4^1 
of carbon and hydrogen, &c. 
standing over water and oil, to unknown, but much smaller 
proportions. It is therefore an object in the analysis of oil 
and coal gas, to possess means by which their presence and 
quantity may be ascertained ; and this I find may be done 
with considerable exactness by the use of sulphuric acid, oil, 
&c. in consequence of their solvent power over them. 
Sulphuric acid is in this respect a very excellent agent. It 
acts upon all these substances instantly, evolving no sul- 
phurous acid ; and though, when the quantity of substance is 
considerable as compared with the acid, a body is left unde- 
composed by, or uncombined with the acid, and volatile, so 
as constantly to afford a certain portion of vapour ; yet when 
the original substance is in small quantity, as where it exists 
in vapour in a given volume of gas, this does not interfere, in 
consequence of the solubility of the vapour of the new com- 
pound produced by the action of the acid in the acid itself in 
small quantities: and I found that when i volume of the 
vapour of any of the products of the oil gas liquor was acted 
upon, either alone, or mixed with i, 2, 3, 4, up to 12 volumes 
of air, oxygen or hydrogen, by from half a volume to a volume 
of sulphuric acid, it was entirely absorbed and removed. 
When olefiant gas is present, additional care is required 
in analytical experiments, in consequence of the gradual 
combination of the olefiant gas with the sulphuric acid. I 
found that 1 volume of sulphuric acid in abundance of ole- 
fiant gas, absorbed about 7 volumes in 24 hours in the dull 
light of a room ; sun-shine seemed to increase the action a 
little. When the olefiant gas was diluted with air or hydro- 
gen, the quantity absorbed in a given time was much dimi- 
nished ; and in those cases it was hardly appreciable in 
