Experiments on the Gas from Coal.. 413 
with gas have, to my knowledge, been led, 
by the increase of the quantity of gas which 
is obtained by passing it through red hot 
tubes, to imagine, .'that an advantage is thus 
gained; and they have not been aware, that 
the gas, when thus treated, sustains a much 
more than proportional Joss of. illuminating 
power. 
~ The quantity of quicklime required for the 
absorption of a cubic foot of carbonic acid, or 
of the same volume of sulphuretted hydro- 
gen gas, will be found on calculation not to 
exceed 1050 grains, or about 22. ounces 
avoird. A volume of coal gas containing a 
cubic foot of each of those impurities will re- 
quire, therefore, at least 5 ounces of lime ap- 
plied in the:best possible manner. But it is 
never found in practice that the whole of any 
gas, when sparingly diffused through another, 
can be taken out entirely, without using 
much more of the appropriate agent than, 
from its known powers of saturation, might 
have been deemed equivalent to the effect. 
The proportion employed by Mr. Lee is five 
pounds of fresh burned lime to 200 cubic feet 
of gas. The lime, after the addition of the 
quantity of water necessary to reduce it into 
powder, is passed through a sieve, and then 
mixed with a cubic foot (about 7% wine gal- 
