Properties of a Inquid connected with its Surface Tension 149 
On the Properties of a Liquid connected with its Surface 
Tension. By R. D. KiEEMmAN, D.Sc. (Adelaide), B.A., Emmanuel 
College. 
[Received 18 December 1912.] 
Calculation of the Absolute Mass of the Hydrogen Atom. — 
If no transition layer were formed on a liquid surface the 
equation * 
could be used to calculate the absolute molecular weight mz, of 
a molecule where U denotes the energy expended against mole- 
cular attraction in separating the molecules of a gram of substance 
an infinite distance from one another, p, the density of the sub- 
stance, and i, the surface tension that would exist if no transition 
layer were formed. At low temperatures when the density of 
a liquid is large in comparison with that of its saturated vapour 
U=L the internal heat of evaporation, if the internal energy of 
a molecule is practically independent of the vicinity of other 
molecules, which is very likely the case. But although a tran- 
sition layer is formed the equation may be used to obtain an 
approximate value of the quantity in question. It was found that 
if values of m, are calculated by equation (1) for different tem- 
peratures of a liquid, substituting for 2 in the equation the 
values 2 found in practice, and plotted against the corresponding 
temperatures, the points obtained lie approximately on a straight 
line. Now the effect of the transition layer on the surface 
tension decreases with decrease of temperature+, and at the abso- 
lute zero is probably negligible. According to a formula given 
by the writer? the surface tension at the absolute zero is about 
sixteen times that at room temperature, and the effect of the 
transition layer on the surface tension therefore small according 
to the paper first quoted. An approximate value of the absolute 
molecular weight is therefore given by the intercept of the straight 
lime on the m, axis. 
* Phil. Mag. Dec. 1912, p. 883. 
+ Loe. cit. 
+ Ibid. Jan. 1911, pp. 99—101. 
