Chemical Science. 377 



Carbonic oxide and oxygen form carbonic acid ; nitrous gas is 

 decomposed by hydrogen at the common temperature, by con- 

 tact with spongy platinum ; and a mixture of olefiant gas, with suf- 

 ficient oxygen is changed into water and carbonic acid at 572° F. 



These philosophers then observe that certain metals have the 

 property of decomposing ammonia, without absorbing either of 

 its elements, at a temperature at which the ammonia by itself would 

 be quite unchanged ; 150 grains of iron wire are thus sufficient for 

 decomposing nearly the whole of a rapid current of ammoniacal 

 gas, continued for S or 10 hours, whilst thrice as much platina wire 

 does not produce a like effect, even at a much higher temperature. 

 These results depend, perhaps, on the same causes which make 

 gold and silver effectual in combining oxygen and hydrogen, at 572° 

 F., massive platinium at 518° F., and spongy platinum at common 

 temperatures. Now as iron so well separates the elements of am- 

 monia, and scarcely at all effects the combination of hydrogen with 

 oxygen, whilst with platinum it is the reverse ; the authors are induced 

 to suppose that some gases tend to combine under the influence of 

 metals, and others to separate, the effect varying with the nature of 

 each ; but they refrain from offering conjectures until supported by 

 experiments. 



MM. Dulong and Thenard, have also ascertained that spongy 

 palladium will inflame hydrogen as platina does; that iridium in 

 the same form became hot and produced water ; that cobalt and 

 nickel in masses, cause the gases to combine at about 300° F. ; that 

 cold spongy platina formed water and ammonia, with nitrous gas 

 and hydrogen ; and acted also on mixed hydrogen and nitrous oxide 

 gases. 



Mr. W. Herapath* has made experiments on this subject, most 

 of which being of a similar nature to some of those already des- 

 cribed, we omit to specify. His attention was particularly directed 

 to the temperature at which the effect first began to take place, and 

 he states as the results of his experiments on this point, that if the 

 gases have a temperature of 55°, the platina requires a tempera- 

 ture so high as 9S° to cause them to unite. 



Mr. Garden of Oxford Street, has also experimented on this 

 subject t, and has found, that the black powder, consisting of iridium 

 and osmium, left when crude platina is digested in nitro-muriatic 

 acid, if heated red hot and then suffered to cool, acts as well as 

 spongy platina itself. He also ascertained that a jet of hydrogen 

 cooled to 32°; if thrown upon spongy platina cooled also to 32°, 

 quickly heated it to whiteness, and became inflamed, a result which 

 contradicts Mr. Herapath's statement, and shews that the limit of 

 temperature at which spongy platina ceases to act on mixed oxygen 

 and hydrogen gas has not yet been attained. 



* Philosophical Mag. lxii. 256. t Amah Phil. N. S., vi. 406. 



