12 Mr. J. Napier on Electrical Endosmose. 



allowed to pass until the negative solution was completely 

 exhausted of copper, which required sixty-lour hours, the 

 battery not renewed during the experiment. At the end of 

 the experiment, the electrodes being again weighed, the posi- 

 tive had lost 257 grains, the negative had increased 250 grains. 

 The positive solution had lost 6 ounces by measure, the nega- 

 tive had gained 4 ounces. The greatest portion of this change 

 took place within the last ten hours. The 2 ounces lost are 

 mostly from evaporation. The positive solution was evapo- 

 rated and crystallized, and there were obtained 905 grains of 

 sulphate of copper, 95 less than was originally dissolved ; but 

 the partition being saturated with salt may account for a por- 

 tion of the loss. The 500 grains which were originally in the 

 negative solution would only contain 127 grains of metallic 

 copper; but there is nearly double of this deposited, showing 

 that the salt had been transferred by some means from the 

 positive to the negative, in quantity amounting to nearly the 

 whole of the salt originally dissolved in the positive solution. 



II. 100 grains of sulphate of copper were dissolved in 4 

 ounces of water and put into each division, in the same man- 

 ner as the last experiment. The partition in this case was 

 much closer in texture than the other; the same battery 

 power was used, and continued till the negative solution was 

 exhausted, which was nineteen hours. The negative electrode 

 being weighed, it had increased 34*4 grains ; the negative 

 solution had increased one-fourth of an ounce; the positive 

 solution had lost three-eighths of an ounce. Comparing this 

 experiment with the last, there is a great discrepancy, the 

 only known cause being the closer texture of the diaphragm ; 

 the transfer of the salt is only in the proportion of one-third 

 that of the former, and the measurable endosmose is still fur- 

 ther out of proportion, being only one-sixteenth; while the 

 amount of decomposition is only one-seventh of the 500 grains. 

 The electrodes in both experiments were the same in size. 



The question now suggested itself whether the transfer of 

 the copper salt from the positive to the negative cell was the 

 result of endosmose or of electrolysis, corresponding with the 

 results of the late Professor Daniell and Professor Miller, who 

 supposed that certain bases underwent electrolytic transfer in 

 fractional proportions, and that these proportions might vary 

 according to the texture of the diaphragm, or that kind of 

 peculiar resistance given to the passage of a current when 

 passing from one solution to another. 



In order to determine which was the true cause, the nega- 

 tive cell was charged with a weak solution of caustic potash, 



