ELECTRICAL PRODUCTS--CALCIUM CARBIDE.
Another important use to which electricity is put at Niagara Falls is
the manufacture of a new product, called calcium carbide. Like
carborundum and aluminum, this product could not have been produced in
commercial quantities in advance of a means for producing electricity in
enormous volume.
Calcium carbide is a compound of calcium and carbon. Calcium is a white
metal not found in the natural state, but exists chiefly as a carbonate
of lime, which is ordinary limestone, including the various forms of
marble. As a pure metal it is hard to obtain and very hard to maintain,
as it readily oxidizes when in contact with the air. The symbol for
calcium carbide is CaC_{2}, which means that a molecule of this carbide
is compounded of one atom of calcium and two atoms of carbon. Ca stands
for calcium and C for carbon. When the symbol has no figure following
it, it means that one atom only enters into the compound; but if a
figure follows, it means that as many atoms enter in as the figure
represents.
The process of manufacturing calcium carbide is as follows: Ordinary
lime before it is slacked is ground to a fine powder; then it is mixed
with powdered coke or carbon in the proper quantities, so that when a
chemical union takes place the proportion will be as before stated, one
atom of calcium to two of carbon. As is well known, lime is procured by
exposing ordinary limestone to a red heat for some hours together. The
heat disengages the carbon dioxide, leaving only a combination of
calcium and oxygen, which is common lime.
The mixture of ground lime and coke is put into a crucible that
surrounds the arc of an electric light of enormous dimensions; the
carbon conductors amounting to an area of one square foot or more. In
order to cause the carbon to unite with the calcium a very intense heat
is required, such a heat as can be obtained only in the arc of an
electric light. When the enormous current is turned on (amounting to
over 3000 horse-power) the mixture is melted, and after an exposure to
this intense heat for a given length of time the oxygen of the unslacked
lime is thrown off and the carbon unites with the calcium, which remains
in the proportions of one atom of calcium to two of carbon, as before
stated. This, it will be noted, is purely a heat process, and an intense
one at that. No electrolytic action being required, the alternating
current is used without transformation to the direct current, as is
necessary in the manufacture of bleaching-powder and aluminum, both of
which are electrolytic processes.
When the operation is completed the current is turned off and the
compound allowed to cool. In cooling it assumes a slate color, which is
slightly iridescent when exposed to light. It also crystallizes to a
certain extent.
The value of this new product consists in its ability to evolve
Acetylene gas in large quantities. A molecule of acetylene gas is
composed of two atoms of carbon to two of hydrogen. To evolve the gas it
is necessary only to pour water upon the calcium carbide, when a union
takes place between the carbon of the carbide and the hydrogen of the
water in the proportions above stated. If there is water enough the
whole of the carbon will pass off with the gas, leaving a residuum of
slacked lime.
The value of acetylene gas lies in its very intense illuminating power.
This is due to the fact that the gas is very rich in carbon as compared
with other illuminating gases. It burns with a pure white light when
properly mixed with air or oxygen, but if there is a lack of air it
burns with a smoky flame. In this case the carbon is not all consumed
and escapes into the air in the form of soot or smoke, but when burned
with the proper mixture of oxygen or common air it becomes one of the
most brilliant of illuminants. Acetylene, like most other gases, becomes
explosive when mixed with air in certain proportions. Whether it is more
dangerous to handle than ordinary illuminating gases the writer is not
prepared to say, as he has not had the opportunity to make a thorough
comparison between it and other gases from an experimental standpoint.
Experiment, after all, is the only sure road to absolute knowledge.
Theories are beautiful in books and lectures, but they often fail in the
laboratory.
Acetylene is now being introduced as an illuminating gas for domestic
and other purposes. Several methods of handling it have been proposed.
One is to condense it into strong metal cylinders and deliver it in that
form; another is to erect generators at convenient places and generate
the gas as it is used. A very ingenious contrivance has been invented
for regulating the generation of the gas. A certain amount of the
calcium carbide is placed in a gas-tight vessel containing water. As
soon as the water comes in contact with the carbide the evolution of the
gas begins. When the pressure on the inside of the vessel has reached a
certain degree it is made, through mechanical contrivances, to lift the
carbide out of the water and thus stop the evolution of the gas. When
the pressure is relieved through the consumption of the gas at the
burners it allows the carbide to drop into the water, when the evolution
of the gas begins again.
Of course there is the same objection to this mode of lighting that
attends all open burners; it is constantly discharging into the air the
products of combustion, chiefly carbon dioxide, which is poisonous to
animal life. As has been explained in some of the chapters on heat, in
Volume II, the illuminating property of any gas is determined by the
number of carbon particles that are contained in it, which become heated
to incandescence as soon as they come in contact with the oxygen of the
air, and remain so, for a brief period, during their passage between the
two extremes of the flame. While acetylene equals electricity in its
illuminating properties, the latter still stands without a rival when
considered from a sanitary standpoint, as the use of electricity does
not in any degree vitiate the air in a room where it is used.
We have now given somewhat in detail the following processes that are
carried on at Niagara Falls through the agency of electricity, viz.: The
reduction of aluminum from its oxide alumina; the production of the new
and useful compound called carborundum; the formation of calcium carbide
used for the production of acetylene gas, and a large chemical works,
where bleaching-powder is made. In addition to these works, there is an
establishment for the production of sodium from caustic potash, which is
one of the products arising from the decomposition of salt in the
bleaching-powder works. There is also another establishment for the
production of phosphorus made from the bones and shells obtained from
the phosphate beds that abound in some of the southern states, on the
coast of the Atlantic Ocean. There is in process of construction a plant
for the purpose of manufacturing chlorate of potash by an electrical
process. In addition to these establishments mentioned, the electricity
is furnished for power purposes to the Niagara Electric Light Company;
to the electric railway between Niagara and Buffalo; to the Niagara
Falls Railway, on the opposite side of the river; to the Niagara Power
and Conduit Company of Buffalo, and the Niagara Development Company.
This is only a small beginning of the uses to which electricity will be
put as an agent for the development of heat, light and power as well as
for the production of all substances where electrolysis is the chief
factor. Sixteen companies or more are now using electricity from the
Niagara power-house,--the whole amounting to about 35,000 horse-power.