NH4HF2

NH4HF2, ammonium bifluoride, is an inorganic salt consisting of the ammonium cation (NH4+) and the bifluoride anion (HF2−). It is commonly prepared by reacting ammonium fluoride (NH4F) with hydrofluoric acid (HF): NH4F + HF → NH4HF2. At room temperature it forms a white, crystalline solid that is hygroscopic and highly soluble in water. In aqueous solution, NH4HF2 acts as a fluoride donor and can release hydrofluoric acid (HF) upon dissociation.

Applications for ammonium bifluoride center on its role as a fluoride source in various industrial processes. It is used for glass etching and cleaning, as a flux in metal finishing and brazing, and for rust removal on steel surfaces. It can also appear in certain fluoride baths and ceramic glaze formulations where a controlled fluoride source is required.

Safety and handling are important considerations with NH4HF2. It is highly corrosive and toxic; contact with skin or eyes can cause severe chemical burns, and inhalation of powders or vapors can irritate or damage the respiratory tract. In solution, it liberates HF, a highly hazardous acid capable of deep tissue injury. Handling should occur under a fume hood with appropriate PPE, including chemical-resistant gloves and eye/face protection. Store in tightly closed containers in a cool, dry, well-ventilated area away from acids and moisture. In case of exposure, rinse skin or eyes promptly with water and seek medical attention; HF exposure may require specialized treatment such as calcium gluconate for local injuries.