The Romance of Modern Chemistry

HIGH TEMPERATURES carried out in the winning of this metal from its ores. The furnace in which the platinum is melted must obviously be of some material which has a higher melt- ing point still, and quicklime is found to fulfil this requirement. Pipe-clay, when put in the oxyhydrogen flame, is immediately fused to a sort of glass, while gold and silver not only melt, but vaporise into a dense smoke. Even the temperatures of the oxyhydrogen or oxy- coal-gas flame, however, are comparatively chilly in comparison with those which are now attainable in the electric furnace. Within the last fifteen or twenty years the efficiency of this furnace has been so improved that temperatures of 6000* Fahrenheit can be reached, and under these conditions many common substances are found to behave in a most extraordinary manner. Such a furnace consists essentially of a hollow box made of some non-conducting material, into the cavity of which project two carbon rods. An electric arc is established between these rods, with the result that an extraordinary degree of heat is attained in the cavity of the furnace. As was said in a previous chapter, electricity is gener- ated as a rule in a dynamo, driven by an engine, which in its turn depends for its power on the chemical process of combustion. In the electric furnace we merely get back a certain fraction of the heat which was produced in the combustion, and the reader might be inclined to consider the whole affair a wasteful cycle of opera- tions. Economical it certainly is not, but the advantage lies in this, that in the electric furnace the heat, which originally was distributed over a considerable space, is concentrated in a fraction of a cubic foot. The effect is locally intensified, the temperature is higher, and this 197