<h2><SPAN name="CHAPTER_XXV" id="CHAPTER_XXV"></SPAN>CHAPTER XXV.</h2>
<h3>ELECTRICAL PRODUCTS—CARBORUNDUM.</h3>
<p>The production of electricity in such enormous
quantities as are generated at Niagara
Falls has led to many discoveries and will lead
to many more. Products that at one time existed
only in the chemical laboratory for experimental
purposes, have been so cheapened by
utilizing electrical energy in their manufacture,
as to bring them into the play of every-day
life. Still other products have only been
discovered since the advent of heavy electrical
currents. A substance called carborundum,
which was discovered as late as 1891, has now
become the basis of an industry of no small
importance. It is a substance not unlike a
diamond in hardness, and not very unlike it in
its composition. The chief use to which it is
put is for grinding metals and all sorts of
abrasive work. It is manufactured into
wheels, in structure like the emery-wheel, and
serves the same purpose. It is much more expensive
than the emery-wheel, but it is claimed
that it will do enough more and better work
to make it fully as economical.<span class="pagenum"><SPAN name="Page_210" id="Page_210"></SPAN></span></p>
<p>It was my pleasure and privilege to visit
the factory at Niagara Falls, and through
the courtesy of Mr. Fitzgerald, the chemist in
charge of the works, I learned much of the
manufacture and use of carborundum. The
crude materials used in the manufacture of
carborundum are, sand, coke, sawdust and
salt; the compound is a combination of coke
and sand. It combines at a very high heat,
such as can be had only from electricity.
When cooled down the product forms into
beautiful crystals with iridescent colors. The
predominating colors are blue and green, and
yet when subjected to sunlight it shows all
the colors of the solar spectrum to a greater or
less degree. The crystals form into hexagonal
shapes, and sometimes they are quite large,
from a quarter to a half inch on a side. The
salt does not enter into the product as a part
of the compound, neither does the sawdust.
The salt acts as a flux to facilitate the union
of the silica and carbon. The sawdust is put
into the mixture to render it porous so that
the gases that are formed by the enormous
heat can readily pass off, thus preventing a
dangerous explosion that might otherwise
occur. In fact, these explosions have occurred,
which led to the necessity of devising some
means for the ready escape of the gases.</p>
<p>The process of manufacture as it is carried
on at Niagara is interesting. The visitor is<span class="pagenum"><SPAN name="Page_211" id="Page_211"></SPAN></span>
first taken into the rooms where are stored the
crude material, the sand, coke, sawdust and
salt. The sand is of the finest quality and
very white. The coke is first crushed and
screened, the part which is reduced to sufficient
fineness is mixed by machinery with the
right proportion of sand, salt and sawdust.
The coarser pieces of coke are used for what
is called the core of the furnace, which will be
described later on.</p>
<p>This mixture is carried to the furnace-room,
which has a capacity for ten furnaces,
but not all of these will be found in operation
at one time. Here the workmen will be taking
the manufactured material from a furnace
that has been completed, and there another
furnace is in process of construction, while a
third is under full heat, so that one sees the
whole process at a glance. These furnaces are
built of brick, about sixteen feet in length and
about five feet in width and depth. The ends
and bed of the furnace are built of brick, and
might be called stationary structures. The
sides are also built of brick laid up loosely
without mortar; each time the material is
placed in the furnace, and each time the furnace
is emptied, the side-walls are taken
down.</p>
<p>A furnace is made ready for firing by
placing a mass of the mixture on the bottom,
and building the sides up about four feet<span class="pagenum"><SPAN name="Page_212" id="Page_212"></SPAN></span>
high (or half the height when it shall be completed).
A trough, about twenty or twenty-one
inches wide and half as deep, is scooped
out the whole length of the pulverized stuff,
and in this is placed what has before been referred
to as the core of the furnace, namely,
pure coke broken into small pieces, but not
pulverized, as in the case of the other mixture.
The amount used is carefully weighed, so as
to have the core the proper size that experiment
has proved to give the best results. The
core is filled in and rounded over till it is in
circular form, being about twenty-one inches
in diameter. At each end of the furnace the
core connects with a number of carbon rods—about
sixty in all—that are thirty inches long
and three inches in diameter. These carbon
rods are connected with a solid iron frame that
stands flush with the outer end of the furnace.
On the inside the spaces between the
rods are packed full of graphite, which is
simply carbon or coke with all the impurities
driven out, so as to make good electrical connections
with the core. This core corresponds,
electrically speaking, to the filament in an ordinary
incandescent lamp, only it is fourteen
feet long and twenty-one inches in diameter.
The mixed material is now piled up over this
core, and the walls at the sides are built up
until the whole structure stands about eight
feet from the floor—a mass of the fine pulver<span class="pagenum"><SPAN name="Page_213" id="Page_213"></SPAN></span>ized
mixture, with a core of broken coke electrically
connected at the ends. It is now
ready for the application of electricity, which
completes the work.</p>
<p>Let us go back to the transformer-room and
examine the electrical appliances that bring
the current down to a proper voltage to produce
the heat necessary to cause a union between
the silica of the sand and the carbon of
the coke, which results in the beautiful carborundum
crystals that we have heretofore described.</p>
<p>The current is delivered from the Niagara
Power Company under a pressure of 2200
volts. The conductors run first into the transformer-room,
which adjoins the furnace-room,
and is there transformed down from 2200 volts
to an average of about 200 volts. The transformers
at these works have a capacity of
about 1100 horse-power. About 4 per cent
of this power is converted into heat in the
process of transformation, making a loss in
electrical energy of a little over 40 horse-power.
This heat would be sufficient to destroy
the transformer if some arrangement
were not provided to carry it off. We have already
described how this is done through the
medium of a circulation of oil. Because of the
low voltage and enormous quantity of the current
passing from the transformer to the furnace
very large conductors are required. The<span class="pagenum"><SPAN name="Page_214" id="Page_214"></SPAN></span>
two conductors running to the furnace have a
cross-section of eight square inches, and this
enormous current, representing over 1000
horse-power, is passed through the core of the
furnace, and is kept running through it constantly
for a period of twenty-four to thirty-six
hours.</p>
<p>Let us consider for a moment what 1000
horse-power means; as this will give us some
conception of the enormous energy expended
in producing carborundum. A horse-power is
supposed to be the force that one horse can
exert in pulling a load, and this is the unit of
power. However, a horse-power as arbitrarily
fixed is about one-quarter greater than the
average real horse-power. If 1000 horses were
hitched up in series, one in front of the other,
and each horse should occupy the space of
twelve feet, say, it would make a line of horses
12,000 feet long, which would be something
over two miles. Imagine the load that a string
of horses two miles long could draw, if all were
pulling together, and you will get something
of an idea of the energy expended during the
burning of one of these carborundum furnaces.</p>
<p>Within a half hour after the current is
turned on a gas begins to be emitted from the
sides and top of the furnace, and when a match
is applied to it, it lights and burns with a
bluish flame during the whole process. It is
estimated that over five and one-half tons of<span class="pagenum"><SPAN name="Page_215" id="Page_215"></SPAN></span>
this gas is thrown off during the burning of a
single furnace. This gas is called carbon
monoxide, and is caused by the carbon of the
coke uniting with the oxygen of the sand.
When we consider the vast amount of material
that comes away from the furnace in the form
of gas it is easy to see why it is necessary to
introduce sawdust or some equivalent material
into the mixture, in order to give the whole
bulk porosity, so that the gas can readily escape.
We should also expect that after five
and one-half tons had been taken away from
the whole bulk that it would shrink in size.
This is found to be the case. The top of the
mass of material sinks down to a considerable
extent by the end of the time it has been exposed
to this intense heat. Gradually, after
the current has been turned on, the core becomes
heated, first to a red, and afterwards to
an intense white heat. This heat is communicated
to the material surrounding the core,
producing various effects in the different
strata, owing to the fact that it is not possible
to keep a uniform heat throughout the whole
bulk of material. Some of it will be "overdone"
and some of it "underdone." The material
which lies immediately in contact with
the core will be overheated, and that, which at
one stage was carborundum, has become disintegrated
by overheating.</p>
<p>The silica of the compound has been driven<span class="pagenum"><SPAN name="Page_216" id="Page_216"></SPAN></span>
off, leaving a shell of graphitic substance
formed from the coke.</p>
<p>After the current is shut off and the furnace
has cooled down, a cross-section through
the whole mass becomes a very interesting
study. The core itself, owing to the intense
heat it has been subjected to, has had the impurities
driven out of the coke, leaving a substance
like black lead, that will make a mark
like a lead-pencil, and is really the same substance,
known as plumbago, in one of its
forms. It is the carbon left after the impurities
have been driven out of the coke. Surrounding
the core for a distance of ten or
twelve inches, radiating in every direction,
beautifully colored crystals of carborundum
are found, so that a single furnace will yield
over 4000 pounds of this material. Beyond
this point the heat has not been great enough
to cause the union between the carbon and
silica, which leaves a stratum of partly-formed
carborundum; outside of that the mixture is
found to be unchanged.</p>
<p>These carborundum crystals are next crushed
under rollers of enormous weight, after which
the crushed material is separated into various
grades for use in making grinding-wheels of
different degrees of fineness. This crushed material
is now mixed with certain kinds of clay,
to hold it together, and then pressed into
wheels of various sizes in a hydraulic press,<span class="pagenum"><SPAN name="Page_217" id="Page_217"></SPAN></span>
and afterward carried into kilns and burned
the same as ordinary pottery or porcelain.
These wheels vary in size from one to sixteen
inches. The substances used as a bond in
manufacturing wheels are kaolin, a kind of
clay, and feldspar.</p>
<p>While carborundum has already a large
place as a commercial product, there is no
doubt but that the uses to which it will be
put will vastly increase as time goes on. This
product may be called an artificial one, and
never would have been known had it not been
for the intense heating effects that are obtained
from the use of electricity. It certainly
never could have been brought into play as
one of the useful agencies in manufacturing
and the arts. It is not known to exist as a
natural product, which at first thought would
seem a little strange in view of the evidences
of intense heat that at one time existed in the
earth. Its absence in nature is explained by
Mr. Fitzgerald by the fact that "the temperatures
of formation and of decomposition lie
very close together."</p>
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