ELECTRICAL PRODUCTS--BLEACHING-POWDER.
Another industry that has assumed large proportions at Niagara Falls,
owing to the vast quantity of electricity produced there, is the
manufacture of a commercial product called bleaching-powder, or chloride
of lime. Every one knows that chloride of sodium is simply common salt,
so extensively used wherever people and animals exist. Simple and
harmless as it is, while it exists as a compound of the original
elements, when separated into those elements they are each very
unpleasant and even dangerous substances to handle. Salt is one of the
most common substances in nature. It is found in many parts of the world
in solid beds, and is one of the prominent constituents of sea-water.
Salt is a compound of chlorine and a metal called sodium. Sodium in its
pure state has a strong affinity for oxygen, so much so that when a lump
of it is thrown into water it takes fire and burns violently with a
yellow flame. Chlorine, the substance with which it unites to form
common salt, is a greenish-colored gas, the fumes of which are very
offensive and very dangerous even to breathe, if the quantity is very
considerable.
It is a curious fact in nature that two such substances as chlorine and
sodium, both of them so difficult and dangerous to handle, should unite
together to form such a useful and harmless compound as common salt. The
important element in bleaching-powder is the chlorine which it contains.
It is extensively used in the manufacture of paper and in all other
materials where bleaching is required. The object of combining it with
lime, forming a chloride of lime, is simply to have a convenient method
of holding the chlorine in a safe and convenient manner until it is
needed for use.
The chemical works at Niagara Falls manufacture bleaching-powder on a
very large scale. The part that electricity plays is to separate the
chlorine from the sodium as it exists in common salt. At the works I was
first taken into a room where a large quantity of salt was stored. A
belt with little carrier-buckets on it picked up this salt and carried
it into another room, where it was thrown into a vast mixing-vat
containing water. The salt was mixed with water until a saturated
solution was obtained. In a large room, covering one-half acre or more
of ground, were assembled a great number of shallow vessels, about 4 by
5 feet square and 1 foot deep. These vessels were sealed up so that they
were gas-tight. Communicating with all of these vessels were pipes
connecting with the great tank containing the saturated solution of
salt.
From the top or cover of each vessel is a pipe running to a main pipe
that carries off the chlorine gas into another room as fast as it is
formed. Through each one of these vessels a current of electricity
passes; the whole system consuming about 2000 horse-power. The electric
current, as it passes through the brine, separates the chlorine from the
sodium, the chlorine passing in the form of gas up through the pipes,
before mentioned, into the main pipe, where it is carried into another
large room and discharged into a system of gas-tight chambers. Upon the
floor of these chambers is spread a coating of unslacked lime ground
into a fine powder. The lime has a strong affinity for the chlorine gas
and rapidly absorbs it, forming chloride of lime. When the lime is fully
saturated with the chlorine the gas is turned off from that chamber,
which is then opened up and the chloride taken out for shipment. A new
coating of lime is now spread in the chamber and the gas is turned on
and the process repeated.
There are a number of these chambers, so that the operation in all of
its phases is going on continuously. The room where the chlorine gas is
formed is thoroughly ventilated, a precaution which is very necessary in
case any one of the vats should spring a leak, as they sometimes do.
In each one of these vats where the electrolytic process is going on
there are two products constantly passing off; one, as before mentioned,
is chlorine gas, and the other caustic soda in solution. The solution in
the vat is constantly being renewed by the saturated solution of salt
from the reservoir before mentioned. There is one stream continuously
coming into the vat and two going out, caused by the decomposing power
of the electric current. The solution of caustic soda is carried to
large evaporating-pans, where the water is driven out of it, leaving the
caustic soda in dry, white sticks of crystalline formation. In this
process the electric current, which comes from the power-house with an
energy of 2000 horse-power, has to be transformed twice; first, to bring
it to the proper voltage for the work of decomposition, and, secondly,
to change it from an alternating to a direct current, by which all
electrolytic processes are carried on.
You will notice that the electrical energy expended in this
establishment is double that used in the manufacture of carborundum.
The caustic soda, which is one of the products from the decomposition of
salt, is taken to another establishment, where, by still another
electrical process, metallic sodium is manufactured. The process here
being a secret one, the writer did not have the privilege of examining
the details.