6 The late Dr. Turner's Chemical Examination of the 



bonic acid gas which was produced. As this was a uniform 

 result in all the samples, it is manifest that the constitution 

 of the inflammable principle of fire-damp is identical with 

 that of marsh gas or light carburetted hydrogen. The pro- 

 portions of carbon and hydrogen indicated by analysis, suffi- 

 ciently demonstrate the absence of such gases as hydrogen, 

 carbonic oxide, and defiant gas. Their absence, however, 

 was proved by other methods. A portion of fire-damp was 

 mixed in a tube with chlorine of known purity, and the mix- 

 ture 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 chlorine. The absence of 

 defiant and carbonic oxide gases was also proved by means of 

 spon"-y platinum. In 1824, soon after the curious action of 

 spongy platinum in causing the combination of oxygen and 

 hydrotren gases was made known by Doebereiner, both Dr. 

 Henry and myself pointed out the obstacles to that action, oc- 

 casioned by carbonic oxide, olefiant gas, and some other 

 gases*. (Philosophical Transactions, and Edinburgh Philoso- 

 phical Journal 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 action of platinum. Agreeably to those 

 researches, it follows that, if fire-damp contained merely 

 marsh gas, oxygen, and nitrogen, spongy platinum introduced 

 at common temperatures, or even heated to 300° Fahr., would 

 not produce any sensible effect ; and that if a small quantity 

 of an explosive mixture t made with one measure of oxygen, 

 and two measures of hydrogen gases, were added to the fire- 

 damp, spongy platinum should cause a production of water 

 corresponding to the quantity of explosive mixture so intro- 

 duced, without the production of any carbonic acid. But if 

 carbonic oxide or olefiant gas were present, then cold spongy 

 platinum would not act at all, a small proportion of explosive 

 mixture being employed ; and if the action were forced by 

 using hot spongy platinum, or by the free introduction of ex- 

 plosive mixture, then would carbonic acid as well as water 

 be generated. 



To apply these facts to the case in point, some very active 

 jilatinum balls, of the size of peas, were made from a mixture 

 of pipe-clay, spongy platinum, and the yellow amnion iacal chlo- 

 ride of platinum, the materials being mixed with water so as 



I • Dr. Henri's paper on this subject, from the Philosophical Trans- 

 actions, will be found in Pliil. Mag. First Series, vol. Ixv. p. 269. — Edit.] 



f By the expression " explosive mixture," 1 hereafter mean a mixture 

 made with one measure of oxygen and two measures of hydrogen gases. 



