1917-18.] 
Thermodynamics of Adsorption. 
27 
formed out of contact with the gas. For this surface let a — <j 0 and A = A 0 . 
Let the surface contract so that it has minimum surface negligible, we 
will suppose, compared with A 0 . Let it now be introduced to the gas and 
expanded to A at P, T. The total change of energy is given by 
dg 7 p, t 
and the heat of immersion will therefore be 
A P " = A 
(ii') 
cr„ — — A(V P — T^°’ 1 
0\ "0 
d T 
dT 
If we use equation (9) to define a, we can replace a in the above 
expressions. Thus 
r= - 
— °"o 
1 da 
V dp 
p 
W dp 
(9) 
.'0 
aV 
dp 
o A 
-p 
A J p 
RT f P adp 
assuming A constant and pV = RT. 
Again, since 
RT [ P adp 
<r P - a 0 = - 
A Jo p 
r r f plP 
a 
A Jo p/P 
dp/P 
dan — 
c r. 
dT 
p/p 
Now 
R p /p a , /T) RT f p/p /da\ dp/P 
-A 1 PP cWP ~A.L (wLw 
R f p a RT f p / 0a\ dp 
~ A Jo p P ~ Tjo \dij p /pj ‘ 
/da 
\ /da\ /da\ /0p\ 
V0T Jp/p \8T/p + \S pk' \3T/j>/p 
A (?P'\ 
0p/ r r\3T/a 
da \ p dP 
dp )\ 
P dT 
or 
- ET \f ( - ? 1 4 S4 
= RT 2 r d -^SJ } da - Ifl A lQ g F . 
0T dT 
a T 
( 12 ) 
This equation for the heat of immersion is derived on the assumption 
that pV = RT and A does not vary, and might have been expected from 
the analogy with solution. Expressions for the heat of immersion when 
