gaseous mixtures , and its application to their analysis. 285 
oxide, olefiant, and carburetted hydrogen for example) 
may be made to take place in succession ; and by removing 
the carbonic acid, formed at each operation, it may be ascer- 
tained how much of each of the two first gases has been de- 
composed. The carburetted hydrogen indeed always remains 
unchanged, and its quantity must be determined by firing it 
with oxygen by the electric spark. If hydrogen also be pre- 
sent, it is difficult to prevent the olefiant gas from being par- 
tially acted upon ; but this is of little consequence, as I had 
shown that it is easy to remove that gas in the first instance 
by chlorine.* It may be remarked, that this method of ope- 
rating on the aeriform compounds of charcoal gives more 
accurate results than rapid combustion by the electric spark, 
being never attended with that precipitation of charcoal, which 
is often observed when the gases are exploded with oxygen. 
A regulated temperature, also, effects the analysis of such 
mixtures much more correctly than the action of the sponge 
or balls, because in the latter case the heat produced is un- 
certain ; and though sometimes adequate to the effect, yet 
there is always a risk that it may exceed, or fall short of 
that degree, which is required for the successful result of the 
analytic process. 
From the facts which have been stated, I derived a method 
of obtaining carburetted hydrogen gas perfectly free from 
olefiant gas, hydrogen, and carbonic oxide, and mixed only 
with a little oxygen, which, had it been necessary to my pur- 
pose, might also have been separated. The early product of 
the distillation of pit-coal was washed with a watery solution 
* Philosophical Transactions, 1821, p. 147. 
