5898. Mercury

Properties

Silver-white, heavy, mobile, liquid metal; slightly volatile at ordinary temp; solid mercury is a tin-white, ductile, malleable mass which may be cut with a knife. mp 38.87°; bp 356.72°; d²⁵ 13.534. Heat capacity at constant pressure (25°) 6.687 cal/mole deg. Vapor pressure (25°): 2 × 10³ mm; heat of vaporization (25°): 14.652 kcal/mole: Busey, Giauque, J. Am. Chem. Soc. 75, 806 (1953). Surface tension (25°): 484 dynes/cm; electrical resistivity (20°): 95.76 μohm cm. Corrosive; poisonous. When pure does not tarnish on exposure to air at ordinary temp, but when heated to near the boiling point slowly oxidizes to HgO. Forms alloys with most metals except iron and combines with sulfur at ordinary temperatures. E⁰ (aq) Hg/Hg²⁺ 0.854 V; E⁰ (aq) 2 Hg/Hg₂²⁺ 0.789 V. Soly in water (25°): 0.28 μmoles/l; data on soly in organic solvents: Spencer, Voigt, J. Phys. Chem. 72, 464 (1968). Reacts with HNO₃ and hot, concd H₂SO₄; does not react with dil HCl, cold H₂SO₄, or alkalies. Reacts with ammonia solns in air to form Hg₂NOH, Millon's base. Mercury salts when heated with Na₂CO₃ yield metallic Hg and are reduced to metal by H₂O₂ in the presence of alkali hydroxide. Cu, Fe, Zn and many other metals ppt metallic Hg from neutral or slightly acid solns of mercury salts. Soluble ionized mercuric salts give a yellow ppt of HgO with NaOH and a red ppt of HgI₂ with alkali iodide. Mercurous salts give a black ppt with alkali hydroxides and a white ppt of calomel with HCl or sol chlorides. They are slowly dec by sunlight.

Caution

Readily absorbed via respiratory tract (elemental mercury vapor, mercury compd dusts), intact skin, and G.I. tract, although occasional incidental swallowing of metallic mercury is without harm. Spilled and heated elemental mercury is particularly hazardous. Acute: sol salts have violent corrosive effects on skin and mucous membranes; severe nausea, vomiting, abdominal pain, bloody diarrhea; kidney damage; death usually within 10 days. Chronic: inflammation of mouth and gums, excessive salivation, loosening of teeth; kidney damage; muscle tremors, jerky gait, spasms of extremities; personality changes, depression, irritability, nervousness. Phenyl and alkyl mercurials can cause skin burns and be absorbed by the skin. Burning sensation is delayed several hours and thus gives no warning. Alkyls have affinity for brain tissue and may cause permanent damage. Phenyls are no more toxic than inorganic Hg. Antidote: Dimercaprol (BAL). See E. Browning, Toxicity of Industrial Metals (Appleton-Century Crofts, New York, 2nd ed., 1969) pp 226-242.