A mercury coordination entity made up of linear triatomic molecules in which a mercury atom is bonded to two chlorines. Water-soluble, it is highly toxic. Once used in a wide variety of applications, including preserving wood and anatomical specimens, embalming and disinfecting, as an intensifier in photography, as a mordant for rabbit and beaver furs, and freeing gold from lead, its use has markedly declined as less toxic alternatives have been developed.