104 Messrs. Wright and Thompson on the Determination of 
of cuprous-chloride crystals suspended in *25 CuCl, 100 H,O*. 
The values of the two series of observations combined were as 
follows :— 
Maximum Hi, Mialeeee ar. |) es ee 
Minimums). SMe itre se; «Dane ve par mOoes 
Average | a : on a pO 
Probable error of average allie - « OOS 
It is noticeable in this connection that precisely analogous 
results were obtained with other sets of cells, containing, on 
the one hand, cupric chloride alone, and on the other a magma 
of cuprous-chloride crystals and cupric chloride, when op- 
posed to cadmium; whilst similarly various mercury cells 
gave substantially the same values whether pure metallic 
mercury and corrosive-sublimate solution were used, or mer- 
cury anda magma of calomel and ‘corrosive- enorepats solution 
§ 183 
\ It ay from the above average value that the voltaic 
constant for electro-copper immersed in *25 CuCl, 100 H,O 
(or, what is the same thing, a magma of this solution and 
crystals of cuprous chloride) is +1:0985, when referred to 
amalgamated zinc immersed in 25 ZnCl, 100 H,O as zero. 
Sensibly the same value results as the sum of the H.M.F.’s of 
zinc-cadmium and cadmium-copper cells in solutions of 
strength -25 MC], 100 H,O throughout. With the latter cells 
the following numbers were obtained :— 
Masini ae eee ae ee ee 
Nii pee ee oer: ae 
WAVCT ADS Tee RAs ke ATO 
Probable error . . . .+:°0018 
' Voltaic constant from Zinc-copper cells. . . . =1:0985 
Do. from Zine-cadmium -+ ees 330 +:769=1°099 
copper cells . 
Mean) (0." 205099 
The heat of displacement of copper from cuprous chloride 
by zine with formation of :25 ZnCl, 100 H,O results from 
Thomsen’s values, thus :— 
Zin, Clz, age) i. 20. 12840 
Gi, Cl, Beir sa mood 0 
47090=1:038 volt. 
* The cuprous chloride was prepared by boiling together copper- 
sulphate solution with common salt and spongy copper, filtering hot, 
and allowing cuprous chloride to crystallize out on cooling. 
