270 CHEMICAL TRANSFORMATIONS. 



stituents. In this respect, its decomposition depends evidently 

 upon the same causes. as those which effect that of iodide of ni- 

 trogen, or of fulminating silver. Yet it is singular that the cause 

 of the sudden separation of the component parts of peroxide of 

 hydrogen has been viewed as different from those of common 

 decomposition, and has been ascribed to a new power termed the 

 catalytic force. Now, it has not been considered, that the 

 presence of the platinum and silver serves here only to accele- 

 rate the decomposition ; for without the contact of these metals, 

 the peroxide of hydrogen decomposes spontaneously, although 

 very slowly. The sudden separation of the constituents of per- 

 oxide of hydrogen differs from the decomposition of gaseous 

 hypochloious acid, or solid iodide of nitrogen, only in so far as 

 the decomposition takes place in a liquid. 



A remarkable action of peroxide of hydrogen has attracted 

 much attention, because it differs from ordinary chemical phe- 

 nomena. This is the reduction which certain oxides suffer by 

 contact with this substance, on the instant at which the oxygen 

 separates from the water. The oxides thus easily reduced, are 

 those of which the whole, or part at least, of their oxygen is re- 

 tained merely by a feeble affinity, such as the oxides of silver 

 and of gold, and peroxide of lead. 



Now, other oxides very stable in composition, effect the decom- 

 position of peroxide of hydrogen, without experiencing the small- 

 est change ; but when oxide of silver is employed to effect the 

 decomposition, all the oxygen of the silver is carried away with 

 that evolved from the peroxide of hydrogen, and as a result of 

 the decomposition, water and metallic silver remain. When 

 peroxide of lead is used for the sa'me purpose, half its oxygen 

 escapes as a gas. Peroxide of manganese may in the same man- 

 ner be reduced to the protoxide, with the liberation of oxygen, if 

 there be present an acid to exercise an affinity for the protoxide 

 and convert it into a soluble salt. If, for example, we add to 

 peroxide of hydrogen sulphuric acid, and then peroxide of 

 manganese in the state of fine powder, much more oxygen is 

 evolved than the compound of oxygen and hydrogen could yield ; 

 and on examining the solution, we find a salt of the protoxide of 



