ehyde. About 20 ounces of the
formalin should be used for each 1000 cubic feet of space. With this
agent, however, as with sulfur, the penetrating power of the gas is not
very great, and such things as mattresses and clothing should be sent to
a steam sterilizer rather than be trusted solely to the power of the
formaldehyde.

In using this gas, the same care about pasting up cracks and crevices in
the room should be followed as already prescribed for the use of sulfur,
and, as with sulfur, a reasonable precaution against fire should be
taken by placing the apparatus in a tub of water or in a large pan of
sand where accidents cannot happen. The room should be kept closed for
at least twelve hours, and then should be thoroughly aired, and if the
room is to be used again soon, the disagreeable odor may be removed by
the free use of ammonia, either sprinkling it around in the room or by
placing about saucers of ammonia.

_Liquid disinfectants._

More common than gases and most readily suggested as disinfectants are
certain liquids which have been proved both by laboratory
experimentation and by actual experience to have the power of killing
bacteria when brought into contact with them. Those liquids which have
commended themselves particularly have additional advantages in not
destroying fabrics, metals, or tissue with which they are brought in
contact and in being purchasable at moderate prices.

There is little choice between a number of such liquids, and the number
of modifications or combinations which are made and bottled and sold
under some fancy name is legion. But the label, the name, and the
additional price add nothing to the value of the basic chemical from
which they are all compounded, and except for their convenience, they
have little to recommend them.

_Carbolic acid as disinfectant._

Carbolic acid is one of the most useful of these liquids, and in its
various forms appears in almost all disinfectants. It may be obtained
from the drug store in two forms, either as a crystal or as a
concentrated solution.

A 2 per cent solution, that is, one pint of carbolic acid to six gallons
of water, is the proper strength for all such uses as wiping off wooden
surfaces, furniture, floors, etc. A stronger (5 per cent) solution is
used when it is intended to destroy organic matter containing large
quantities of germs. This is practically a saturated solution, so that
if a bottle be partly filled with the crystals