THE 
LONDON, EDINBURGH, anp DUBLIN 
PHILOSOPHICAL MAGAZINE 
AND 
JOURNAL OF SCIENCE. 
[FIFTH SERIES. ] 
PAN UA hi Y 28885; 
I. On the Determination of Chemical Affinity in terms of 
_ Electromotive Force.—Part IX. By C. R. ALDER WricHT, 
D.Sc. (Lond.), F.RS., Lecturer on Chemistry and Physics, 
and ©. THompson, F.C.S., Demonstrator of Chemistry, in 
St. Mary's Hospital Medical School*. 
On Voltaic and Thermovoltaic Constants. 
164. eae experiments described in Part VIII.+ show that 
the difference in E.M.F. between two two-fluid 
cells containing metallic salts in solution, and alike in all 
respects save that one of the fluids is of different degrees of 
concentration in the two cells respectively, can be readily 
obtained by opposing the two cells to one another, and mea- 
suring the current set up through a total resistance large 
enough to reduce the current to such an extent that its den- 
sity, in reference to the plate-surfaces in the cells, falls below 
a certain limiting value variable with the details of the con- 
struction of the cells; and, further, that the same value is 
obtained by means of “‘diffusion-cells,” consisting of two 
vessels containing respectively the two solutions of different 
degrees of concentration but containing the same salt, united 
by a siphon-tube, or constituting a “ gravity’? arrangement, 
If a be the increment in E.M.F. thus measured, due to a given 
Increase in the strength of the fluid surrounding the plate 
acquiring the higher potential, and 6 be the corresponding 
* Communicated by the Physical Society. Read November 8, 1884, 
t Phil. Mag. vol. xvii, pp. 282, 377. 
Phil. Mag. S. 5. Vol. 19. No. 116. Jan, 1885. B 
