S Messrs. Wright and Thompson on the Determination of 
of the zinc-sulphate solution in which the lead sulphate is 
suspended up to a certain strength, after which the value 
again decreases, the sign being negative throughout. Thus 
the following Table represents the relative values of a and 6 
for solution-strengths mZnS8O, 100 H,0, the values of 6 being 
those described in § 153 for amalgamated-zinc plates, and 
those of a similarly obtained by means of a series of diffusion- 
celis set up with electro-coated lead plates immersed in mag- 
mas of recently precipitated well-washed lead-sulphate and 
zinc-sulphate solutions of varying strengths; the values are 
given in millivolts. 
Value of mm. (it. b. 
iL 0 0 
5 — 6-0 +11-1 
1-0 — 95 +163 
2:0 —14:0 +22°6 
30 —18-0 +27°7 
4:0 —16°5 +33°9 
5-0 —11-0 +389°5 
5:5 — 35 +43°5 
Curve no. 1, fig. 1, indicates these values of a as ordinates, 
the values of m being abscisse. 
On substituting solutions of cadmium sulphate for those of 
zinc sulphate as the menstrua in which to suspend lead sul- 
phate in cells containing lead and its sulphate as one half of 
the element, analogous results were obtained as regards the 
general character of the curve, the mean numerical values of 
a obtained by means of diffusion-cells being given in milli- 
volts in the following Table, and represented by curve no. 2; 
Bigs 1: 
Millivolts. 
the third column in the table and curve no. 3 represent the 
corresponding values obtained with diffusion-cells containing 
