Salt is a chemical compound composed of two elements, sodium and
chlorine. Chemically it is known as sodium chloride.
[Illustration: A SALT WELL]
It is one of the things which comes into our lives daily, perhaps more
than any other, with the exception of water. Probably no other thing
than water is used more by all civilized people than salt.
Nature provides salt for us in three different forms. First, in sea
water in solution; second, in salt springs; and third, in the form of
salt rock.
From time immemorial man has obtained salt from sea water. This is still
being done on our sea coasts, but the salt obtained by evaporating the
water is very crude and usually contains many impurities.
It has been possible to obtain a large supply of salt from what are
known as salt springs. These springs are usually the result of water
flowing over a deposit of salt rock. The amount of salt obtained from
evaporating this spring water is, however, so small that salt springs
are an impractical source of supply when it comes to making salt for
commercial purposes.
Rock salt forms the most common and practical source of supply. It is
found in all parts of the world and reasonably near the surface. The
deposit is said to be what is left of ancient salt seas. In the United
States the largest deposits of salt are found in the states of Michigan,
New York, Ohio, Utah, Louisiana, Kansas, Texas and California. The
above-mentioned states are the largest producers of salt in this
country.
[Illustration: SALT HEATERS AND FILTERS]
One of the largest sources of salt supply in Europe is at Wielizka in
Poland. This deposit of salt is said to be the largest in the world, the
bed of salt rock being 500 miles long, 20 miles wide and 1,200 feet
thick. Some of the salt mines in Poland are so extensive that it is said
some of the miners spend all of their lives in them, never coming to the
surface of the earth.
Most of the deposits of salt rock contain impurities which need to be
removed before the salt is fit for use commercially; however, some
deposits show a very pure salt rock and when ground up this rock salt is
suitable for table use. In general, however, the salt made from crude
salt rock is only fit for the crudest commercial uses. The most common
impurity is gypsum and it is necessary to remove this gypsum before the
salt can be considered pure.
[Illustration: _Photo by Brown Bros._