Metals mercury

Primary. Mercury metal is produced from its ores by standard methods throughout the world. The ore is heated in retorts or furnaces to... 

Other recovery methods have been used (10). These include leaching ores and concentrates using sodium sulfide [1313-82-2] and sodium hydroxide [1310-73-2] and subsequentiy precipitating with aluminum [7429-90-3], or by electrolysis (11). In another process, the mercury in the ore is dissolved by a sodium hypochlorite [7681-52-9] solution, the mercury-laden solution is then passed through activated carbon [7440-44-0] to absorb the mercury, and the activated carbon heated to produce mercury metal. Mercury can be extracted from cinnabar by electrooxidation (12,13). 

Secondary. Scrap material, industrial and municipal wastes, and sludges containing mercury are treated in much the same manner as ores to recover mercury. Scrap products are first broken down to Hberate metallic mercury or its compounds. Heating in retorts vaporizes the mercury, which upon cooling condenses to high purity mercury metal. Industrial and municipal sludges and wastes may be treated chemically before roasting. 

Electrolytic Preparation of Chlorine and Caustic Soda. The preparation of chlorine [7782-50-5] and caustic soda [1310-73-2] is an important use for mercury metal. Since 1989, chlor—alkali production has been responsible for the largest use for mercury in the United States. In this process, mercury is used as a flowing cathode in an electrolytic cell into which a sodium chloride [7647-14-5] solution (brine) is introduced. This brine is then subjected to an electric current, and the aqueous solution of sodium chloride flows between the anode and the mercury, releasing chlorine gas at the anode. The sodium ions form an amalgam with the mercury cathode. Water is added to the amalgam to remove the sodium [7440-23-5] forming hydrogen [1333-74-0] and sodium hydroxide and relatively pure mercury metal, which is recycled into the cell (see Alkali and chlorine products). 

Pharmaceuticals. A variety of mercury compounds have had pharmaceutical appHcations over the years, eg, mercury-containing diuretics and antiseptics. Whereas some mercury compounds remain available for use as antiseptics such as merbromin [129-16-8] mercuric oxide, and ammoniated mercury [10124-48-8] or as preservatives such as thimerosal [54-64-8] in dmgs and cosmetics, most have been supplanted by more effective substances. A detailed discussion of mercury-containing antiseptics is available (37). Many hospitals use mercury metal to serve as weight for keeping nasogastric tubes in place within the stomach. 

Many mercury compounds are labile and easily decomposed by light, heat, and reducing agents. In the presence of organic compounds of weak reducing activity, such as amines (qv), aldehydes (qv), and ketones (qv), compounds of lower oxidation state and mercury metal are often formed. Only a few mercury compounds, eg, mercuric bromide/77< 5 7-/7, mercurous chloride, mercuric s A ide[1344-48-5] and mercurous iodide [15385-57-6] are volatile and capable of purification by sublimation. This innate lack of stabiUty in mercury compounds makes the recovery of mercury from various wastes that accumulate with the production of compounds of economic and commercial importance relatively easy (see Recycling). 

Another method of preparing mercuric acetate is the oxidation of mercury metal using peracetic acid dissolved in acetic acid. Careful control of the temperature is extremely important because the reaction is quite exothermic. A preferred procedure is the addition of approximately half to two-thirds of the required total of peracetic acid solution to a dispersion of mercury metal in acetic acid to obtain the mercurous salt, followed by addition of the remainder of the peracetic acid to form the mercuric salt. The exothermic reaction is carried to completion by heating slowly and cautiously to reflux. This also serves to decompose excess peracid. It is possible and perhaps more economical to use 50% hydrogen peroxide instead of peracetic acid, but the reaction does not go quite as smoothly. 

Mercurous Chloride. Mercurous chloride7/f /12-91 -17, Hg2Cl2, also known as calomel, is a white powder, insoluble in water. It sublimes when heated in an open container, but this probably occurs at least in part as a result of dissociation to mercury metal and mercuric chloride ... 

After the water and nitrogen oxide are driven off, continued heating drives off vapors of nitric acid, additional water, NO2, and some mercury—metal vapor ... 

When an aqueous effluent stream containing organomercurials cannot be recycled, it may be treated with chlorine to convert the organomercury to inorganic mercury. The inorganic compounds thus formed are reduced to metallic mercury with sodium borohydride. The mercury metal is drained from the reactor, and the aqueous solution discarded. The process utilising sodium borohydride is known as the Ventron process (27). 

FIGURE 11.22 When ammonia is added to a silver chloride precipitate, the precipitate dissolves. However, when ammonia is added to a precipitate of mercury(l) chloride, mercury metal and mercury(ll) ions are formed in a redox reaction and the mass turns gray. Left to right silver chloride in water, silver chloride in aqueous ammonia, mercury(l) chloride in water, and mercury(l) chloride in aqueous ammonia. 

Self-Test 16.2B Calculate E° for a cell powered by the reaction of mercury metal and nitric acid to form mercury(I) and NO. 

Use Appendix 2B to determine whether an acidic-potassium permanganate solution can oxidize (a) chloride ions to chlorine and (b) mercury metal to mercurv(I) ions under standard conditions. 

There are several environmentally significant mercury species. In the lithosphere, mercury is present primarily in the +II oxidation state as the very insoluble mineral cirmabar (HgS), as a minor constituent in other sulfide ores, bound to the surfaces of other minerals such as oxides, or bound to organic matter. In soil, biological reduction apparently is primarily responsible for the formation of mercury metal, which can then be volatilized. Metallic mercury is also thought to be the primary form emitted in high-temperature industrial processes. The insolubility of cinnabar probably limits the direct mobilization of mercury where this mineral occurs, but oxidation of the sulfide in oxygenated water can allow mercury to become available and participate in other reactions, including bacterial transformations. 

C02-0032. Liquid mercury metal can be obtained from a mercury ore called cinnabar simply by heating the ore in air. There is a significant mass loss when this process occurs. How can this mass loss be reconciled with conservation of mass ... 

Mercury metal and most of its compounds are extremely poisonous. The vapor of the metal is particularly dangerous. 

Spencer, J.N. and A.F. Voigt. 1961. Thermodynamics of the solution of mercury metal. I. Tracer determination of the solubility in various liquids. Jour. Phys. Chem. 72 464-470. 

The outer tube has a porous fiber tip, which acts as the salt bridge to the analyte solution and the other half-cell. A saturated solution of potassium chloride is in the outer tube. The saturation is evidenced by the fact that there is some undissolved KC1 present. Within the inner tube is mercury metal and a paste-like material known as calomel. Calomel is made by thoroughly mixing mercury metal (Hg) with mercurous chloride (Hg2Cl2), a white solid. When in use, the following half-cell reaction occurs ... 

A common type of button battery, shown here, contains silver oxide or mercury(ll) oxide. Mercury is cheaper than silver, but discarded mercury batteries release toxic mercury metal into the environment. 

Joseph Priestley (1733-1804) heated mercury with air and formed a red powder (mercuric oxide) that, when heated in a test tube, produced small globs of mercury metal on the inside of the glass tube, as well as a gas that caused other substances to burn more rapidly than they did in air. Priestley did not know it at the time, but he had separated oxygen from the compound HgO. 

Mercury metal is a very toxic and accumulative poison (it is not easily eliminated by the body). When inhaled as vapors, ingested as the metal or as part of a compound, or even absorbed when in contact with the skin, it can build up to deadly amounts. The fumes of most compounds are poisonous and must be avoided. Anyone who ingests mercury should contact a poison center immediately. 

If mercury metal is spilled, it needs to be carefully gathered so as not to spread the little globs, but rather combine them for easy collection. 

Mercury Metal - persistent - bioaccumulates - contaminates many species of fish. Widely used in industrial processes. Causes developmental neurotoxicity -children most susceptible... 

The phosphorus atom in hypophosphorus acid is in the lowest oxidation state, + 1. The compound is, therefore, a powerful reducing agent. It combines readily and often explosively with oxidizing agents. For example, the acid reduces mercury(II) nitrate or mercury(II) oxide into mercury metal violently. 

Mercury metal forms both mercury(I) and mercury(II) salts. Oxidizing acids in excess amounts and under hot conditions yields mercury(ll) salts. Thus, heating mercury with concentrated nitric or sulfuric acid yields mer-cury(ll) nitrate or mercury(ll) sulfate ... 

Alternatively, the compound may be made by reacting mercury metal with peracetic acid or hydrogen peroxide (50%) dissolved in acetic acid under careful temperature control. 

When heated at elevated temperatures, it partially dissociates to mercury metal and mercury(ll) chloride ... 

Mercury(II) chloride, like mercury(I) chloride, is most conveniently made by dry methods that involve either heating a mixture of mercury(ll) sulfate and sodium chloride or heating mercury metal with excess chlorine ... 

Elemental composition Hg 79.40%, C 9.51%, N 11.09%. Aqueous solution is analyzed for mercury metal by AA-cold vapor techniques or by ICP/AES (see Mercury). The cyanide ion may be measured by cyanide ion-specific electrode or by ion chromatography after appropriate dilution. 

Mercury fulminate is prepared by the reaction of mercury metal with strong nitric acid and ethanol. The preparative method involves pouring a nitric acid solution of mercury(II) nitrate into ethanol. The reaction is not well understood. 

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