Electrolysis of Secondary Compounds, 183 



ent states of oxygenation. It has been already staled, that in 

 the electrolysis of the former, carbonic acid and oxygen were 

 found to be given off at the zincode in equivalent proportions 

 to the alkali and hydrogen at the platinode; proving those 

 salts to be oxy-carhions of the respective metals*. When 

 oxalate of ammonia was treated in the same way, carbonic 

 acid alone was evolved at the zincode, and ammonia with hy- 

 drogen at the platinode*. Here the oxalion (or sub-oxycar- 

 bion) contains the elements of two equivalents of carbonic acid 

 (CgOg + O) = 2(002). I" numerous repetitions which we 

 now made of these experiments, we found that although in the 

 electrolysis of oxalate of ammonia (CgOg + O) was always ex- 

 actly evolved, yet that it was not invariably in the form of car- 

 bonic acid, but in different proportions of oxalic acid with free 

 oxygen and carbonic acid. It was thus proved that the burn- 

 ing of the oxalic acid into carbonic acid by its associated oxy- 

 gen was a secondary process, and that the (CgOg+O) which 

 travelled in the circuit was in some way different from 2(C02). 



(/.) A similar comparison was then made between the sul- 

 jjJiites and sulphates. In the electrolysis of the latter, it has 

 been shown that sulphuric acid with an equivalent of oxygen 

 (which is evolved) travels to the zincode f. To determine the 

 results of the former, all the cells of the diaphragm apparatus 

 were charged with sulphite of potassa, and a voltameter was 

 included in the circuit ; hydrogen was given off from the pla- 

 tinode in exact proportion to that from the voltameter ; but 

 no oxygen was evolved from the zincode. 



The experiment was by itself ambiguous, for it did not de- 

 termine whether (SOg + O) travelled as SO3, or whether sul- 

 phuric acid was formed at the zincode by the secondary action 

 of the oxygen upon the sulphurous acid. Judging from the 

 analogy of the preceding instances, it is most probable that the 

 oxygen with which the sulphurous acid is associated in the 

 sub-oxysulphion is in a different state from that of the third 

 equivalent in dry sulphuric acid, and that the sulphuric acid 

 evolved at the zincode in the last experiment is the result of 

 secondary action. Some sulphurous acid was evolved in the 

 zincode cell, which doubtless arose from the action of the sul- 

 phuric acid upon the sulphite in contact with which it was 

 produced. 



[]c.) The experiment was varied by substituting hyposulphite 

 of soda (NaO, SgOg) for the sulphite, and with analogous re- 

 sults. Hydrogen was given off abundantly at the platinode, 

 but no gas was evolved at the zincode. There was a strong 

 odour of sulphurous acid at the latter, with a gradual deposi- 

 * Second Letter, p. 222. f First Letter, pp. 107 et seq. 



