV much free energy runs down when the gases are each 
separately expanded to the volume of the mixture, and adding these amounts. This 
result, either in the present form or expressed with reference to entropy, has been 
sanctioned, explicitly or tacitly, as axiomatic by Maxwell^; and other authorities, 
when apYjlied to gases whose molecules do not exhibit sensible mutual attraction: the 
change of configuration arising from the two mutually independent systems occupying 
the same space, instead of different ec[ual spaces, is rightly held to involve no change 
in the available energy. The principle above employed is of precisely similar 
nature. 
If we imagined two gases in which the molecular mass differed only infinitesimally, 
* In the same way, if a gaseous reaction were of ternary type, so tliat three atoms or ions had to 
unite to form a molecule, it must proceed far more slowly than a binary reaction, and may not get 
established at all, except by the help of the catalytic action of some other substance, snch as water 
vaponr, in reducing it to binary stages or facilitating the simultaneous presence of the three kinds of 
atoms in the same molecular sphere of action. 
t W. C. D. Whetuaji, “ Solution and Electrolysis,” 1895, pp. 142, 155. 
J ‘ Encyc. Brit.,’ Art. “ Diffusion” : Collected Papers, 11., p. 644. 
