Decomposition of certain Gaseous Compounds. 
39 
gas. The effect referred to is exhibited when oil-gas, compressed into vessels by a 
power equal to that of 30 atmospheres, is suddenly allowed to escape through a 
small aperture into the air. Ir. was first observed accidentally, in consequence of 
the derangement of the valve of a large apparatus, into which the gas had been com- 
pressed to 27 atmospheres. The gas escaped with immense velocity, and when an 
examination took place of what had happened, it was found that all the metallic 
part of the valve upon which the gas l ad rushed was covered with a black, moist, 
carbonaceous substance, and the contiguous brick wall with dry, black carbon, the 
moisture in this case having been absorbed by the brick. Since that time, Mr. Gor- 
don has repeatedly shown the effect, by allowing the gas to rush out with very 
great violence from a portable lamp against a piece of white paper, which becomes 
immediately covered with black carbonaceous deposit. 
The general conclusion is, that as the gas thus rapidly expands, a partinl decom- 
position takes place, and carbon is separated. If this explanation should ultimately 
prove, by further experiments, <to be true, it will lie highly important, as affording 
Hu instance of the exertion of mechanical and chemical powers in those circumstances 
where they most closely verge upon each other. At present, we have but little 
knowledge of such phenomena, though the announcement in France of the produc- 
tion of several new compound bodies, possessed of peculiar properties solely by the 
exertion of physical powers, may lead us to hope for an accession of information on 
the subject ; that which we thought we had, was in part rendered uncertain by the 
contrary conclusions arrived at by Mr Perkins and Dr Brewster, the one believing 
that in a case of crystallization the effect was produced entirely in consequence of 
pressure*; the other, that pressure had been the only cause why bodies, otherwise 
ready to crystallize, had retained the fluid state. 
A naturul suspicion, upon first hearing of and seeing the results obtained by Mr. 
Gordon, was, that the rapidity of the current of gas had carried away a minute 
portion of the metal from the surface of the valve past which it rushed, or- of the in- 
terior of the air-way against which it was thrown, and that that metal had caused 
the stain upon the paper ; but upon examination, this proved not to be the case; for 
the black deposit upon a card, when subjected to acids, remained insoluble, and 
when burnt and tested chemically, gave no traces of copper. 
Further examination of the substance showed that it Was not a pure carbon, but 
one of those compounds, containing a very large proportion of carbon, combined 
with a small quantity of hydrogen analogous to tar, pitch, or asphaltum, for it dis- 
solved readily in the fluid hydro carbons obtained by the compression of oil-gas. 
As these black carbonaceous compounds are formed in the process of making oil-^as, 
a suspicion cannot but arise, that the effect observed may have been produced by 
the current of gas having swept off small portions of such substances previously 
deposited, or slowly formed in the interior of the vessels at former periods ; and 
have left them upon the wall in the accidental result, or upon the paper placed in 
the current of the gas, when the effect has been purpose) y shown. 
It may, however, be remarked that, in experiments made in the laboratory of the 
Royal Institution, upon the fluid product obtained by condensing oil gas at high 
pressures, it was observed that, after rectifying the products and separating the 
more fixed from the more volatile, that although they were perfectly clear and 
transparent at first, yet by spontaneous evaporation through the corks which closed 
the vessels, and after a lapse of time, chemical changes were produced ; for, ultimate- 
ly, there remained nothing in several of the receivers but a brown substance, hed- 
vy, adhesive, like honey or treacle, and in certain cases even almost solid. From 
the circumstances of the experiments, no hesitation could arise in concluding that a 
spontaneous chemical change had taken place; and it does not seem at all unlikely 
that a similar change, or one to a much greater extent, may have occurred suddenly 
during the rapid alteration in the mechanical condition of the gas in Mr. Gordon’s 
experiment ; the moat condensible of the substances in the mixture of elastic mat- 
ters which constitute oil-gas, being perhaps those which are most altered, and in 
that case Mr. Gordon's account of the phenomena would be correct. 
W .—Miscellaneous Notices. 
1. On the Influence of the Atmosphere on the Circulation 0 f the Blood. August 
29, 1825. MM. Cuvier and Dumeril made a report upon the Memoir by Dr. 
Barry, concerning the Influence of the Atmosphere on the Circulation of the Blood . 
* Philosophical Transactions. 
