420 
PROFESSOR J. W. MALLET ON THE ATOMIC WEIGHT OF GOLD. 
from the stronger than from the weaker solution. In every case there was decidedly 
more copper dissolved from the anode than was deposited on the cathode plate. 
2. Effect of Difference in Acidity of Two Solutions, otherwise of the Same Strength .— 
With the same proportion of cupric sulphate in both solutions, one was made to 
contain but one-tenth as much free sulphuric acid as the other; all other conditions 
remained the same for both. As before, the difference of result was insignificant, and 
somewhat variable in direction, wuth an apparent tendency towai’ds a very slightly 
greater deposit on the cathode plate in the less acid as compared with the more acid 
solution. As before, there was in every case a distinctly greater loss of copper from 
the anode than gain on the cathode plate, especially in the more acid solution. 
3. Effect of Difference in Temperature of the Two Solutions. —The proportion of 
cupric sulphate and of free acid being the same for both solutions, and all other 
conditions the same, one of the two, however, being maintained at 72°, 47°, or 37° C., 
while the other was at 2° C., thus establishing a difference in temperature of 70°, 45°, 
or 35° respectively, there was distinctly in every instance rather more copper thrown 
down on the cathode plate in the colder than in the warmer solution. The loss of 
weight of the anode plate was always greater than the gain at the cathode, and the 
difference in this respect was greater in the warmer than in the colder solution. 
4. Effect of Difference in the Size of the Plates. —All other conditions being the 
same in both the electrolysis cells, the plates in one were made to present but 
one-fourth the surface of those in the other, so that the “ current density ” was 
proportionally increased in the former. Under these circumstances there was a 
constant, though but small, diflerence in the amount of copper deposited on the 
two cathodes, the quantity being greater on the cathode plate with smaller, surface. 
The tendency seemed to be towards a greater excess of metal removed from the anode 
over that deposited on the cathode plate in the case of the larger plates, as compared 
with the smaller. 
5. Effect of Difference in the Distance hetioeeyi the Plates. —The plates of both pairs 
being equal in size, and all other conditions being uniform, the plates in one of the 
two electrolysis cells were placed at a distance apart only one-fifth that intervening 
between those of the other pair. It was not clear that any constant difierence of 
result could be detected, but the tendency seemed to he rather toward a very slightly 
greater deposit on the cathode plate in the case in which the plates were farther 
apart as compared with that in which they were nearer together. There was no 
recognisable difference in the proportion of metal dissolved ofi“ from the anode plate. 
Similar experiments were made with two pairs of plates of pure silver, thus checking 
the results obtained with copper, and contrasting the behaviour of one at least of the 
less chemically alterable metals with that of the more easily alterable copper. It was 
intended to make a set of similar experiments also with gold plates only, but the 
available supply of pure gold in the form of rolled plates was not sutficient for the 
numerous experiments required. The silver solution used was one of potassium 
