The supply was not equal to the demand until Acheson
worked out the process of making it by packing powdered anthracite
between the electrodes of his furnace. In this way graphite can be
cheaply produced in any desired quantity and quality.
Since graphite is infusible and incombustible except at exceedingly high
temperatures, it is extensively used for crucibles and electrodes. These
electrodes are made in all sizes for the various forms of electric lamps
and furnaces from rods one-sixteenth of an inch in diameter to bars a
foot thick and six feet long. It is graphite mixed with fine clay to
give it the desired degree of hardness that forms the filling of our
"lead" pencils. Finely ground and flocculent graphite treated with
tannin may be held in suspension in liquids and even pass through
filter-paper. The mixture with water is sold under the name of
"aquadag," with oil as "oildag" and with grease as "gredag," for
lubrication. The smooth, slippery scales of graphite in suspension slide
over each other easily and keep the bearings from rubbing against each
other.
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