384 
Proceedings of the Royal Society of Edinburgh, [Sess. 
then when the E.M.F, is in the direction of transferring salt from 
alcohol to water the equation will be 
E = A'-A + T- 
dt 
If is greater than A, then, remembering that A and A" mean heat absorbed, 
this process is endothermic. 
If the concentrations, however, are so arranged as to transfer the salt 
from water to alcohol, then, A" being assumed, as above, to be the greater, 
the equation becomes 
E = A-A' + Tj^, 
and the cell is exothermic. 
If the cell is so arranged as to concentrations that at temperature T, E 
equals 0, that is, that the solutions are in partition equilibrium, then 
A - = T— 
dt 
from equation (1). 
That is, still assuming A' to be greater than A, A — A', and therefore 
de . . 
T has a positive value, and therefore the E.M.F. is rising with increase 
of temperature ; and similarly from equation (2) 
de 
and therefore has a negative value, and the E.M.F. is falling with rise 
of temperature. 
As has already been pointed out, in order to determine the difference 
between the latent heats of solution in dilute solutions by this method, 
we require to know as well the relative transport numbers of the salt 
in the two solutions, so as to know the quantity of salt transferred 
by unit current in each case. 
If we next take the particular case of two solutions in contact which 
are both saturated at the particular temperatures selected, we can obtain 
the same result from a different point of view, and thus confirm the 
conclusion that the latent heats are the only available source of energy. 
Let us suppose the same salt dissolved in two different solvents which 
do not mix to any appreciable extent, and let the two solvents be called 
A and B. 
If both solvents are saturated with the salt, and the solvents have no 
action on each other, then the saturated solutions will be in partition 
equilibrium and the cell will have no E.M.F, 
