determined than that of any other substance of the class. Chemistry
affords two general methods of determining the constituent principles of
bodies, the method of analysis, and that of synthesis. When, for
instance, by combining water with alkohol, we form the species of liquor
called, in commercial language, brandy or spirit of wine, we certainly
have a right to conclude, that brandy, or spirit of wine, is composed of
alkohol combined with water. We can produce the same result by the
analytical method; and in general it ought to be considered as a
principle in chemical science, never to rest satisfied without both
these species of proofs.
We have this advantage in the analysis of atmospherical air, being able
both to decompound it, and to form it a new in the most satisfactory
manner. I shall, however, at present confine myself to recount such
experiments as are most conclusive upon this head; and I may consider
most of these as my own, having either first invented them, or having
repeated those of others, with the intention of analysing atmospherical
air, in perfectly new points of view.
I took a matrass (A, fig. 14. plate II.) of about 36 cubical inches
capacity, having a long neck B C D E, of six or seven lines internal
diameter, and having bent the neck as in Plate IV. Fig. 2. so as to
allow of its being placed in the furnace M M N N, in such a manner that
the extremity of its neck E might be inserted under a bell-glass F G,
placed in a trough of quicksilver R R S S; I introduced four ounces of
pure mercury into the matrass, and, by means of a syphon, exhausted the
air in the receiver F G, so as to raise the quicksilver to L L, and I
carefully marked the height at which it stood by pasting on a slip of
paper. Having accurately noted the height of the thermometer and
barometer, I lighted a fire in the furnace M M N N, which I kept up
almost continually during twelve days, so as to keep the quicksilver
always almost at its boiling point. Nothing remarkable took place during
the first day: The Mercury, though not boiling, was continually
evaporating, and covered the interior surface of the vessels with small
drops, at first very minute, which gradually augmenting to a sufficient
size, fell back into the mass at the bottom of the vessel. On the second
day, small red particles began to appear on the surface of the mercury,
which, during the four or five following days, gradually increased in
size and number; after which they ceased to increase in either respect.
At the end of twelve days, seeing that the calcination of the mercury
47