Evening star. [volume] (Washington, D.C.) 1854-1972, 1911-03-05
Waters Properties

| top instead of at the bottom. The behavior
of water at different temperatures is so ir-
regular as to set the substance water in a
class by itself in chemistry and to make its
actions peculiarly interesting. At temper
allure of thirty-nine degrees Fahrenheit
water is at its greatest density; that is, it
| cannot become any smaller. If it is heated
to forty degrees, it will become larger and
consequently lighter per unit volume. If it
is cooled to thirty eight degrees, it will be
larger and consequently lighter per unit vol
slider glassful of water at this temperature
of thirty-nine degrees. If it is cooled, the
water will run over the sides; if it is heated,
the water will run over the sides.
Now, conceive what takes place over a
body of water in the winter time. The air
is getting colder, and will consequently make
the water colder. When the temperature of
the air above falls, the water on the surface
is cooled so that the surface water gets
heavier per unit volume and sinks to the
bottom. When the surface water gets to
thirty-nine degrees, it will be very heavy and
will sink to the bottom. This process will
60 on with varying rapidity till the whole
mass of the water is at thirty degrees.
If the outside temperature keeps on falling,
the top water becomes colder and conse
therefore remain on top.
This process goes on till the top water
freezes into ice. At the moment it freezes
it becomes about one-fourteenth larger than
the water it was Immediately before. So if
one sees piece of ice sticking out of the
water he may calculate how much more is
the volume hidden underneath. It will be
about fourteen times as much as is seen.
1t might be asked why the pond of water
does not freeze all the way down after it
started at the top, as the whole mass of
water is very close to the freezing point and
it has top layer of ice. One reason is that
this top layer is poor conductor of heat
and does not permit of the lower waters
losing what heat it has. Another and a
more peculiar reason is also found here. The
surface water when it freezes actually gives
out heat. Thus the water Immediately be-
low becomes slightly warmer than it was be-
fore. This is common property of al
liquids when they freeze: they give out
heat. The fact is utilized in many ways in
the commercial world.
Laurence HODGES
Industrial Value of Pure Water
THE people are fully aroused to the value
of pure drinking water, and have plenty
of statistics to show how the mortality of
towns and cities is kept down by proper fill
tration plants; but few are probably cogni-
zant of the fact that pure water for indus
trial purposes is of immense value to the
country, and that manufacturers were ahead
of city boards in insisting upon clean, pure
water for their plants. In the ordinary
steam plant impure water may be pumped
into the boilers; but only pure water passes
out in the form of steam. The impurities of
boiler feed water are deposited in the form
of scale on the inside of the water tubes, and
as result it requires more fire in the furnace
to heat water to the steaming point. This
loss sometimes amounts to ten to twenty
per cent. Then, too, the scale encrusted
boiler wears out much more quickly, and
grows so weak in time that it easily explodes
under ordinary steam pressure.
Pure water is therefore essential to steam
production, and most plants and railroads
treat their water by chemical or mechanical
methods of publication. By the introduce
ton of chemicals in water before it enters
the boiler the solids are precipitated and re-
moved. Filters of enormous capacity are
also employed, and many varieties of water
softeners.
In dyeing printing, bleaching wool wash
ing, paper making, soap making, laundering,
and tanning ca1CareOl1S waters are very in