Page:Popular Science Monthly Volume 73.djvu/321

Rh lay in graphite mines such as those in the United States, England and Ceylon.

Artificial graphite is now made from any amorphous carbon which contains an admixture of some carbide forming substance and though other carbonaceous substances are used anthracite coal has been found to be the most satisfactory and economical carbonaceous material from which to make graphite.

Graphite is made by heating anthracite coal to a very high temperature, approximating 7,500° Fahrenheit. Into a long fire brick furnace is placed anthracite coal and through it a carbon rod passes. The heat generated by the resisted passage of the electric current through the charge is so great that practically all the impurities of the coal are volatilized, leaving its carbon content in the graphitic form.

Mr. Acheson has lately perfected a process whereby artificial graphite can be treated with gallotannic acid in such a way as to produce graphite so fine that it is well nigh molecular.

In the year 1892 it was accidentally discovered that if ordinary quicklime and coke were fused together, the resulting chemical combination would, by the addition of water, produce an illuminating gas of great brilliancy. The gas formed in this peculiar way is acetylene gas and the material from which it is generated is calcium carbide.

Calcium carbide is made at Niagara Falls by placing an intimate mixture of about three parts of powdered quicklime to two parts of powdered coke into an electric furnace of the so-called arc type. The current of electricity generates an intense heat which chemically combines the calcium of the quicklime with the carbon of the coke, the oxygen of the quicklime uniting with some of the carbon to form carbon monoxide gas which escapes.

It is interesting to know that the discovery of calcium carbide was almost simultaneously announced by two independent workers in electrochemistry, Moissan, the great French chemist, and Thomas L.