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.

Carbon is the material employed in the manufacture of arc light electrodes
and other electrical appliances that must stand extreme heat. Yet these two
substances are forced into combination in the manufacture of calcium
carbide. It is the excessively high temperature attainable in the electric
furnace that causes this combination and not any effect of the electricity
other than the heat produced.

A mixture of ground coke and lime is introduced into the furnace through
which an electric arc has been drawn. The materials unite and form an ingot
of very pure carbide surrounded by a crust of less purity. The poorer crust
is rejected in breaking up the mass into lumps which are graded according
to their size. The largest size is 2 by 3-1/2 inches and is called "lump,"
a medium size is 1/2 by 2 inches and is called "egg," an intermediate size
for certain types of generators is 3/8 by 1-1/4 inches and called "nut,"
and the finely crushed pieces for use in still other types of generators
are 1/12 by 1/4 inch in size and are called "quarter." Instructions as to
the size best suited to different generators are furnished by the makers
of those instruments.

These sizes are packed in air-tight sheet steel drums containing 100 pounds
each. The Union Carbide Company of Chicago and New York, operating under
patents, manufactures and distributes the supply of calcium carbide for the
entire United States. Plants for this manufacture are established at