Electrolysis of Secondary Compounds* 



Ml 



hypothesis, that the voltaic decomposition of an electrolyte is 

 not only effected by the disengagement of its anion and cation 

 at their respective electrodes, but by the equivalent transfer 

 of each to the electrodes ; so that the measure of the quantity 

 of matter translated to either side of the diaphragm might be 

 taken as the measure of the electrolysis. 



This was the mode which was necessarily adopted in the 

 investigation before adverted to, where attempts were made to 

 compare the results of the electrolysis of aqueous solutions of 

 acids* and alkalies f with the simultaneous decomposition of 

 saline solutions. One circumstance, however, was then over- 

 looked, which it is necessary to attend to in making the com- 

 parison, viz. that the disengagement of whole equivalents of the 

 ions at the electrodes is only accompanied, upon the hypothesis 

 assumed, by the actual transfer of half an equivalent to either 

 side. This will clearly appear from the following diagram. 



Let A, B, C, &c. in the preceding diagram represent a series 

 of particles of chlorine, ar, 5, c, &c. a series of particles of po- 

 tassium in combination with the particles of chlorine in the 

 row above them, X, Y a central line or diaphragm, and Z and 

 P the electrodes. If 1 represent the arrangement before the 

 current passes, the particles A and a, B and 6, &c. being com- 

 bined to form compound particles of chloride of potassium, 2 

 would represent the arrangement after a single equivalent of 

 each ion had been disengaged at the electrodes. Each par- 

 ticle would thus necessarily have moved forward half a step, 

 combining with the next adjacent particle, so that B «, C ^, 

 D c, &c. M^ould now form the chain between the electrodes. 

 If another equivalent be now supposed to be set free at each 

 * First Letter, p. 108. f Second Letter, p. 216. 



Phil. Mag. S. 3. Vol. 25. No. 165. Sept. 1844. N 



