Dr. Henry’s Description of an Apparatus, &c. 283 
and precise for this purpose, would require a larger appro- 
priation of time, than I have the prospect of being able to be- 
stow ; and I can only on the present occasion, offer an example 
of the method, in which it appears to me that the analysis of 
this class of substances will be most successfully attempted. 
When a vegetable substance, composed (as may be as- 
sumed to simplify the statement) of oxygen, hydrogen, and 
carbon, united in the form of a ternary compound, is submitted 
to distillation, at a temperature not below that of ignition, the 
equilibrium of affinities, which constituted the triple com- 
bination, is destroyed ; and the elements, composing it, are 
united in a new manner. Those, which are disposed to enter 
into permanently elastic combinations, escape in the state of 
gas. The carbon, uniting with oxygen, either composes car- 
bonic acid gas, or, stopping short of that degree of oxygena- 
tion, which is essential to change it into an acid, is converted 
into carbonic oxide. The hydrogen, combining with a por- 
tion of carbon, constitutes a binary compound of those two 
ingredients, forming either what has been called carbureted 
hydrogen gas, or super-carbureted hydrogen, better known by the 
appellation of olefiant gas. Towards the close of the process, 
a portion of simple hydrogen gas is also mingled with the 
products. Perhaps in no instance is any one of the gases, 
which have been enumerated, obtained perfectly pure, by the 
distillation of a vegetable substance. The aeriform fluids, 
which are thus generated, are found to be possessed of almost 
every degree of specific gravity ; and to yield, by combus- 
tion, extremely different results, according to the temperatime 
at which they have been formed ; the stage of the process at 
which they have been separated ; and other modifying cir- 
cumstances. It becomes an interesting question, whether 
O o 2 
