93 On the aériform Compounds of Charcoal and Hydroger. 
or twenty minutes, and then quickly washing the remaining gat 
with dilute solution of potash, in order to remove the excess of 
chlorine. From the volume of the residuary gas, it was neces- 
sary to deduct the amount of impurity previously ascertained to 
exist in the chlorine ; and the remainder, taken from the volume 
of mixed gases whieh had been operated on, showed how much 
olefiant gas had been condensed by the chlorine. When very 
narrow tubes were employed, and the column of gases mixed 
with chlorine was of considerable length, a longer continuance of 
the experiment was found necessary, and the gases were suffered 
to remain in contact during an hour or more. In this way it 
was ascertained, that olefiant gas may be accurately separated by 
chlorine from hydrogen, carburetted hydrogen, or carbonic oxide 
gases, or from mixtures of two or more of those gases, which are 
left quite unchanged in volume and in chemical properties, when 
light has been carefully excluded from the mixture. 
This property of chlorine is the foundation of a fresh analysis, 
to which I have thought it expedient to submit the gases from 
coal and oil, in order to decide what aériform fluids remain after 
the separation of that portion which is condensible by chlorine ; 
—whether the residue consists, as I have heretofore maintained, 
of carburetted hydrogen chiefly, with variable proportions of hy- 
drogen and carbonic oxide; or whether, according to the new 
view of the subject, it consists of hydrogen gas only. 
In the experiments made for this purpose, I operated gener ally 
on from 60 to 80 cubic inches of oil gas or coal gas, assaying a 
small specimen first, as a guide to the quantity of ‘chlorine which 
it would be necessary to employ. The volume of chlorine thus 
found to be requisite, and about half as much more, was passed 
into.an air receiver standing over water, and completely shaded 
by an opake cover which was fitted over it. The oil or coal gas 
was then added by degrees, if much condensation was expected, 
because in that case a cousiderable increase of temperature would 
have been produced by the sudden admixture of large quantities ; 
or at ouce, if only a moderate action had been indicated by the 
previous assay. The mixture was allowed to stand, completely 
guarded from the light, during 30 or 40 minutes, or even longer, 
and the residue was expeditiously washed with liquid potash, and 
a small portion again assayed, to ascertain that the action of the 
chlorine was complete. The specific gravity of the washed gas. 
was then carefully taken, that of the entire gas having been pre- 
viously determined: and the results of its combustion with oxy- 
gen examined, and compared with those of the gas in its original 
State. 
[The Continuation of this Paper, containing Experiments on the Gas from 
Oil and from Coal, in our next. | 
XVIII, On 
ee 
