Mercury state

The apparent threshold for emission of the potassium D-lines in K + Hg collisions is 4 0 (+0-4) eV the absolute size of the emission cross section at 10 eV has been estimated69 to 3 A2. Again no emission from excited potassium states other than 42P has been observed up to 100 eV collision energy upper limits for emission at 4050 and 6930 A are 1 % of that at 7680 A. No emission from excited mercury states at 5440 and 5780 A was observed either. 

Therefore, the pressure due to a standard atmosphere is equal to the pressure created at a base of a 760-mm-tall column of mercury. Stated another wy, 1 atm = 760 mm ... 

These results i.e. the great influence on the dissociation of the pseudo rotation angular momentum 1 about the Hg -N-N axis has also been demonstrated in theoretical calculations by Jouvet and Beswick (i ). The states of the excited Hg N2 complex are represented for the perturbed mercury by I J (= L + S), Q > as II, O" " > and II, 1 > and as 10,0 > for the Pq state. There the coupling between the 0" state ( Pi) and 0 ( Pq) is essentially 0 even through higher mercury states owing to the +, - parity difference. On the other hand, this interdiction is lifted when 1=1 vibrations become excited as we have observed. Nesbitt et al( ) observed the influence of the +, - parity upon the coupling of TT "/" and I" " vibrations in the NeHF predissociation, with similar conclusions. 

Exists as the (Hg —Hg) ion. Other polymercury cations, e.g. Hgj (Hg plus AsFj), Hg4 etc., are also known. All positive oxidation state compounds of Hg are readily reduced to the metal, mercury chlorides... 

As stated above for the TBP distillation, petroleum cannot be heated above 340°C without its molecules starting to crack. Because of this, analytical distillation of heavy fractions is done according to the ASTM D 1160 method for petroleum materials that can be partially or completely vaporized at a maximum temperature of 400°C at pressures from 50 to 1 mm of mercury (6.55 to 0.133 kPa). 

It has long been known that the form of a curved surface of mercury in contact with an electrolyte solution depends on its state of electrification [108, 109], and the earliest comprehensive investigation of the electrocapillary effect was made by Lippmann in 1875 [110]. A sketch of his apparatus is shown in Fig. V-10. 

The more noble metals (for example copper, mercury and silver) can form oxides, and exhibit variable oxidation state in such compounds (for example CU2O, CuO), but it is not easy to prepare such oxides by direct action of oxygen on the metal, and elevated temperatures are necessary. Moreover, in the case of silver and mercury, loss of oxygen from the oxide by heating is easy. The oxidesare, however, basic (for example Ag20 - Ag, CuO - Cu in acids). 

Halogens can act as ligands and are commonly found in complex ions the ability of fluorine to form stable complex ions with elements in high oxidation states has already been discussed (p. 316). However, the chlorides of silver, lead(Il) and mercury(l) are worthy of note. These chlorides are insoluble in water and used as a test for the metal, but all dissolve in concentrated hydrochloric acid when the complex chlorides are produced, i.e. [AgCl2] , [PbC ] and [Hg Clj]", in the latter case the mercury(I) chloride having also disproportionated. 

These elements formed Group IIB of Mendeleef s original periodic table. As we have seen in Chapter 13, zinc does not show very marked transition-metaf characteristics. The other two elements in this group, cadmium and mercury, lie at the ends of the second and third transition series (Y-Cd, La-Hg) and, although they resemble zinc in some respects in showing a predominantly - - 2 oxidation state, they also show rather more transition-metal characteristics. Additionally, mercury has characteristics, some of which relate it quite closely to its immediate predecessors in the third transition series, platinum and gold, and some of which are decidedly peculiar to mercury. 

One other cause of hysteresis remains to be mentioned. As was pointed out earlier (p. 177) the contact angle may be different as the mercury is advancing over or receding from a solid surface, and it depends also on the chemical and physical state of the surface the mercury may even react with the surface layer of the solid to form an amalgam. A change in 9 of only a few degrees has a significant effect on the calculated value of pore radius (cf. Table 3.15). 

Figure 8.18 shows an X-ray photoelectron spectrum of gold foil with mercury absorbed onto the surface. Both the gold and mercury doublets result from the removal of a 4/ electron leaving /2 and /2 core states for which L = 3, S = and J = or Less than 0.1 per cent of a monolayer of mercury on a gold surface can be detected in this way. 

Three forms of caustic soda are produced to meet customer needs purified diaphragm caustic (50% Rayon grade), 73% caustic, and anhydrous caustic. Regular 50% caustic from the diaphragm cell process is suitable for most appHcations and accounts for about 85% of the NaOH consumed in the United States. However, it caimot be used in operations such as the manufacture of rayon, the synthesis of alkyl aryl sulfonates, or the production of anhydrous caustic because of the presence of salt, sodium chlorate, and heavy metals. Membrane and mercury cell caustic, on the other hand, is of superior quaUty and... 

Mercury(II) fluoride has been used in the process for manufacture of fluoride glass (qv) for fiber optics (qv) appHcations (11) and in photochemical selective fluorination of organic substrates (12). It is available from Advance Research Chemicals, Aldrich Chemicals, Johnson/Matthey, Aesar, Cerac, Strem, and PCR in the United States. The 1993 annual consumption was less than 50 kg the price was 800—1000/kg. 

Disulfur decafluoride does not react rapidly with water, mercury, copper, or platinum at ambient temperatures. There is evidence that it slowly decomposes on various surfaces in the presence of water when stored in the vapor state (118). It is decomposed by molten KOH to give a mixture of potassium compounds of sulfur and fluorine. The gas reacts vigorously with many other metals and siUca at red heat (114). At ca 156°C it combines with CI2 or Br2 to form SF Cl or SF Br (119,120). At ca 200°C, S2F2Q is almost completely thermally decomposed into the hexa- and tetrafluoride (121). 

Coalition ofJSlortheast Governors. The CONEG model heavy-metal guideline is implemented through state regulations and limits total metal content of lead, chromium, mercury, and cadmium. The limitation of 100 parts per million total is aimed at protecting the environment from the disposal of post-consumer waste. 

Atomic Absorption Spectroscopy. Mercury, separated from a measured sample, may be passed as vapor iato a closed system between an ultraviolet lamp and a photocell detector or iato the light path of an atomic absorption spectrometer. Ground-state atoms ia the vapor attenuate the light decreasiag the current output of the photocell ia an amount proportional to the concentration of the mercury. The light absorption can be measured at 253.7 nm and compared to estabUshed caUbrated standards (21). A mercury concentration of 0.1 ppb can be measured by atomic absorption. 

Chlor—alkah production is the largest iadustrial source of mercury release ia the United States (see Alkali and chlorine products). For the 1991 reporting year, chlor—alkah faciUties accounted for almost 20% of the faciUties that reported releases of mercury to the U.S. Environmental Protection Agency (EPA) for inclusion onto the Toxics Release Inventory (TRI) (25). 

Regulations. In order to decrease the amount of anthropogenic release of mercury in the United States, the EPA has limited both use and disposal of mercury. In 1992, the EPA banned land disposal of high mercury content wastes generated from the electrolytic production of chlorine—caustic soda (14), accompanied by a one-year variance owing to a lack of available waste treatment faciUties in the United States. A thermal treatment process meeting EPA standards for these wastes was developed by 1993. The use of mercury and mercury compounds as biocides in agricultural products and paints has also been banned by the EPA. 

The State of New Jersey has passed a law restricting the sale and disposal of batteries (qv) containing mercury, requiring manufacturers to reduce the mercury content of each battery to 1 ppm by weight by 1995, and to estabhsh a collection program for spent batteries (14). Another New Jersey law bans the sale of products having cadmium, mercury, or other toxic materials in the packaging (14) (see Cadmiumand cadmium alloys Cadmium compounds Mercury compounds). 

California and Minnesota have placed restrictions on the disposal of fluorescent light tubes, which contain from 40—50 mg of mercury per tube, depending on size. After batteries, fluorescent lamps are the second largest contributor of mercury in soHd waste streams in the United States (3,14). A California law classifies the disposal of 25 or more fluorescent lamp tubes as hazardous waste. In Minnesota, all waste lamps generated from commercial sources are considered hazardous waste. Private homes are, however, exempt from the law (14). Other states have proposed similar regulations. Several companies have developed technologies for recovering mercury from spent lamps (14). 

A goal of reducing total mercury releases in the United States by 33% between 1988 to 1992, and 50% by 1995 was set by the EPA. The 1992 goal was more than achieved United States reportable mercury releases were reduced by 39% by 1991 (26). In the United States, discards of mercury in municipal soHd waste streams were approximately 643 t in 1989 (3). As a result of increased restrictions on the use and disposal of mercury, by the year 2000 mercury in municipal soHd waste streams is expected to be about 160 t (3). 

Exposure. The exposure of humans and animals to mercury from the general environment occurs mainly by inhalation and ingestion of terrestrial and aquatic food chain items. Pish generally rank the highest (10—300 ng/g) in food chain concentrations of mercury. Swordfish and pike may frequently exceed 1 p.g/g (27). Most of the mercury in fish is methyl mercury [593-74-8]. Worldwide, the estimated average intake of total dietary mercury is 5—10 p-g/d in Europe, Russia, and Canada, 20 pg/d in the United States, and 40—80 pg/d in Japan (27). 

Mercury consumption in the United States is summarized through 1992 in Table 7. Overall worldwide consumption of mercury declined in the 1980s and early 1990s. A detailed discussion of the uses and appHcations of mercury is available (3). 

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). 

Explosives. Mercury, in the form of organic complexes, eg, mercury fulminate [628-86-4] has had long usage in explosives (see Explosives and propellants). In the United States all mercury for use in explosives is diverted to military uses. An explosive based on mercuric 5-nitrotetra2ole [60345-95-1] has been developed, but its use is on a small scale and in research and development only (3). 

Mercury salts exist ia two oxidation states mercurous, Hg", and mercuric, The former exist as double salts for example, mercurous... 

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). 

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