1894.] Atmospheres which extinguish Flame. 3 



The gaseous mixture was considered to be in extinctive proportions 

 if the flame was extinguished during its downward passage, or imme- 

 diately upon attaining its lowest position in the cylinder. The 

 mixture was considered to contain the minimum necessary quantity of 

 extinctive gas, when another mixture containing 1 per cent, less of 

 the extinctive gas allowed the flame to continue burning in it for a 

 few seconds only. 



The limiting differences between the results of repeated trials 

 corresponded to 1 per cent, of the extinctive gas in the air. 



This minimiim necessary percentage of extinctive gas is recorded 

 below in tabulated form. 



It was considered necessary to take the immediate extinction of the 

 flame as the criterion of extinctive power, since the composition 

 of the atmosphere was rapidly affected by the combustion of the 

 flame. 



3. Influence of the Size of the Flame. 



As a matter of convenience, the flames were, in all cases, set to a 

 height of 0'75 inch. But a series of experiments was undertaken 

 with the same flame of varying size, in order to ascertain if the pro- 

 portion of extinctive gas necessary to extinguish the flame varied with 

 the size of the flame. 



The results of these experiments with flames of hydrogen and 

 alcohol, varying from 0'4 in. to 1*5 in. in height, show that the vary- 

 ing dimensions .of the flame, within the wide limits included in the 

 trials, are without influence on the proportion of carbon dioxide in the 

 air necessary to produce extinction. 



4. Method of Preparation of Gases Used. 



The carbon dioxide employed for the experiments was prepared in 

 the usual way by the action of dilated hydrochloric acid upon marble. 

 It was washed with water, and was proved to be practically free 

 from air. 



The nitrogen was prepared by heating an aqueous solution contain- 

 ing potassium nitrite, ammonium chloride, and potassium dichromate. 

 An analysis of the resulting gas proved that it contained 99'7 per 

 cent, of nitrogen. 



5 Residts obtained by the Experiments. 



In the following table the number entered is the average of 

 numerous closely concordant experimental results. The percentage 

 volume of nitrogen in air is taken as 21. 



Cu 

 a 



