olutions of 1:15,000 it stops decomposition;
in solutions of 1:2,000 it kills bacteria in two hours; and in a
strength of 1:500 it acts very quickly as a germicide for all
bacteria, and even for spores. Corrosive sublimate dissolves in
sixteen parts of cold and three parts of boiling water, but for
disinfecting purposes it should be colored so that it may not be
inadvertently used for other purposes, as the normal solutions are
colorless and may accidentally be used internally. The action of the
bichloride is increased by heat.

=Formalin= is a forty per cent solution of formaldehyde gas, and its
uses and methods of employment have already been considered.

=Potassium Permanganate= is a good germicide, and weak solutions of it
are sufficient to kill some bacteria, but the objections against its
use are that solutions of potassium permanganate become inert and
decompose on coming in contact with any organic matter. Furthermore,
the chemical would be too expensive for disinfecting purposes.

=Ferrous Sulphate= (copperas) was formerly very extensively used for
disinfecting purposes, but is not so used at present, owing to the
fact that it has been learned that the germicidal power of this
material is very slight, and that its value depends mostly upon its
deodorizing power, for which reason it is used on excreta in privy
vaults, etc.

=Lime.=--When carbonate of lime is calcined the product is common
lime, which, upon being mixed with water, produces slaked lime; when
to the latter considerable water is added, the product is milk of
lime, and also whitewash. Whitewash is often used to disinfect walls
and ceilings of cellars as well as of rooms; milk of lime is used to
disinfect excreta in privy vaults, school sinks, etc. Whenever lime is
used for disinfecting excreta it should be used generously, and be
thoroughly mixed with the material to be disinfected.

_Disinfection of Rooms_

Practical disinfection is not a routine, uniform, and thoughtless
process, but demands the detailed, conscientious application of
scientific data gained by research and laboratory experiments.
Disinfection to be thorough and successful cannot be applied to all
objects, material, and diseases in like manner, but must be adjusted
to the needs of every case, and must be performed conscientiously.
Placing a sulphur candle in a room, spilling a quart of carbolic acid
or a couple of pounds of chlorinated lime upon the floors or objects,
may b