The Romance of Modern Chemistry

METALS, COMMON AND UNCOMMON an inch in diameter, and its melting-point is exceedingly high, so high that the fine wire may be raised to a white heat by an electric current without melting. The tantalum lamp, then, which is now on the market, is exactly analogous to the electric glow lamp, except that the filament is made of tantalum instead of carbon. As regards efficiency, the tantalum lamp compares favour- ably with the ordinary glow lamp, and it is said to have a longer life. So the time may come, if sufficient tantalum can be procured, when the carbon filament will have become merely a curiosity. Tungsten and osmium are other out-of-the-way metals which have recently found an important application in the manufacture of electric lamps, so that tantalum is not the only competitor in the field against the carbon filament. The application of electricity to all sorts of objects has led to extended demands for other metals than those just quoted. Copper, for instance, which offers very slight resistance to the passage of a current, is much in demand for electric wiring; enormous quantities of the metal are now devoted to this purpose. Copper enters also into the composition of many alloys—brass, bronze, and the like; but the subject of alloys is a big one, and must be reserved for another chapter. 71