p
insect repellant and fungicide. It is used in in
dustry in metallurgical processes, chemicals, cer
amics, leather manufacture, refrigeration, and in
many other ways.
Germany, the United Kingdom, China, Italy,
France, and India rank, in that order, behind the
U. S. in salt production. Salt is still being dis
covered in different parts of the world. For ex
ample, Denmark, formerly forced to import all of
her salt, discovered a rock salt deposit in 1946
which now takes care of most of her needs.
INEXHAUSTIBLE SUPPLY
Salt is plentiful today. The oceans, lakes and
seas of the world contain enough salt to blanket
the entire earth with a snowy-white covering more
than 100 feet deep. And there are almost inex
haustible deposits of salt deep in the earth formed
by the drying up of pre-historic seas.
Outside the United States, most salt is taken
from sea water, which is run into shallow pools at
high tide, trapped there, and evaporated by the
sun, leaving a residue at the bottom.
In our country, most salt comes from deposits
underground, yielding a much finer grade than is
usually produced commercially from other sources.
MINING SALT
Two methods are used to reach these deposits.
One is to dig a mine shaft down to the deposit,
blast it out, lift the chunks of salt to the surface
in elevators, and then crush the chunks and screen
the salt. The other method, yielding a far purer
grade of salt, is to drill for it. This method is
used by the Diamond Crystal-Colonial Salt Di
vision of General Foods Corporation at St. Clair,
Michigan, in America’s greatest salt producing
state. The accompanying pictures and the follow
ing text tell how this company drills for and re
fines salt.
Diamond Crystal operates many salt wells,
similar to oil wells, often drilling 2,500 feet (half
a mile) straight down to reach a salt deposit.
Here’s the way the wells work:
In the typical well, there are five pipes, one in
side the other. The outside pipe is sunk far enough
down to prevent surface water from seeping into
the well. The next two pipes go deeper and pre
vent mineral water from underground streams
from entering the well. The fourth pipe reaches
down to the top.of the salt deposit. Down this
pipe fresh water is pumped. The water eats away
the rock salt, which becomes brine and sinks to
the bottom of the well. Then the brine is forced
up to the surface through the fifth and innermost
pipe.
The work of refining and purifying the salt
begins right in the well. Because the salt is dis
solved before coming to the surface, insoluble
rock, dirt, and other impurities that remain in
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SOAPSTONE
LIMESTONE
UMESTOHi
SALT
Salt deposits are found far below the earth's
surface, as this diagram shows. The figures
at left are the number of feet below the sur-
fiice.