Section III., 1912. [71] Trans. R.S. C. 
Notes on the Molecular Attraction in Liquids and in Liquid Films. 
By M. M. GARVER. 
Presented by JAMES Loupon, LL.D. 
(Read May 16, 1912). 
In a recent paper on “A Thermodynamic Measure of the Degree of 
Polymerization of Liquid Substances” I was led to the conclusion and 
so stated, that the tensile strength of liquid films is independent of the 
mass of the attracting molecules constituting the film. In other 
words, that although polymerization of the molecules constituting the 
film increased the density of the liquid in the film yet the tensile strength 
of the film was not increased by the polymerization but depended only 
on the number, irrespective of the mass, of the individual molecules. 
This conclusion seems to be so at variance with all the ordinary con- 
ceptions of what constitutes molecular attraction in liquids that a special 
examination of the grounds for such a conclusion seems necessary. 
The basis for the statement and conclusion is found in the following 
equations which seem to be established beyond successful dispute, 
namely: 
where w is the vapor pressure, ¢ the vapor density, R the general gas 
constant, m the molecular weight, T the absolute temperature, y the 
surface tension, p the liquid density and 7 the thickness of the liquid 
film. 
If the above equations are generally applicable to a homogeneous 
substance at ordinary temperatures at which the substance exists in 
either of the two fluid phases, then we are obliged to conclude that at- 
traction in the film is independent of the polymerization. It therefore 
seems necessary to conclude that a heavy polymerized molecule exerts 
no more attraction in the film than a lighter, less complex one, if p and m 
vary proportionally. But p and m can vary proportionally only if a 
polymerized molecule occupies the same volume as a simple molecule, 
unless we are permitted to suppose that the thickness of the film varies 
inversely with the density p. This seems to be a highly improbable 
