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54
DISINFECTION OF ROOMS.
in a gaseous condition for conveniently and safely disinfecting rooms.
It was found to be soluble in water to the extent of 40 per cent. (the
solution being known as "Formalin"). Attempts have been made
by heating the solution under pressure, and with the addition of
various chemicals, to liberate the gas for disinfecting purposes.
These did not prove successful or were inconvenient in use. A
curious action takes place when a solution of the gas is evaporated
or concentrated above 40 per cent., two molecules of the gas
unite, forming a white soapy body (paraform aldehyde) and when
this is dried in vacuo over sulphuric acid (which absorbs the
moisture) a white powder (trioxymethylene) results. This is equal
to three molecules of the gas which is given off on being heated in
the presence of moisture in a suitably constructed apparatus, such as
the lamp made by the Formalin Hygienic Company. This lamp is
inexpensive (12s. 6d.), light, and may be easily carried in a handbag.
Heat is supplied from a methylated spirit lamp in the base and a cup
at the top contains the powder above referred to, which for convenience
in using is cast into tablets. The moisture produced by the burning
spirit is allowed to escape through slits in the upper part of the
apparatus, so that it may mix with the gas and prevent it
again being polymerized. Care has to be taken that the wick
of the lamp should project but little above the neck of the burner,
else the tablets may become ignited, and rendered inert for disinfecting
purposes. Ten tablets are used for disinfecting each 1,000
cubic feet of space. Fireplaces, windows and doors are sealed (as
in sulphur fumigation) with strips of brown paper, the vessel
charged with the tablets and the lamp lighted; the room is
then closed for four, six, or more hours as may be required.
At the end of that time the air of the room is found to be full of the
gas whieh though irritating to the mucous membrane of the eyes,
nose and mouth does not appear to have any injurious effect upon
animal life, and the temporary irritation soon passes off. But the
gas may always be neutralised by introducing some ammonia into
the room, or the door may be left open for a few minutes before any
one enters.