21.2 CHEMISTRY
Mercury exists in three oxidation states: Hg0 (metallic), Hgþ (mercurous), and Hg2þ
(mercuric) mercury. In organometallic derivatives, mercuric mercury is covalently
bound to one or two carbon atoms, and the organic part of the molecule is often an
alkyl group or an alkoxialkyl group. The former compounds are more toxic because they
are more easily absorbed and more slowly metabolized. In its elemental form,mercury is
a dense, silvery-white, shiny metal, which is liquid at room temperature and boils at
357C. At 20C, the vapor pressure of the metal is 0.17 Pa (0.0013mm Hg), and a
saturated atmosphere at this temperature contains 14mg Hg/m3, which is more than 100
times the occupational exposure limit. Mercury compounds differ greatly in their
solubility. Thus, at 25C, the solubility of metallic mercury, mercurous chloride, and
mercuric chloride in water are 60 mg/L, 2mg/L, and 69 g/L, respectively (IARC, 1994).