Process for the preparation of boric acid as well as process for the preparation of silica using boric acid thus obtained.

摘要

Boric acid is prepared by reaction of a fluoroboric acid solution at elevated temperature with calcium carbonate and separation of the calcium fluoride precipitate formed from the remaining solution of boric acid. The fluoroboric acid solution used is preferably obtained by conversion of hexafluorosilicic acid with boric acid (formed from fluoroboric acid) and separation of the preciptated silica. Highly pure silica and valuable calcium fluoride can be prepared in a cyciic process using by-product hexafluorosilicic acid and cheap calcium carbonate.