Of mercury metal

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. 

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. 

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. 

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. 

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 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. 

Medium-pressure arc mercury lamps consist of a sealed cylindrical quartz tube with tungsten electrodes on each end. The tube contains a small amount of mercury metal and vapor and starter gas (usually argon). An example of such a lamp is shown in Figure 3.1.4... 

Electrolytic Recovery of Mercury Metal from a Mercuric Chloride-Containing Waste... 

Electrolytic methods have been applied to the treatment of other metal waste streams generated in the electroplating or metal finishing industries. Pollution engineering processes have been designed and implemented for the removal of hexavalent chromium, trivalent chromium, nickle, copper, zinc and cadmium.Besides the Edwards patent, there seems to be no documentation of electrolytic methods for removal and recovery of mercury metal from waste streams. 

A standard solution of B-5 fixative containing a concentration of mercuric chloride of 60 g/1 was plated for 8 hours and yielded 60% recovered mercury metal. Two liters of solution were plated, thus a total of 120 g of mercuric chloride were processed. The stoichiometric amount of mercury metal from the reduction of 120 g of mercuric chloride equals 88 g. The recovered mercury metal totaled 53 g, thus demonstrating a 60% recovery efficiency. During the eight hour process the aluminum cathodes were changed once. The solution pH was between 3.6-3.8. 10 g of calcium chloride were added in order to... 

The original waste solution was comprised of mercuric chloride, mercury bound tissue, and, possibly, mercury metal. The metal may be a result of the reduction of mercuric chloride by formaldehyde.6 The varying proportions of mercury in these different forms cause the amount of mercury metal recovered to vary. The assumption is made that the process will have a recovery efficiency comparable to the efficiency in the electrolysis of the standard solution (60%). 

The electrolysis of the mercuric chloride waste solution in this study resulted in the recovery of significant amounts of mercury metal. The recovery was sufficient to reduce the average volume of mercuric chloride waste disposed of off-site 8 fold. The estimated reduction in annual disposal costs is 1500. Furthermore, no liability costs for the transportation and disposal of the recovered mercury are... 

For reductions, hanging mercury drop electrodes or mercuryfilm electrodes are frequently used owing to their microscopic smoothness and because of the large overpotential for hydrogen evolution characteristic for this electrode material. Mercury film electrodes are conveniently prepared by the electrochemical deposition of mercury on a platinum electrode from an acidic solution of an Hg2+ salt, e.g. the nitrate. However, the oxidation of mercury metal to mercury salts or organomercurials at a low potential, 0.3-0.4 V versus the saturated calomel electrode (SCE), prevents the use of these electrodes for oxidations. 

In addition to the uses of mercury metal, mercury compounds have a number of applications. Mercury(II) oxide, HgO, is commonly used as a raw material for the manufacture of other mercury... 

Polymeric (SN)X has some unusual properties. For example, it has a bronze color and metallic luster, and its electrical conductivity is about that of mercury metal. Values of the conductivity of (SN) depend on the purity and crystallinity of the polymer and on the direction of measurement, being much greater along the fibers than across them. A conjugated single-bond/double-bond system can be formulated, in which every S-N unit has one antibonding tt electron. The half-filled overlapping tt orbitals combine to form a half-filled conduction band, in much the same way as the half-filled ns orbitals of alkali metal atoms... 

Ammonia solution black precipitate which is a mixture of mercury metal and basic mercury(II) amidonitrate, (which itself is a white precipitate)... 

Glossy copper sheet or copper coin If a drop of mercury(I) nitrate is placed on a glossy copper surface, a deposit of mercury metal is formed ... 

Spot test in the presence of aniline Treat a drop of the test solution on a filter paper or a spot plate with a drop of tin(II) chloride solution and a drop of aniline. A brown or black stain of mercury metal is produced. 

But even as recendy as the mid-20th cenmry, there was relatively litde concern about mercury metal and many mercury compounds. High school chemistry students often played with tiny droplets of mercury in the laboratory. They used mercury to coat pennies and other pieces of metal. Mercury was also widely used in dentistry. It was used to make amalgams, alloys of mercury with other metals, used to fill teeth. Most people even today are likely to have dental fillings that contain a small amount of mercury metal. The question of whether mercury is still safe to use in... 

Today, the primary use of mercury(II) sulfide is in the production of metallic mercury. The sulfide is heated in a furnace to temperatures of 6oo°C to 700°C (i,ioo°F to i,3oo°F), resulting in the formation of sulfur dioxide and mercury metal. In a second process, the sulfide is treated with lime (CaO), resulting in the formation of mercury metal, calcium sulfide (CaS) and calcium sulfate (CaS04). 

Hg3 can be synthesized in GaCl3-benzene solution either by a symproportionation of Hg2 " and mercury metal or by direct oxidation of mercury metal by GaCL. The latter route has interesting implications, since mercury metal is only very sparingly soluble in neat, molten GaCb. It therefore seems plausible that interactions with benzene stabilizes Hgj in such solutions and therefore renders mercury metal more susceptible to oxidation. Cluster-arene interactions are discussed in more detail in Sec. 1.29.4.6. 

The most common species determined by cathodic stripping voltammetry are anions such as halides or sulphide, at a mercury electrode. This involves formation of a film of mercury(I) salts on the electrode in the deposition step. The anodic oxidation process involved in the deposition step is in fact the oxidation of mercury metal to mercury(I) ions. These immediately precipitate insoluble mercury(I) salts with the halide ion etc, on to the surface of the electrode. The anodic deposition potential required depends on the anion concerned. The subsequent cathodic stripping peak for the mercury(I) salt of each anion has at its own individual potential. 

It is mercury ion in solution that is extremely hazardous. Since mercury metal does not react with hydrochloric acid (the acid in gastric juice), it does not dissolve and passes through the human body unchanged. Nitric acid (not part of human gastric juices) dissolves mercury metal (see Problem 19.113) if nitric acid were secreted by the stomach, ingestion of mercury metal would be fatal. 

A small amount of mercury metal aids initiation of transmetalation, but is not essential. The apparatus used in all three reactions is shown in Fig. 1 of synthesis number (Section) 72. This consists of a 100-mL Schlenk flask... 

The cell room and laboratory facilities should be inspected routinely for spills or accumulations of mercury metal. These should be picked up promptly and disposed of with the plant s mercury waste or taken in secure containers to the mercury-recovery facility. 

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