may be taken care of by
some method of water treatment but such water should be submitted to an
authority on the subject before any treatment apparatus is installed.

[Illustration: 3000 Horse-power Installation of Cross Drum Babcock &
Wilcox Boilers and Superheaters Equipped with Babcock & Wilcox Chain
Grate Stokers at the Washington Terminal Co., Washington, D. C.]

Boiler Compounds--The method of treatment of feed water by far the most
generally used is by the use of some of the so-called boiler compounds.
There are many reliable concerns handling such compounds who
unquestionably secure the promised results, but there is a great
tendency toward looking on the compound as a "cure all" for any water
difficulties and care should be taken to deal only with reputable
concerns.

The composition of these compounds is almost invariably based on soda
with certain tannic substances and in some instances a gelatinous
substance which is presumed to encircle scale particles and prevent
their adhering to the boiler surfaces. The action of these compounds is
ordinarily to reduce the calcium sulphate in the water by means of
carbonate of soda and to precipitate it as a muddy form of calcium
carbonate which may be blown off. The tannic compounds are used in
connection with the soda with the idea of introducing organic matter
into any scale already formed. When it has penetrated to the boiler
metal, decomposition of the scale sets in, causing a disruptive effect
which breaks the scale from the metal sometimes in large slabs. It is
this effect of boiler compounds that is to be most carefully guarded
against or inevitable trouble will result from the presence of loose
scale with the consequent danger of tube losses through burning.

When proper care is taken to suit the compound to the water in use, the
results secured are fairly effective. In general, however, the use of
compounds may only be recommended for the prevention of scale rather
than with the view to removing scale which has already formed, that is,
the compounds should be introduced with the feed water only when the
boiler has been thoroughly cleaned.

FEED WATER HEATING AND METHODS OF FEEDING

Before water fed into a boiler can be converted into steam, it must be
first heated to a temperature corresponding to the pressure within the
boiler. Steam at 160 pounds gauge pressure has a temperature of
approximately 371 degrees Fahrenheit. If water is fed to the boi