1895.] Extinctive Atmospheres produced ly Flames. 353 



IV. " The Composition of the Extinctive Atmospheres produced 

 by Flames." By FRANK CLOWES, D.Sc. Lond. Communi- 

 cated by Professor ARMSTRONG, F.R.S. Received February 

 7, 1895. 



In a former paper (* Roy. Soc. Proc.,' vol. 56), the author 

 communicated the results obtained by mingling gases, which were 

 extinctive of flame, with air, until a flame burning in the air was 

 just extinguished. The gases used in the experiments were carbon 

 dioxide and nitrogen. Each of these gases was separately intro- 

 duced into the air, and the composition of the atmosphere thus pro- 

 duced, which just extinguished flame, was determined by chemical 

 analysis. 



The general results arrived at were : 



1. That wick-fed flames require atmospheres of very similar com- 



position to extinguish them: while gas-fed flames require 

 atmospheres of widely different composition. 



2. That nitrogen must be added in larger proportion than carbon 



dioxide, in order to extinguish the same flame. 



3. That the minimum proportion of extinctive gas which must be 



mingled with air in order to extinguish a flame is independent 

 of the size of the flame. 



A supplementary series of experiments has now been undertaken 

 in order to determine the composition of the atmosphere extinctive 

 of each flame, which is produced by the flame itself when burning in 

 an inclosed volume of air at atmospheric pressure. 



Preliminary trials showed that in order to secure trustworthy 

 results, the atmosphere must not be in contact with water. It was 

 further found necessary to avoid change of pressure in the inclosed 

 atmosphere during the combustion of the flame. 



These neceissary conditions were complied with by allowing the 

 flames to burn in a bell-jar, the bottom of which was closed by 

 dipping into a sufficiently deep vessel of mercury. The neck of the 

 bell-jar was closed by a cork bearing a (J -shaped mercury gauge, 

 and a glass tube with a stopcock. 



While the flame was burning, the pressure of the air within the 

 bell-jar was maintained uniform by raising or lowering the bell-jar 

 sufficiently to maintain the mercury levels unchanged in the pressure 

 gauge. As soon as the flame was extinguished by the atmosphere 

 around it, the vessel was allowed to stand until the atmosphere within 

 had become uniform in temperature with the air around. A portion 

 of the gases within the bell- jar was then removed by means of the 

 stopcock-tube to a Hempel gas-burejtte, and was subjected to ordinary 



