diminution of their bulk takes place in a far greater degree as the
pressure increases.

Again, if ammoniacal gas is reduced by a compressing force to
one-sixth of its volume, or carbonic acid is reduced to one
thirty-sixth, a portion of them loses entirely the form of a gas,
and becomes a liquid, which, when the pressure is withdrawn, assumes
again in an instant its gaseous state--another deviation from the
law of Marriotte.

Our process for reducing gases into fluids is of admirable
simplicity. A simple bent tube, or a reduction of temperature by
artificial means, have superseded the powerful compressing machines
of the early experimenters.

The cyanuret of mercury, when heated in an open glass tube, is
resolved into cyanogen gas and metallic mercury; if this substance
is heated in a tube hermetically sealed, the decomposition occurs as
before, but the gas, unable to escape, and shut up in a space
several hundred times smaller than it would occupy as gas under the
ordinary atmospheric pressure, becomes a fluid in that part of the
tube which is kept cool.

When sulphuric acid is poured upon limestone in an open vessel,
carbonic acid escapes with effervescence as a gas, but if the
decomposition is effected in a strong, close, and suitable vessel of
iron, we obtain the carbonic acid in the state of liquid. In this
manner it may be obtained in considerable quantities, even many
pounds weight. Carbonic acid is separated from other bodies with
which it is combined as a fluid under a pressure of thirty-six