158 
CHEMISTRY: W. D. HARKINS 
and similar relations hold for any molecule of the polar-nonpolar type with 
reference to the pair of interfaces, polar Hquid-vapor, and polar Hquid-less 
polar liquid. Similar work is now in progress, a metal being used as one of 
the phases, and vapor, water, or an organic hquid as the other. The results 
of this work are very interesting, but space is wanting for their discussion. 
They indicate that, corresponding to the greater drop in intensity of the 
stray field between metal and vapor, in comparison with that between water 
and vapor, the adsorption at the metalhc surface is much greater than that at a 
water surface for the same concentration of the adsorbed component in the 
nonmetallic phase. 
0— 
— o-*.^ 
\ \ 
\ \ 
\ 
\ b 
BUTYRIC -AC 
\ 
N 
\ 
\ 
\ 
ID 
\ v — 
^ V 
\ > 
\ 
\ 
9 
\ 
\ 
A striking result obtained was that the number of molecules per square 
centimeter in the 'constant concentration' film between water and benzene 
was found to be 2.79 X 10^^, while that between water and air was found to 
contain 2.77 X 10^^ molecules, showing that the number of molecules in 
such a film is independent of the presence of the second liquid phase, and 
therefore depends only on the dimensions of the molecules. 
These results were obtained by the drop weight and capillary height 
methods for determining surface tension, as they have been developed in 
this laboratory. For such work a high degree of precision is essential. The 
results for butyric acid are presented in a graphic form in Figure 1, where 
