Abstract: Silica white and ammonium fluoride were prepared by using ammonia continually react with fluosilicic acid which is a by-product of wet-process phosphoric acid.As a reinforcing material with superior performance,silica white has a broad market;ammonium fluoride can be reacted with strong acid to form hydrofluoric acid.Optimized technologic conditions were as follows:the mass fraction of fluosilicic acid was 10%,the mass fraction of ammonia was 10%,the reaction temperature was 20 ℃,the stirring speed was 700 r/min,and average residence time was 15 min.Specific surface area of silica white produced under these technological conditions could reach 350 m²/g,and other chemistry indexes met with the quality requirements of HG/T 3061—1999.So this route is relatively effective for the integrated utilization of fluosilicic acid. 

Key words: fluosilicic acid, silica white, continuous process, specific surface