Mercury

Description

Elemental mercury, a silver-white metal, is also known ‘quicksilver’ or ‘hydrargyrum.’ Mercury has been discovered in Egyptian tombs dating as far back as 1500 BC. The chemical symbol, Hg, is derived from the Greek word hydrargyros, meaning ‘water silver.’ Mercury was known in antiquity and used by alchemists. Its neurological effects were recognized early, and its use in the hat-making trade gave rise to the phrase ‘mad as a hatter.’ Mercury has been used commercially and medically for centuries. In the past it was a common constituent of many medications, for example, it was used in the treatment of syphilis. Use of mercury has been drastically reduced in recent years. Within the twentieth century, mercury used to be in every physician’s or pharmacist’s armamentarium, for example, calomel was commonly used in infant teething powders in the 1930s and 1940s.

Chemical properties

Mercury is a silvery, mobile, odorless, extremely heavy liquid , sometimes found native. Insoluble in hydrochloric acid; soluble in sulfuric acid upon boiling; readily soluble in nitric acid; insoluble in water, alcohol, and ether; soluble in lipids; extremely high surface tension.

History

The name of Hg derives from the Roman god “Mercury”, the nimble messenger of the gods, since the ancients used that name for the element, which was known from prehistoric times. The name mercury originated in 6th-century alchemy, in which the symbol of the planet was used to represent the metal; the chemical symbol Hg derives from the Latin hydrargyrum, “liquid silver or quick silver.” Although its toxicity was recognized at an early date, its main application was for medical purposes.

The Uses of Mercury

Amalgams, catalyst, electrical apparatus, cathodes for production of chlorine and caustic soda, instruments (thermometers, barometers, etc.), mercury vapor lamps, extractive metallurgy, mirror coating, arc lamps, boilers, coolant, and neutron absorber in nuclear power plants.

The Uses of Mercury

Cadmium is used in electroplating, in nickelcadmiumstorage batteries, as a coating forother metals, in bearing and low-meltingalloys, and as control rods in nuclear reactors.Cadmium compounds have numerousapplications, including dyeing and printingtextiles, as TV phosphors, as pigments andenamels, and in semiconductors and solarcells.
Vegetables and cereals are the main sourcesof dietary Cd while meat and fish contain themetal to a lesser extent.

The Uses of Mercury

Electrical apparatus; measurement and control systems such as thermometers and sphygmomanometers; agricultural and industrial poisons; catalyst; antifouling paint; dental practice; gold mining

Definition

Metallic element of atomic number 80, group IIB of the periodic table, aw 200.59, valences = 1,2; 4 stable isotopes and 12 artificially radioactive isotopes.

Production Methods

Mercury is mined primarily in underground mines as the metal or as the red sulfide cinnabar (HgS). Like HgO, the sulfide decomposes at higher temperatures. Heating of the ore and condensation of the mercury vapor constitute a convenient procedure for reducing, extracting, and purifying mercury from its ore. In the United States, mercury is produced primarily from secondary sources; this involves recycling a variety of industrial waste products. A survey in 1980 conducted by the U.S. National Institute for Occupational Safety and Health suggested that about 70,000 workers were exposed to mercury and its compounds; the majority of these exposures involves mercury vapor. However, this number has probably already decreased considerably, and occupational mercury vapor exposure has now become fairly rare in industrialized countries. On the other hand, numbers of workers exposed to mercury vapor from informal mining in developing countries has increased disproportionally and is causing health risks to workers and their families, including children.

General Description

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.

Reactivity Profile

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.).

Hazard

Central nervous system impairment, peripheral nervous system impairment, and kidney damage. (1) Mercury, metallic: Highly toxic by skin absorption and inhalation of fume or vapor, absorbed by respiratory and intestinal tract. FDA permits zero addition to

Health Hazard

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.

Fire Hazard

Behavior in Fire: Not flammable

Flammability and Explosibility

Mercury is not combustible.

Safety Profile

Poison by inhalation. Human systemic effects by inhalation: wakefulness, muscle weakness, anorexia, headache, tinnitus, hypermotihty, darrhea, liver changes, dermatitis, fever. An experimental teratogen. Experimental reproductive effects. Questionable carcinogen with experimental tumorigenic data. Human mutation data reported. Used in dental applications, electronics, and chemical synthesis. bromopropyne, alkynes + silver perchlorate, ethylene oxide, lithium, methylsilane + oxygen (explodes when shaken), peroxyformic acid, chlorine dioxide, tetracarbonylnickel + oxygen. May react with ammonia to form an explosive product. Mixtures with methyl azide are shockand spark-sensitive explosives. The vapor iptes on contact with boron diiodophosphide. Reacts violently with acetylenic compounds (e.g., acetylene, sodmm acetylide, 2-butyne-l,4 do1 + acid), metals (e.g., aluminum, calcium, potassium, sodium, rubidium, exothermic formation of amalgams), Cl2, ClO2, CH3N3, NazCz, nitromethane. Incompatible with methyl azide, oxidants. When heated to decomposition it emits toxic fumes of Hg. See also MERCURY COMPOUNDS.

Potential Exposure

Mercury is used as a catalyst, in dental applications; and in pharmaceuticals; as a liquid cathode in cells for the electrolytic production of caustic and chlorine. It is used in electrical apparatus (lamps, rectifiers, and batteries) and in control instruments (switches, thermometers, and barometers)

First aid

If this chemical gets into the eyes, remove any contact lenses at once and irrigate immediately for at least 15 min, occasionally lifting upper and lower lids. Seek medical attention immediately. If this chemical contacts the skin, remove contaminated clothing and wash immediately with soap and water. Seek medical attention immediately. If this chemical has been inhaled, remove from exposure, begin rescue breathing (using universal precautions, including resuscitation mask) if breathing has stopped and CPR if heart action has stopped. Transfer promptly to a medical facility. When this chemical has been swallowed, get medical attention. Give large quantities of water and do induce vomiting. Do not make an unconscious person vomit. Antidotes and special procedures for medical personnel: The drug NAP (n-acetyl penicillamine) has been used to treat mercury poisoning, with mixed success. Note to physician: For severe poisoning BAL [British AntiLewisite, dimercaprol, dithiopropanol (C3H8OS2)] has been used to treat toxic symptoms of certain heavy metals poisoning including mercury. Although BAL is reported to have a large margin of safety, caution must be exercised, because toxic effects may be caused by excessive dosage. Most can be prevented by premedication with 1-ephedrine sulfate (CAS: 134-72-5).

Carcinogenicity

There is no conclusive evidence from epidemiological studies that mercury increases cancer risk in humans.12 In the few studies in which increases have been reported, concomitant exposure to other known carcinogens has confounded the results. The IARC has determined that there is inadequate evidence in humans for the carcinogenicity of mercury and mercury compounds.12 In animals there is inadequate evidence for carcinogenicity of metallic mercury and limited evidence for the carcinogenicity of mercuric chloride.

Environmental Fate

Mercury cycles through various environmental phases by exchange from ground to air and back again. Metallic and dimethylmercury, which are volatile, will be released as mercury vapor that can travel long distances before being redeposited. When found in surface waters and soils it will degas into the surrounding air where natural currents and winds spread the materials until they are deposited back on the surface waters and soils. The majority of mercury returned to the soil or water is by wet partition and accounts for almost all of the mercury found in lakes with no other input source. Inert mercury will deposit bound to particulates in aerosols. Once deposited, mercury must adsorb to soil or sediment particulates or be returned to the atmosphere. This cycle continues with a portion of the mercury revolatilizing into the atmosphere in each cycle.

storage

Precautions should be taken to prevent spills of mercury because drops of the liquid metal can easily become lodged in floor cracks, behind cabinets, and equipment, etc., with the result that the mercury vapor concentration in the laboratory may then exceed the safe and allowable limits. Containers of mercury should be kept tightly sealed and stored in secondary containers (such as a plastic pan or tray) in a well-ventilated area. When breakage of instruments or apparatus containing significant quantities of Hg is possible, the equipment should be placed in a plastic tray or pan that is large enough to contain the mercury in the event of an accident. Transfers of mercury between containers should be carried out in a fume hood over a tray or pan to confine any spills.

Shipping

UN2809 Mercury, Hazard class: 8; Labels: 8-Corrosive material, 6.1-Poisonous material

Purification Methods

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.]

Toxicity evaluation

Mercury has a great affinity for sulfhydryl moieties and, hence, binds and inactivates a variety of enzymes. Methylmercury also initiates lipid peroxidation, which can produce alterations in cell membranes. Mercury damages the microtubules in the brain by reacting with the protein tubulin.

Incompatibilities

Heating mercury causes the formation of toxic mercury oxide fumes. Reacts violently with alkali metals; acetylene, azides, ammonia gas; chlorine, chlorine dioxide; many acids; most metals; ground mixtures of sodium carbide, and ethylene oxide. Contact with methyl azide forms shock- and spark-sensitive explosives. Attacks copper and many other metals, forming amalgams

Waste Disposal

Consult with environmental regulatory agencies for guidance on acceptable disposal practices. Generators of waste containing this contaminant (≥100 kg/mo) must conform to EPA regulations governing storage, transportation, treatment, and waste disposal. Accumulate for purification and re-use if possible. Mercury vapors may be adsorbed or treated with sulfide solutions and then sent to mercury recovery operations