Metallic zirconium and its alloys have recently been employed in metallurgy. The pure metal can be obtained by the calcium reduction of Kuzel and Wedekind (_vide_ p. 316); zirconia is not reduced by powdered aluminium (Goldschmidt’s process), but alloys of zirconium and iron can be easily obtained by the reduction of mixtures of the two oxides by this method. Alloys can be obtained containing up to 35 per cent. of zirconium; this ferro-zircon, as it is called, has been used to some extent recently in place of ferro-titanium (_vide infra_) for the purification of steels.[599] Addition of small quantities of zirconium to steels, brass, copper, etc., is said to secure sound castings, and to increase considerably the strength and resistance to acids of the metal. [599] _Vide_ Weiss, _E._ 29376, 1910, and Lesmüller, _D. R. P._ 231002, February, 1911. ~The Technical Uses of Zirconia.~--Since the discovery of Baddeleyite, the natural oxide of zirconium (_vide_ p. 75), which occurs in large quantities in Brazil, many proposals have been brought forward for the employment of this compound. Its application to the manufacture of glasses and enamels will be referred to in the next chapter. Patents have been taken out protecting its use for the preparation of white pigments,[600] as a toilet-powder,[601] and as a polishing powder,[602] for it is extremely stable towards chemical reagents, very voluminous, and at the same time very hard. It has long been employed for coating the lime and magnesia pencils used in the Drummond or ‘lime’ light; and recently it has been employed for the headlights of automobiles, in the Blériot lamp,[603] in which a rod of zirconia is heated in a blowpipe flame fed with oil vapour and oxygen. [600] _D. R. P._ 235495. [601] _Ibid._ 237624. [602] _Ibid._ 230757. [603] _Ibid._ 174313, September, 1906. By far the most important property of the oxide, from the technical point of view, is the ease with which it resists high temperatures. The natural oxide can be freed, to a very large extent, from the iron oxide which it encloses, by the prolonged action of hydrochloric acid; experiments were carried out on the material so obtained by Simonis,[604] who showed that by prolonged heating at a high temperature, the remaining impurities, chiefly ferric oxide and silica, could be volatilised, leaving the zirconia unchanged. Riecke[605] showed that whilst the oxide is very suitable for the manufacture of highly resistant crucibles, its use is restricted by the fact that it is easily reduced by carbon at high temperatures, forming the carbide. [604] _Sprechsaal_, 1908, ~41~ (1), 210. [605] _Ibid._ 214.