of Silver and of Copper. 



407 



mercial copper sulphate as from the various specimens of 

 pure sulphate experimented on; and for the first few hours no 

 difference was found, whether acid had or had not been added 

 to the solution. If, however, the same solution is to be used 

 for several successive experiments, acid should be added, as 

 will be evident from the results given in Table IV. The first 

 column of this table gives the numbers of the experiments in 

 the order in which they were made ; the second column the 

 ratio of the electrochemical equivalent of copper to that of 

 silver, obtained from the experiments when the current-density 

 at the cathode was one fiftieth of an ampere per square 

 centimetre ; the third column the same ratio when the current- 

 density at the cathode was one two hundred and fortieth of an 

 ampere per square centimetre. Two or more silver cells were 

 always in circuit with the copper cells, but as the differences 

 between them, except in one or two cases where one of them 

 was known not to be reliable because of silver lost previous 

 to weighing, were never so great as to enter into the figures 

 here given, it does not seem necessary to record the numbers 

 in detail. 



Table IV. 



Number 



of 

 Experi- 

 ment. 



Eatio of the Electro- 

 chemical equivalent of Cop- 

 per to that of Silver. 



Remarks. 



Ai*ea of plate 

 50 sq. cms. 

 per ampere. 



Area of plate 

 240 sq. cms. 

 per ampere. 



1. 

 2. 

 3." 

 4. 

 5. 

 6. 



7. 

 8. 



•2939 



•2944 



•2941 



•2942 



•2944 



•2947 

 f -2940 1 

 \ -2940 

 [ -2940 J 

 f -2941 

 \ -2941 

 [ -2940 



•2930 

 •2929 

 •2935 

 •2939 

 •2942 

 •2932 



•2934 I 



•2930 } 

 •2932 I 

 •2929 J 



Fresh solutions. 

 Solutions interchanged. 

 Solutions aa in 2. 



>> >» 



>j >) 

 Solutions again interchanged. 



New solutions once previously 

 used. 



Fresh solutions containing a 

 little acid. 



In all these experiments, with the exception of the 8th, no 

 acid was added to the solution. The quantity of liquid con- 

 tained in the cells for the experiments 1 to 6 was about 100 

 cubic centimetres and was the same for the large as for the 

 small plates. The total area of copper plate, including both 

 gain and loss plates, was about 30 square centimetres for the 

 small plates and 60 square centimetres for the large plates. 



2F2 



