TRANSACTIONS OF SECTION B. 605 



The following Reports and Papers were read : — 



1. Report of the Committee on an International Standard for the 

 Analysis of Iron and Steel. — See Reports, p. 237. 



2. Report of the Committee on Electrolytic Methods of Quantitative 

 Analysis. — See Reports, p. 160. 



3. On tlie Proportions of Carbonic Acid in Air which are Extinctive to- 

 Flame, and tvhich are Irrespirahle. By Frank Clowes, D.Sc, Pro- 

 fessor of Chemistry in the University College, Kottingham. 



It is generally maintained that a man cannot breathe air which contains suf- 

 ficient carbon dioxide to extinguish a candle-flame. Tne correctness of this state- 

 ment is of great importance to those who have occasion to work in an atmosphere 

 which may contain large proportions of carbonic acid, such as that in a colliery ob 

 mine, or in a well-shaft. _ . 



The careful determination of the proportion of carbonic acid in air which is 

 just sufficient to extinguish flame has been made by the author, the method adopted 

 differing essentially from the methods previously employed. Experiments by earlier 

 investigators had shown very wide discrepancies. 



The author finds that the flames of candles, oil, paraffin, and alcohol are extin- 

 guished by air containing from 13 to 16 per cent, of carbonic acid. The flame of 

 coal-gas, however, required the presence of at least 83 per cent, of the extinctive 

 gas, and the flame of hydrogen was not extinguished until the amount of carbonic 

 acid in the air reached 58 per cent. 



Taking 15 per cent, of carbonic acid as the proportion in air which is extinctive 

 of ordinary portable illuminating flames, it is of interest to note that this percentage 

 of the gas in air appears from the recent experiments of Mr. J. R. Wilson ' to be 

 quite harmless when breathed. Mr. Wilson found that a rabbit which had 

 breathed for an hour air containing 25 per cent, of carbonic acid was none the 

 worse for its experience, but appeared at the end of the hour more lively than at 

 the beginning. Air containing 60 per cent, of carbonic acid, however, proved fatal 

 to the rabbit after it had been breathed for a few minutes only. Unfortunately no 

 intermediate proportions were experimented with. 



It is therefore apparently safe to say that air containing at least 10 per cent, 

 of carbonic acid more than that required to extinguish a candle-flame can be 

 breathed with impunity. Probably a much higher proportion of carbonic acid 

 than this can be breathed. 



Dr. Angus Smith and many others fully support from experience the statement 

 that a man can breathe and work in air containing more than sufficient carbonic 

 acid to extinguish a flame. 



The extraordinary vitality of the hydrogen-flame in the presence of high propor- 

 tions of carbonic acid renders it valuable for maintaining the flame in a miner's safety- 

 lamp in foul air. The composite safety-lamp described by the author at the 

 Nottingham Meeting of the British Association - serves this purpose well. It can 

 burn either an oil-flame or a hydrogen-flame or both together. _When used for 

 gas-testing, one of the flames only is used as occasion may require. But it has 

 been found that when the lamp runs the risk of being carried into foul air, it is 

 most advantageous to burn the hydrogen-flame alongside the illuminating oil-flame. 

 A comparatively low proportion of carbonic acid extinguishes the oil-flame, and 

 this would leave the miner in darkness and without the means of recovering his 

 light, since the lamp may not be opened and relighted in the mine. But the 

 hydrogen-flame continues burning in the presence of over 50 per cent, of carbonic 



' American Journ. Pharm., 50, No. 1 2. 

 ' British Assoc. Report, 1893, p. 723. 



