Electrical mercury compounds

AppHcations of mercury include use in batteries (qv), chlorine and caustic soda manufacture (see Alkali and chlorine products), pigments (see Pigments, inorganic), light switches, electric lighting, thermostats, dental repair (see Dental materials), and preservative formulations for paints (qv) (1—3). As of the end of the twentieth century, however, increased awareness of and concern for mercury toxicity has resulted in both voluntary and regulatory reduction of mercury usage (see also Mercury compounds). 

Fire Hazards - Flash Point Not flammable Flammable Limits in Air (%) Not flammable Fire Extinguishing Agents Not pertinent Fire Extinguishing Agents Not To Be Used Not pertinent Special Hazards of Combustion Products Smoke may contain toxic mercury compounds Behavior in Fire Not pertinent Ignition Temperature Not pertinent Electrical Hazard Not pertinent Burning Rate Not pertinent. 

One form of calomel electrode is shown in Fig. 15.1(a). It consists of a stoppered glass vessel provided with a bent side tube fitted with a three-way tap which carries a short upper and a long lower tube the latter is drawn out to a constriction at the bottom end. A short platinum wire is fused into the bottom of the vessel so that it protrudes into the interior, and a narrow glass tube sealed to the bottom of the vessel is bent round parallel to the vessel. A little mercury placed in the bottom of this tube provides electrical connection with the interior of the vessel through the sealed-in platinum wire. Mercury and mercury compounds must be handled with care (see Section 16.8). 

CH3 -Zn with superstoichiometric (defect) zinc atoms (Zn -impurity centres of conductivity). The larger is the electric positivity of the metal in these complexes, the larger is the ionicity of the carbon-metal bond, carbon being at the negative end of the dipole. Thus, in the case of C - K bond, ionicity amounts to 51%, whereas for C - Mg and C - Zn bonds ionicity amounts to 35% and 18%, respectively [55]. Consequently, metalloorganic compounds are characterized by only partially covalent metal-carbon bonds (except for mercury compounds). 

The major use of mercury compounds is as agricultural pesticides. It is also used in the chlorine-alkali industry, in paints, as a catalyst in chemical and petrochemical industries, in electrical apparatus, cosmetics, thermometers, gauges, batteries, and dental materials. For this reason, it is a very common pollutant in wastewaters. 

Human activities have resulted in the release of a wide variety of both inorganic and organic forms of mercury. The electrical industry, chloro-alkali industry, and the burning of fossil fuels (coal, petroleum, etc.) release elemental mercury into the atmosphere. Metallic mercury has also been released directly to fresh water by chloro-alkali plants, and both phenylmer-cuiy and methylmercury compounds have been released into fresh and sea water -phenylmercury by the wood paper-pulp industry, particularly in Sweden, and methyl-mercury by chemical manufacturers in Japan. Important mercury compounds which also may be released into the environment include mercury(II) oxide, mercury(II) sulfide (cinnabar), mercury chlorides, mer-cury(II) bromide, mercury(II) iodine, mer-cury(II) cyanide, mercury(II) thiocyanate, mercury(II) acetate, mercury nitrates, mercury sulfates, mercury(II) amidochloride monoalkyl- and monoarylmercury(II) halides, borates and nitrates dialkylmercury compounds like dimethylmercury, alkoxyal-kylmercury compounds or diphenylmercury (Simon and Wiihl-Couturier 2002) (for quantities involved, see Section 17.4). 

Solutions of sodium metal in liquid ammonia are blue and have high electrical conductivities the main current carrier of such solutions is the solvated electron. Such solutions are used in both organic and inorganic chemistry as efficient reducing agents. Sodium also forms a number of alkyl and aryl derivatives by reaction with the appropriate mercury compound, e.g. ... 

When liquid mercury is struck with a hammer, it scatters in an impressive way. Elemental mercury and mercury compounds also scatter through the environment. The major source of mercury emissions is coal-fired electric utilities. Mercury and mercury compounds occur extensively in nature and are found in coal. As coal burns, mercury compounds decompose to elemental mercury then, as the flue gas cools and exits the plant, the majority of the mercury quickly oxidizes — probably catalytically, due to the presence of other metals in the gas — to its ionic form Hg. This form is water soluble, so it dissolves in rain and falls back to Earth. 

Mercury. Sometimes called quicksilver, mercury is the only common metal that is liquid at ordinary temperatures. It is a feir conductor of electricity and of high density. It is used in barometers and thermometers, to recover gold from its ore, and to manu-fecture chlorine and sodium hydroxide. Its vapor is used in street lights, fluorescent lamps, and advertizing signs. Mercury compounds have various uses, such as insecticides, rat poisons, disinfectants, paint pigments, and detonators. Mercury easily is alloyed with silver, gold, and cadmium. 

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