A12 Experiments on the Gas from Coal. 
unburned a very offensive smell, resembling’ 
that of bilge water, or the washings of a 
gun-barrel, and the inconvenient property of 
tarnishing silver plate; and during combus- 
tion, gives rise to the same suffocating fumes 
(sulphurous acid) which are produced by the 
burning of a brimstone match. The most 
obvious method of absorbing both the carbo- 
nic acid and the sulphuretted hydrogen, is to 
bring the recent gas into contact with quick- 
lime; and the cheapness of that substance, 
and facility of applying it, led me, several 
years ago, to propose it for the purpose.* It 
has since, I believe, been suggested that the 
sul phuretted hydrogen may be removed by 
chlorine ; but a sufficient objection to this 
agent is, that it would also separate the most 
valuable part of the product, the olefiant gas. 
The transmission of the gas through ignited 
tubes has also been proposed; but it is a well 
known property of both the varieties of car- 
buretted hydrogen, that they deposit char- 
coal when strongly heated ; and M. Berthollet 
has shewn that the amount of this effect is 
proportionate to the increase of temperaturef. 
‘Some persons, practically engaged in lighting 
* Phil. Trans. 1808. page 303. 
+ Mem. de laSoce. d’Arcueil, iii, 154. 
