418 
Dr. G. Bakker on the 
fig. 2 HGPK presents the theoretical isotherm, and surface 
^HADN gives the absolute value of the integral fi = tydp. 
Fig. 2. 
Surface a SAD ■ Sf. EECS 
ABC ^p t -vCwTv 
VoUijn - Ajcjls 
If the points A and C correspond with the points of the 
spherical surfaces, which limit the capillary layer, the 
equality of the thermodynamical potentials requires there- 
fore : 
Surface NHADN = Surface NKCQN. 
We put: NH = Vx, KN = t? 2 , DA = r/ and QC = i? 2 / , and we 
consider approximately NHAD as a trapezium. We have 
then : 
(v l + v 1 , )(p 1 -p l ) = (v 2 -rv 2 ')(p-p v ). . . (12) 
In this equation v l and v 2 indicate respectively the specific 
volume of the liquid and vapour in contact with a plane 
capillary layer ; v± and v 2 ' on the contrary denote respectively 
the specific volume of the liquid and vapour in contact with 
a capillary layer, which limits a spherical bubble of vapour. 
In the same manner p x indicates the pressure of the vapour 
in contact with a plane capillary layer, while pi and p v are 
respectively the pressures in the liquid and in the vapour, 
when these homogeneous phases are separated by a capillary 
layer, which has the form of a spherical shell. 
From the equations (10) and (11) we may deduce : 
2\ 2 dV 
A dh 2 
R dh 
= /M 1 —fl, 
(10 a) 
where yu : = ^ indicates the value of the thermodynamical 
potential in the liquid. 
By differentiating (10 a), we obtain : 
, 2 ^ 2 V 2\ 2 , dV 
Xd dh*-^L d dh = - vd P> 
