Catalytic Pfumomena with Allotropy. 255 



exploding hydrogen which this metal experiences when dipped 

 in certain gases, as sulphuretted hydrogen, seleuiui-etted hydrogen, 

 &c., and which is occasioned by a coating of sulphur, &c. being 

 formed about it. By the application of heat, this sulphur is expelled 

 just as is the hydrochloric acid from charcoal, and the platinum 

 again acquires the property of determining the formation of water 

 from oxygen and hydrogen. 



The fact recently ascertained by me, that iodate of potash mixed 

 with peroxide of manganese or graphite splits up into free iodine, 

 common oxygen, and potash, at a temperature which lies consider- 

 ably below the fusing-point of the salt (see the Abhandlungen der 

 Naturforschenden Gesellschaft van Basel, part 3, new series), 

 also belongs, in my opinion, to the class of catalytic phsenomena, 

 and depends immediately on a conversion of the of iodic acid 

 into 0. 



Nitric acid I consider to be a compound of NO^ + 30, of which 

 three equivalents of ozonized oxygen one is more easily transform- 

 ed into than the other two. It is known of anhydrous nitric 

 acid, that it is^much more easily decomposed into hyponitric 

 acid (NO- + 20) and common oxygen, than even peroxide of 

 hydrogen into water and 0, for the acid undergoes this decom- 

 position with an explosion even at the gentlest heat. 



By the chemical association of this acid with water it certainly 

 attains a greater constancy; but even its first hydi-ate is still 

 tolerably easily decomposed by light and heat into hyponitric 

 acid and oxygen. Finely-divided charcoal also acts like these 

 agents on the monohydrate even at ordinary temperatures, and, 

 according to my experiments, even below the freezing-point, 

 without the production of an appreciable quantity of cai'bonic 

 acid. It is therefore scarcely to be doubted that charcoal powder 

 would catalyse anhydrous nitric acid just as easily as peroxide of 

 hydrogen. 



On account of its distinguished oxidizing property, perman- 

 ganic acid (Mn^O^ = Mn^O^ + 50)isoneof the most remarkable 

 oxygen compounds ; for even in the cold it gives up with the 

 greatest readiness a part of its oxygen to oxidizable substances, 

 and gcnei'ally three equivalents; in other words, most of its 

 reactions are such, that the hydrated acid may be considered as 

 a compound of peroxide of manganese with peroxide of hydrogen 

 = 2MnOO + 3I10 6. Of the five equivalents of 6 which we have 

 to assume in permanganic acid, three at any rate are more readily 

 transferable to oxidizable substances than tlie other two ; from 

 whicli it arises that these generally precijntatc hydrated peroxide 

 of manganese from the hydrated acid. P^-ominherz has already 

 shown that vegetable charcoal decomposes this acid into peroxide 

 of manganese and common oxygen, without itself undergoing au 



