206 Chemical Examination of the Fire-Damp. 



the whole series of successful analyses, the carbonic acid gas may 

 be taken as exactly equal to half the condensation due to the 

 formation of water, and as containing half the oxygen which was 

 required for complete combustion. The quantity of marsh gas 

 present was equal to half the oxygen required for its complete 

 combustion, to half the condensation due to generated water, and 

 to the volume of carbonic acid gas which was produced. As this 

 was a uniform result in all the samples, it is manifest that the con- 

 stitution of the inflammable principle of fire-damp is identical with 

 that of marsh gas or light carburetted hydrogen. The proportion 

 of carbon and hydrogen indicated by analysis, sufficiently de- 

 monstrate the absence of such gases as hydrogen, carbonic oxide, 

 and olefiant gas. Their absence, however, was proved by other 

 methods. A portion of fire-damp was mixed in a tube with chlo- 

 rine of known purity, and the mixture kept for a quarter of an 

 hour in a dark place, when the chlorine was absorbed by milk of 

 lime ; the original quantity of fire-damp was always recovered, 

 except a slight loss due to the mere washing to absorb the chlo- 

 rine. The absence of olefiant and carbonic oxide gases was also 

 proved by means of spongy platinum. In 1824, soon after the 

 curious action of spongy platinum in causing the combination of 

 oxygen and hydrogen gases was made known by Doebereiner, 

 both Dr. Henry and myself pointed our the obstacles to that ac- 

 tion, occasioned by carbonic oxide, olefiant gas, and some other 

 gases.* (Philosophical Transactions, and Edinburgh Philosophi- 

 cal Jour, for 1824.) And Dr. Henry at the same time showed that 

 marsh gas differs remarkably in this respect from carbonic oxide 

 and olefiant gases, as it offers scarcely any impediment to the ac- 

 tion of platinum. Agreeably to those researches, it follows that, if 

 fire-damp contained merely marsh gas, oxygen and nitrogen, 

 spongy platinum introduced at common temperature, or even 

 heated to 300° Fahr., would not produce any sensible effect ; and 

 that if a small quantity of an explosive mixturef made with one 

 measure of oxygen and two measures of hydrogen gases, were 

 added to the fire-damp, spongy platinum should cause a produc- 



[* Dr. Henry's paper on this subject, frpm the Philosophical Transactions, will be 

 found in Pliil. Mag. First Series, vol. Ixv, p. 269.— Edit. Phil. Mag.] 



t By tlie expi-ession " explosive mixture," I hereafter mean a mixture made with 

 one measure of oxygen and two measures of hydrogen gases. 



