If we were inclined to generalise, and to place nitrous oxide among
a known class of bodies, its properties would certainly induce us
to consider it as more analogous to the acids than to any other
substances; for it is capable of uniting with water and the alkalies,
and is insoluble in most of the acids. It differs, however, from the
stronger acids, in not possessing the sour taste,[165] and the power
of reddening vegetable blues: and from both the stronger and weaker
acids, in not being combinable when in a perfectly free state, at
common temperatures, with the alkalies. If it should be proved by
future experiments, that condensation by cold gave it the capability of
immediately forming neutro-saline compounds with the alkalies; it ought
to be considered as the weakest of the acids. Till those experiments
are made, its extraordinary chemical and physiological properties are
sufficient to induce us to consider it as a body _sui generis_.
[165] The different persons who have respired nitrous oxide have, as
will be seen hereafter, given different accounts of the taste; the
greater number have called it sweet, some metallic. One of my friends,
in a letter to me dated Nov. 13, 1799, containing a detail of some
experiments made on the respiration of nitrous oxide, at Birmingham,
denotes the taste of it by the term “sweetish faintly acidulous.” To
me the taste both of the gas and of its solution in water, has always
appeared faintly sweetish.
It is a singular fact that nitrous gas, which contains in its
composition a quantity of oxygene so much greater than nitrous oxide,
should nevertheless possess no acid properties. It is uncombinable with
alkalies, very little soluble in water, and absorbable by the acids.