eous disinfectants, formic aldehyde
has of late years taken foremost place. The vapour is a powerful
disinfectant and deodorant, and for the surface disinfection of rooms,
fulfils all requirements when used in sufficient amount. It acts more
rapidly than equal quantities of sulphurous acid, and it does not affect
colours. It is non-poisonous, though irritating to the eyes and throat.
With the exception of iron and steel it does not attack metals. It can
be obtained in paraform tabloids, and with a specially constructed
spirit lamp disinfection can be carried out by any one. Twenty tabloids
must be employed for every 1000 cubic ft. of space. Disinfection by
sulphurous acid fumes is of great antiquity, and is still in very
general use; for the purpose of destroying vermin it is more powerful
than formic aldehyde. Camphor and some volatile oils have also been
employed as air disinfectants, but their virtues lie chiefly in masking,
not destroying, noxious effluvia. In the 2nd class--non-gaseous
disinfecting compounds--all the numerous antiseptic substances may be
reckoned; but the substances principally employed in practice are
oxidizing agents, as potassium manganates and permanganates, "Condy's
fluid," and solutions of the so-called "chlorides of lime," soda and
potash, with the chlorides of aluminium and zinc, soluble sulphates and
sulphites, solutions of sulphurous acid, and the tar products--carbolic,
cresylic and salicylic acids. Of the physical agents heat and cold, the
latter, though a powerful natural disinfectant, is not practically
available by artificial means; heat is a power chiefly relied on for
purifying and disinfecting clothes, bedding and textile substances
generally. Different degrees of temperature are required for the
destruction of the virus of various diseases; but as clothing, &c., can
be exposed to a heat of about 250 deg. Fahr. without injury, provision is
made for submitting articles to nearly that temperature. For the
thorough disinfection of a sick-room the employment of all three classes
of disinfectants, for purifying the air, for destroying the virus at its
point of origin, and for cleansing clothing, &c., may be required.

DISMAL, an adjective meaning dreary, gloomy, and so a name given to
stretches of swampy land on the east coast of the United States, as the
Dismal Swamp in Virginia and North Carolina. The derivation has been
much discussed. In the early examples of the use the word