Mercury - Elemental

For the general population, a WHO expert group estimated an average daily intake of between 3.8 and 21 pg mercury vapor from dental amalgam, and only 0.030 tg from 

Because of its hpophilicity, absorbed mercury vapor quickly crosses the blood-brain barrier in humans (Hursh et al. 1976, Aschner and Aschner 1990) and the placenta in animals (Clarkson etal. 1972, Vimy etal. 1997, Yoshida etal. 1989) and humans (Drasch et al. 1994, Yang et al. 1997). 

In blood, Hgi initially penetrates the red blood cells, and at 20 min after exposure 

Human volunteers exhaled approximately 7-12% of a retained dose of mercury vapor within the first few days after exposure (Hursh etal. 1976, Sandborgh-Englund etal. 1998). Under normal circumstances, the excretion of Hg via sweat is negligible, but in the case of acute mercury vapor inhalation at toxic dosage, the proportion of mercury excreted in the sweat was of similar magnitude to that excreted renally (Lovejoy etal. 1973, EPA 1997). 

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Miscellaneous Atomization Methods A few elements may be atomized by a chemical reaction that produces a volatile product. Elements such as As, Se, Sb, Bi, Ge, Sn, Te, and Pb form volatile hydrides when reacted with NaBH4 in acid. An inert gas carries the volatile hydrides to either a flame or to a heated quartz observation tube situated in the optical path. Mercury is determined by the cold-vapor method in which it is reduced to elemental mercury with SnCb- The volatile Hg is carried by an inert gas to an unheated observation tube situated in the instrument s optical path. 

The reaction of trifluoromethyl radicals, generated in a radio-frequency discharge process, with elemental mercury f/7i], mercury halides [174], dime-thylmercuiy [24], or HgO [175] has been used for the preparation of CFjHgX and (CF3)2Hg. Direct fluorination of dimethylmercury with elemental fluorine gives (CF3)2Hg [176],... 

Knabe has introduced mercuric acetate plus ethylenediaminetetraacetic acid (EDTA) as an oxidizing agent for tertiary amines (74). The solvent employed is 1 % aqueous acetic acid. In this system, the complexed mercuric ion is reduced to elemental mercury. Knabe s studies have centered on the... 

It is useful in this sense to make a dear distinction between the conception of an element as a separate homogeneous substance, and as a material but invisible part of a compound. Mercury oxide does not contain two simple bodies, a gas and a metal, but two elements, mercury and oxygen, that, when free, are a gas and a metal. Neither mercury as a metal nor oxygen as a gas is contained in mercury oxide it only contains the substance of the elements, just as steam only contains the substance of ice, but not ice itself, or as corn contains the substance of the seed but not the seed itself (4). 

Lead azide, Pb(N,)2, is used as a detonator, i i) What volume of nitrogen at STP (1 atm, 0°Ci does 1.5, of It id azide produce when it decomposes into lead metal and nitrogen gas (b) Would 1.5 g of mercury(ll) azide, Hg(N which is also used as a detonator, produce a larger or smallei volume, given that its decomposition products i c elemental mercury and nitrogen gas (c) Metal azides in general are potent explosives. Why ... 

Mason, R. P., Fitzgerald, W. F. and Morel, F. M. M. (1994). The biogeochemical cycling of elemental mercury Anthropogeruc influences. Geochim. Cosmochim. Acta 58, 3191-3198. 

Elemental mercury and inorganic mercury compounds human health aspects (No. 50, 2003) Ethylenediamine (No. 15, 1999)... 

Thus, both elemental mercury and the mineral form cinnabar (HgS) can release Hg++, the mercuric ion. Bacteria can then methylate it to form sequentially CH3 Hg+, the methyl mercuric cation, and dimethyl mercury. The latter, like elemental mercury, is volatile and tends to pass into the atmosphere when formed. The methylation of mercury can be accomplished in the environment by bacteria, notably in sediments. 

Wildlife toxicologists should be attuned to developments in human health mercury, as assays that have been used successfully on humans may be suitable or adaptable for other vertebrate species. Echeverria and co-workers (Echeverria et al. 2005, 2006 Heyer et al. 2006) have characterized a gene encoding coproporphyrinogen oxidase, a gene in the heme biosynthetic pathway. Polymorphism in this gene predicts differential response to elemental mercury exposure in human subjects. Plans to modify this assay for other mercury species in matrices from wildlife are under way. 

Weiss-Penzias P, Jaffe DA, McClintick A, Prestbo EM, Landis MS. 2003. Gaseous elemental mercury in the marine boundary layer evidence for rapid removal in anthropogenic pollution. Environ Sci Technol 37 3755-3763. 

At first, Carothers worked alone, experimenting with 75 pounds of elemental mercury. Breathing the vapor from elemental mercury was known to cause neurological problems, including agitation and depression. In many... 

Some metals can be converted to a less toxic form through enzyme detoxification. The most well-described example of this mechanism is the mercury resistance system, which occurs in S. aureus,43 Bacillus sp.,44 E. coli,45 Streptomyces lividans,46 and Thiobacillus ferrooxidans 47 The mer operon in these bacteria includes two different metal resistance mechanisms.48 MerA employs an enzyme detoxification approach as it encodes a mercury reductase, which converts the divalent mercury cation into elemental mercury 49 Elemental mercury is more stable and less toxic than the divalent cation. Other genes in the operon encode membrane proteins that are involved in the active transport of elemental mercury out of the cell.50 52... 

Turyan and Mandler [483] determined ppt levels of mercury in seawater by first converting mercury salts to elemental mercury using stannous chloride, the mercury was then trapped on gold deposited on platinum gauze and released by heating prior to determination by inductively coupled plasma mass spectrometry. 

Mercury Hg reduced to elemental mercury, extract which is swept AAS 0.2 pM (absolute)... 

Due to its chemical inertness, vaporizable nature (enthalpy of vaporization = 59.15 kJ/mol), and low water solubility (at 20°C, 2 x 10 6 g/g), elemental mercury vapor has over one year of residence time, long-range transport, and global distribution in the atmosphere [3-8]. 

Mason RP, Fitzgerald WF, Morel FMM (1994) The Biogeochemical Cycling of Elemental Mercury - Anthropogenic Influences. Geochim Cosmochim Acta 58 3191-3198... 

Terrestrial plants function as conduits for the transport of elemental mercury from the geosphere to the atmosphere (Leonard et al. 1998a). Estimated mercury emissions from plants in the Carson River Drainage Basin of Nevada over the growing season (0.5 mg Hg/m2) add to the soil mercury... 

Property Elemental Mercury Mercurous Chloride Mercuric Chloride Methylmercury Chloride... 

The precipitated mercurous chloride separates as a sludge. In the original process, some of this mercurous chloride was chlorinated to mercuric chloride for re-use. In a later version of the process, all the mercuric chloride is electrolytically converted to elemental mercury and chlorine. As of 1994 the electrolytic version had been installed in three plants. Developed by Boliden, Sweden, and Norzink, Norway, and now offered for license by Boliden Contech. 

With respect to Cr a distinction should be made between Cr(III), which is the common oxidation state in the soils, being rather immobile and so toxic, and Cr(VI), which is very mobile and very toxic. With respect to Hg, the situation is even more complex, due to the occurrence of mercuric mercury (Hg2+), mercurous mercury (Hg2+), elemental mercury (Hg°) and organic mercury species, such as methyl mercury, (CH3)2Hg (see Section 18.5). Furthermore, volatilization of elemental mercury and organic mercury species is common. A description of these... 

The main advantage of Weston s cell was its insensitivity to temperature, and the emf of almost 1 V to be precise, 1.0183 V at 20 °C. It is usually constructed in an Id-shaped glass vessel. One arm contains a cadmium amalgam electrode beneath a paste of hydrated cadmium sulphate (3CdS04 5H20) cadmium sulphate and mercury sulphate. The other arm contains elemental mercury. Its schematic is Cd(Hg) CdS04(aq), Hg2S04 Hg. 

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