Experiments on the Gas from Coal. 41% 
on this subject, I employed the agency of 
‘chiorine to condense both these impurities, 
and estimated how much of the absorption 
was dueto each, by arule which [have stated.* 
Recent experience, however, has led me to 
distrust this method; and after comparing 
the effects of several other agents, by expe- 
riments on mixtures of known composition, 
‘T now prefer the white carbonate of lead, pre- 
‘cipitated from acetate of lead by carbonate of 
ammonia without heat, and therefore fully sa- 
turated with carbonic acid. This precipitate 
it is better not to dry, but, after washing it 
sufficiently, to leave it under as much water 
as will give it, when wanted for use, a due de- 
gree of fluidity. ‘This mixture may be applied 
by means of a tube of the capacity of a cubic 
inch, divided into 100 equal parts, and ac- 
curately ground into a short and wider piece 
of tube, which ought not to contain more 
than three or four tenths of that quantity. 
The wider tube being filled with the fluid 
carbonate of lead, and placed with its mouth 
upwards under water, the graduated measure 
full of gas is fitted to it; and the gas and li- 
quid are brought into contact by alternately 
- inverting the two tubes, all violent agitation 
* Phil Trans. 1808, page 295. 
