Abstract: Process for the preparation of alkali metal fluotitanates by fluorination of a titanium ore, reaction with an alkali metal compound, precipitation and separation of the formed alkali metal fluotitanates, wherein the titanium ore is mixed with a hydrofluosilicate solution, the resulting suspension is evaporated at a temperature of 90.degree.-110.degree. C., the residue is subsequently taken up in water or in a mineral acid and the residue solution is neutralized with an alkali metal compound.

Abstract: Process for preparing pure silicon dioxide from a hexafluorosilicic acid solution by controllably and vigorously admixing, stirring or blending a hexafluorosilicic acid solution with a quantity of ammonium hydroxide solution amounting to about 40 to about 75 percent by weight of the quantity stoichiometrically required for the converting hexafluorosilicic acid to ammonium fluoride and silicon dioxide to thereby form a reaction mixture and a precipitate therein; separating out this precipitate; treating the precipitate-free liquid with ammonium hydroxide and then recovering the pure silicon dioxide. The silicon dioxide is pure enough to be useful as a catalyst support or as a substitute for quartz.