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naturally suggested that Formic Aldehyde might have true
disinfecting properties. Nicolle has exposed little squares
of cloth, infected with typhoid, diphtheria, tubercle and other
matters, to the gas and found that it always destroyed the
infection. J. J. Kinyoun and Geddings have made some
elaborate researches ; they found that when various disease
producing bacteria were exposed to the gas they were
killed in a very short space of time ; but if the infective
matters were covered over with layers of material, then the
results were inconstant. With regard to damage to goods,
they found that brasswork, nickel, zinc, copper, and gilt
things generally, were not in any way injured ; on the other
hand iron and steel were attacked. They experimented on
225 samples of wool, silk, cotton, linen, leather, and hair, and
found that the Aldehyde gas produced no change in texture,
nor did it, as a rule, aftect colours ; two shades of violet and
a light red alone were bleached.
Trillat and Roux have made a number of experiments
in the disinfection of rooms, and their results have been
uniformly successful.
Since Formic Aldehyde in solution in water is in
commerce, it might be thought that the solution could be
used as an aerial disinfectant by simply putting saucers or
large photographic dishes about a room filled with
" Formalin," or that the Formic Aldehyde could be boiled
out of a solution; this has not been found practicable, the
reason being that Formic Aldehyde possesses a curious
property of changing into a white solid, in chemical
language polymerisation takes place, CHOH being changed
into C3H3O3H3. This solid substance possesses disinfectant
properties, but to a feebler degree.
It was, however, discovered by Roux and Baudet, that
when the gas was dissolved in a solution of calcium
chloride and heated under pressure, practically dry Formic
Aldehyde was evolved, which did not polymerise, and
therefore all that was required for the utilization of the
disinfecting powers of the gas was a suitable apparatus to
heat a chloride of calcium solution under pressure.