Page:Popular Science Monthly Volume 57.djvu/305

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N the following pages an effort is made to apply some of the results of recent chemical research to the earlier-history of the earth. It is hoped that the main facts brought out may be readily grasped by those who have never studied chemistry, and that each link in the chain of events will be made evident to those who have mastered the rudiments of this science.

Chemical action involves change of composition. Substances more or less complex may be broken down into simpler substances, or from several simpler substances a complex substance may be built up. From the complex ore of copper found in nature the simple element copper is obtained. From the elements sulphur and oxygen and the simple substance water the complex sulphuric acid is built up. Within the last few years the high temperature of the electric arc—the heat generated by a powerful electric current playing between two carbon poles—has been employed in bringing about chemical changes which do not occur at ordinary temperatures nor at those obtainable by burning fuel. The electric furnace is used industrially to make calcium carbide from lime and coke, carbon silicide (carborundum) from coke and sand, and the metal aluminum from its compounds.

Chemical changes at high temperatures have long been an object of research, but it was not until the introduction of the electric furnace that it was possible to command temperatures high enough to make exhaustive studies. In the last few years several chemists, especially Moissan, of Paris, and his pupils, have done systematic work with the aid of the arc furnace. The furnace used in the laboratory for high temperature work is a small and simple apparatus; Moissan's furnace is a block of quick lime a little longer and wider than a page of this magazine and about three inches thick. A rectangular cavity is cut on the upper surface of this block. A similar block forms the cover. In opposite grooves between the top and bottom piece are placed the carbons, such as are used in ordinary arc lights. The arc plays across the cavity in such a manner that the substance to be heated is not brought into the arc itself, which is vaporized carbon, but below it. The cavity thus represents a tiny reverberatory furnace; the arc heats the roof and sides to an intense heat, which is radiated on the open dish