Hydrogen fluoride (HF) is a fluid chemical compound whose molecules consist of one atom of hydrogen and one atom of fluoride. It occurs as both a colorless, odorless gas and a liquid, and is highly poisonous in both forms. This substance forms from reactions between sulfuric acid and pure fluorite. Because both sulfuric acid and the mineral fluorite may be found in volcanic regions, hydrogen fluoride can sometimes form from volcanic activity. It dissolves readily in water to form hydrofluoric acid.
