( 169 ) 
7 : scab 
or, if we substitute 4 for —: 
7, 
r r 
den we Ba x R R 
nod? ae r i Rien (RA) a 
Je 
Starting from the function ¢ (7) = f= : (Thermodynami- 
sche Theorie der Kapillar. Zeitschrift für phys. Chem. XIII, 4, 
1894 p. 721) Prof. van DER WAALS finds: 
>| 
a =) 
‚he En OLON 
P= = ta folk — 
a 
The coefficient is the same as in the more general form of the 
potential function. If we take the more general expression 
r fi 
Ae” r+ Ber ; 
g(r) = E sn “for B=0 and A = — f, we get the function 
of VAN DER WAALS. 
The theory of capillarity requires forces, which decrease with the 
distanee and are attractive. The latter condition furnishes: 
— g'(r) negative or p'(r) positive. 
We have: 
Agee ie Be etree Bex 
Pp (r) = — r2 dn a Àr 
So: 
aes bd Lie, r 
aient) 
for all positive values of r. 
If we take r=A, we get: 
ea < Be @ 
€ 
from which follows that A must be negative. Put A==—/, in 
which f represents a positive value, the last inequality but one 
becomes : 
—fe~3(14+7) < Bex (4-1) 
