Hydrofluoric acid (HF) is a solution of hydrogen fluoride in water. Its chemical formula is HF. It is a very dangerous acid, being very corrosive and extremely toxic. It can dissolve glass to make hexafluorosilicic acid. If it gets on the skin, it can kill you. It is made by reacting fluorite with sulfuric acid. It is used in the processing of petroleum. It is also used to make various other chemicals containing fluorine, such as teflon (the coating in a frying pan), freon (the cooling agent in an air conditioner), and fluorocarbons (used as propellants in aerosol cans). It is used to clean metals. It is very toxic because it bonds with calcium ions in the body and makes them so they cannot be used. As an acid, it can be deprotonated to produce fluorides, which are also the salts of hydrofluoric acid.