Renewal time: 2011-11-01 11:03:24
        Pure fluoroboric acid has never been produced but aqueous solutions of HBF4 can be produced by dissolving boric acid in aqueous hydrofluoric acid solution at 20-25 °C. Three equivalents of HF react to give the intermediate boron trifluoride and the fourth gives fluoroboric acid.

B(OH)3 + 4 HF → H3O+ + BF4− + 2 H2O

        Aqueous solutions of fluoroboric acid can also be prepared by treating impure hexafluorosilicic acid with solid boric acid followed by removal of precipitated silicon dioxide. Anhydrous solutions can be prepared by treatment with acetic anhydride.