Mercury thermally-released

Mercury, by virtue of its coexistence with many types of base metal and precious metal deposits and its high vapour pressure, often forms secondary halos above ore deposits, including in soils. When soil is heated, Hg is released at different temperatures according to the form in which it occurs in the soil (Fig. 13-1). The choice of a particular temperature for thermal release of Hg in a certain form can produce geochemical data that are useful for locating deep blind ore deposits. Comparison of data obtained by thermal release at different temperatures allows the discrimination of significant anomalies related to such mineralisation from false anomalies related to various forms of pollution. 

Ethylated mercury species are volatile and can therefore be purged from solution at room temperature and then collected on adsorbent materials such as Carbotrap or Tenax. After thermal release, individual mercury compounds are separated by cryogenic or isothermal GC. As the species are eluted they are thermally decomposed (pyrolized) at 900°C and measured as Hg° using a CV-AFS detector, which achieves very low detection limits (< 10 g). A CV-... 

Windmoller CC, Wilken RD, Jardim WDF. Mercury speciation in contaminated soils by thermal release analysis. Water Air Soil Pollut 1996, 89, 399-416. 

Raposo C, Windmoller CC, Junior WAD. Mercury speciation in fluorescent lamps by thermal release analysis. Waste Manag 2003,23, 879-86. 

Regulations. In order to decrease the amount of anthropogenic release of mercury in the United States, the EPA has limited both use and disposal of mercury. In 1992, the EPA banned land disposal of high mercury content wastes generated from the electrolytic production of chlorine—caustic soda (14), accompanied by a one-year variance owing to a lack of available waste treatment faciUties in the United States. A thermal treatment process meeting EPA standards for these wastes was developed by 1993. The use of mercury and mercury compounds as biocides in agricultural products and paints has also been banned by the EPA. 

Magnesium reacts with incandescence on heating with cadmium cyanide, cobalt cyanide, copper cyanide, lead cyanide, nickel cyanide and zinc cyanide. With gold cyanide or mercury cyanide, the cyanogen released by thermal decomposition of these salts reacts explosively with magnesium. 

Nicolson [139] has described a rapid thermal decomposition technique for the atomic absorption determination of mercury in soils. In this method, air is used to sweep mercury vapour from the heated (650-750 °C) sample onto gold foil. In the second stage, heating of the gold foil releases mercury vapour into a cold vapour atomic absorption spectrometer. 

The sensitive techniques require the release of CO from hemoglobin into a gas phase CO can then be detected directly by a number of methods such as infrared absorption, difference in thermal conductivity between CO and the carrier gas, amount of ionization following conversion of CO to methane, or the release of mercury vapor resulting from interaction of CO with mercuric oxide. 

MERCURY CYANIDE or MERCURY(II) CYANIDE (592-04-1) Hg(CN)2 Slowly decomposes in light. A moderate impact- and heat-sensitive explosive. Violent reaction with metal chlorates, fluorine, hydrogen cyanide, magnesium, nitrates, nitrites, metal perchlorates, sodium nitrite. Contact with strong acids evolves flammable and poisonous hydrogen cyanide gas, which can be detonated by this material. Thermal decomposition releases toxic nitrogen oxides, mercury, and hydrogen cyanide. On... 

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