The usefulness of graphite depends upon its peculiar softness and scaliness, as well as upon its chemical inertness, infusibility, and conductivity for electricity. For the manufacture of black-lead pencils natural graphite itself was formerly used, being cut up into strips of the required size. Now, however, powdered graphite is mixed into a paste with fine clay, and the mixture is pressed through a hole so as to form a thread.
Graphite crucibles are made from a mixture of powdered graphite and fine clay. They are moulded like pottery and then fired. They are employed for melting metals, and especially in the manufacture of crucible steel.
A well-known application of graphite is for protecting iron - e.g. grates - from rust. It is also used in electrotyping, the surface on which electrodeposition of metal is to take place being covered with a layer of graphite, which is a conductor.
It is likewise employed as a lubricant for machinery, and as a coating for gunpowder to prevent absorption of moisture. The efficiency of the powder is, however, somewhat diminished by the graphite. |