Too little attention has been paid heretofore to the antiseptic
powers of certain gases. It is a well known fact, that some of the
gases which are the result of animal and vegetable decomposition are,
to a certain extent, the means of their own disinfection; hence,
some of these are endowed with deodorizing as well as antiseptic
properties.
We have already given at length the properties of chlorine. Carbonic
acid gas is another of those antiseptic agents which will occupy our
attention.
It exists in the atmosphere as a product of combustion and of
the respiration of animals; it is a result, also, of the slow
decomposition of most vegetable substances, and is evolved in great
quantities from the ground in volcanic countries. In the formation of
sugar it is produced in abundance, along with alcohol.
For the purposes of the chemist, it is generally prepared by
decomposing marble by means of some stronger acid. From its cheapness
and the solubility of the residual salt, muriatic acid is generally
employed.
The properties of carbonic acid are very remarkable; it is perfectly
colorless and invisible; it is irrespirable, producing, when an
attempt is made to breathe it, violent spasms of the glottis. If it
be respired mixed with air, even in the proportion of one to ten, it
gradually produces stupor and death, acting as a narcotic poison.
Hence, when disengaged in large quantities, whether by natural
operations or in process of manufacture, it accumulates in all
cavities within its reach, and may cause fatal accidents to animals
who enter unadvisedly.
Carbonic acid does not support combustion; a taper plunged into a jar
full of the gas is instantly extinguished. Carbonic acid is also a
check on putrefaction, and arrests decay.