Mercuric mercury HgS

Once absorbed, metallic and inorganic mercury enter an oxidation-reduction cycle. Metallic mercury is oxidized to the divalent inorganic cation in the red blood cells and lungs of humans and animals. Evidence from animal studies suggests that the liver is an additional site of oxidation. Absorbed divalent cation from exposure to mercuric compounds can, in turn, be reduced to the metallic or monovalent form and released as exhaled metallic mercury vapor. In the presence of protein sulfhydryl groups, mercurous mercury (Hg+) disproportionates to one divalent cation (Hg+2) and one molecule at the zero oxidation state (Hg°). The conversion of methylmercury or phenylmercury into divalent inorganic mercury can probably occur soon after absorption, also feeding into the oxidation-reduction pathway. 

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 (Hg- ), mercurous mercury (Hg2 +), elemental mercury (Hg ) and organic mercury species, such as methyl mercury, (CH3)2Hg (see Chapter 8, Section 2). Furthermore, volatilization of elemental mercury and organic mercury species is common. A description of these processes, in combination with other interactions of Hg in soil, such as reduction, absorption and complexation, is extremely difficult and the approach can only be considered as very approximate for mercury. This also holds to a lesser extent for chromium. 

FIGURE 1-1 Cycling of Hg in aquatic system. CH3Hg% methylmercuiy ion CH3HgCH3, dimethylmercury Hg(ll), mercuric mercury Hg°, elemental mercuiy H2S, hydrogen sulfide HgS, ciimabar. Source Adapted from EPA 1997b. 

Chronic exposure to low levels of inor-gaiuc mercuric compounds produces tremors, excess salivation, and psychological changes characterized by irritability and excitement. Collectively, this is often described as the mad hatter syndrome. Mercuric mercury (Hg +) is a potential toxic chemical, although it is poorly absorbed by the GI tract and other body parts. Accidental or suicidal ingestion of mercuric chloride or other mercuric salts produces corrosive ulceration, bleeding, necrosis of the intestinal tract, and are usually accompanied by shock and circulatory collapse. If the patient... 

With mercuric acetate (Hg(OOCCH2)2), olefins and / fZ-butyl hydroperoxide form organomercury-containing peroxides (66,100). The organomercury compound can be treated with bromine or a mild reducing agent, such as sodium borohydride, to remove the mercury. 

A third form of cadmium pigments includes the mercury cadmiums. Mercuric sulfide (HgS) forms soHd solutions up to about 20 mol % with the oranges, reds, and maroons. The heat stabiUty is improved up to 370°C, and the costs are somewhat lower than the CP grades. The mercury cadmiums are slightly more reactive, but have excellent bleed resistance. 

Mercury. In recovering mercuiy from cinnabar ores, the ore is crushed to minus 1.5 cm and fed to rotary Idlns, where it is calcined to over 800 K. Since the mercuiy exists as mercuric siilfide (HgS), the sulfur is oxidized to SO9 and the mercuiy vaporized. The gases are passed through cooling chambers, where the mercuiy condenses and is collected. Mercuiy vaporizes at 625 K. 

Mercury/mercurous sulphate (Hg/HgSOj, SOJ ) Silver/silver chloride (Ag/AgCl, Cl )... 

Antimony/antimony oxide (Sb/Sb O, H ) Mercury/mercuric oxide (Hg/HgO, OH")... 

Mercury (Mercuric) Sulfocyanate (Mercuric thiocyanate, Mercuric rhodamide). Hg(SCN)2, mw 316.77, white powd mp (decompn), poisonous si sol in w (0.07g/100g at 25°), sol in ale and in NH3 NH4 salts. Can be prepd by pptn of Hg nitrate with Amm sulfocyanate and subsequent soln in a large quant of hot w, followed by crystn. Used in prepn of Pharaoh s Serpent and other fireworks (Ref 4)... 

Mercurous chromate, molecular formula, properties, and uses, 6 562t Mercury (Hg), 16 31-58. See also Hg entries... 

Mercury oxide (HgO) exists in two forms, red and yellow mercuric oxides, and is related to mercurous oxide (Hg O), which is black. All have industrial uses, ranging from antiseptics to pigments. 

Mercuric sulfide (HgS) is a fine, very brilhant scarlet powder that is deadly if ingested. Also known as the mercury ore cinnabar and metacinnabar, it is used as a pigment in the manufacture of paints. 

Raiko (Army) or Raisansuigin (Navy) Thunder Mercury . Mercuric Fulminate, Hg(ONC)2 mw 284.65, N 9.84% white to gray pdr, d 4.43, mp—decomp or detonates without melting Brisance by Sand Test—ca 55% TNT Expin Temp 210° in 5 secs Impact Sensitivity, BurMinesApp, 2-kg wt—5cm Power by Trauzl Test—51% TNT Rate of Deton 5000 at d 4.0 (AMCP 706-177, listed as Ref 8, p 201). Used straight by the Japanese in Instantaneous Fuzes, in Blasting Caps and in mixture called Bakufun (Ref 1, p 25 Ref 5, p 369)... 

Preparation.—1. If metallic mercury be heated to its boiling-point with access of air, it gradually absorbs oxygen, being converted into mercuric oxide, Hg"0. This compound, when more strongly heated, is resolved into its elements,... 

A widely used method for removing mercury from polluted water is addition of sodium sulfide. Insoluble mercuric sulfide (HgS), which forms is removed as a sludge (Price et al. 1972) that is then landfilled. It has been assumed that HgS remains permanently insoluble, thus preventing movement of mercury into the surrounding environment. Mercury waste has been treated and buried in this manner for many years. 

The existence of the mercury-mercury bond in the mercurous ion, Hg ++ and in molecules such as mercurous chloride, Cl—Hg—Hg—Cl,... 

Another flavoprotein constructed on the glutathione reductase pattern is the bacterial plasmid-encoded mercuric reductase which reduces the highly toxic Hg2+ to volatile elemental mercury, Hg°. A reducible... 

Fulminic acid. HONC, and the fulminates are violently explosive. Utilizing this properly, mercuric fulminate. Hg(ONC) - HiO. is used as a detonator for other explosives. Mercury fulminate is made by the reaction of ethyl alcohol and mercuric nitrate in excess of nitric acid, from which insoluble mere-uric fulminate separates. Silvei fulminate. Agl ONC). is more explosive than mercuric fulminate, and is used in the manufacture of firecrackers Free fulminic acid may be obtained by reaction of potassium fulminate and excess of ether. It volatilizes with the ether upon distilling, and changes rapidly to meiufulminic acid. Related to fulminic acid is fulminuric acid, (HONCn. or NOy-CH(CN)-CONH-. 

---