
Diffusion in Solution of Dissociated Gases. 273 
The rate of flow through the unit area of the slab is therefore 
ek ( dC bende }= fn f ‘(x fe K& No" 
Chdaleidks, ae pea 
This expression is independent of 2, and therefore satisfies 
the equation of continuity. 
The most important case that arises is when the diseeia- 
tion is small outside the solution. In this case we may take 
1 


A,=(koP)", when the equation for the distribution of the 
gas ei 
“e+ te 4-5 )s "Bs —S el 
pin A 
We see ov wt total te consists of two terms, one of which 
is directly proportional to the pressure, and the other to its 
nth root. ‘The relative importance of the two terms depends 
on the coefficients of diffusion, the solubility and the dissocia- 
tion constant. It will therefore, in all probability, vary 
considerably with the temperature. 
By substituting the value of C in terms of ¢ and 2 from 
the above equation in the certs, 
Hn de 
n dx” 
and solving the resulting differential equation, we could 
obtain the distribution of the separate concentrations along 
the thickness of the slab, but this does not appear to be of 
any great interest, from an experimental point of view, in 
the present state of the subject. 
There is, of course, no need to restrict ourselves to the 
case where the external concentration vanishes on one side 
of the slab. With the same notation, if the pressure be P) 
on one side of the slab and P, on the other, in the case where 
the external dissociation is small we obtain : 


=0, 
# (C—AP,)+ i(e—aP») = [2 (P= -P)A+* (Py ~P»)] 
Vv 
whence we see that the rate of flow consists as before of two 
terms, one of which is proportional to the gradient of the 
pressure and the other to that of its nth root. 
Case of a Gas which combines Chemically with the Solvent. 
Another case may arise in which a gas is capable of 
diffusing through a solid partition, viz., when the gas is 
capable of combining i ina reversible manner with the material 
of which the partition is composed. For instance, we might 
eS 
d’ 
