[658] _Vide_, _e.g._ _D. R. P._ 189364, 218316, 115016, 207001; _F._ 438908, etc. [659] _Sprechsaal_, 1911, ~44~, 72. These two oxides find employment to a small extent in the manufacture of ‘Siloxide’ quartz glass.[660] Quantities up to 1·5 per cent., added to the molten silica, reduce the difficulty of working the material. Exhaustive tests carried out by Thomas[661] indicate that the vessels made from this material are, on the whole, to be preferred to ordinary quartz glass, resisting high temperature better, and showing less tendency to become crystalline and therefore brittle when maintained for considerable times at high temperature. [660] Wolf-Burckhardt and Borchers, _F._ 432786, October, 1911. [661] _Chem. Zeitg._ 1912, ~86~, 25. * * * * * Much work has been carried out during the last few years with the object of utilising titanium compounds for the ‘fixation’ of nitrogen. The metal combines very vigorously with the gas at about 800°C. (_vide_ p. 224), forming the nitride. If the gas, or air, be passed over a heated mixture of the dioxide with powdered coke, formation of the cyanonitride occurs at comparatively low temperatures (1100°-1300°C.) if a small quantity of an alkali salt be present,[662] the action being apparently catalytic; if excess of carbon is used, considerable quantities of the cyanide may be formed. Numerous experiments carried out by the chemists of the Badische Anilin- und Soda-Fabrik have shown that at high temperatures, the action of water and a suitable oxidising agent, or in the presence of metallic compounds, the action of steam alone, will liberate considerable quantities of ammonia from both these derivatives,[663] whilst in the presence of platinum compounds, if air be pumped in, the higher oxides of nitrogen are formed. One or two examples may be given: (1) Ti₂N₂ + 4NaOH + H₂O + 2CuO = 2NH₃ + Cu₂O + 2Na₂TiO₃--autoclave at 180°C. (2) 2Ti₂N₂ + 2H₂SO₄ + 6H₂O + O₂ = 4TiO₂ + 2(NH₄)₂SO₄--autoclave at 120°-140°C. (3) Ti₂N₂ + 3H₂O = Ti₂O₃ + 2NH₃--steam at 500°-600°C. [662] _Vide_ Bosch, _U. S. P._ 957842, May, 1910. [663] _Vide_, _e.g._ _D. R. P._ 202563 and 203748 of March, 1907; 204204 and 204475 of November, 1908; _E._ 2414, 1908; _F._ 387002 of June, 1908; _U. S. P._ 957843 of May, 1910, gives a résumé of all the processes. In the second case, the oxygen is derived from air pumped into the apparatus, and ferrous sulphate is used as a catalyst. In the third case, a metallic salt, oxide, or hydroxide is required as a catalyst. In view of the success of the cyanamide method for the fixation of atmospheric nitrogen, these processes, though of considerable theoretical interest, do not seem likely to become of practical importance. * * * * *