100 THE ROYAL SOCIETY OF CANADA 
since the heat equivalent of the work due to the forces, is independent of 
whether the force is an externally applied pressure or an internal molecular 
attraction, irrespective of all polymerization in the molecules that cause the 
attraction. This being established, it follows that the ratio 
L 
fie Pav 

will be unity for an isothermal change in volume from a vapour to a 
liquid in which there is no change in the number of the molecules con- 
cerned in the process. 
Unfortunately the value of H as thus determined, being a pure 
energy relation, does not lend itself directly and readily to the determina- 
tion of the molecular weights of liquids as compared with the molecular 
weights of the corresponding vapours; but the relative values themselves 
are interesting and instructive. , Also when applying the theory it is 
necessary to take into consideration the principle disclosed in Clausius’ 
theorem of the virial, that in the case of a liquid one-half the excess heat 
given out represents potential energy and one-half kinetic. That is, 
with the disappearance of the molecular kinetic energy from the substance, 
molecular forces to the same extent also disappear, for when the molecules 
coalesce the potential energy due to molecular attractive forces also disappears 
to the same extent. Since the whole theory turns on this point and is 
likely to be misapprehended, some additional discussion is necessary 
before proceeding to illustrative application of the theory. 
Some Points of Conflict with the Current Theory 
The view of polymerization and of the relation the energy changes 
bear to polymerization presented above is of course incompatible with 
that conception of the kinetic theory which regards molecules as spheri- 
cal masses necessarily separated from each other by a distance equal 
to the two radii and that they collide and rebound from each other like 
billiard balls. On the contrary, it seems to me that the experimental 
facts indicate that the union of two molecules to form one molecule 
requires us to conclude that the two molecules after union have the same 
centre of mass, so that the two molecules after union occupy only the 
amount of space, or volume, previously occupied by each constituent 
separately. The more recently developed theory of the corpuscular, 
or electron, theory of the atom necessitates this view of a molecular 
union, and consequently leads to a different interpretation of the 6 in 
the factor (v — b) of van der Waals’ equation. Coalescence, or poly- 
merization, of molecules affords us a perfectly rational explanation of 
