110 Messrs. Wright and Thompson on the Determination of 
It is noticeable that suspending silver chloride in zinc-, cad- 
mium-, or copper-chloride solution affects the H.M.F. of a cell 
in the same way as the use of the same fluids for the suspen- 
sion of cuprous chloride (§ 181), viz. that the H.M.F’. is lowest 
with zine and highest with copper-chloride solution. 
Since the E.M.F. of a zinc-silver-chloride cell continually 
diminishes as the solution-strength rises, just as with a Clark’s 
cell (§ 179), it is evident that De-la-Rue and Miiller’s cell 
must possess an H.M.F’. variable with the strength and nature 
of the solution used. A number of rods of pure silver chlo- 
ride fused round strips of pure silver were obtained from 
Messrs. Johnson and Matthey, and set up opposed to zinc and 
cadmium in various solutions of their chlorides respectively. 
Variations of 4 to 5 centivolts were observed in the H.M.F. 
of such cells with different silver-chloride rods, everything 
else being the same, and the observations being made with the 
electrometer to avoid possible diminution in H.M.F. The 
average values found were slightly lower than those found 
with the same solution-strengths and precipitated silver chlo- 
ride, as might perhaps be expected, inasmuch as the silver 
strips inside the fused rods were not electro-coated but were 
of bright metal, which has been found in the case of sulphate- 
cells to give lower values than electro-coated metal (§ 125). 
Zine-Silver, . Cadmium-Silver. 
25 Zn Cl, | 20 ZnCl, || -25 CaCl, | 2:0Cacl, 
100H,0. | 100H,0. || 100H,0. | 100H,0. 
Moimiuna ts 7 tees atece 1:097 1:048 “776 ‘740 
Marmimiumi <7. e8sca. 2 het oe - 1:058 "995 "726 ‘714 
Wyerage au. taste nee 1-075 1-020 “750 ‘730 
Value with precipitated \ 1-080 1:037 ‘761 
silver chloride ......... Et 
IV. Mercury. 
183. When metallic mercury and corrosive-sublimate 
solution are brought into contact, calomel is formed ; so that 
by agitating the two together almost the whole of the metal 
and chlorine are removed from solution. Hence it is to be 
expected that the same peculiarity would apply to these cells 
as to copper cells (§ 181), viz. that much the same E.M.F. 
will be given whether mercury be in contact with corrosive- 
sublimate solution, or with a magina of calomel and corrosive- 
sublimate solution. In point of fact this is the case; cells set 
