( 534 ) 
or €, is zero in the homogeneous layer. Instead of the former 
formula we may put 
2 
x 
dn 
Dy == Ph = SBB Of Ede en a an 
de 
Zh 
Introducing now for «,, the series that follows from (6) and (6’) we 
find for the pressure 
*dn d?sn 
d°sn; 1 doe des 
i Pi WR Oe JW Cop | ——— dz. 
es ‚a de 2 (5) di dz dzs VEE 
00 
9 
zh 
It follows from the above reductions that we obtain for the 
C dn, erde 
Px =P Ny - == 
Pe BN as Ni Bere, ago ae ) + 
S= 0 A=s—l 
pressure p‚ 
In, d2s—*n, 1 dn, \? 
= Ra Oy ae “na anak me heee (VL 
S= 2 A= 
An approximation for p, may be obtained by breaking eff the 
series at s=1: we then find a formula, which agrees with one 
given by VAN DER Waats namely 
d De L fan, \* F 
Pr = Ph + Caf nx de = a ae ts 
1) In order to reduce the integrals contained in the sum, we have the formula 
Zr Zr 
dn ds dn, d*s—! n, In d2s—1y 
— == de = SS he ee 
dz dz?s da, dee! dz* de?! 
Zh Zh 
Where the remaining integral may again be transformed by the same operation. 
In this way we are finally led to a term in which the integration may be per- 
formed namely 
den ds+1n (—1)s (dsn,\? 
nf a ; 
des des! Br Ades 
zh 
It follows from (VIII) together with the above reductions that by integrating 
from the one homogeneous phase Aj to the other /, we obtain: 
Ph, = Pho 
which is the well kwown condition for thermodynamical equilibrium. 
