Dr THOMAS THOMSON on a New Combustible Gas. 21 



specific gravity, as it depends upon the proportion of nitrous gas, 

 a proportion not determined with perfect accuracy. 



I am disposed to consider it as not unlikely, that the propor- 

 tion of nitrous gas may have been rather underrated. On that 

 supposition, I think it very probable, that the true constituents 

 of a volume of the gas are, 



1 volume carbon vapour, 0'4166 

 1 volume hydrogen gas, 0'0694 

 1^ volume chlorine gas, 37500 



4-2361 



This would make the specific gravity of the gas 4.2361 ; which 

 only exceeds the specific gravity found by about y^th part. A 

 difference certainly not greater than might be looked for in de- 

 termining the quantity of nitrous gas mixed with it. 

 The gas, then, is a compound of 



1 atom hydrogen, 0'125 

 1 atom carbon, 0'750 

 1^ atom chlorine, 6'750 



7-625 

 and its atomic weight is 7.625. 



It contains only half the carbon and hydrogen, but 1^ times 

 the chlorine which exists in a volume of chloro-carbonic acid. 



As it will be requisite to distinguish this new inflammable 

 gas by a name, perhaps the term sesqui-chloride of carbo-hydrogen, 

 may be employed as giving an accurate idea of its composition. 



The discovery of this gas was gratifying to me, for a reason 

 which it may be worth while to explain. In the " First Prin- 

 " ciples of Chemistry" vol. i. p. 249, I pointed out a remarkable 

 property of the compound of one atom carbon and one atom hydro- 

 gen. This compound we may distinguish by the name carbo-hydro- 

 , since the appropriate term carburetted hydrogen has been un- 



