CARBIDE
Calcium carbide is a chemical combination of the elements carbon and
calcium, being dark brown, black or gray with sometimes a blue or red
tinge. It looks like stone and will only burn when heated with oxygen.
Calcium carbide may be preserved for any length of time if protected from
the air, but the ordinary moisture in the atmosphere gradually affects it
until nothing remains but slaked lime. It always possesses a penetrating
odor, which is not due to the carbide itself but to the fact that it is
being constantly affected by moisture and producing small quantities of
acetylene gas.
This material is not readily dissolved by liquids, but if allowed to come
in contact with water, a decomposition takes place with the evolution of
large quantities of gas. Carbide is not affected by shock, jarring or age.
A pound of absolutely pure carbide will yield five and one-half cubic feet
of acetylene. Absolute purity cannot be attained commercially, and in
practice good carbide will produce from four and one-half to five cubic
feet for each pound used.
Carbide is prepared by fusing lime and carbon in the electric furnace under
a heat in excess of 6,000 degrees Fahrenheit. These materials are among the
most difficult to melt that are known. Lime is so infusible that it is
frequently employed for the materials of crucibles in which the highest
melting metals are fused, and for the pencils in the calcium light because
it will stand extremely high temperatures.
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