After air has been bubbled through mercury for several hours to oxidise metallic impurities, it is filtered to remove coarser particles of oxide and dirt, then sprayed through a 4-ft column containing 10% HNO3. It is washed with distilled water, dried with filter paper and distilled under vacuum. [Schenk in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol I p8 1963.]
Behavior in Fire: Not flammable
Mercury mostly is obtained from its sulfide ore, cinnabar. The process involves roasting cinnabar in a furnace between 600 to 700°C. Mercury vapors are cooled and condensed into metal:
HgS + O2 → Hg + SO2
Mercury may also be extracted from cinnabar by reduction of the ore with lime at elevated temperature:
4HgS + 4CaO → 4Hg + 3CaS + CaSO4
Smaller quantities of metal are recovered from mercury-containing industrial and municipal wastes, such as amalgams and batteries. The scrap material is heated in a retort and the vapors of mercury are condensed into highpurity metal.
Although mercury is known from early times and was used by alchemists, its first modern scientific applications date back to 1643 when Torricelli used it in the barometer to measure pressure and about eight decades later Fahrenheit used it in the thermometer to measure temperature. Before this, mercury’s use was confined to decorative work, gold extraction and medicines. The element was named after the planet mercury and its symbol Hg is taken from the Latin word hydrargyrum, which means liquid silver.
The element does not occur in nature in native form. Its principal mineral is cinnabar, the red mercuric sulfide, HgS. Black mercuric sulfide, metacinnabar, also is found in nature. Other ores are livingstonite, HgSb4S7; coloradite, HgTe; tiemannite, HgSe; and calomel, HgCl. Its concentration in the earth’s crust is estimated to be 0.08 mg/kg. The average concentration in sea water is about 0.03 µg/L.
Elemental mercury and all its compounds are highly toxic by all routes of exposure. The element has significant vapor pressure at ambient temperatures (0.0018 torr at 25°C) that can produce severe inhalation hazard. The symptoms from short exposure to high concentration of mercury vapors are bronchitis, coughing, chest pain, respiratory distress, salivation and diarrhea (Patnaik, P. 1999. A Comprehensive Guide to the Hazardous Properties of Chemical Substances, 2nd ed., New York: John Wiley and Sons). Other symptoms are tremor, insomnia and depression. Mercury can cause damage to kidney, liver, lungs and brain. Organomercury compounds and inorganic salt solutions can be absorbed into the body through skin contact and cause severe poisoning. It accumulates as Hg2+ in the brain and kidneys. US EPA has classified mercury as one of the priority pollutant metals in environmental matrices.
An odorless, silvery metallic liquid. Insoluble in water. Toxic by ingestion, absorption and inhalation of the fumes. Corrosive to aluminum. Used as a catalyst in instruments, boilers, mirror coatings.
MERCURY forms an explosive acelylide when mixed with acetylene. Can form explosive compounds with ammonia (a residue resulting from such a reaction exploded when an attempt was made to clean MERCURY off a steel rod [Chem. Eng. News 25:2138. 1947]. Chlorine dioxide (also other oxidants, such as: chlorine, bromine, nitric acid, performic acid), and MERCURY explode when mixed [Mellor 2, Supp. 1:381. 1956]. Methyl azide in the presence of MERCURY is potentially explosive [Can. J. Chem. 41:1048. 1963]. Ground mixtures of sodium carbide and MERCURY can react vigorously [Mellor 5:848. 1946-47]. Ammonia forms explosive compounds with gold, MERCURY, or silver. (Eggeman, Tim. mmonia Kirk-Othmer Encyclopedia of Chemical Technology. John Wiley & Sons, Inc. 2001.).
Mercury is a non-specific toxin, attacking many of the body s systems. At low levels of exposure, symptoms are mainly related to nerve and brain function and include memory loss, mood instability, tremor, and other stress-like symptoms: poor coordination, headache, and visual and hearing problems. Recently, reproductive health has been shown to be affected, with abnormalities in menstrual cycle, poor outcome of pregnancy, and subfertility in both men and women. The immune system is also damaged by mercury exposure.
Some of the most important uses of mercury are in the electrical and electrolytic applications. A broad range of such applications include mercury batteries and cells in portable radios, microphones, cameras, hearing aids, watches, smoke alarms, and wiring and switching devices. Other notable applications are in mercury vapor lamps, fluorescent tubes and electrical discharge tubes. Mercury electrodes are widely used in electrolytic cells. Mercury cathodes are employed in the electrolysis of sodium chloride to produce caustic soda and chlorine. Another major use, as mentioned earlier, is in thermometers, manometers, barometers and other pressure-sensing devices. Mercury also is used as a catalyst in making urethane foams and vinyl chloride monomers. Mercury and its compounds long have been used as fungicides in paints and in agriculture. Mercury compounds are used in medicines, pigments and analytical reagents.
In mercury arc lamps producing ultraviolet rays; in mercury boilers; manufacture of all mercury salts, mirrors; as catalyst in oxidation of organic Compounds; extracting gold and silver from ores; making amalgams, electric rectifiers, mercury fulminate; also in dentistry; in determining N by Kjeldahl method, for Millon's reagent; as cathode in electrolysis, electroanalysis, and many other uses. Also in pharmaceuticals, agricultural chemicals, anti-fouling paints.