﻿Molecular Thermodynamics, 229 



" physical " forces, and it is our present conclusion that such 

 forces are capable of forming only transitory associations — 

 ' f episodes in the thermal motion " — essentially different from 

 what we regard as molecules. 



\\ hen, as in the weaker acids and bases almost certainly, 

 we really have partial ionization, or rather partial association 

 of the ions to form u undissociated molecules," the latter 

 must be regarded as produced and held together not by such 

 ordinary electrostatic forces, but by " chemical forces " with 

 the peculiar property already discussed. 



With regard to " strong electrolytes/' the work of Debye 

 and Bragg oives good reason to believe that the molecule in 

 the salt crystal is the ion. If this be so, it appears necessary 

 to admit that the solid salt is essentially a mixed crystal whose 

 special simplicity and homogeneity is due simply to the 

 polarity of the electrostatic forces which dominate its 

 " growth." 



Now, it would seem altogether inconsistent to suppose that 

 the chemical " association " which does not take place in the 

 intimate contact of the solid state, ensues when the ions are 

 dispersed in a solvent, so that until the calculated effect of 

 the electrostatic forces between the ions upon their thermo- 

 dynamic behaviour can be shown to be inadequate when 

 compared with experiment, the " complete-ionization " theory 

 seems the only rational theory for strong electrolytes. 



Another application of the above general conclusions is to 

 be found in the important question of " solvation " of solutes, 

 which is treated in a paper to follow this. 



There occur in the literature of this subject such state- 

 ments or suggestions as that " the solvates need not be 

 definite chemical compounds," and vague theories of the 

 " solvate molecule " as a mere indefinite conglomerate. 

 From the preceding, at any rate, it is our conclusion that, 

 unless the u solvate molecule " is produced and maintained 

 by ' f chemical forces " in the sense already considered, so that 

 it fulfils the requirement of our " rider," it will not, for 

 the purposes of molecular thermodynamics, be a molecule 

 at all. 



With regard to this remarkable characteristic of u chemical 

 forces " which appears to be reduced to its lowest terms in 

 the expression " discontinuity of action," this seems to mark 

 out the problem of molecule formation (including, be it noted, 

 reaction-velocity) as one of those many whose solution may 

 be hoped for from the new quantum- dynamics of phenomena 

 on the atomic scale. Indeed, it is tempting to believe that 

 Bohr's conception of u electron-binding " may be the solution 



