108 Messrs. Wright and Thompson on the Determination of 
cadmium-iron-sulphate cells above described, in that the metal 
actually acquiring the higher potential is not the one predic- 
able from the formation-heats of the electrolytes, but the 
other one—a result indicated by the’— sign prefixed to the 
values of H. 
Cadmium-Silver. Copper-Silver. 
Maximum E.M.F. observed...... ‘758 — 017 
Minimum 4 BA St sa "743 —'025 
Average oy RIC “751 --'020 
Probableverror vscsee cases eeseace: +:0017 +:0015 
: (|+ .751 — -020 
Value of thermovoltaic con- | |+ “8380 +1:099 
stant deduced from average{ | ~~ Sea 
d EMF, 0.00... | [FLO8l +1-079 
oben | |—1-192 — 1192 
UP Se Sot eS 2 
The general average of the three values —*112, —:111, and 
— ‘113 thus obtained with zinc-silver, cadmium-silver, and 
copper-silver ceils respectively is —:112, representing the 
thermovoltaic constant for electro-silver in contact with preci- 
pitated silver chloride suspended in zinc-chloride solution of 
strength ‘25 ZnCl, 100 H,0. 
In precisely similar fashion six other kinds of cells were 
examined, containing respectively zine in zinc-chloride, cad- 
mium in cadmium-chloride, and copper in cupric-chloride 
solutions, opposed in one series to silver immersed in silver 
chloride suspended in cadmium-chloride solution, and in the 
other to silver immersed in silver chloride suspended in cupric- 
chloride solution, the solution-strength being ‘25 MCI, 
100 H,O throughout. In the copper-silver cells, where the 
silver chloride was suspended in cadmium-chloride solution, 
the same peculiarity is observable as when suspended in zinc- 
chloride solution, viz. that the copper, and not the silver, 
acquires the higher potential ; but where the silver chloride 
is suspended in cupric-chloride solution this is not the case, 
the silver here acquiring the higher potential, and the current 
flowing in the direction predicable from the heats of formation 
of the electrolytes, and not in the opposite direction. The 
following values were obtained :— 
