Ammonium tetrafluoroborate

Ammonium tetrafluoroborate (or ammonium fluoroborate) is an inorganic salt composed of the ammonium cation and the tetrafluoroborate anion, with the chemical formula NH₄BF₄. When heated to decomposition, ammonium tetrafluoroborate releases toxic fumes of hydrogen fluoride, nitrogen oxides, and ammonia.

Preparation

Ammonium tetrafluoroborate can be prepared by reacting ammonium fluoride with boric and sulfuric acid:

8 NH₄F 2 H₃BO₃ 3 H₂SO₄ → 2 NH₄BF₄ 3 (NH₄)₂SO₄ 6 H₂O

References