The compounds of zirconium and thorium with elements of group VB, according to two German patents,[597] are suitable for the preparation of metallic filaments in much the same way. Thorium, titanium, and zirconium are also among the metals which, it is claimed, can be obtained in the pure fused state by heating in an electric arc in vacuo, so that filaments can be drawn directly.[598]
[597] D. R. P. 153958 and 154299, September, 1904.
[598] Ibid. 169928, April, 1906.
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.