364 Dr. C. Henry's Experiments on the Action of Metals 



and were but slightly affected by prolonged contact with it. 

 Since obtaining these results, 1 have observed that Thenard 

 had previously given the same testimony*. 



The almost total absence of the power of absorbing gaseous 

 matter in spongy platina, indicated by these experiments, is 

 irreconcileable with the properties attributed to the black 

 powder of Liebig, which is regarded by him as nothing more 

 than pure metallic platina in a state of extreme subdivision. 



But the following experiments render it probable that, if 

 not a suboxide of platina, the powder of Liebig is either a 

 mixture of suboxide and metal, or at least retains much oxy- 

 gen in the state of adhesion, and that the absorption of hy- 

 drogen is mainly due to its conversion into water. 



Five grains of the powder, prepared according to the pro- 

 cess described by Liebig, were compressed into the end of a 

 glass tube, and protected, by a cork removeable at plea- 

 sure, from the action of mercury, with which it rapidly amal- 

 gamates. The tube was then filled with mercury and in- 

 verted. Hydrogen in measured quantity was admitted. On 

 withdrawing the cork and allowing contact of the gas and 

 powder, there was a rapid absorption of the gas, with evident 

 deposition of moisture. When the powder had ceased to act, 

 it was found that '49 cubic inch of hydrogen had disappeared. 

 Supposing this diminution to be entirely due to the formation 

 of water, five grains of the powder must have contained '245 

 cubic inch of oxygen. 



To the same weight of black powder '72 cubic inch of car- 

 bonic oxide was admitted. There was a diminution to '61, 

 which, when washed with potassa, left '19. Hence *42 cubic 

 inch of carbonic oxide had been converted into carbonic acid, 

 for which '21 cubic inch of oxygen are required, a number 

 according as nearly as can be expected with that given by 

 the former experiment +. 



But if we even admit the powder of Liebig to be metallic 

 platina in a finely divided state, this admission will not ex- 

 plain the combining powers of laminated or spongy platina, 

 which induces gaseous union, but does not absorb any ap- 

 preciable volume of the separate gases. The theory of Dr. 

 Faraday, so far at least as respects the two leading principles, 



* Traite de Chimie, torn. ii. p. 633. (G*"^ edit.) 



t In the few trials I have hitherto made with the powder of Liebig, its 

 combining powers were in no degree interfered with by the presence of 

 foreign gases. When introduced into an explosive mixture of hydrogen 

 arrd oxygen, to which an equal volume of either carbonic oxide, olefiant 

 gas, or even sulphuretted hydrogen had been added, the powder instantly 

 glowed, and caused rapid combustion of the gaseous mixture; and when 

 admitted into a mixture of carbonic oxide and oxygen, it occasioned instant 

 combination with incandescence of the powder. 



