4t4 Experiments on the Gas from Coal. 
lons) of water. This is found to be enough 
to purify the gas sufficiently for ordinary pur- 
poses; but it still retains a minute proportion 
of sulphuretted hydrogen, which, from the 
shade of colour produced in the test, may be 
estimated at about one ten thousandth of its 
volume. For some purposes, the same gas ~ 
is therefore washed a second time with a si- 
milar proportion of fresh lime, which, with- 
out being removed from the cistern, is again 
employed to give the first washing to another 
quantity of fresh gas. After the second puri- 
fication, the gas produces no change what- 
ever in the test, which preserves its perfect 
whiteness, thereby demonstrating the com- 
plete removal of the sulphuretted hydrogen, 
In this state of purity, its odour, also, is so 
much diminished, as scarcely to be at all 
offensive. . 
In order to ascertain whether any, and 
what portion of olefiant or carburetted hydro- 
gen gas is lost by the action of the lime li- 
quor, I compared, with the greatest care, 
the products of the combustion of the re- 
cently, prepared gas, and of the same gas 
after one and two washings with lime and 
water. 
