; while municipal
authorities usually construct very large steam disinfecting plants. A
steam disinfector is made of steel or of wrought iron, is usually
cylindrical in shape, and is covered with felt, asbestos, etc. The
disinfector has doors on one or both ends, and is fitted inside with
rails upon which a specially constructed car can be slid in through
one door and out through the other. The car is divided into several
compartments, in which the infected articles are placed; when thus
loaded it is run into the disinfector. The steam disinfectors may be
fitted with thermometers, vacuum formers, steam jackets, etc.

_Gaseous Chemical Disinfectants_

Physical disinfectants, however valuable and efficient, cannot be
employed in many places and for many materials infected with disease
germs, and therefore chemicals have been sought to be used wherever
physical disinfectants could not for one or more reasons be employed.
Chemicals are used as disinfectants either in gaseous form or in
solutions; the gaseous kinds are of especial value on account of their
penetrating qualities, and are employed for the disinfection of rooms,
holds of ships, etc. There are practically but two chemicals which are
used in gaseous disinfection, and these are sulphur dioxide and
formaldehyde.

=Sulphur Dioxide.=--Sulphur dioxide (SO2) is a good surface
disinfectant, and is very destructive to all animal life; it is one of
the best insecticides we have, but its germicidal qualities are rather
weak; it does not kill spores, and it penetrates only superficially.
The main disadvantages of sulphur dioxide as a disinfectant are: (1)
that it weakens textile fabrics; (2) blackens and bleaches all
vegetable coloring matter; (3) tarnishes metal; and (4) is very
injurious and dangerous to those handling it.

There are several methods of employing sulphur in the disinfection of
rooms and objects, e. g., the pot, candle, liquid, and furnace
methods.

In the pot methods crude sulphur, preferably ground, is used; it is
placed in an iron pot and ignited by the aid of alcohol, and in the
burning evolves the sulphur dioxide gas. About five pounds of sulphur
are to be used for every 1,000 cubic feet of space. As moisture plays
a very important part in developing the disinfecting properties of
sulphur dioxide, the anhydrous gas being inactive as a disinfectant,
it is advisable to place the pot in a large pan filled with water, so
that the evaporated water