1910-11.] Temperature Coefficient of Concentration Cells. 381 
If the results are plotted, two roughly logarithmic curves are obtained 
with approximate temperature coefficients ; — 
This is evidently quite different from the curves for an ordinary concentration 
cell, which are of this form, the curves for two different temperatures, 
crossing at the zero E.M.F. concentration : — 
This result seemed so interesting that it was worth testing in a cell 
made up with quite different materials, and therefore nitrobenzene and 
water were selected for the purpose. 
Potassium iodide is almost insoluble in nitrobenzene, but dissolves freely 
in presence of iodine to give a complex series of poly-iodides (Dawson). 
A solution of ’025 molecules KI and '025 molecules I 2 in nitrobenzene 
was placed in one electrode, and *025 KI molecules and '01 I 2 molecules 
in water was placed round the other electrode. 
The E.M.F. was positive (that is, in the direction of transferring 
potassium iodide from nitrobenzene to water, and iodine from water to 
nitrobenzene), and amounted to ’43 volts. 
The two solutions were next shaken up together for some hours in the 
