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Extinctive Atmospheres produced by Flames. [Feb. 21, 



According to the statements published by Dr. J. Haldane (' Roy. 

 Soc. Proc.,' December 6, 1894), an atmosphere of the average com- 

 position of expired air, or of that left by the combustion of candles or 

 lamps, although it is extinctiveof the flames of candles and of lamps, 

 can be breathed by most people without producing any distinctly 

 noticeable effect. With some people, the increased proportion of 

 carbon dioxide would cause the inspirations to be somewhat deeper 

 than usual, but in no case would injury to health result from breath- 

 ing such an atmosphere. 



The statement made by the author in a previous paper ('Roy. Soc. 

 Proc.,' vol. 56), that men could apparently breathe with safety an 

 atmosphere which just extinguished the flame of a candle or of a 

 lamp, is therefore fully borne out by the above results. This agrees 

 with the statements made by experienced mining authorities. 

 Accordingly the extinction of such ordinary illuminating flames can- 

 not be considered as proof that an atmosphere is not respirable with 

 safety. 



The residual atmosphere produced by the hydrogen flame is 

 undoubtedly not respirable, on account of the greatly diminished 

 proportion of oxygen which it contains. The colour of the hydrogen 

 flame undergoes a distinct change in colour from reddish-purple to 

 blue as the proportion of oxygen in the atmosphere is diminished. 

 Since a similar change of colour is noticed when carbon dioxide is 

 present in the atmosphere, it is probably due to the lowering of 

 temperature of the flame : all attempts to detect the production of 

 carbon monoxide by this flame, when it is burning in air containing 

 carbon dioxide, have failed. 



The conclusions which may be drawn from the above results are 

 that : 



1. The flames of the combustible gases and liquids, which were 



experimented upon, produce, at the point of extinction in an 

 enclosed atmosphere, a change in the proportion of oxygen in 

 the air generally corresponding to that produced by preparing 

 extinctive atmospheres by artificial mixture. 



2. The flames of candles and lamps, when they are extinguished by 



