Mercury is a metal which is liquid at normal temperatures and pressures. It forms salts in two ionic states mercury(I) and mercury (II). Mercury (II), or mercuric, salts are very much more common than mercury(l) salts, and hence it is mercuric salts which will be mainly considered here. Mercury also forms organometallic compounds, some of which have found industrial and agricultural use. "Organometallic" is used here to indicate a covalently-bonded compound, and does not include mercury bound to proteins nor salts formed with organic acids. These organometallic compounds are stable, though some are readily broken down by living organisms, while others are not readily biodegraded. Elemental mercury gives rise to a vapour which dissolves only slightly in water.