ometer lost at the same time. Both of these are of very
inconsiderable consequence in extensive experiments, and they are even
capable of being valued in our calculation of the results.

In a particular memoir, I shall give an account to the Academy of the
difficulties inseparable from this kind of experiments: These are so
insurmountable and troublesome, that I have not hitherto been able to
obtain any rigorous determination of the quantities of the products. I
have sufficient proof, however, that the fixed oils are entirely
resolved during combustion into water and carbonic acid gas, and
consequently that they are composed of hydrogen and charcoal; but I have
no certain knowledge respecting the proportions of these ingredients.

SECT. V.

_Of the Combustion of Alkohol._

The combustion of alkohol may be very readily performed in the apparatus
already described for the combustion of charcoal and phosphorus. A lamp
filled with alkohol is placed under the jar A, Pl. IV. Fig. 3. a small
morsel of phosphorus is placed upon the wick of the lamp, which is set
on fire by means of the hot iron, as before directed. This process is,
however, liable to considerable inconveniency; it is dangerous to make
use of oxygen gas at the beginning of the experiment for fear of
deflagration, which is even liable to happen when common air is
employed. An instance of this had very near proved fatal to myself, in
presence of some members of the Academy. Instead of preparing the
experiment, as usual, at the time it was to be performed, I had disposed
every thing in order the evening before; the atmospheric air of the jar
had thereby sufficient time to dissolve a good deal of the alkohol; and
this evaporation had even been considerably promoted by the height of
the column of mercury, which I had raised to EF, Pl. IV. Fig. 3. The
moment I attempted to set the little morsel of phosphorus on fire by
means of the red hot iron, a violent explosion took place, which threw
the jar with great violence against the floor of the laboratory, and
dashed it in a thousand pieces.

Hence we can only operate upon very small quantities, such as ten or
twelve grains of alkohol, in this manner; and the errors which may be
committed in experiments upon such small quantities prevents our placing
any confidence in their results. I endeavoured to prolong the
combustion, in the experiments contained in the Memoirs of the Academy
for 1784, p. 593. by lighting the