404 Experiments on the Gas from Coal. 
nated with 15 measures of azote in every 
hundred, the oxygen, required for saturating 
100 measures of the really combustible part 
of it, may be stated at 195; and the carbo- 
nic acid produced at 110. It may be neces- 
sary to observe, that in comparing the value 
of gases produced from different kinds of - 
coal, or from thesame kind of coal differently 
treated, it is not enough to determine the 
quantity of aériform products; and no satis- 
factory conclusion can be drawn respecting 
the relative fitness of any variety of coal for 
affording gas, or the advantages of different 
modes of distillation, unless the degrees of 
combustibility of the gases compared be de- 
termined, by finding experimentally the pro- 
portion of oxygen gas required for their sa- 
turation. 
The results expressed in the first table, 
when contrasted with those which I formerly 
obtained by the destructive distillation of 
small quantities of coal, present several cir- 
cumstances of disagreement, as to the qua- 
lity of the products at different stages of the 
operation. In small experiments, the sul- 
phuretted hydrogen and carbonic acid gases 
were evolved only at the early stages of the 
process; and sulphuretted hydrogen, espe- 
cially, could not by the nicest tests be disco- 
