6 Composition of Atmospheres which extinguish Flame. [May 10, 



the heavy gas is mingled with the air, it adds to the density of the 

 mixture, and renders the atmosphere more sluggish in its movement 

 towards the flame to supply the necessary oxygen. 



It had been anticipated that in the presence of the hydrogen 

 flame, and possibly of other flames, carbon dioxide would have 

 suffered partial deoxidation, as it is well known to do in the presence 

 of burning magnesium vapour. No such action appeared to occur, 

 else the above relation between the extinctive powers of carbon 

 dioxide and nitrogen could not well exist. 



The cause of the comparative uniformity of the proportion of 

 extinctive gas required for wick-fed flames has been already hinted 

 at. The flames are starved of combustible nutriment by the lowering 

 of the temperature of the flame. This cause seems to operate with 

 strikingly similar results upon the different solid and liquid com- 

 bustibles. 



The cause of the want of conformity to theoretical considerations 

 in the case of the gaseous flames fed from jets is not at once 

 apparent. 



It is of practical interest to note that the introduction of a mini- 

 mum of 15 per cent, of carbon dioxide into air is necessary to cause 

 it to extinguish ordinary wick-fed flames, the oxygen being reduced 

 by this admixture from the normal proportion of 21 per cent, to 18 per 

 cent. For the extinction of a coal-gas flame, however, the addition of 

 33 per cent, of carbon dioxide is necessary, and the oxygen being 

 thus reduced to 14 per cent. The hydrogen flame has far greater 

 vitality, requiring the admixture of 58 per cent, of carbon dioxide 

 with air, and the consequent reduction of the oxygen to 8'8 per cent., 

 before it suffers extinction. This fact is of great importance, since it 

 shows that the hydrogen flame in the composite miner's safety lamp 

 (' Boy. Soc. Proc.,' vol. 52, p. 486) may be used as an auxiliary to 

 prevent the loss of flame when the lamp is being carried through 

 mine-air containing large proportions of carbon dioxide. 



I have to thank one of my senior students, Martin E. Feilmann, 

 B.Sc., for conducting much of the experimental work involved in this 

 research. 



[April 2Sth, 1894. Recent experiments seem to prove that a 

 rabbit can breathe with impunity, for at least an hour, air containing- 

 25 per cent, of admixed carbon dioxide (J. R. Wilson, ' American 

 Journal of Pharmacy,' 50, No. 12). If this is the case, the extinction 

 of an ordinary flame does not prove the surrounding atmosphere to 

 be irrespirable. The introduction of 15 per cent, of this gas ex- 

 tinguishes a flame, whilst the air seems to be still respirable, even 

 after it has been mingled with an additional 10 per cent, of carbon 

 dioxide. F. C.I 



