Man's physical universe

xanabras

628 C'RKATIVK CHKMISTRV

" Life Would Be Rather Dull without Graphite, although the Material

Itself Is One of the Dullest of All Substances." '

Graphite is widely used in "lead" pencils and as a lubricant, stove

polish, and paint pigment because of its soft, greasy, chemically inert

properties. It is an electrical conductor and is therefore used to make

electrodes for dry cells and electric furnaces, commutator brushes for

generators, and in making electrotypes for printing. Because of its

inertness and resistance to high temperatures, it is used to make

refractory bricks and crucibles.

Graphite may be prepared by heating anthracite coal in an electric

furnace. Prepared in this way, graphite is generally superior to naturally

occurring graphite.

The Diamond Is the Hardest Substance Known.

The highly crystalline, colorless, transparent properties of pure

diamonds cause them to be highly prized as gems, but it is the great

hardness of diamonds that makes them of importance in

industry in

providing a cutting edge for core drills and for grinding purposes.

Diamonds which contain impurities which discolor them, sometimes

almost black, are used for industrial purposes. Artificial diamonds of

small size have been made by crystallizing carbon in cast iron, but no

diamonds have been produced which are large enough for use as gems.

Amorphous Forms of Carbon Vary According to Their Methods of Preparation.

Anthracite Coal Is Nearly Pure Carbon.

Coal is produced by changes

in plant matter, and anthracite coal is the product in which these

changes have gone the farthest. The various stages in the decomposition

of plant materials (chiefly cellulose) are represented by peat,

lignite, bituminous coal (soft coal), and anthracite coal (hard coal).

Anthracite is a very desirable fuel because it burns with the production

of the maximum amount of heat and the minimum amount of

smoke and sulfurous. fumes. Only about 0.65 per cent of the coal

resources of the United States are of the anthracite variety. At the

present rate of consumption our anthracite coal resources will be

exhausted in about one hundred years.

Coke Is Obtained by Heating Bituminous Coal in the Absence of Air.

When bituminous coal is heated in the absence of air, fuel gases (artificial

gas), ammonia, and coal tar are important materials which are

driven ofT from the coal, leaving the mineral matter and carbon in

1 C. C. Furnas, The Storehouse of Civilization, Columbia University Press, New York,

1939, p. 144.

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