222 Dr. Thomson on [Sept. 



eudiometer, with determinate quantities of oxygen gas. The 

 following are the results which I obtained : 



One hundred volumes of the inflammable gas required for 

 complete combustion 42*1 volumes of oxygen gas. After the 

 combustion, the bulk was diminished by 34-2 volumes, and the 

 residue consisted of a mixture of 25*8 volumes of carbonic acid 

 gas and of 82-2 volumes of azotic gas, which must have escaped 

 the action of the combustion. We must, therefore, consider the 

 gas to have consisted of 



Azotic gas . . 82 volumes. 



Carbon .... 26 volumes. (From the carbonic acid.) 



{(From the 16 volumes of oxygen 

 consumed above what entered 

 into the carbonic acid.) 



140 



So that the constituents of it, if they had been merely mixed 

 together without any chemical union, would have occupied 140 

 volumes instead of 100 volumes, 



I am disposed to consider this gas as a mere mixture of 82 

 Tolumes of azotic gas with 18 volumes of a gas composed of 



26 volumes carbon 

 32 volumes hydrogen 



condensed into the third part of their volume. The specific 

 gravity of such a gas would be 0'6743 ; and the specific gravity 

 of a mixture of 18 volumes of such a gas and 82 volumes of 

 azotic gas would be 0-9196. This rather exceeds the specific 

 gravity given above. But as I made only a single experiment, 

 1 might not improbably have committed an error of six per cent, 

 which constitutes the difl:"erence between the two numbers. 



If any confidence can be put in the accuracy of these experi- 

 ments, this inflammable gas constitutes a new species of carbu- 

 retted hydrogen, differing in its composition from all those 

 previously known. It seems to be a compound of 13 atoms 

 carbon and 16 atoms hydrogen, or more probably of 3 atoms 

 carbon and 4 atoms hydrogen condensed into one-third of their 

 Tolume. It is intermediate between the common species of 

 carburetted hydrogen gas and olefiant gas, and might also be 

 considered as a mixture of equal volumes of these two gases ; 

 for olefiant gas is a compound of two atoms hydrogen and two 

 atoms carbon ; while carburetted hydrogen is a compound of one 

 atom carbon and two atoms hydrogen. We have, therefore, 



Carbon Hydrogen. 



1 volume olefiant gas composed of 2 atoms + 2 atoms 

 1 volume carburetted hydrogen . . 1 +2 



Constituting our inflammable gas. 3 +4 



