By heating crystallized silicon with boron in the electric furnace H.
This advantage is especially observed in some cases in which the charge of the furnace is liable to attack the containing vessel at high temperatures, as it is often possible to maintain the outer walls of the electric furnace relatively cool, and even to keep them lined with a protecting crust of unfused charge.
For basic linings, magnesia crystallized in the electric furnace is being extensively used, replacing dolomite to some extent (see E.
Heated in the electric furnace in a current of air, it yields calcium cyanamide (see Cyanamide).
The electric furnace has several advantages as compared with some of the ordinary types of furnace, arising from the fact that the heat is generated from within the mass of material operated upon, and (unlike the blastfurnace, which presents the same advantage) without a large volume of gaseous products of combustion and atmospheric nitrogen being passed through it.
Carbides of chromium are known; when the metal is heated in an electric furnace with excess of carbon, crystalline, C2Cr 3, is formed; this scratches quartz and topaz, and the crystals are very resistant to the action of acids; CCr 4 has also been described (H.
There is, however, one (not insuperable) drawback in the use of the electric furnace for the smelting of pure metals.
In this article the general principles of metallurgical furnaces will be treated; the subject of gasand oil-heated furnaces is treated in the article Fuel, and of the electric furnace in the article Electrometallurgy.
The metal may be obtained by heating the trioxide with carbon in the electric furnace (H.
By heating the amorphous form in the electric furnace H.