1910-11.] Temperature Coefficient of Concentration Cells. 385 
With a view to fixing our ideas, let us suppose that solution A is much 
weaker than solution B when equilibrium is established, so that if solution 
A and B are of equal concentration there will be an E.M.F. transferring 
the salt from A to B. 
Let us now proceed to consider the effect of temperature on such a 
cell. Let us suppose a cell in which both solutions are saturated and 
are therefore in equilibrium, and let us suppose the cell to be raised 
from temperature T 1 to T 2 . The electromotive force of such a cell may 
be stated as follows : — 
E = RTj (log C |i_logC') = 0, 
when Sj is the solubility of the salt in A, is the solubility in B, and 
C and C' the concentration in A and B respectively at temp. T r 
Let the cell be now raised in temperature to T 2 , then 
E + de = RT, (log C ^ - log C' ), 
b 2 
when S' 2 , S 2 are the solubilities of the salt at the new temperature T 2 . 
Evidently if the rate of increase of solubility in both solutions is the 
same, and E t = 0, then E 1 + de = 0. 
For in an ordinary concentration cell, if 
Ej = RTj (log C- log C') = 0, 
then 
E 1 + de= RT 2 (log C - log C') = 0. 
Let us suppose the solubility coefficients with temperature are not the 
same : then 
(E, + de) - Ej = RT 2 (log c|* - log C') - RT, (log c|a - log O'). 
But E x = 0, therefore 
* = RT S ( log ^ - log (1) 
Now according to the Van’t Hoff equation, if X is the latent heat of 
solution (heat absorbed being reckoned positive) and S p S 2 the solubilities 
of the salt, at T v T 2 the 
los 
4 * 
Let X be the latent heat of solution A and X' of solution B, then 
Therefore 
VOL. XXXI. 
25 
