178 Prof. Daniell a?id Dr. Miller on the 



electrode, one particle of each ion would have passed the cen- 

 tral line, one equivalent would thus be tratisferred, whilst two 

 had been disengaged, as in fig. 3. 



In the instances above referred to, the transfer of one quarter 

 of an equivalent represented half of an equivalent of the hy- 

 drates respectively electrolysed. Little stress however need 

 be laid upon this correction, inasmuch as we shall presently 

 show that the hypothesis upon which it is founded, although 

 generally received, is itself destitute of foundation. 



1. Our first object was to ascertain more clearly than had 

 yet been done, the influence of water in the aqueous solution 

 of an electrolyte, by comparison with the results of the elec- 

 trolysis of the same compound when in the state of igneous 

 fusion. It had been already determined, that with regard to 

 the chlorides no difference occurred, and that the amounts of 

 chlorine evolved in the same circuit from fused chloride of 

 lead*, and from dissolved chloride of sodium and muriate of 

 ammonia, were the samef. In the last case, ammonia and 

 hydrogen were evolved at the platinode in equivalent propor- 

 tions to the chlorine at the zincode. Here a compound cation 

 (NH4) was separated from an elementary anion. 



When nitrate of silver in solution is subjected to electrolysis, 

 the simple cation, silver, separates from the compound anion 

 (NOg), and upon substituting the salt in a state of fusion, for 

 the solution, we obtained the same result. No gas was evolved, 

 but crystallized metallic silver was deposited upon a silver pla- 

 tinode, which gradually increased in length, as it was slowly 

 withdrawn from the liquid salt, just as in the analogous expe- 

 riment with fused chloride of silver, devised by Dr. Faraday. 

 Nitrous fumes were at the same time given off" from the plati- 

 num zincode in abundance. From these experiments it is 

 evident that neither the grouping of a compound cation, nor 

 of a compound anion, is necessarily altered by water in the 

 transit to their respective electrodes. 



2. We now turned our attention to that most interesting 

 group of salts, i\\e phosphates, which has been so ably discussed 

 by Prof. Graham I; not without hopes of confirming by elec- 

 trolysis the beautiful theory of their constitution, which he has 

 derived from considerations purely chemical. The double dia^ 

 phragm cell, which we chiefly employed in these experiments, 

 is represented in the annexed woodcut. 



A and B are the two halves of a stout glass cylinder, accu- 

 rately ground so as to fit with shoulders liquid tight. C is a 



* First Letter, p. 108. f Ibid. p. 110. 



[f Abstracts of Prof. Graham's researches on the phosphates will be 

 found in Phil. Mag. S. 3. vol, iii. p. 451, 459.— Edit.] 



