Scientific American, Volume 56, No. 9, February 26, 1887Various
Science
Scientific American, Volume 56, No. 9, February 26, 1887
Various
Science -- Periodicals; Technology -- Periodicals
The operations are carried on in large cast steel crucibles, and
the charges consist of caustic soda and a finely ground artificial
compound of carbon and iron, which is the reducing agent. This compound
is made by coking a mixture of fine iron and pitch. The crucibles
containing these materials are first heated in a small furnace at
a low temperature, the object being to expel the hydrogen from the
caustic alkali and bring about quiet fusion. The crucibles are then
removed from this furnace, by means of a little truck, and placed upon
a movable platform, which is operated by hydraulic power. They are
then by this means raised into the large furnace, where the crucible
covers are fixed stationary. The edges of the crucible and cover coming
together form a tight joint, and from this cover projects a small tube
to the outside of the furnace into a narrow rectangular box, known as
the condenser. The reduction of the sodium commences soon after the
crucible containing the charge is in its place, the vapors and gases
passing from the fused mixture through the exit pipe from the cover
into the condenser, where the metallic vapors are condensed to metal,
while the uncondensed gases escape by a small outlet tube. After the
charge is exhausted, the crucible is lowered, and one containing a
fresh charge raised in its place; in this manner the process might
almost be called continuous.
The actual temperature used in this process to bring about reduction,
as measured by experts, has been found to be 850° Cent. By the older
method the temperature necessary is about 1,400° Cent. This is
practically the great point of economy in this process, as the high
price of sodium has hitherto been owing to the excessive heat used in
the older process and the consequent destruction of the wrought iron
vessels. Sodium at present costs about four shillings per pound to
produce, while the materials necessary for this quantity, were nothing
wasted, would hardly cost four pence. The difference between these two
figures represents the wear and tear to the furnace, the destruction
of the wrought iron cylinders, the loss and waste of materials, the
excessive labor and care necessary to employ in manufacturing, and
fuel. Approximately, the cost of these items in producing one pound of
sodium by the older process is as follows:
Two shillings is due to the destruction of wrought iron, etc.
One shilling is due to the loss and waste of materials, of which three
times the theoretical quantity must be employed.
Eightpence is due to the labor.
Fourpence is due to the fuel.
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