he water is strained it is
in good condition for cleaning purposes. Ammonium carbonate is used to
some extent as a softening and cleaning agent, and is valuable, as there
is no injurious effect upon clothing, because it readily volatilizes.
Caustic potash and caustic soda are sometimes employed for softening
water, but they are very active and are not adapted to washing colored
or delicate fabrics. They may be used for very heavy and coarse articles
that are greasy,--not more than a gram in a gallon of water. Bleaching
powder is not generally a safe material for cleansing purposes, as it
weakens the texture of clothing. After a contagious disease, articles
may be soaked in water containing a little bleaching powder and a few
drops of carbolic acid, followed by thorough rinsing and bleaching in
the sun. But as a rule formaline is preferable for disinfecting
clothing. It can be used at the rate of about one pound to 100 gallons
of water. Bleaching powder, caustic potash or soda, and strong soap are
not suitable for cleaning woodwork, because of the action of the alkali
on paint and wood; they roughen the surface and discolor the paint.
Waters vary so in composition, that a material suitable for softening
one may not prove to be the best for softening another. The special kind
must be determined largely by trial, and it should be the aim to use as
little as possible. When carbolic acid, formaline, bleaching powder, and
caustic soda are used, the hands should be protected and the clothes
should be well rinsed.

[Illustration: FIG. 64.--TYPHOID BACILLI.]

278. Economic Value of a Pure Water Supply.--From a financial point of
view, the money spent in securing pure water is one of the best
investments a community can make. Statisticians estimate the death of an
adult results in a loss to the state of from $1000 to $5000; and to the
losses sustained by death must be added those incurred by sickness and
by lessened quality and quantity of work through impaired
vitality,--all caused by using poor drinking water. Wherever plants have
been installed for improving the sanitary condition of the water supply,
the death rate has been lowered and the returns to the community have
been far greater than the cost of the plant. Impure water is the most
expensive food that can be consumed.

CHAPTER XX

FOOD AS AFFECTED BY HOUSEHOLD SANITATION AND STORAGE

279. Injurious Compounds in Foods.--An ordinary chemical analysis of a
fo