Quite recently, the question of the separation of titanium compounds from ilmenite used for the manufacture of pig iron has attracted considerable attention. It has been already mentioned (_vide supra_) that titaniferous iron ores have been shown to be perfectly amenable to blast-furnace treatment, the old and deeply rooted idea that titanium-bearing slags are stiff and troublesome being entirely contrary to facts, when suitable conditions are observed;[610] moreover, it is shown that the pig iron obtained is of unusually good quality. Rossi has suggested[611] that if sufficient carbon be added to reduce all the silica and oxides of iron, with enough lime to slag off the titanium dioxide as calcium titanate, the latter can be used as a source of titanium compounds or alloys, whilst a ferro-silicon will be obtained as pig metal; the temperature must be carefully adjusted to ensure reduction of the silica without loss of titanium dioxide. Another patent[612] proposes the reduction of the ore in an electric furnace, and the treatment of the crude ferro-titanium in a converter with a blast of air or nitrogen; the titanium nitride formed is then driven out of the metal by a blast of superheated steam--any ammonia or cyanogen formed being collected--and removed, the iron remaining being ‘Bessemerised’ directly in the same converter; the titanium nitride can be used as a manure, or for the manufacture of ammonia or nitric acid (_vide infra_). The removal of iron as the volatile carbonyl has also been suggested,[613] the titanium being subsequently transformed into the nitride. [610] _Vide_, _e.g._ _Iron Age_, 1909, ~84~, 1149 and 1223. [611] _E._ 3582, 1901. [612] Sinding-Larsen and Willumsen, _D. R. P._ 220544, April, 1910. [613] Sinding-Larsen, _E._ 17632, 1910. ~Employment of the Element in Metallurgy.~--It has been already mentioned that titanium itself is quite unsuitable for direct incorporation with steel. Besides the relatively low specific gravity (5·2), which would render mixing very difficult, the very high melting-point (given by Weiss and Kayser[614] as 2350°) would prevent uniform dissemination. The element is therefore generally used in the form of a ferro-titanium of low titanium content, 10-15 per cent. being the proportion usually employed. The addition should be made at the end of the Bessemer process, and after the addition of the required quantities of manganese and silicon alloys; the calculated quantity of ferro-titanium is added as the steel runs from the converter into the ladle. A suitable proportion is said to be one-half per cent. of alloy, so that the actual proportion of titanium to steel is somewhere about 1·5-1·8 lb. per ton. Six or eight minutes should be allowed after the addition, for the titaniferous slag to come to the surface. [614] _Zeitsch. anorg. Chem._ 1910, ~65~, 345.