1910-11.] Temperature Coefficient of Concentration Cells. 379 
also in electrical equilibrium (the electrical equilibrium depending on the 
ions alone), and the relationship is given by Abel’s equation, 
k„=k*A. 
With reference to experimental determinations of the E.M.F.s of cells of 
this type, Abel comes to the conclusion that when the liquids do not mix 
it is necessary to have the cell in four divisions for reliable readings, the 
two central divisions being in partition equilibrium, and that in the case of 
interdiffusing liquids the measurements will be seriously disturbed by this 
interdiffusion. The magnitude of the corrections due to these conditions 
would require special researches to decide. 
In the case of the alcohol water cells with silver silver iodide electrodes 
there are changes of E.M.F. which are evidently taking place at the 
electrode which is immersed in the alcohol solution, the cause of which is 
very obscure. 
While I have found such large changes in the liquid contact conditions 
of alcohol water cells, as introducing a solution of potassium iodide in 
glycerine, produce little or no change in the E.M.F. (thus going far to 
demonstrate that the errors at the liquid contacts due to interdiffusion are 
not serious), I have on the other hand found sudden capricious changes of 
E.M.F. take place to as much as 20 per cent, or 30 per cent, in the silver 
silver iodide, potassium iodide, alcohol, water cell, with which I have 
principally experimented — changes the cause of which defied investigation 
in spite of hundreds of measurements. 
Probably the best plan with cells of this type is, for each concentration, 
to determine the ratios for zero E.M.F., thus eliminating at any rate some 
sources of error. 
All such measurements must, however, be received with great caution 
until more is known about the conditions of reliable readings. 
As far as this paper is concerned, however, qualitative results are all 
that are needed to demonstrate the correctness of the theory developed as 
to the behaviour of these cells with changes of temperature ; while in the 
latter part of the paper, where the actual quantitative results are necessary, 
they have been confirmed by readings taken under various conditions, and 
have been shown to be in harmony with other experimental facts, and 
therefore justify the conclusions arrived at. 
The first experiments, then, were made with the cell already 
described. 
Round one platinum electrode was placed a solution of ‘025 molecules of 
