in determining: Gaseous Combination^ 361 



"to 



the force of cohesion restrains the affinity of the metal for 

 oxygen, and thus enables the hydrogen to exert, at a tempe- 

 rature of about 650° Fahrenheit, that stronger attraction for 

 oxygen which, when directed upon a Jinely divided metal or 

 oxide, it does not manifest below an incipient red heat. 



Finally, it appears probable that the particles of oxygen 

 and hydrogen are brought within their combining distances 

 on the surface of iron or copper as well as on that of platina, 

 but that on the oxidizable metals their combination is pre- 

 vented by the stronger affinity of the contiguous atoms of 

 metal for oxygen. 



Another argument, in favour of the view which has been 

 taken, is the inactivity of platina itself, noticed by Dr. Faraday, 

 when introduced into mixtures of hydrogen and chlorine, 

 gases which are so much more readily combinable by other 

 means tlian hydrogen and oxygen. This inactivity is most 

 probably due to an interfering affinity of platina for chlorine, 

 — an electro-negative which manifests far more energetic affi- 

 nities for the metals than oxygen exerts, and is indeed, the 

 only solvent of gold and platina, when presented to them, in 

 its nascent state, in aqua regia. 



The power which certain gases exercise of suspending or 

 wholly preventing the action of platina on mixtures of hydro- 

 gen and oxygen, was several years ago ascribed to the similar 

 interference of an opposing affinity. (Dr. Henry on the Action 

 of Spongy Platina on Gaseous Mixtures, in the Philosophical 

 Transactions for 18ti4?*.) In that essay it was shown that the 

 . only gases possessing this singular property are such as are 

 capable, under the influence of platina, of combining with 

 oxygen, either at atmospheric or at moderately elevated tem- 

 peratures. Thus, carbonic oxide — which, when added in the 

 proportion of half a volume to one volume of a mixture of 

 hydrogen and oxygen, prevented the action of the sponge, — is 

 known to combine slowly with oxygen in presence of the 

 sponge at ordinary temperatures, and rapidly at a heat be- 

 tween 300° and 340° Fahrenheit. It is there, also, proved that 

 the affinity of carbonic oxide for oxygen greatly surpasses that 

 of hydrogen for oxygen within a considerable range of tem- 

 perature. " When carbonic oxide and hydrogen gases in equal 

 volumes, mixed with oxygen sufficient to saturate only one of 

 them,were heated in contact with the sponge to 340°, four fifths 

 of the oxygen united with the carbonic oxide, and only one 

 fifth with the hydrogen." A similar relation between the 



• [Dr. Henry's paper will be found also in Phil. Mag. (First Series), 

 vol. Ixv. p. 269.— Edit.] 



Third Series. Vol. 6. No. 35. Mai/ 1835. 3 A 



