. . . "Prior art cited3.1 D1 discloses a method for purifying highly dispersed halide-bearing oxides, particularly silica, comprising continuously feeding the oxide co-currently with steam, optionally diluted with an inert gas such as air upwardly such as to form a fluidised bed in an upright column, the temperature in the fluidised bed being in the range from about 450 ??C to about 800 ??C, whereby the" .