316 Messrs Higgins and Draper mi Electrical Decompositions. 



the water, and to melt the hydrate ; one equivalent of the oxy- 

 gen is given ofF from the water of the hydrate, and its corres- 

 ponding equivalent of hydrogen uniting with the oxygen of the 

 potassa, the metal is separated. The process is analogous, when 

 the hydrate of potassa is decomposed in a gun-barrel. The iron 

 unites with the oxygen of the water of the hydrate, at a white 

 heat, and the nascent hydrogen separates the oxygen from the 

 potassium, the water produced being simultaneously decom- 

 posed by the iron. The facility of this decomposition is doubt- 

 less owing, in a great degree, to the volatile nature of the potas- 

 sium, and the fixidity of the oxygen of iron. But we may be 

 certain that hydrogen is the main cause, for oxide of potassium 

 is decomposed, in like manner, at a white heat. Gay Lussac 

 and Thenard have shewn * that hydrogen cannot decompose 

 hydrate of potassa, on account of the water it contains, which 

 must be decomposed before any action on the oxide can be pro- 

 duced. 



At temperatures between 40° and 120° F., no decomposition 

 can be effected by the voltaic battery, if hydrogen gas does not 

 exist in the substance, and is not presented to it in a nascent 

 state. And as, at the same temperatures, no substance is a con- 

 ductor which does not contain oxygen as one of its elements, 

 therefore water must always be present in all galvanic arrange- 

 ments for decomposition at those temperatures. But at tempera- 

 tures greater than 300° F., we meet with many fluids of such 

 conducting power that, without the presence of either hydrogen 

 or oxygen, they may be decomposed by the battery. This is 

 the case with liquid iodine of potassium and chloride of sodium. 



Every instance of reduction effected by the galvanic battery, 

 at temperatures between 40** and 120° F., may be performed by 

 chemical means, when hydrogen gas is employed, and evolved 

 under similar circumstances, provided the temperature be high- 

 er than a red heat. 



These few results, from a long series of experiments, are pre- 

 sented to the scientific, as important principles in electrical de- 

 compositions. It is, 'however, much to be regretted that galva- 

 nic arrangements have been so little improved. Nearly all the 

 results mentioned in this paper have l>een determined by expe- 

 • Recherches Physico-Chimiques. 



