Chemical Affinity in terms of Electromotive Force. 9 
mercurous sulphate suspended in zinc-sulphate solutions of 
varying strengths, the plate-surfaces being in this case pure 
mercury (the “ plates ”’ being the upper surfaces of mercury oc- 
cupying the lowest portions of the vessels constituting the cells). 
Values of @ in cells Values of ain cells 
containing lead sul- containing mercurous 
Waines of 7. phate Beaded in sulphate Saree in 
mOdSO, 100 H,0. mZo08O, 100 H,0. 
me 0 0 
“ak —2'3 — 50 
1:0 —52 — 66 
2°0 —9-2 — 95 
3:0 —81 —116 
4:0 —69 —12:2 
5:0 —56 —12°7 
55 —50 —13°0 
6:0 
—43 
it is here evident that whilst the sign of a@ is in all cases 
negative, the numerical value attains a maximum in the case 
of lead sulphate suspended in either zinc- or cadmium-sul- 
phate solution and then diminishes, whereas it continually 
increases in the case of mercurous sulphate suspended in 
zinc sulphate. On the other hand, cells containing electro- 
silver plates immersed in magmas of recently precipitated 
well-washed silver chloride and solutions of zine chloride of 
varying strengths, gave values for a negative in sign for low 
solution-strengths, and increasing in numerical value to a 
negative maximum as the strength increased, after which 
the value diminished again to 0, finally becoming positive, 
and increasing continuously ; these values are given in 
millivolts in the following table, and indicated by curve 
no. 4. 
Value of a in cells containing 
Value of m. silver chloride suspended 
in mZnCl, 100 H,O. 
“25 0 
5 — 50 
1-0 —12°0 
2:0 —20-1 
30 —10°2 
6-0 + 01 
10:0 + 7:0 
Analogous values were obtained with cells containing 
mercurous chloride suspended in zine-chloride solution, a 
being negative in sign with strengths where. m<6-0, but 
positive where m=10°0. 
168. It is evident that cells of the type now under discus- 
sion, where the electrolyte surrounding the plate acquiring 
