122 Messrs. Wright and Thompson on the Determination of 
From these figures sensibly identical values result for the 
voltaic constant of electro-silver in nitrate solution:— 
m—*25. m=1:0. m=2'0. 
Zine= T1Ver sac especies seine 1:495 1°540 1:556 
5 : : 1:109 
Zinc-Copper + Copper- [ : es ae 446 
Silver Rejalaiels}s[elolelexelsiolelsislal~ fo Se 1495 emia § 1:539 a 1-555 
r "580 588 591 
Zinc-Lead + Lead-Silver) + -914 951 "965 
404 ——  1:539 —— 1556 
Mean ...| 1-495 1539 1556 
The heats of dilution of silver-nitrate solutions being as yet 
undetermined, the value of Hg can only be exactly calculated 
for the strength *25 Ag,(NO3). 100 H,O. The subjoined 
values for the higher strengths are calculated on the suppo- 
sition that the heat of dilution of silver- and zinc-nitrate 
solutions is the same; so that Hy remains the same for all: 
solution-strengths Ag,, O, N,O; aq. =16780. 
Mm. Hi. Hy. E—Hy. 
25 1-495 1-890 —°395 
1:0 1:539 1:890 —'351 
2-0 1:556 1:890 — ‘334 
Hence the thermovoltaic constant for silver in nitrate solu- 
tion is not widely different from that in sulphate solution, 
being in each case far greater than that for silver in contact 
with silver chloride, whether suspended in zinc cadmium 
or cupric-chloride solution. Withall three kinds of silver salt, 
however, under all circumstances, the value is negative in 
sign. 
V. Mercury. 
192. Mercuric-nitrate solution, like mercuric chloride, 
becomes rapidly and completely converted into mercurous 
salt by agitation with mercury. In order to prepare mer- 
curous nitrate with but little excess of acid, mercury was 
dissolved in nitric acid, and the crystallized mass washed on 
the filter-pump with a little water, and then well agitated with 
water and mercury. The solution thus obtained was free from 
