174 Dr Fyfe on the Use of Steam, 



The action of water on incandescent charcoal was, I believe, 

 first noticed by Priestley, and the examination of the gaseous 

 product was afterwards undertaken by Cruickshank, and also 

 by Berthollet ; the former of whom was inclined to consider it 

 a compound of carbon, hydrogen, and water ; 100 cubic inches 

 (weighing 14.5 gr.) containing, according to him, 4 gr. carbon, 

 1.3 of hydrogen, and 9 [of water, while Berthollet concluded, 

 from his experiments, that it is composed of 5 by weight of car- 

 bon, and 4 of hydrogen. 



These discordant results shew, either that the gas generated 

 varies in its composition, according to the method followed in 

 its preparation, or, that there were sources of fallacy in the ex- 

 periments, owing to the imperfect means of analysis then in use. 

 In preparing the gas for my experiments, I had recourse to the 

 usual method, viz. passing steam through a porcelain tube, stuffed 

 sometimes with charcoal, sometimes with coke, and heated to 

 redness in a furnace ; always taking care to have them heated 

 for some time before propelling the steam over them. The gas 

 was collected generally over a water trough. It was at first 

 slightly opaque, but soon became transparent. When kept over 

 lime-water there was a diminution, and the water became tur- 

 bid, shewing the presence of carbonic acid. In one instance 

 in which the gas was collected over mercury, the diminution 

 amounted to 18 per cent. After removing the carbonic acid the 

 sp. gr. was found to be in general about 470; occasionally, how- 

 ever, it was a little higher, but never beyond 480. When heated 

 in contact with air it burns with a blue flame, and carbonic acid 

 and water are formed, shewing the presence of carbon and hy- 

 drogen. In its combustion it differs from light hydro-carbon, not 

 only in the appearance of its flame, but also in its combustibility 

 with different proportions of air and of oxygen. The light hy- 

 dro-carbon cannot be exploded by means of electricity, with 

 more than two and a fourth of oxygen, whereas this gas may be 

 exploded with four limes its bulk of it. The action with spongy 

 platinum is pecuhar. When propelled against the sponge, 

 there is no action at a natural temperature ; but when the sponge 

 is heated it inflames the gas. A mixture of equal parts of the 

 gas and oxygen is not acted on by the sponge unless previously 

 heated. Even when kept in contact with the sponge before a 

 fire, there is no immediate action, but in the course of a few 



