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ABSTRACT A mathematical model based on simple cake filtration theory was coupled to a previously developed two-stage mathematical model for mercury (Hg) removal using powdered activated carbon injection upstream of [...]

Using phase-matched third-harmonic generation we determine the effective nonlinear susceptibilities in [Hg.sub.2][Cl.sub.2] (Calomel) to [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] and [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] for type I and type II phase matching, respectively. The type III phase matching uses the same tensor components as type I and is deduced to be [MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII]. The effective third-order susceptibilities of [Hg.sub.2][Cl.sub.2] are two orders of magnitude higher than those of CaC[O.sub.3], and the tensor components [[chi].sub.11] - 3[[chi].sub.18] exceed the components of ADP by a factor of 5. These measurements demonstrate that Calomel might be a promising material to be used for nonlinear optical devices. OCIS codes: 160.4330, 260.1440, 190.4160, 190.4720, 190.4400, 190.2620.

X-ray diffraction, vibrational spectroscopy, and calorimetry in the solids and solutions were utilized to characterize the coordinating properties of the soft sulfur-donor solvent N,N-dimethylthioformamide and the unexpected hydrogen-bonding ability. Pseudotetrahedral HgX(sub 2)(SCHN(CH3)2)2 complexes was shown to be consisted of isomorphous compounds with increasing Hg-X bond strength in the order X = Cl, Br, and I with Hg-S only slightly weaker than Hg-Cl.

The effects of the steric and electronic factor balance on the change in the coordination number of the solvated zinc, cadmium, and mercury (II) ions were analyzed by x-ray crystallographic studies. Results have shown that the change to four coordination found for the solvated zinc ion with the same ligand cannot be secondary to increasing ligand-to-ligand repulsion. It was also indicated that the bond character and the structure of the strongly solvated zinc and mercury(II) ions were affected more than for the cadmium ions.

The bonding and coordination geometry of the solvated zinc, cadmium, and mercury(II) ions in N,N-dimethylthioformamide solution was investigated through large-scale scattering and vibrational spectroscopic studies. Data indicated that the most distinguishing coordination geometry of mercury(II) is the formation of two strong collinear bonds, often occuring in the solid state with some weak equatorial secondary bonds.

A series of osmium-mercury carbonyl clusters that was synthesized from the reactions of alkyl- or arylmercury(II) halides with the [Os3(CO)10(NCMe)2] activated triosmium cluster. The [{Os3(CO)10(mu-X)}2(mu4-Hg)] (X = Cl, I) cluster was formed by the rapid redistribution of the asymmetric mercurial [Os3(CO)10(mu-X)(mu-HgR)]. The presence of different reactions rates during the formation of the osmium-mercury carbonyl clusters were also caused by differences in the rates of the corresponding redistribution reactions.

The reactivity of the bis(triphenylphosphonio)isophosphindolide triflate was analyzed during the reaction of the bis(phosphonio)isophosphindolide cation with Hg2+. A phosphinito complex was formed by the reaction of the bis(phosphonio)isophosphindolide cation with HgCl2 and H2O or MeOH. The conversion of bis(triphenylphosphonio)isophosphindolide to phosphonium ions also involved 1,1-oxidative additions at the two coordinate phosphorus which was similar to isoelectronic compounds.

The O K-edge X-ray-absorption near-edge structure (XANES) spectra of a series of (Hg0.5Pb0.5)Sr2(Ca0.7Y0.3)Cu2O7-delta were analyzed to determine the hole distribution of oxygen sites and their role in superconductivity. Analysis of the XANES spectral patterns of the mercury-based superconducting compound indicated the role of the out-of-plane oxygen in controlling the increase in resistance temperature. Furthermore, the hole concentration within the out-of-plane oxygen sites decreases with increasing Ba doping.

Magnetic circular dichroism and electronic absorption for Hg3(dppm)3(SO4)2 in 5:3:2 v/v ethanol-methanol-ether solvent at 295 K revealed two minima at 2.99 and 3.41 micrometer(super -1) which was resolved into a positive A term at 3.12 micrometer(super -1) and a negative B term at 3.4 micrometer(super -1) at 80 K. The data were interpreted in terms of 6s 6s sigma to sigma* and 6s 6p sigma to pi metal-centered transitions. The A term in the region of the lowest energy band was attributed to the transition to the sigma to pi transition to E'((super3)A(sub 2)').

The chemoselective reduction of vinylmercury chlorides with tributylstannane and a radical inhibitor produced several vinylmercury hydrides. The vinylmercury hydrides are composed of a mercury unit with a bonding angle of 180 degrees. The HgH bond of the methylmercury hydride has the lowest harmonic frequency among the vinylmercury hydrides. Diethenylmercury has the largest Hg-C bond shortening compared to the monosubstituted compounds.

Mass spectroscopy and multinuclear NMR spectroscopy help characterize 9-CF3CO2Hg-1,7-C2B10H11, formed by the reaction between 1,7-C2B10H12 and 1 equiv of mercuric oxide. Structural studies of a byproduct indicate the presence of a cyclic array containing four Hg centers in the byproduct, and four trifluoroacetate anions exhibit simultaneous interaction with each macrocycle. Two macrocycles share each of the four trifluoro-acetate anions, forming a self-assembled 1:2 polymeric array. Electrostatic interactions and hydrogen bonds in the byproduct are discussed.

X-ray crystal structure analysis of pinchite, Hg(5)Cl(2)O(4), reveals that the crystals have three different Hg positions and the structure consists of Hg(3)O(4) and HgCl layers similar to that seen in terlinguaite. Four Cl and two O atoms exhibit distorted octahedral coordination with the Hg1 position while two Cl and four O atoms show a bi-diminished, Siamese dodecahedral coordination with Hg2. Four O atoms display a distorted tetrahedral coordination with Hg3.

The present work describes an improved method for the determination of total and organic mercury by decreasing analysis time (use of a dual circuit), sample size, and handling procedures and eliminating the need for a clean room condition while maintaining the detection limit below the parts per trillion (pptr) level. Total mercury was analyzed after reduction by a one-stage gold amalgamation before transfer to an atomic fluorescence spectrometer. The detection limit was 0.07 ng [L.sup.-1] for aqueous samples and 1 ng [g.sup.-1] for biological tissue. Analysis time was 5 min. Organic mercury was first derivatized using sodium tetraethylborate and then trapped onto a graphitized carbon trap before transfer to an isothermally controlled GC column coupled to a cold vapor atomic fluorescence spectrometer. The detection limit for methylmercury was 0.05 ng [L.sup.-1] for aqueous samples and 1.4 ng [g.sup.-1] for biological tissue. Samples were analyzed in 10 min. The outlined analytical protocol permits a semiautomation of both inorganic and organic mercury analyses.

Solutions of the Boltzmann transport equations, obtained from a full band structure and Fermi-Dirac (FD) statistics, are used to calculate the electron mobility in Hg(0.78)Cd(0.22)Te alloy. This technique is useful when the transport characteristics of narrow-gap materials with nonparabolic band structures are evaluated using FD statistics. Defects in mobility at low carrier concentration and shape changes at high carrier concentrations are described without using extra scattering coefficients.

Molybdenum(V) chloride and Lewis acids initiated the stereoelectronically controlled, skeletal rearrangements of an organomercury steroid, a stable compound requiring activation before the reaction. The transmetalation of Hg to Mo did not occur during the rearrangements. High oxophilicity of Mo(V) and steroelectronic effects controlled the major reaction.

The reactions of a 1, 1'-bis(diphenylphosphino)ferrocenyl ligand with several mercury(II) salts were studied. The phosphorus atom on the disubstituted Cp ring and the two tertiary nitrogens are coordinated to one metal center and the phosphorus on the second Cp ring is coordinated to a different metal center in the cationic complexes. The one- and two-dimensional solution and solid-state structures of the chiral complexes were then determined by nuclear magnetic resonance methods.

Mixed-metal Pt-Hg complexes of the nucleobases 1-methylcytosine and 1,5-dimethylcytosine were described. It was shown that the heteronuclear compounds contain two bridging cytosyl ligands, binding Pt through N3 and Hg via deprotonated exocyclic amino groups of the nucleobases. 1H nuclear magnetic resonance spectra of the various Pt-Hg compounds show 195Pt and 199Hg coupling. Moreover, the mixed-metal Pt-Hg species, when reacted with a large variety of N and S donor ligands X, tend to decompose with formation of trans-(a2PtL2)2+ and HgX2.

Mercury-mercury(II) halide systems are studied using Raman spectrometry. The structural properties of the systems are presented. The system consists of the dissolution of mercury metal in molten mercury halides. Temperatures ranged from 550 to 818 K. The molecular mercury species are analyzed to show the formation of molecular subhalides. The importance of the study lies in the exploration of phenomena of the high solubility of mercury in mercury melts.

Use of a Pb-manometer in a study of the variation of pressure with the oxidation of superconducting Hg-1212 and Hg-1223 compounds, up to 17 kbar, shows a linear and nonlinear variation of pressure before and after the oxidation process, respectively. The pressure effect dTc/dP decreases with the increase in oxidation for Hg-1212 and increases for Hg-1223. The positive value of dTc/dP indicates a possibility of high values of Tc.

The article discusses some recent advances in spectrometric methods for mercury speciation analysis of environmental samples with a focus on isotope dilution techniques for determination of mercury species' concentrations in gaseous samples and reaction rates in soils and sediments.

Byline: P. Avila-Perez, G. Zarazua-Ortega, I. Barcelo-Quintal, A.L. Bussy, C. Diaz-Delgado In this paper, mercury concentration in the soluble, particulate and total fractions of water and in the sediment from the Jose Antonio Alzate Dam in the State of Mexico was evaluated using neutron activation analysis in order to determine the bioavailability and distribution of this metal. Sampling was carried out on three separate seasons - cold dry season, hot dry season and rainy season - such that, at least one complete hydrological cycle in the dam was covered. Results show that mercury constitutes a significant problem in the dam. Concentration in the water column is higher than the maximum acceptable level (10 ng/L) as established by national environment criteria and is present at considerable levels in the bottom sediments (up to 500 [acute accent]g/kg). In the water, mercury presents a seasonal variation, where the highest concentrations are found during the dry period and the lowest concentrations at the end of the rainy season due to dilution of the metal in water. Sediment concentration of mercury shows evidence of self-cleaning mechanisms in the dam in which, principally through processes of sedimentation, part of the metal is removed from the water column, improving the outflow water quality.

The structures of the Hg(II) and Pb(II) complexes of DOTAM are reported. The structures of the Hg(II) complex of DOTAM are considered in relation to the coordination geometry around the Hg(II), and how this relates to the Pb(II) structure.

A presentation of the analytical equations of state for fluid mercury in metal, nonmetal, and in-metal-nonmetal transition states. In addition, investigations of monovalent liquid cesium and rubidium indicate a gradual metal-nonmetal transition near the critical region, a gradual metal-non-metal transition near the critical region, but the properties of this transition for a divalent metal are completely different.

To simplify the material thought to student, the Zn group is forced into d block, as the resulting periodic tables are thought to be more symmetric and easier to memorize for students. For the same purpose the Cu group is forced into group I along with alkali metals.

Cyclopentadienyl derivatives of mercury have been proven to behave in a nonfluxional manner through three observation results. These findings show that the 13C{1H} CP MAS MAS, particularly for the eta1 bound C atoms, shifts are very similar to those in solution. Moreover, none of the chemical shifts for 1H, 13C{1H} and 29Si{1H} solution state were highly temperature dependent. Also, the nJ(13C-199Hg) couplings constantly stayed within the range +30 to -38 degree centigrades. The results show that a single Si substitutent for mercury cyclopentadienyl derivatives allows a suitable electronically unique shite within the cyclopentadienyl ligand.

The electrochemical reduction of HgSe2 by K in NH3 in 2.2.2-cryptand led to the formation of [K(2.2.2-cryptand)]2[HgSe2] while the electrochemical reduction of HgSe2 cathode led to the synthesis of [PPh4]2[Hg(Se4)2].en. Analysis of the [PPh4]2[Hg(Se4)2].en and [K(2.2.2-cryptand)]2[HgSe2] products by nuclear magnetic resonance spectroscopy indicated the absence of the [HgSe2]2- anions. Furthermore, the formation of an electrode with high electrical conductivity was mediated by excess Se.