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graphite enveloping each grain acts as a protection against the
absorption of moisture.
Graphite, on account of its extreme softness and unctuous
ness, is admirably suited for use as a lubricant. It is used in
two manners; namely, dry, or mixed with oil or grease. In the
accompanying tables, showing the consumption of minerals,
graphite used in the manufacturing of these mixed lubricants
is included, but only in a few cases record is made of the graphite
used in the dry form as a lubricant. Flake graphite in various
grades of fineness, from about 20 mesh to 200 mesh, is that
employed and should be free from gritty matter.
Large quantities of graphite are used in the manufacturing
of paints for special purposes, such as for covering structural
steel work, iron and steel tanks, and steel stacks. It produces
a good weather and fume resisting paint. For this purpose a
very fine, air-floated flake graphite is used. It should be free
from grit and sulphide minerals.
In the casting of iron, it is desirable to coat the inner surface
of the mould with some material which will prevent the metal
from coming into contact with the sand of which the mould is
made, and at the same time give to the casting a smooth surface.
Graphite possesses certain properties which suit it to this purpose,
and large quantities are used by the foundry men. A fine grain,
flake graphite is used, either alone or mixed with talc or ‘sea-
coal.’
Lead pencils are made by encasing thin rods of prepared
graphite in wood to give the necessary strength. These rods
are formed by mixing very finely ground amorphous graphite
with clay, which is then moulded into shape and baked. The
hardness of the finished product depends upon the proportion
of clay used and the temperature and duration of baking.
In electrical work graphite finds many uses on account
of its conductivity, refractoriness, and softness. For different
uses various grades are employed, in all of which a high degree
of purity is required, especially for the making of dynamo and
motor brushes, in which case it must contain no grit.
Graphite is used by electrotypers for giving an electro-
conductive surface to the matrix on which the electrotype is