276 Dr. Henry on the Analysis of Gase&us Mixtures 



out any light being evolved; that carbonic oxide is as inflam- 

 mable as hydrogen ; that olefiantgas is fired by iron and char- 

 coal heated to redness; but that carburetted hydrogen, to be in- 

 flamed, requires that the wire should be white-hot. Now^ 

 this is precisely the order in which the three compound gases 

 require hydrogen to be added to them, in order to be rendered 

 susceptible of being acted upon by the platinum sponge ; 

 carbonic oxide being acted upon with the smallest proportion 

 of hydrogen, olefiant gas requiring more hydrogen, and car- 

 buretted hydrogen a still larger proportion. It is extremely 

 probable then, that the temperature, produced by the union of 

 the hydrogen and oxygen forming part of any mixture, is the 

 circumstance which determines the combustible gases to unite, 

 or not, with oxygen, by means of the sponge. It was desirable, 

 however, to ascertain the exact temperatu're at which each of 

 those three gases unites widi oxygen with the intervention of 

 the spongy platinum. For this purpose the gases, mixed with 

 oxygen enough to saturate them, were severally exposed in 

 small retorts containing a platinum sponge, and immersed in 

 a mercurial bath, to a temperature which was gradually raised 

 till the gases began to act on each other. In this way the fol- 

 lowing facts were determined. 



1st. Carbonic oxide began to be converted into carbonic 

 acid at a temperature between 300° and 310° Fahrenheit. By 

 raising the temperature to 340°, and keeping it at that point 

 for 10 or 15 minutes, the whole of the gas was acidified, the 

 condensation of volume in the mixture being equivalent to the 

 oxygen which had disappeared. 



2d]y. Olefiant gas, mixed with sufficient oxygen, and in 

 contact with the sponge, showed a commencement of decom- 

 position at 480° Fahrenheit, and was slowly but entirely 

 changed into carbonic acid by a temperature not exceeding 

 520° Fahrenheit. MM. Dulong and Thenard state the same 

 change to take place at 300° Cent. = 572° Fahrenheit; but 

 having repeated the experiment several times, I find no reason 

 to deviate from the temperature which I have assigned. 



3dly. Carburetted hydrogen, exposed under the same cir- 

 cumstances, was not in the least acted upon by a temperature 

 of 655° Fahrenheit, the highest to which, by an Argand's 

 lamp, I was able to raise the mercurial bath. This, however, 

 must have been near the temperature required for combination ; 

 for on removing the retort from the mercurial bath, and ap- 

 plying a spirit lamp, at such a distance as not to make the re- 

 tort red-hot, a diminution of volume commenced, and conti- 

 nued till all the carburetted hydrdgen was silently converted 

 into water and carbonic acid. 



4th ly. 



