Mercury exists in various chemical forms. The important forms from a toxicological
viewpoint are the metallic form, also called the elemental form, the divalent inorganic forms and
methylmercury compounds. Elemental (Hg0) mercury has a high vapor pressure and the vapor
causes a number of cases of poisoning via inhalation. Classical mercury poisoning is characterized
by a triad of signs, namely tremors, erethism and gingivitis