Mercury sulfide, solubility

Sulfur Polymer Cement. SPC has been proven effective in reducing leach rates of reactive heavy metals to the extent that some wastes can be managed solely as low level waste (LLW). When SPC is combined with mercury and lead oxides (both toxic metals), it interacts chemically to form mercury sulfide, HgS, and lead sulfide, PbS, both of which are insoluble in water. A dried sulfur residue from petroleum refining that contained 600-ppm vanadium (a carcinogen) was chemically modified using dicyclopentadiene and oligomer of cyclopentadiene and used to make SC (58). This material was examined by the California Department of Health Services (Cal EPA) and the leachable level of vanadium had been reduced to 8.3 ppm, well below the soluble threshold limit concentration of 24 ppm (59). 

Elemental sulfur is present in most soils and sediments (especially anaerobic), and is sufficiently soluble in most common organic solvents that the extract should be treated to remove it prior to analysis by ECD-GC or GC-MS. The most effective methods available are (1) reaction with mercury or a mercury amalgam [466] to form mercury sulfide (2) reaction with copper to form copper sulfide or (3) reaction with sodium sulfite in tetrabutyl ammonium hydroxide (Jensen s reagent) [490]. Removal of sulfur with mercury or copper requires the metal surface to be clean and reactive. For small amounts of sulfur, it is possible to include the metal in a clean-up column. However, if the metal surface becomes covered with sulfide, the reaction will cease and it needs to be cleaned with dilute nitric acid. For larger amounts of sulfur, it is more effective to shake the extract with Jensen s reagent [478]. 

With this, the complex iron pigment does indeed deserve to be called insoluble, as only one part of dissolved Iron Blue can statistically be found in 100,000,000,000,000,000,000,000,000,000 parts of water (1029). The actual solubility would therefore be less by a factor of 102° as determined by Tananaev el al., which would come pretty close to values calculated for other so-called insoluble compounds, like mercury sulfide (HgS). However, one must consider that the chemistry of Fe3+ in aqueous solutions doesn t justify the terms dissolved or precipitated , since a multitude of complexes do exist in the... 

The natural global bio-geochemical cycling of mercury is characterized by degassing of the element from soils and surface waters, followed by atmospheric transport, deposition of mercury back to land and surface waters, and sorption of the compound to soil or sediment particulates. Mercury deposited on land and open water is in part revolatilized back into the atmosphere. This emission, deposition, and revolatilization creates difficulties in tracing the movement of mercury to its sources (WHO 1990). Particulate-bound mercury can be converted to insoluble mercury sulfide and precipitated or bioconverted into more volatile or soluble forms that re-enter the atmosphere or are bioaccumulated in aquatic and terrestrial food chains (EPA 1984b). 

Precondition for a voltammetric determination of trace elements in urine is a sample pretreatment. The problem of losses of mercury with classic mineralization methods is described above. To avoid this problem, the authors have developed an acid digestion method with the addition of thioacetamide. All mercury in the sample is converted by this to the extremely poorly soluble mercury sulfide (HgS), which is stable under the conditions chosen. Subsequently hydrogen peroxide is added to oxidize the HgS and liberate the Hg ion [113]. 

Soluble sulfides such as sodium sulfide, potassium sulfide, and calcium polysulfides have been used to precipitate mercury salts from alkaline solutions. When this procedure is used, exercise of caution is requked to maintain the pH within a given alkaline range so as to prevent evolution of H2S. Because the solubiUty of mercuric sulfide in water is 12.5 flg/L at 18°C or 10.7 ppb of mercury, use of this method for removal of mercury is adequate for most purposes. However, the presence of excess alkah, such as sodium hydroxide or sodium sulfide, increases the solubiUty of mercuric sulfide as shown ... 

Precipitation is the most promising method for immobilizing dissolvable metals such as lead, cadmium, zinc, and iron.15 Some forms of arsenic, chromium, mercury, and some fatty acids can also be treated by precipitation.47 The common precipitating chemicals for metal cations are sulfide, phosphate, hydroxide, or carbonate. Among them, sulfide is the most promising, because sulfides have low solubility over a broad pH range. Precipitation is most applicable to sites with sand or coarse silt strata. 

When hydrogen sulfide reacts, with mercuric chloride in neutral or acid solution, or when mercury and sulfur are ground together, black mercuric sulfide is formed. Under certain conditions, this material can be converted into the red modification by the continued action of soluble alkali sulfides. The reaction of mercuric chloride and sodium thiosulfate gives the red form if the ratio of the concentrations is higher than 1 4d The red sulfide is also produced when the substance Hg(SH)NCS is boiled with concentrated ammonium thiocyanate solution or when hydrogen sulfide is conducted into a warm mercuric salt solution in the presence of acetic acid and an excess of ammonium thiocyanate, or thiourea.2,3... 

Magnesium chloride, anhydrous, 29 Manganous chloride, anhydrous, 29 Mercuric sulfide, red, 19 Mercury, solubility of metals in, 6 Metals, solubility in mercury, 6 Monochloroamine, 59 analysis of, 62... 

Some metal thiosulfates are inherendy unstable because of the reducing properties of the thiosulfate ion. Ions such as Fe3+ and Cu2+ tend to be reduced to lower oxidation states, whereas mercury or silver, which form sulfides of low solubility, tend to decompose to the sulfides. The stability of other metal thiosulfates improves in the presence of excess thiosulfate by virtue of complex thiosulfate formation. 

Mercury, in its elemental form or in a chemical compound is highly toxic. Water-soluble mercury compounds, such as mercu-ry(II) nitrate, can be removed from industrial wastewater by adding sodium sulfide to the water, which forms a precipitate of mercury(II) sulfide, which can then be filtered out. 

Metal-Sulfides. Sulfide precipitation has been one of the most widely used methods to precipitate many of the heavy metals. The low MCLs required for some of the highly toxic metals (e.g., mercury), are often achievable only by precipitation as sulfides, since they generally have solubilities several orders of magnitude lower than the hydroxides, carbonates, or phosphates throughout the pH range of 6-9. However, metal sulfides can resolubilize in an oxidizing environment. 

Estimates of the abundance of zinc in the sun, in meteorites, in the Earth s core and crust, and in the oceans are very difficult to make, but its abundance in the Earth s crustal rocks and soils is of the order of 100 ppm, about 1000 times as abundant as its congeners cadmium and mercury. All three elements are Chalcophiles so that, in the reducing atmosphere that prevailed when the earth s crust solidified, they were deposited in the sulfide phase giving rise to the sulfide ores, their most important source. Eater, as weathering took place, zinc became soluble only to be precipitated as the carbonate, silicate, or phosphate. 

The in situ precipitation technique and transmission electron microscopy have been used to investigate the effect of DMSO on percutaneous absorption in the mouse barrier [27] and human SC [46]. Sharata and Burnette examined ultrastructural changes in mouse stratum comeum by determining the distribution of sulfide precipitates of topically applied, water-soluble tracers (Hg and Ni ) after application of enhancer [27]. For skin pretreated with DMSO, mercury and nickel precipitates were found within swollen basal stratum comeum cells as well as intercellularly and associated with the cell envelopes, but not below the stratum comeum-stratum granulosum interface. It was concluded that treatment with DMSO, as well as with other dipolar aprotic solvents such as DMF and DMA, alters the passive intercellular diffusion pathway by expanding the size of the basal stratum comeum cells, resulting in an increased free volume for tracer diffusion. 

The mercuric compounds, in which mercury is bipositive, differ somewhat in their properties from the corresponding compounds of zinc and cadmium. The differences are due in part to the very strong tendency of the mercuric ion, Hg + +, to form covalent bonds. Thus the covalent nvstal mercuric sulfide, HgS, is far less soluble than cadmium sulfide or zinc sulfide (Chap. 22). 

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