Mercurous Mercury

Mercuration. Mercury(II) salts react with alkyl-, alkenyl-, and arylboranes to yield organomercurials, which are usehil synthetic intermediates (263). For example, dialkyhnercury and alkyhnercury acetates can be prepared from primary trialkylboranes by treatment with mercury(II) chloride in the presence of sodium hydroxide or with mercury(II) acetate in tetrahydrofuran (3,264). Mercuration of 3 -alkylboranes is sluggish and requires prolonged heating. Alkenyl groups are transferred from boron to mercury with retention of configuration (243,265). 

Merkuri-. mercuric, mercuri-, mercury(II). Merkuriah en, pi. Pharm.) mercurials. Merkuriahnittel, n. Pharm.) mercurial. Merkuri-ammoniumchlorid, n. mercuriammo-nium chloride, -azetat, n. mercuric acetate, mercury(II) acetate, -chlorid, n. mercuric chloride, mercury(II) chloride, -cyamd, n. mercuric cyanide, mercury(II) cyanide, -cyanwasserstoffs ure, /. mercuricyanic acid, cyanomercuric(II) acid. 

Merkuro-. mercurous, mercury (I), -azetat, n. mercurous acetate. mercury(I) acetate, -chlorld, n. mercurous chloride, mercury(I) choride. -chrom, n. (Pharm.) mercuro chrome, -jodid, n. n ercurous iodide, mer-cury(I) iodide. -nitrat, n. mercurous nitrate, mercury(I) nitrste. -oxyd, n. mercurous oxide, mercury(I) oxide, -salz, n. mercurous salt, mercury (I) salt, -sulfat, n. mercurouasulfate, mercury(I) sulfate, -sulfid, n. mercurous sulfide, mercury(I) sulfide, -verbindung, /. mercurous compound, mercury (I) compound. 

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 major part of absorbed mercuric mercury is excreted in urine and faeces in about equal parts in rat [49] and man [2, 50]. Since absorption rates from the lung or gastrointestinal tract do not vary greatly from one animal species... 

Selenium lessens the toxicity of divalent mercury in animals, the protection being less at continuous mercury exposure. Selenium has been found to affect the distribution of mercuric mercury in mice [134], rats [135], rabbits [136, 137] and pigs [ 138]. Mercury forms a mercury-selenium protein complex with selenium with little biological activity [139]. Mercury is thus retained longer in the blood, liver and spleen and as a consequence lessens accumulation in the kidney. In fish, selenium pretreatment probably retarded mercury uptake rather than promoting mercury excretion [140]. 

Information concerning the effects of selenium in man is lacking and it is doubtful whether administration of selenium in man has any effect on the toxicity of mercuric mercury. However, mercury and selenium were found in the cellular lysozomes in renal tubular cells in two patients with inorganic mercury poisoning [143]. 

Similarly, pyridine can be 3-sulfonated with hot sulfuric acid, or oleum, if mercuric [mercury(II)] sulfate is present as a catalyst (Scheme 2.5). The process is not straightforward and may involve a C-mecuriated pyridine intermediate [it is known, for example, that pyridine reacts with mercuric acetate at room temperature to form a pyridinium salt that decomposes at 180 °C into 3-(acetoxymercuri)pyridine (X = OAc)]. Without the catalyst, long reaction times and a temperature of 350 C are necessary even then, the yield of pyridine-3-sulfonic acid is poor. 

When an alkali perarsenate is added to aqueous solutions of metallic salts, precipitates containing active oxygen are obtained thus salts of the alkaline earths, zinc, cadmium, silver, mercurous mercury, lead and bismuth yield white precipitates, mercuric salts give red precipitates, copper blue, manganese pink, nickel greenish-white and ferrous salts bluish-green. With auric chloride oxygen is liberated, and with ferric chloride feme hydroxide is precipitated. 

P. C. Ray and 8. C. Mukherjee found the degree of ionization to be 0-11 for a mol of the salt in 32 litres. P. C. Ray and N. Dhar found that if the aq. soln. be kept in a closed vessel for some time, some of the mercuric nitrite forms mercurous nitrate and a basic salt is formed thus in 3 weeks, a soln. of sp. gr. 1-065 contained mercuric mercurous mercury as 13-7 1. P. C. Ray and N. Dhar found that the conductivity measurements of aq. soln. of mercurous nitrite agree with the assumption that a complex Hg2(N02) 5-ion is present this corresponds with mercurosic nitrite, HgN02.2Hg(N02)2. For a dilution v=187, A—62-33, and when c=561, A=80-10. With dil. soln., hydrolysis occurs. If the aq. soln. be sealed up in an... 

D. Holt, and M. Webb, The toxicity and teratogenecity of mercuric mercury in the pregnant rat. Arch. Toxicol. 58 243-248, 1986. 

The halides of all the metals except silver, lead, mercurous mercury, and cuprous copper are soluble in water, but with the ions of these metals, the halide ions give characteristic precipitates. The precipitates are valuable as tests for identifying either the halogens or the metals in qualitative analysis. 

Most every chloride s soluble. That s what we ve always read. Save silver, mercurous mercury. And (slightly) chloride of lead. 

Chemical Reactions.—The iodine can be replaced by chlorine, using either the gas itself or chlorides, such as those of mercuric mercury, arsenic, antimony and tin. A sulphoiodide is formed when the triiodide is heated with the trisulphide —... 

All chlorides, bromides, and iodides are soluble except those of silver, mercurous mercury (mercury with oxidation number 4-1), and lead. PbClg and PbBtjj are sparingly soluble iii cold water (1 g per 100 ml at 20°) and more soluble in hot water (3 g, 5 g, respectively, per 100 ml at 100°). 

The precipitation of mercurous chloride and its change in color from wnite to black on addition of ammonium hydroxide are used as the test for mercurous mercury in qualitative analysis. The effect of ammonium hydroxide is due to the formation of finely divided mercury (black) and mercuric aminochloride (white) by an auto-oxidation-reduction reaction ... 

Mercuric mercury compounds are inorganic salts with mercuric ions (Hg " ), e.g. mercuric chloride and mercuric iodide. Mercurous mercury compounds are salts with Hg " ions having an apparent valence of +1, e.g. calomel (mercurous chloride, Hg2Cl2). 

After inhalation, 70-80% of metallic vapor is retained and absorbed. Little is taken up in the gastrointestinal tract, and less than 10% is absorbed. In the body, it is oxidized to mercuric mercury, which binds to reduced sulfhydryl groups. The kidney is the main depository following exposure to both metallic and mercuric mercury. In addition to other organs, it passes into the brain and fetus. 

Mercury is a metal element that occurs naturally in the environment. Metallic or elemental mercury (Hg°) is the main form of mercury released into the air by natural processes. Mercury bound to other chemicals may have valence states of either +1 (Hg+1) or +2 (Hg+2). Mercury with a valence state of+1 is referred to as mercurous mercury, and mercury with a valence state of +2 is referred to as mercuric mercury. Many inorganic and organic compounds of mercury can be formed from the mercuric (divalent) cation (Hg+2). For information on the physical and chemical properties of mercury, refer to Chapter 3. 

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. 

Following exposure to metallic mercury, the elimination of mercury can occur via the urine, feces, and expired air. Following exposure to inorganic mercury (mercuric), mercury is eliminated in the urine and feces. Organic mercury compounds are excreted predominantly via the feces in humans. In animals, methylmercury is excreted in the feces, and phenylmercury compounds are initially excreted in the feces and then in the urine. Organic mercury compounds are excreted predominantly in the inorganic form. Both inorganic mercury and methylmercury are excreted in breast milk. 

The rate of oral absorption of mercuric mercury compounds in rats is dependent on several factors (e.g., intestinal pH, compound dissociation) (Endo et al. 1990). Age and diet also can influence the extent of absorption in mice (Kostial et al. 1978). One-week-old suckling mice absorbed 38% of the orally administered mercuric chloride, whereas adult mice absorbed only 1% of the dose in standard diets. 

Mercury can accumulate in human hair following oral exposure to mercuric chloride (Suzuki et al. 1992). Hair mercury levels, determined using segmental hair analysis, can be used to monitor exposure to mercury and may leave a historical record of exposure or uptake. In hair cut 41 days after mercuric mercury ingestion (13.8 mg/kg), a sharp peak (40 nmol/g [8 g/g]) was found in the 1 cm segment... 

Methylmercury transport between all compartments except brain and hair is modeled as plasma flow limited (i.e., plasma levels rapidly equilibrate with erythrocytes). Mercuric mercury transport parameters... 

Table 2-6. Intercompartmental Mass Transport Parameters Used to Model Methylmercury and Mercuric Mercury Pharmacokinetics in Rats...

The assumptions in the model were incorporated into a series of mass-balance differential equations that account for the changes in the amount of methylmercury and mercuric mercury in each compartment. 

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