506 
PROFESSOR J. J. THOMSON ON SOME APPLICATIONS OF 
an equation which connects, the alteration in the coefficient of affinity with the 
alteration in the potential energy. 
The layers of gas condensed on the surfaces of solids in contact with the gas may, 
perhaps, be looked upon as corresponding to the surface films of liquids, and as 
possessing energy different from that possessed by the same volume of gas when not 
attached to the sides of the vessel. In this case part of the energy of the gas would 
depend upon the surface of the solids in contact with it, just as in a liquid the 
existence of surface-tension makes part of the energy of a fluid proportional to its 
surface. It is, perhaps, worthy of notice that, according to the vortex ring theory of 
gases, part of the energy of a gas at a given pressure and volume depends upon the 
surface (J. J. Thomson, ‘Treatise on the Motion of Vortex Rings,’ p. 112). If the 
layer of condensed gas were to contain an abnormal amount of energy, we could 
easily explain the influence exerted in some cases of chemical combination by the 
walls of the vessel in which the combination takes place (J. H. Van ’t Hoff, ‘Etudes 
de Dynamique Chimique,’ p. 58), and also the influence exerted by finely divided 
charcoal and platinum where a very large surface is exposed. For the explanation 
given above shows that, if the energy of unit area of the condensed gas varies as 
chemical combination goes on, the action of the surface layer will either promote or 
impede chemical combination. It will promote it if the energy per unit surface 
decreases as combination goes on; impede it, if this energy increases. 
If the specific inductive capacity of the mixture of gases alters as the chemical 
combination goes on, their combination will be effected by placing them in an electric 
field. The chemical action will be checked if the specific inductive capacity increases 
as combination goes on; promoted, if it diminishes. 
§ 12. The equations contained in the preceding investigation express the result of 
actions which are usually termed by the chemists “ mass actions.” These, however, 
have been chiefly studied in the case of very dilute solutions, so that it is important 
to endeavour to apply our results to this case. 
If we regard a solution of one substance A in another B as equivalent to a distri¬ 
bution of the molecules of A through the volume occupied by B, then these molecules 
will behave with respect to each other very much like the molecules of a gas, and 
we may suppose that the value of L is expressed by an equation of the same form. 
This view would have to be modified if the nature of the solvent should be found to 
influence the equilibrium of a mixture of various reagents, and we should have to 
apply the more general method which we shall discuss later on. In those cases, how¬ 
ever, where the solvent is without influence the above assumption that the solvent 
only separates the molecules of the substances dissolved seems legitimate. 
If this be so, the investigation by the Hamiltonian principle of the case, when dilute 
solutions of four reagents, A, B, C, D, act upon each other, is the same in form as that 
investigated on p. 503,%vhere four gases, A, B, C, D, act upon each other. Let us 
suppose that when A acts on B it produces C and D, and when C acts on D it pro- 
