284 Dr. Henry’s Description of an Apparatus j or the 
these gases, so much diversified in their physical and chemical 
properties, are mixtures of a few binary compounds, with 
which chemists are already acquainted ; or whether, on the 
contrary, their elements are capable of uniting in indefinite 
proportions, and of composing ternary compounds of oxygen, 
hydrogen, and carbon, or varieties of oxy -carbureted hydrogen. 
It would encroach too much on the time of the Royal Society, 
to enter upon this controversy. And, as neither opinion admits, 
at present, of demonstrative evidence, I may be permitted, in 
explaining the following experiments, to assume that theory, 
which appears to me most probable ; viz. that the aeriform 
products of the distillation of vegetable substances, are mix- 
tures of carbonic acid, carbonic oxide, olefiant, carbureted 
hydrogen, and simple hydrogen gases ; or of two or more of 
these in various proportions. 
The analysis of these compound gases has hitherto been at- 
tempted solely by their rapid combustion With oxygen gas, in 
the following manner : a mixture of the inflammable gas with 
oxygen gas in known proportions, is admitted into a Volta’s 
Eudiometer, inflamed over mercury by the electric spark ; and 
the diminution ascertained. To the remainder caustic potash 
or lime water is added, by which it sustains a second diminution 
of bulk ; and the amount of this denotes the quantity of carbonic 
acid formed by the combustion. The quantity of nitrogen gas, 
in the oxygen employed, as well as in the residue left by 
potash, being determined by a fit eudiometrical test, it is easy to 
infer what quantity of oxygen has been absorbed by the deto- 
nation. And as it is proved that oxygen gas sustains no change 
of bulk by conversion into carbonic acid, we may conclude that, 
after deducting from the volume of oxygen gas expended, 
that of the carbonic acid which has been formed, the remain- 
