Chemical Affinity in terms of Electromotive Force. 
43 
C.G.S. 
current. 
Difference of potential set up. 
A. 
B. 
0. 
D. 
•00002 
•00005 
•0001 
•0002 
•0005 
•001 
■0015 
•002 
■0025 
•029 
•044 
•063 
•084 
•146 
•230 
•311 
•389 
•476 
•317 
•334 
■354 
•381 
•451 
•547 
•636 
•730 
•830 
1-069 
1-086 
1-107 
1-139 
1-210 
1-310 
1-403 
1-498 
1-598 
1-490 
1-509 
1-530 
1-562 
1-636 
These figures yield the following- six sets of values of e 2 — e-i 
for the corresponding pairs of + electrodes compared. 
Current. 
Zinc- 
Zinc- 
Zinc- 
! Cadmium - 
Cadmium- 
Copper- 
cadmium. 
copper. 
silver. 
| copper. 
silver. 
silver. 
•00002 
•288 
1-040 
1-461 
| -752 
1-173 
•421 
■00005 
•290 
1-042 
1-465 
•752 
1-175 
•423 
•0001 
•291 
1-044 
1-467 
■753 
1-176 
•423 
■0002 
•297 
1-055 
1-478 
1 -758 
1 1-181 
•423 
•0005 
•305 
1-064 
1-490 
I -759 
1-185 
•426 
•001 
■317 
1-080 
•763 
•0015 
•325 
1-092 
1 -767 
•002 
•341 
1-109 
| -768 
•0025 
•354 
1-122 
•768 
Not only does the value of e 2 — e 1 increase with the current- 
density in every case, but, further, the rate of increase is 
greater when zinc is compared with silver than with copper, 
and greater then than when compared with cadmium ; simi- 
larly the rate of increase with cadmium and silver is greater 
than with copper and silver, and so on. It is farther notice- 
able that in each case a value of e 2 — e x with some particular 
current-strength is deducible which is sensibly the same as 
the E.M.F. of a cell after DanielPs construction containing 
the same metals and sulphate solutions of equal molecular 
strength ; so that in general it may be said that, for a current- 
density below a particular limit, the value of ^ 2 —^i is less than 
that of the corresponding Daniell form of cell, whilst for a 
current-density above this limit it is greater. 
144. The following experiment seems to show that the sub- 
stitution of dilute sulphuric acid for zinc-sulphate solution as 
the electrolyte makes no material difference in the end result, 
the — electrode being made of platinum, and the disturbing in- 
fluence of dissolved air being eliminated . Two precisely similar 
U-tube cells (§ 85) were filled with recently boiled dilute sul- 
phuric acid (11'5 grammes H 2 S0 4 per 100 cubic centim.), and 
