Electrolysis of Secondary Compounds. 353 



circuit cannot perform more than an equivalent proportion of 

 work at any other point of the same circuit." — " The sum of 

 the forces which held together any number of ions in a com- 

 pound electrolyte, could, moreover, only have been equal to 

 the force which held together the elements of a single elec- 

 trolyte, electrolyzed at the same moment in one circuit." 



In the electrolysis of the solution of sulphate of soda, and 

 many of the other salts, " water seemed to be electrolyzed ; at 

 the same time acid and alkali appeared in equivalent propor- 

 tion with the oxygen and hydrogen at the respective electrodes." 

 — " We must conclude," from the above-mentioned principle, 

 " that the only electrolyte which yielded was the sulphate of 

 soda, the ions of which, however, were not the acid and alkali 

 of the salt, but an anion composed of an equivalent of sul- 

 phur and four equivalents of oxygen and the metallic cathion 

 sodium ; from the former, sulphuric acid was formed at the 

 anode by the secondary action and evolution of one equiva- 

 lent of oxygen ; and from the latter, soda at the cathode by the 

 secondary action of the metal and the evolution of an equiva- 

 lent of hydrogen." 



To avoid circumlocution (but only when speaking of elec- 

 trolytic decomposition), Mr. Daniell proposes to adopt the 

 word ion, introduced by Dr. Faraday, as a general termina- 

 tion to denote the compounds which in the electrolysis of a salt 

 pass to the zincode, and that they should be specifically distin- 

 guished by prefixing the name of the acid slightly modified, 

 as is shown in the following table : — 



Ordinary chemical formula. Electrolytic formula. 



Sulphate of copper (S+3 0)+(Cu + O) = (S + 40) + Cu. Oxysulphion 



of copper. 

 Sulphate of soda (S + 3 0)+ (Na + O) = (S+4 O) -f Na. Oxysulph. of 



sodium. 

 Nitrate of potassa (N+5 0)+(Ka + O) = (N + 6 O) + Ka. Oxynitrion 



of potassa. 

 Phosphate of soda (P+3§ 0)+(Na+0) = (P+3£ 0)4- Na. Oxyphosph. 



of soda. 



The following experiments seem to remove all doubt that 

 the view just sketched is correct; they were, in fact, suggested 

 to Prof. Daniell by the theory itself. 



" A small glass bell, with an aperture at top, had its mouth 

 closed by tying a piece of thin membrane over it. It was half 

 filled with a dilute solution of caustic potassa, and suspended 

 in a glass vessel containing a strong neutral solution of sul- 

 phate of copper, below the surface of which it just dipped. 

 A platinum electrode, connected with the last zinc rod of a 

 large constant battery of twenty cells, was placed in the solution 

 of potassa ; and another, connected with the copper of the first 

 cell, was placed in the sulphate of copper immediately under 



Phil Mag. S. 3. Vol. 17. No, 111. Nov. 1840. 2 A 



