1837.] On the Decomposition of certain Hydrocarbons. 219 



action on the mercury or the glass, would have made its way 

 out in the same manner. There is every reason for believing 

 that a small quantity of grease round the stoppers would have 

 made them perfectly tight. 



On the probable Decomposition of certain Gaseous Compounds 

 of Carbon and Hydrogen during sudden expansion* . 



SOME very singular appearances have been observed by Mr. 

 Gordon, of the Portable-Gas Works, which have led him to 

 believe that chemical changes are occasioned by the sudden 

 expansion of oil-gas, which do not happen when the expansion 

 is gradual ; a striking result of the change being the separa- 

 tion of carbon from the gas. The effect referred to is ex- 

 hibited when oil-gas, compressed into vessels by a power equal 

 to that of thirty atmospheres, is suddenly allowed to escape 

 through a small aperture into the air. It was first observed 

 accidentally, in consequence of the derangement of the valve of 

 a large apparatus, into which the gas had been compressed to 

 twenty-seven 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 had 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, Gordon 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 carbo- 

 naceous deposit. 



The general conclusion is, that as the gas thus rapidly ex- 

 pands, a partial decomposition takes place and carbon is sepa- 

 rated. If this explanation should ultimately prove by further 

 experiments to be true, it will be highly important, as affording 

 an 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 pro- 

 duction of several new compound bodies, possessed of peculiar 



* Quarterly Journal of Science, xxiii. 204. 



