XXII THE ROYAL SOCIETY OF CANADA 



Ordinary coal gas thus obtained consists chiefly of lighter hydro- 

 carbons with hydrogen and carries also about 6% of carbon monoxide 

 and gaseous sulphur compounds. 



These sulphur compounds must be almost completely removed 

 from the gas before it is distributed. 



True coal gas unlike water gas has a very distinct odour and 

 hence its presence even in small quantity in a room can be immediately 

 detected. It is not toxic in the true sense; but in large quantity it 

 suffocates by replacing the oxygen of the air in a room. Unlike the 

 victims of poisoning by water gas or illuminating gas carrying a high 

 percentage of carbon monoxide, persons rendered unconscious by true 

 coal gas can usually be quickly and completely restored to conscious- 

 ness through artificial respiration when removed to pure air. 



Later on water gas was introduced as an illuminant, and was 

 adopted largely in the United States in preference to soft coal gas. 



Most gas companies in the United Kingdom have a coal-gas 

 plant and an auxilliary water gas plant for use when the coal supply 

 is stopped by reason of strikes among the miners. 



Water gas is manufactured by throwing steam into a retort 

 full of red-hot coal or carbon, by which the steam is decomposed into 

 hydrogen, the oxygen of the water combining with the carbon of the 

 coal to form carbon monoxide. This gas has heating power, but little 

 illuminating quality and therefore it is necessary to carburet it, 

 which is done by the addition of a sufficient quantity of carburetting 

 material of the benzine series. 



This water gas is highly poisonous; it contains when carburetted 

 about 40% carbon monoxide and if it escapes unburnt and is taken 

 into the lungs the actively poisonous carbon monoxide combines with 

 the haemoglobin of the blood with which it remains firmly fixed and 

 prevents the absorption of atmospheric oxygen, thus rapidly causing 

 asphyxiation. It is this carbon monoxide which is the poisonous ele- 

 ment in the deadly after-damp which occurs in coal mine explosions. 



An excellent account of the effects produced by carbon monoxide 

 is given by Dr. Ivor J. Davies in an article in the British Medical 

 Journal of July 11th, 1914, wherein he described the effects of poison- 

 ing by carbon monoxide in the terrible explosion in the South Wales 

 colliery, Senghenydd mine, in which 440 men were killed. He treated 

 36 cases of poisoning, 18 of which recovered, the others died. 



Numerous evidences of the poisonous character of this gas are 

 to be found in newspaper reports of firemen being overcome by 

 smoke. 



At the present day water gas is also supplied for cooking pur- 

 poses. When used for illuminating purposes it is burned more gener- 



