ON ELECTROLYSIS IN ITS PHYSICAL AND CHEMICAL BEARINGS. 323 



Table II. — Ratio of Weight of Silver to Weight of Copper — continued. 



Date 



Time 

 in miu. 



Weight 

 of silver 



in 

 grammes 



Fori 

 wire 



For 2 

 wires 



For 4 

 wires 



For 8 



wires 



For IS 

 wires 



Current 

 in am- 

 peres 



Remarks 



Copper lett in hot 

 chamber "too long, 

 and was discoloured 



A copper cracible 

 in tlie same circuit 

 gave 3-407 



Discussion of the Obseetations. 



The numbers quoted in the table give the ratios of the amounts of silver to the 

 corresponding amounts of copper deposited to the 4th significant figure. The 

 balance used was a triangular beam Oertling, which could be relied upon for an 

 accuracy reaching 0"1 mgm. The copper deposits generally amounted to about 

 1 gramme, and the accuracy of the weighings (coirected when necessary for the 

 diiferences in the buoyancy of the air at the times of the initial and final deter- 

 mination of the weights) may be assigned as -01 per cent, for copper deposits, and 

 •003 per cent, for silver. The numbers in the table ai-e carried to one place less 

 than the weighings permit. This is done intentionally in order to enable the 

 reader to obtain a better general idea of the whole series of observations. It is 

 easily seen that the differences in the table are real differences, and correspond to 

 some real characteristic of the electrolytic action in the cells. A glance at the sets 

 of observations belonging to the same experiment is sufficient to suggest a dimi- 

 nution of the amount of copper deposited as the current-density diminishes. The 

 area of each wire was about 5 square centimetres, so that the current-density 

 varies for the observations in Table II. between -OOl and -lo ampere per square 

 centimetre, and practically includes all current-densities that can come under 

 observation with this form of cell. In some cases the density was so great in the 

 ' one-wire cell ' that the copper deposit was flocculent, and could not be weighed 

 in consequence ; and in some of the sixteen-wires the deposit was not suffi- 

 cient to cover the wires, but occurred in patches with small groups of copper 

 masses. 



If we proceed, on the assumption of the accuracy of Faraday's law, to attempt 

 to explain the observed differences, we must first look to the action of the solution 

 upon the deposit, since it is known that such an action actually takes place when 

 copper is immersed in a solution of sulphate, and that the weight of copper might 

 be reduced by solution. This action is said to depend upon the solution and the 

 temperature. These considerations make it diilicult to infer the action in the cell 

 from that upon a wire without a current flowing : for, in the first place, the 

 solution is weakened in the Immediate neighbourhood of the cathode by the 

 electrolysis ; and, in the second place, the temperature is altered by the current 

 itself, and was sensibly diflferent in the different cells in some of the experiments; 

 but to measure the temperature and allow for it is not very practicable, as it is 

 not uniform throughout the cell. 



Further, there may possibly be a division of the current between the salt and 

 the solvent, and any action of the kind would probably have an effect upon the 

 action of the solution on the cathode. 



The only plan that has suggested itself to me is to arrange the observations in 

 the order of current-density, and to see if any correction could be applied that 



Discarded. 



Y2 



