A violet emission from optically excited mercury vapour. Kinetics of the formation and decay of excited dimers and trimers

A new electronic systems has been observed from excited Hg vapour, which is assigned to collisionally induced emission from the Hg₂ O^±_g first excited states of the dimer: Hg₂O^±_g + M → 2Hg(6 ¹S₀) + M + hv(γ_max 3950 A). For M = N₂, the rate coefficient is 5.3(±0.7) × 10^?19 cm³ molecule^?1 at 298 K. From time resolved measurements of the luminescence in the afterglow following pulsed excitation, the decay rate of the green emission, in an excess of N₂, is shown to be a linear function of [Hg][N₂]. It is concluded that the reaction which controls the decay of the excitation is formation of an excited trimer in a termolecular reaction; the trimer is the carrier of the green emission: Hg₂ O^±_g + Hg(6 ¹S₀ + Hg(6¹S₀ + N₂ → Hg₃³Π_u + N₂. The rate coefficient is 1.10(±0.07) × 10^?30 cm⁶ molecule^?2 s^?1 at 298 K.     

Nonextractive Trace Level Simultaneous Determination of Mercury(II) and Zinc(II) in Environmental Samples with 2‐(5‐Bromo‐2‐pyridylazo)‐5‐diethylaminophenol and Cetylpyridinium Chloride

Abstract

A simple, rapid, selective, and sensitive method for the derivative spectrophotometric determination of Hg(II) and its simultaneous determination in the presence of Zn(II) using 2‐(5‐bromo‐2‐pyridylazo)‐5‐diethylaminophenol in the presence of cetylpyridinium chloride, a cationic surfactant, has been developed. The molar absorption coefficient and analytical sensitivity of the 1∶1 Hg(II) complex at 558 nm (λ_max) are 5.78×10⁴ L mol^?1 cm^?1 and 0.67 ng mL^?1, respectively. The detection limit of Hg(II) is 1.40×10^?2 ng mL^?1, and Beer's law is valid in the concentration range 0.05–2.40 µg mL^?1. Overlapping spectral profiles of Hg(II) and Zn(II) complexes in zero‐order mode interfere in their simultaneous determination. However, 0.10–2.00 µg mL^?1 of Hg(II) and 0.065–0.650 µg mL^?1 of Zn(II), when present together, can be simultaneously determined at zero cross point of the derivative spectrum, without any prior separation. The relative standard deviation for six replicate measurements of solutions containing 0.134 µg mL^?1 of Hg(II) and 0.620 µg mL^?1 of Zn(II) is 1.72 and 1.47%, respectively. The proposed method has successfully been evaluated for trace level simultaneous determination of Hg(II) and Zn(II) in environmental samples.     

Thiodiethanethiol Modified Silica Coated Magnetic Nanoparticles for Preconcentration and Determination of Ultratrace Amounts of Mercury,Lead, and Cadmium in Environmental and Food Samples

A new magnetic adsorbent, 2,2′-thiodiethanethiol grafted with tetraethyl orthosilicate modified Fe₃O₄ nanoparticles, was developed for the separation and preconcentration of Hg, Pb, and Cd in environmental and food samples. The concentrations of Pb and Cd were determined by inductively coupled plasma–optical emission spectrometry; Hg was determined by cold vapor atomic absorption spectrometry. A comprehensive study on the factors affecting the extraction and desorption efficiencies was performed. Under the optimized conditions, the method was linear in the 0.01–750 ng mL^?1 range (before preconcentration) with detection limits of 4, 8, and 2 ng L^?1 for Hg, Pb, and Cd, respectively. Relative standard deviations of 2.3, 2.9, and 2.4% (concentration 50 ng mL^?1, n = 7) and high preconcentration factors of 291, 285, and 288 were also obtained for Hg, Pb, and Cd. The accuracy of the proposed method was validated by analyzing a water certified reference material with satisfactory recoveries. The method was successfully applied to the determination of the analytes in tap and mineral waters and canned tuna fish samples.     

Combination of metastable and ground-state mercury atoms into ungerade dimer states

The time evolution of the 2537 Å sensitised luminescence of mercury vapour has been examined at 304 K. With a trace of N₂ to generate Hg(6³P_o) and an excess of Ar to chaperon dimer formation, full time profiles of the ultraviolet and green bands have been recorded. The ultraviolet emission is of much shorter duration than the green with these gas mixtures. The reservoir of the ultraviolet band is the O^?_u state of the mercury dimer which correlates with Hg(6³P_o), Hg(6¹S_o) and is generated in the combination of metastable and ground-state mercury atoms. The Hg₂ O^?_u is efficiently relaxed to the O^±_g firstexcited states of the dimer in collision with Hg atoms, but rather inefficiently in collisions with Ar atoms. The rate coefficient for formation of excited trimers in the reaction Hg₂ O^±_g+ Hg(6¹S_o) + N₂ → Hg^*₃ + N₂ has been recorded as 1.95(±0.1) × 10^?30 cm⁶ molecule^?2s^?1 at 304 K.     

Thermodynamic Studies of Bi-Univalent Electrolytes. VI. Thermodynamics of Cadmium Acetate from E. M. F. and Calorimetric Measurements

E. M. F. of the Cell, Cd-Hg (2-phase)/CdAc₂(m), Hg₂Ac₂(s)/Hg was measured at 20°, 25°, 30° and 40°C. The standard e. m. f. of the cell, Cd/CdAc₃(m), Hg₂Ac₂(c)/Hg was evaluated as E°=1.1500?11.09×10^?4T+1.06×10^?8T² The thermodynamic data of the reaction, Cd(c) + Hg₂Ac₂(c)=2Hg(l)+Cd⁺⁺(aq)+2Ac^?(aq) at 25°C were estimated as ΔF°=?42,139, ΔH°=?48,698 cal mole^?1 and ΔS°=?22.0 cal deg^?1 mole^?1 at 25°C. The thermodynamic data for the formation of Hg₂Ac₂(s) were evaluated as ΔF_f°=?202.3, ΔH_f°=?154.5 Kcal mole^?1 and S°=72.9 cal deg^?1 mole^?1. From measurements of the heats of solution of CdAc₂·2H₂O in aqueous solution, the relative partial molal enthalpies of cadmium acetate in aqueous solution were estimated.     

AC impedance study on semiconducting properties of anodic plumbous oxide film

The semiconducting properties of anodic film formed on Pb in 4.5mol·dm^?3H₂SO₄ solution (30°C) at 0.9 V (vs. Hg/Hg₂SO₄) for 2 h were studied using AC impedance method. The phase composition of the film is PbSO₄ and PbO·PbSO₄. The semiconducting properties are due to the latter. The Mott-Schottky plots show that the said film is an n-type semiconductor with flat-band potential of ?0.9 V (vs. Hg/Hg₂SO₄) and donor density of 1×10¹⁶ cm^?3. The surface density measured at 410–2500 Hz is (2–5)×10¹² cm^?2 eV^?1.     

Irreversible electrostatic deposition of Prussian blue from colloidal solutions

Prussian blue (PB) can be deposited from colloidal solutions (5.4?×?10^?3?mol_PB?L^?1, 0.01?mol?L^?1 KNO₃) on glassy carbon, either by potential cycling or potentiostatically, provided that the deposition potential is more positive than ?0.2?V vs. Hg/Hg₂Cl₂. Depending on the deposition potential, the PB particles form either a single layer of Everitt??s salt, of PB, or multilayers of Berlin green. Also depending on the electrode potential, the deposition was accompanied by currents which were either only of capacitive nature, or represent the sum of capacitive and faradaic currents. The currents were always limited by the diffusion of the colloidal particles to the electrode surface, i.e., they obeyed the Cottrell equation. The PB layers were characterized by in situ atomic force microscopy.     

Effects of heating rate (1–300° h−1) on the non-isothermal thermogravimetry of CuSO4 · 5 H2O

The course of the reaction CuSO₄ · 5 H₂O ? CuSO₄ · H₂O + 4 H₂O was studied by non-isothermal thermogravimetry with various heating rates ranging from 1 to 300° h^?. The measurements were made either in static air, in a dry nitrogen stream, or in water vapor at a reduced pressure (9 mm Hg). In static air, the shape of the TG curve changed drastically at a heating rate of 13 to 15° h^?, and this change was explained by considering the nature of the plateaus and inflections present. In a dry nitrogen stream, the dehydration is made much easier at slow heating rates and occurs almost in one step at 2° h^?; in water vapor at 9 mm Hg, on the other hand, a very distinct two-step curve is obtained at 1° h^?. This can reasonably be compared with the phase diagram of copper sulfate.     

Sensitivity enhancement using nanometer silica particles on the surface of a quartz cell in mercury and selenium determination by vapor generation atomic absorption spectrometry

The sensitivity of on-line vapor generation atomic absorption spectrometry of mercury and selenium was improved by using a new atom trap technology. The inner wall of a T-shaped quartz tube was coated with nanometer SiO₂ so increase the residence time of the analyte atoms in the light path. The linear range of the calibration plots thus was increased to a range from 5.0 to 150 ng mL^?1 for mercury, and from 4.5 to 100 ng mL^?1 for selenium. The detection limits are 0.9 ng mL^?1 for Hg and 1.0 ng mL^?1 for Se which is a 2-fold improvement. The technique was applied to the determination of Hg and Se in herbs and hair.     

Die Kristallstruktur des SrHg(SCN)4 · 3 H2O

Crystal Structure of SrHg(SCN)₄ · 3 H₂O SrHg(SCN)₄ · 3 H₂O is orthorhombic, space group Pcca, with a = 19.476(7), b = 8.150(1), c = 8.991(3) Å, V = 1427.1 ų, Z = 4, d_c = 2.67 g · cm^?3, μ(AgKα) = 77.95 cm^?1. The salt consists of nearly tetrahedral Hg(SCN)₄ groups, Sr has a tricapped trigonal prismatic coordination: four N and five O atoms. The thiocyanate groups form end-to-end bridges and connect the Hg and Sr coordination polyhedra.     

Mercury(II) complexes of pyrrolidinedithiocarbamate,crystal structure of bis{[μ2-(pyrrolidinedithiocarbamato-S,S ′)(pyrrolidinedithiocarbamato-S,S ′)mercury(II)]}

Mercury(II) complexes of pyrrolidinedithiocarbamate (PDTC) having the general formula [Hg(PDTC)X] (X = Cl^?, SCN^?, and CN^?) and [Hg(PDTC)₂] have been prepared and characterized by elemental analysis, IR, and NMR. The crystal structure of [Hg(PDTC)₂] has also been determined by X-ray crystallography, showing that the complex is a centrosymmetric dimer, [Hg₂(PDTC)₄] (bis[µ²-(pyrrolidinedithiocarbamato-S,S′)(pyrrolidinedithiocarbamato-S,S′)mercury(II)]) (1). The solid-state structure of 1 contains two crystallographically equivalent Hg(II) centers in a distorted tetrahedron.     

Spectrophotometric study of complexes of mercury(II) with mono- and dithiosemicarbazones

The formation of complexes at pH 4.7 of the Hg(II) with five monothiosemicarbazone and two dithiosemicarbazone has been studied. The mercury(II) reacts with monothiosemicarbazones of salicylaldehyde (λ_max = 363 nm, E = 1.69 × 10⁴liters · mol^?1cm^?1), pi-colinadehyde (λ_max = 363 nm, E = 2.38 × 10⁴liters · mol^?1cm^?1), 6-methyl-picolinaldehyde (λ_max = 363 nm, E = 2.28 × 10⁴liters · mol^?1cm^?1), di-2-pyridylketone (λ_max = 380 nm, E = 2.08 × 10⁴liters · mol^?1cm^?1), and o-naphthoquinone (λ_max = 540 nm, E = 1.03 × 10⁴liters · mol^?1cm^?1) and with dithiosemicarbazones of 1,4-dihydroxyphthalimide (λ_max = 430 nm, E = 2.56 × 10⁴liters · mol^?1cm^?1) and dipyridylglyoxal (λ_max = 363 nm, E = 2.37 × 10⁴liters · mol^?1cm^?1). A critical comparison of the stoichiometry and apparent stability constant of complexes with mono- and dithiosemicarbazones is given.     

Iodide‐Selective Electrodes Based on Bis[N(2‐methyl‐phenyl) 4‐Nitro‐thiobenzamidato]mercury(II) and Bis[N‐phenyl 3,5‐Dinitro‐thiobenzamidato]mercury(II) Carriers

Highly selective poly(vinyl chloride) (PVC) membrane electrodes based on recently synthesized mercury complexes including Hg(Nmpntb)₂ and Hg(Npdntb)₂ as new carriers for iodide‐selective electrodes by incorporating the membrane ingredients on the surface of graphite electrodes are reported. The effect of various parameters including the membrane composition, pH and possible interfering anions were investigated on the response properties of the electrodes. Both sensors exhibited Nernstian responses toward iodide over a wide concentration range of 7×10^?7 to 0.1 M and 1×10^?6 to 0.1 M, with slopes of 59.6±0.8 and 58.9±0.9 mV per decade of iodide concentration and detection limit of 3×10^?7 M and 7×10^?7 for Hg(Npdntb)₂ and Hg(Nmpntb)₂, respectively, over a wide pH range of 3–11. The sensors have response times of ≤5 s and can be used for at least 2 months without any considerable divergence in their potential response. The proposed electrodes show good ability to discriminate iodide over several inorganic and organic anions. The electrodes were successfully applied to direct determination of iodide in synthetic mixture, waste water and drinking water and as indicator electrodes in precipitation titrations.     

Ion activities and copper electrode reactions in magnesium sulphate solutions

Thermodynamic and kinetic studies have revealed conventional mean-ion and convenient single-ion activity coefficients for copper(II), magnesium and sulphate ions and standard exchange rates for either step of the liquid Cu(Hg)/Cu(II) electrode and of the solid Cu/Cu(II) electrode, all in 0.005 mol kg^?1 CuSO₄+0.005 mol kg^?1 H₂SO₄+(x?0.01) mol kg^?1MgSO₄ (for x=0.2 to 3) at 25°C. With increasing x, the sulphate activity coefficient steadily falls, the copper(II) and magnesium activity coefficients go through a minimum near x=1, and the standard rates fall. The kinetic changes with x reveal some information on double-layer and ligand effects.     

60Co-v Radiolysis of a Mixture of Benzene and Cyclohexane in Presence of Diphenyl Mercury

In the radiolysis of cyclohexane in presence of 4×10^?3M diphenylmercury (Hg φ₃) three isomers of hexane, methylcyclopentane (G=0.018), benzene (G=0.42) and cyclohexene (G=0.047) were detected. Addition of benzene in the mixture of cyclohexane and Hg φ₃ formed two isomers of pentane, hexene and one isomer of hexane as additional products, while cyclohexene was eliminated completely. Normally, eight products were detected in presence of 10 to 50% benzene. Total radiolytic yield of products increased in presence of 15 to 25% benzene but in presence of 35 to 50% benzene G values became very low. Considerable amount of hexene is formed in a mixture of benzene and cyclohexane but neither benzene nor cyclohexane in presence of Hg φ₂ formed this compound. In the presence o. benzene and φ₂Hg hexane yield is very much reduced. Protection is observed in presence of 10% as well as 35 to 50% benzene in this system. The plot of benzene concentration in moles/litre versus methylcyclopentane is linear and from the slope of the straight line, the values of rate constants were found to be 2.65×10^?2 litre/mole sec., 5.25×10^?3 litre mole sec., 9×10^?7 litre/mole sec. for methylcyclopentane, cyclohexane and benzene respectively. A plot of G(–c-C₆H₁₂) versus 1/[C₆H₆] also gave a straight line which confirms the sponge type protection in this multicomponent system.     

Homo- and heteroleptic mercury(II) complexes with monoamino complexones in aqueous solution

Reactions of mercury(II) with iminodiacetic (H₂Ida), 2-hydroxyethyliminodiacetic (H₂Heida), and nitrilotriacetic acids (H₃Nta) were studied by spectrophotometry and pH potentiometry. The resulting complexes included [HgIda], [Hg(OH)Ida]^?, [HgIda₂]^2?, [HgHeida], [Hg(OH)Heida]^?, [Hg(Heida)₂]^2?, [HgNta]^?, [HgNta₂]^4?, [Hg(Ida)Heida]^2?, [Hg(Ida)Nta]^3?, and [Hg(Heida)Nta]^3?. The logarithms of their stability constants calculated for I = 0.1 (NaClO₄) and T = 20 ± 2°C were 11.14 ± 0.07, 20.33 ± 0.08, 19.40 ± 0.10, 11.42 ± 0.04, 19.68 ± 0.11, 18.48 ± 0.09, 13.42 ± 0.05, 20.80 ± 0.08, 19.05 ± 0.06, 20.64 ± 0.11, and 20.53 ± 0.16, respectively. The experimental data were analyzed in terms of the mathematical models that predict the existence of a wide spectrum of complex species in solution and allow one to consider only those species that are sufficient for accurate reproduction of the observed pattern.     

Removal of Zn(II) Ions from Aqueous Solution Using BPHA‐Impregnated Polyurethane Foam

Zn(II) ions sorption onto N‐Benzoyl‐N‐Phenylhydroxylamine (BPHA) impregnated polyurethane foam (PUF) has been studied extensively using radiotracer and batch techniques. Maximum sorption (～98%) of Zn(II) ions (8.9 × 10^?6 M) onto sorbent surface is achieved from a buffer of pH 8 solution in 30 minutes using 7.5 mg/mL of BPHA‐impregnated polyurethane foam at 283 K. The sorption data follow Langmuir, Freundlich and Dubinin‐Radushkevich (D‐R) isotherms. The Langmuir constants Q = 18.01 ± 0.38 μ mole g^?1 and b = (5.39 ± 0.98) × 10³ L mole^?1 have been computed. Freundlich constants 1/n = 0.29 ± 0.01 and C_m = 111.22 ± 12.3 μ mole g^?1 have been estimated. Sorption capacity 31.42 ± 1.62 μ mole g^?1, β = ?0.00269 ± 0.00012 kJ² mole^?2 and energy 13.34 ± 0.03 kJ mole^?1 have been evaluated using D‐R isotherm. The variation of sorption with temperature yields ΔH = ?77.7 ± 2.8 k J mole^?1, ΔS = ?237.7 ± 9.3 J mole^?1 K^?1 and ΔG = ?661.8 ± 117.5 k J mol^?1 at 298 K reflecting the exothermic and spontaneous nature of sorption. Cations like Fe(III), Ce(III), Al(III), Pb(II) and Hg(II) and anions, i.e., oxalate, EDTA and tartrate, reduce the sorption significantly, while iodide and thiocyanate enhanced the sorption of Zn(II) ions onto BPHA‐impregnated polyurethane foam.     

Total and inorganic mercury determination in fish tissue by flow injection cold vapour atomic fluorescence spectrometry

A simple and reliable method for Hg determination in fish samples has been developed. Lyophilised fish tissue samples were extracted in a 25% (w/v) tetramethylammonium hydroxide (TMAH) solution; the extracts were then analysed by FI-CVAFS. This method can be used to determine total and inorganic Hg, using the same FI manifold. For total Hg determination, a 0.1% (w/v) KMnO₄ solution was added to the FI manifold at the sample zone, followed by the addition of a 0.5% (w/v) SnCl₂ solution, whereas inorganic Hg was determined by adding a 0.1% (w/v) L-cysteine solution followed by a 1.0% (w/v) SnCl₂ solution to the FI system. The organic fraction was determined as the difference between total and inorganic Hg. Sample preparation, reagent consumption and parameters that can influence the FI-CVAFS performance were also evaluated. The limit of detection for this method is 3.7 ng g^?1 for total Hg and 4.3 ng g^?1 for inorganic Hg. The relative standard deviation for a 1.0 µg L^?1 CH₃Hg standard solution (n = 20) was 1.1%, and 1.3% for a 1.0 µg L^–1 Hg²⁺ standard solution (n = 20). Accuracy was assessed by the analysis of Certified Reference Material (dogfish: DORM-2, NRCC). Recoveries of 99.1% for total Hg and 93.9% inorganic Hg were obtained. Mercury losses were not observed when sample solutions were re-analysed after a seven day period of storage at 4°C.     

Extraction and spectrophotometric determination of mercury(II) with Xylenol Orange in the presence of diphenylguanidine as a synergistic agent

The system Hg(II)/XO/DPG extracted into several alcohols and mixtures alcohol/chloroform (as depressing of the solubility of the alcohol in water) is studied. A ternary complex 1:1:1 Hg(II)/XO/DPG is observed when the mixture 1:1 ($\text{V}\text{V}$) iso-amyl alcohol/chloroform is considered. This complex shows a molar absorptivity 2.3 × 10⁴ liter mol^?1 cm^?1 at 590 nm, pH_ex 8.0, and T ? 18 °C. This complex allows to determine Hg(II) in the concentration range 0.25-5.8 ppm. According to the experimental results a reaction mechanism in which the alcohol and DPG take part in the coordination sphere of Hg(II) ion is suggested. The optimal extraction conditions of XO and its mercury complex are discussed, as well as the study of the interferences.     

Determination of Arsenic,Mercury and Barium in Herbarium Mount Paper Using Dynamic Ultrasound-Assisted Extraction Prior to Atomic Fluorescence and Absorption Spectrometry

A dynamic ultrasound-assisted extraction method using Atomic Absorption and Atomic Fluorescence spectrometers as detectors was developed to analyze mercury, arsenic, and barium from herbarium mount paper originating from the herbarium collection of the National Museum of Wales. The variables influencing extraction were optimized by a multivariate approach. The optimal conditions were found to be 1% HNO₃ extractant solution used at a flow rate of 1 mL min^?1. The duty cycle and amplitude of the ultrasonic probe was found to be 50% in both cases with an ultrasound power of 400 W. The optimal distance between the probe and the top face of the extraction chamber was found to be 0 cm. Under these conditions the time required for complete extraction of the three analytes was 25 min. Cold vapor and hydride generation coupled to atomic fluorescence spectrometry was utilized to determine mercury and arsenic, respectively. The chemical and instrumental conditions were optimized to provide detection limits of 0.01 ng g^?1 and 1.25 ng g^?1 for mercury and arsenic, respectively. Barium was determined by graphite-furnace atomic absorption spectrometry, with a detection limit of 25 ng g^?1. By using 0.5 g of sample, the concentrations of the target analytes varied for the different types of paper and ranged between 0.4–2.55 µg g^?1 for Ba, 0.035–10.47 µg g^?1 for As, and 0.0046–2.37 µg g^?1 for Hg.