290 Mr. J. Daniel on the Polarization upon a 



Passage of the Ions through the Gold-leaf Partition. 



To test this, CuS0 4 solution (17 per cent, i, e. 1 gram 

 CuS0 4 to 5 cub. centim. H 2 0) was used in the outside vessel 

 (anode side of the voltameter), and H 2 S0 4 (30 per cent, 

 solution, sp. gr. 1*23) in the inside vessel (kathode side of 

 the voltameter). These solutions being separated by the 

 gold-leaf partition, the appearance of the ions upon the 

 electrodes and upon the partition, when the current was 

 closed, was roted. The first method of observation was to 

 close the circuit upon the voltameter, read the current- 

 strength by the ammeter, and at stated intervals weigh the 

 Cu deposited on the kathode. This gave Table L, where it 

 may be seen that the amount of Cu deposited was very small 

 at first, not more than 2 per cent, or 3 per cent, the first 

 hour, but increased rapidly with the time. 



This did not settle the question as to whether the current 

 caused the copper to pass through the gold-leaf partition 

 or not. 



The second method was to set up two exactly similar volta- 

 meters at the same time, close the circuit on one leaving the 

 other open, and at stated intervals weigh the Cu deposited on 

 the kathode of the voLameter through which the current had 

 passed, and at the same time make a quantitative analysis of 

 the solution on the kathode side of both the open and the closed 

 voltameters. This was done by extracting 10 cub. centim. 

 from each with a pipette, and depositing the Cu electrolytically 

 in two similar platinum crucibles connected in series. Equi- 

 librium was maintained in the voltameter by adding 10 cub. 

 centim. of the 30 per cent. H 2 S0 4 solution to replace the 10 

 cub. centim. thus removed. Knowing the volume of solution 

 in each voltameter, these analyses were sufficient to determine 

 the total amount of Cu that had passed through the partition 

 during the same interval for each voltameter. Table II. 

 gives the results. 



Here it was observed that imperceptible differences in the 

 specimens of gold-leaf were sufficient to cause enough differ- 

 ence in the diffusion to leave the question unsettled. The 

 amount passing the partition of the open voltameter was as 

 often greater as it was less than that of the closed voltameter. 

 It was now evidently necessary to test one and the same gold- 

 leaf partition for diffusion with circuit open and closed suc- 

 cessively. This leads to the third method shown in Table III. 



It is thought that this is entirely free from objection or 

 serious error, and leads to the conclusion that the current 

 does not sensibly affect the diffusion of CuS0 4 and H 2 S0 4 



