Elektrophorese der halogenokomplexe von Hg(II), Bi(III), Cd(II), Pb(II) und -Cu(II) : Chlorokomplexe in chlorwasserstoffsäure

An apparatus for heavy-current and high-tension electrophoresis on filter paper is described This apparatus enables one to avoid the difficulties that occur in electrophoresis in base electrolytes that are highly concentrated or show greater electric conductivity The zones migrate along the paper strips with constant speed and, consequently, it is possible to measure the mobility The effective length of the filter paper strips is 660 mm Correction of the apparent mobility in the porous adsorbent is treated thoroughly.Diagrams of the electrophoretic mobility of the chloro-complexes of Hg(II), Bi(III), Cd(II), Pb(II), and Cu(II) in hydrochloric acid, are given in the experimental part The concentration of the hydrochloric acid varied between 0.1N and 6N In 6N HCl all the metals investigated are present asani onic complexes. Hg, Bi.Cd, and Pb chloro-complexes show a pronounced maximum of mobility in the anionic range. The sequence of the zones in the direction anode to cathode is Hg, B1, Cd, Pb, Lu al 0.1–2.3N HCl and B1, Hg, Cd, Pb.Cu at2.3–6N HCl.Finally, the electrophoretic separation of a mixture of Hg, Bi, Cd, Pb, Cu in 1N, 2N and 4N HCl is illustrated Complete separation of the zones was achieved in each experiment     

Elektrophorese der halogenokomplexe von Hg(II), Bi(III), Cd(II), Pb(II) und Cu(II): Abhängigkeit der beweglichkeiten von der konzentration des metallions

The dependence was investigated of the mobilities of the chloro-complexes of Hg(II), Cd(II), Pb(II) and Cu(II) on the concentration and the volume of the metal salt solution applied, the experiments being carried out in relatively low concentrations of hydrochloric acid (0.1N, 0.5N and 1N) This dependence is considerable in base clectrolytes of low concentration (Iess than 1N HCl) and insignificant in the case of higher concentrations (greater than 1N HCl)On increasing the concentration and volume of the metal salt applied, the Caitionic mobility of the zones increases and the amonic mobility decreasesUnder certain conditions chloro-, bromo-, and lodo-complcxcs of cadmium showed multispots Wc have occasionally obbcived these multispotsalsom the cicctrophorcsis of other metal complcKCb     

Anreicherung und spektrochemische Bestimmung von Spurenelementen in reinsten Thalliumpr?paraten

Zusammenfassung Zur Anreicherung von Spurenelementen aus Lösungen reinster Thalliumpräparate wird die Matrix Thallium als TlJ ausgefällt. Dabei bleiben die Spuren Mg, Zn, Al, Ga, In, Fe, Co, Ni, Mn, Sn, La, Ce, Th und U quantitativ in Lösung, während Bi, Cu, Pb und Cd sowie die Edelmetalle Ag, Hg, Pd, Au und Pt vom Niederschlag mitgerissen werden. Die Adsorption der für die Reinheitsprüfung des Thalliums wichtigen Elemente Bi, Cu, Pb und Cd kann verhindert werden, wenn sie mit Hilfe von ÄDTA in Komplexanionen übergeführt werden. Als Fällungsmittel wird NaJ verwendet. Zur spektrochemischen Bestimmung werden Pb, Cd, Bi, Ni, Co und In als DDTC-Komplexe mit Chloroform extrahiert. Nach Zusatz einer Mischung von Lithiumcarbonat-Kohle und den Referenzelementen Sn und Pd wird der Eindampfrückstand im Gleichstrombogen analysiert. Cu und Fe werden photometrisch bestimmt.

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Enrichment and spectrochemical determination of trace elements in high-purity thallium preparations

For the enrichment of trace elements in solutions of high-purity thallium samples, thallium is precipitated in form of TlI. In this process the noble metals Ag, Hg, Pd, Au, Pt and also Bi, Cu, Pb and Cd will be co-precipitated, whereas many other elements (Mg, Zn, Al, Ga, In, Fe, Co, Ni, Mn, Sn, La, Ce, Th, U) will remain completely in solution. The adsorption of the four elements Bi, Cu, Pb, Cd, which are important for the purity control of thallium compounds, can be prevented, if they are complexed with EDTA to form complex anions. The precipitating reagent is NaI. For the spectrochemical determination of Pb, Cd, Bi, Ni, Co, and In, the trace elements are extracted as DDTC complexes with chloroform. After the addition of a mixture of Li₂CO₃, carbon, and the reference elements Sn and Pd, the sample is analysed, using the d.c. arc. Cu and Fe are determined spectrophotometrically.

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Wir danken dem Fonds der chemischen Industrie für die finanzielle Unterstützung dieser Arbeit.     

Hg(II), Tl(III), Cu(I), and Pd(II) Complexes with 2,2'-Diphenyl-4,4'-Bithiazole (DPBTZ), Syntheses and X-Ray Crystal Structure of [Hg(DPBTZ)(SCN)2]

Reaction of the ligand 2,2′-diphenyl-4,4′-bithiazole (DPBTZ) with Hg(SCN)₂, Tl(NO₃)₃, CuCl, and PdCl₂ gives complexes with stoichiometry [Hg(DPBTZ)(SCN)₂], [Tl(DPBTZ)(NO₃)₃], [Cu(DPBTZ)(H₂O)Cl]_, and [Pd(DPBTZ)Cl₂]. The new complexes were characterized by elemental analyses and infrared spectroscopy. The crystal structure of [Hg(DPBTZ)(SCN)₂] determined by X-ray crystallography. The Hg atom in the title monomeric complex, (2,2′-diphenyl-4,4′-bithiazole)mercury(II)bisthiocyanate, [Hg(C₁₈H₁₂N₂S₂)(SCN)₂], is four-coordinate having an irregular tetrahedral geometry composed of two S atoms of thiocyanate ions [Hg-S 2.4025(15) and 2.4073(15) Å] and two N atoms of 2,2′-diphenyl-4,4′-bithiazole ligand [Hg-N 2.411(4) and 2.459(4) Å]. The bond angle S(3)-Hg(1)-S(4) of 147.46(5)° has the greatest derivation from ideal tetrahedral geometry. Intermolecular interaction between Hg(1) and two S atoms of two neighboring molecules, 3.9318(15) and 3.9640(18) Å, make the Hg(1) distort from a tetrahedron to a disordered octahedron. The attempts for preparation complexes of Tl(I), Pb(II), Bi(III), Cd(II) ions with 2,2′-diphenyl-4,4′-bithiazole ligand were not successful and also the attempts for preparation complexes of 4,4′,5,5′-tetraphenyl-2,2′-bithizole ligand with Cu(II), Ni(II), Co(II), Co(III), Mn(II), Mn(III), Fe(II), Fe(III), Cr(III), Zn(II), Tl(III), Pb(II), Hg(II), Cu(I), Pd(II) were not successful. This point can be regarded as the initial electron withdrawing of phenyl rings and also their spatial steric effects.     

Diagrammes potentiel—niveau d'acidite dans les milieux H2OH3PO4—I Systemes electrochimiques ne faisant pas intervenir le proton

The conditional potentials of redox systems not involving protons have been studied as a function of phosphoric acid concentration (1–14M), with the ferricinium/ferrocene couple as the comparison system. The following systems were considered: Cu(II)/Cu, Cd(II)/Cd, Sn(II)/Sn, Zn(II)/Zn, Ag(I)/Ag, Pb(II)/Pb, Hg(II)/Hg, Bi(III)/Bi and particularly Fe(III)/Fe(II) and Fe(II)/Fe. The hexacyanoferrate(III)/hexacyanoferrate(II) and iodine/iodide couples were also studied. The results are presented as a potential—H₃PO₄ concentration diagram (or potential—acidity level diagram).     

Polarographic analytical determination of Hg(II), Cu(II), Cd(II), As(III), Sb(III), Ti(IV) and U(VI) in the presence of Fe(III)

The analytical determination of Hg(II), Cu(II), Cd(II), As(III), Sb(III), Ti(IV) and U(VI) in the presence of Fe(III) and 1 M H₂SO₄ are investigated using the polarographic technique. The wave corresponding to the reduction of Fe(III) to Fe(II) was found to be completely suppressed by the addition of 1% pyrogallol. Thus, different mixtures of these elements, viz. Hg(II), Cu(II), Cd(II), As(III) and Fe(III)-mixture (A), Cu(II), Cd(II), Sb(III), As(III) and Fe(III)-mixture (B), and Cu(II), Cd(II), Ti(IV), U(VI) and Fe(III)-mixture (C), were quantitatively determined using 1% pyrogallol and 1 M H₂SO₄ as supporting electrolyte. The i₁/c results give excellent correlations in each case, as indicated from the results of leastsquares regression analysis.     

Determination of trace Pb(Ⅱ), Cd(Ⅱ) and Zn(Ⅱ) using differential pulse stripping voltammetry without Hg modification

In this work,we reported a simultaneous determination approach for Pb(II),Cd(II)and Zn(II)atμg L 1concentration levels using differential pulse stripping voltammetry on a bismuth film electrode(BiFE).The BiFE could be prepared in situ when the sample solution contained a suitable amount of Bi(NO)3,and its analytical performance was evaluated for the simultaneous determination of Pb(II),Cd(II)and Zn(II)in solutions.The determination limits were found to be 0.19μg L 1for Zn(II),and0.28μg L 1for Pb(II)and Cd(II),with a preconcentration time of 300 s.The BiFE approach was successfully applied to determine Pb(II),Cd(II)and Zn(II)in tea leaf and infusion samples,and the results were in agreement with those obtained using an atomic absorption spectrometry approach.Without Hg usage,the in situ preparation for BiFE supplied a green and acceptability sensitive method for the determination of the heavy metal ions.     

Chelating resins for the concentration of trace elements from sea water and their analytical use in conjunction with atomic absorption spectrophotometry

An investigation has been made of the uptake of trace elements from both distilled water and sea water by the chelating ion-exchange resins Chelex-100 and Permutit S1005. The resins retained the following elements with an efficiency of ca. 100%: Ag, Bi, Cd, Cu, In, Pb, Mo, Ni, rare earths, Re (90% only), Sc, Th, W, V, Y and Zn. Manganese was retained quantitatively only by the Chelex resin. The following elements are removed with 100% efficiency by means of₂N mineral acids: Bi, Cd, Co, Cu, In, Ni, Pb, rare earths, Sc, Th, Y and Zn. Ammonia (4 N) completely removes molybdenum, tungsten, vanadium and rhenium. The resins have been used in conjunction with atomic absorption spectrophotometry for the simultaneous determination of zinc, cadmium, copper, nickel and cobalt in sea waters.     

Fullerene-based anodic stripping voltammetry for simultaneous determination of Hg(II), Cu(II), Pb(II) and Cd(II) in foodstuff

Various carbon nanomaterials for use in anodic stripping voltammetric analysis of Hg(II), Cu(II), Pb(II) and Cd(II) are screened. Graphene, carbon nanotubes, carbon nanofibers and fullerene (C₆₀), dispersed in chitosan (Chit) aqueous solution, are used to modify a glassy carbon electrode (GCE). The fullerene-chitosan modified GCE (C₆₀-Chit/GCE) displays superior performance in terms of simultaneous determination of the above ions. The electrodes and materials are characterized by electrochemical impedance spectroscopy, cyclic voltammetry, scanning electron microscopy, Raman spectroscopy, X-ray diffraction and X-ray photoelectron spectroscopy. The excellent performance of C₆₀-Chit/GCE is attributed to the good electrical conductivity, large surface area, strong adsorption affinity and unique crystalline structure of C₆₀. Using differential pulse anodic stripping voltammetry, the assay has the following features for Hg(II), Cu(II), Pb(II) and Cd(II), respectively: (a) Peak voltages of +0.14, ?0.11, ?0.58 and???0.82 V (vs SCE); (b) linear ranges extending from 0.01–6.0 μM, 0.05–6.0 μM, 0.005–6.0 μM and 0.5–9.0 μM; and (c), detection limits (3σ method) of 3 nM (0.6 ppb), 14 nM (0.9 ppb), 1 nM (0.2 ppb) and 21 nM (2.4 ppb). Moreover, the modified GCE is well reproducible and suitable for long-term usage. The method was successfully applied to the simultaneous determination of these ions in spiked foodstuff.

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Graphical abstract Compared with graphene, carbon nanotubes and carbon nanofibers, an electrode modified with fullerene in chitosan electrode displays superior performance for the simultaneous anodic stripping voltammetric detection of Hg(II), Cu(II), Pb(II) and Cd(II).

     

Oximidobenzotetronic acid as a reagent for the separation and gravimetric determination of palladium and cobalt

Oximidobenzotetronic acid is recommended for the separation and gravimetric determination of palladium and cobalt An ethanolic solution of the reagent quantitatively precipitates palladium(II) from solutions which are 0.75 N in acid up to pH 5.1, the complex is weighed as Pd(C₉H₅NO₄)₂. Cobalt(II) can be determined in the filtrate after the precipitation of palladium. With 0.5 N acid solutions, no interference was found from Pt(IV), Ir(IV), Rh(III), Ru(III), Os(IV), Au(III), Ag(I), Cu(II), Fe(III), Ni(II), Hg(II). Pb(II), Bi(III), Cd(II), As(V), Se(VI), Te(IV), Mo(VI), Sb(III), Al(III), Cr(III), Zn(II), Ti(IV), Zr(IV). acetate, oxalate, citrate, tartrate, phosphate and fluoride.     

Thermal Decomposition of Bi(III), Cd(II), Pb(II) and Cu(II) Thiocyanates

Thermal decomposition of Bi(SCN)₃, Cd(SCN)₂, Pb(SCN)₂ and Cu(SCN)₂ has been studied. The thermal analysis curves and the diffraction patterns of the solid intermediate and final products of the pyrolysis are presented. The gaseous products of the decomposition (SO₂ and CO₂) were detected and quantitatively determined. Thermal, X-ray and chemical analyses have been used to establish the nature of the reactions occurring at each stage in the decomposition.This revised version was published online in November 2005 with corrections to the Cover Date.     

Ligandless cloud point extraction of Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II) ions in environmental samples with Tween 80 and flame atomic absorption spectrometric determination

A cloud point extraction (CPE) procedure has been developed for the determination trace amounts of Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II) ions by using flame atomic absorption spectrometry. The proposed cloud point extraction method was based on cloud point extraction of analyte metal ions without ligand using Tween 80 as surfactant. The surfactant-rich phase was dissolved with 1.0 mL 1.0 mol L⁻¹ HNO₃ in methanol to decrease the viscosity. The analytical parameters were investigated such as pH, surfactant concentration, incubation temperature, and sample volume, etc. Accuracy of method was checked analysis by reference material and spiked samples. Developed method was applied to several matrices such as water, food and pharmaceutical samples. The detection limits of proposed method were calculated 2.8, 7.2, 0.4, 1.1, 0.8 and 1.7 μg L⁻¹ for Cr(III), Pb(II), Cu(II), Ni(II), Bi(III), and Cd(II), respectively.     

Synthesis and characterization of some metal complexes of cystine: [Mn(C6H10N2O4S2)]; where MII = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II) and Pb(II)

Cystine forms metal complexes of general formula [M^II(C₆H₁₀N₂O₄S₂)]; where M^II = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hg(II), and Pb(II) in the aqueous medium. Before reacting with metal salts the ligand solution was neutralized by NaHCO₃ solution. The complexes were formulated by comparing the C, H, N, S and metal analysis data. The prepared complexes were characterized by different physicochemical methods. The UV-vis, FTIR spectral analysis, magnetic susceptibility of these complexes are discussed. Cyclic voltammetric studies of some of the complexes are also reported.     

Potentiometric Studies of Some Bivalent Metal Ion Complexes of a New Ligand,o-(2-Thiazolylazo)-4-Ethylphenol

Abstract

The complexations of a new ligand, o-(2-thiazolylazo)-4-ethylphenol(TAEP) with Ca(II), Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II), Hq(II) and Pb(II) have been studied by potentiometric titrations, at 25.0 ± 0.2°C and an ionic strength of 0.1 in 30% v/v dioxane-water mixture. The dissociation constant and spectral data of TAEP and formation constants of the complexes containing various molar ratios of metal ion to ligand, are reported. It is observed that Ca(II) forms only an ML complex in any molar ratios, whereas other metal ions react in two steps forming ML and ML₂ complexes in a 1:3 molar ratio. In the case of 1:1 and 1:2 molar ratios, Mn(II), Co(II), Cd(II) and Hg(II) seemed to form bi- or poly-nuclear complexes because of slightly different formation curves from those of 1:3 molar ratio. The sequence of the first successive formation constant is Cu > Hg > Ni > Pb > Co > Zn > Cd > Mn > Ca, showing Mellor-Maley's order. Further correlation is shown between the formation constants and the second ionization potentials of the metals.     

Liquid-state mercury(II) ion-selective electrode based on N-(O,O-diisopropylthiophosphoryl)thiobenzamide

A liquid ion-exchange electrode containing a complex of mercury(II) with N-(O,O-diisopropylthiophosphoryl)thiobenzamide in carbon tetrachloride is described. The electrode shows excellent sensitivity and good selectivity. The slope of the calibration graph is 29.0 mV/pHg²⁺ in the pHg²⁺ in the pHg²⁺ range 2–15.2 in mercury(II) ion buffers. The electrode can be used for determination of 5 × 10^?5–10^?2 M Hg(II) in the presence of 10^?2 M Cu(II), Ni(II), Co(II), Zn(II), Pb(II), Cd(II), Mn(II), Fe(III), Cr(III), Bi(III) or Al(III) ions and in the presence of 10^?3 M Ag(I) ions. It can bealso used for end-point detection in titrations with EDTA of 10^?3–10^?4 M mercury(II) at pH 2.     

Copper Sensing in Alkaline Electrolyte Using Anodic Stripping Voltammetry by Means of a Lead Mediator

Anodic stripping voltammetry (ASV) is an analysis technique that permits the selective and quantitative analysis of metal ion species in solution. It is most commonly applied in neutral to acidic electrolyte largely due to inherent metal ion solubility. Bismuth (Bi) is a common film used for ASV due to its good sensitivity, overall stability and insensitivity to O₂. ASV, utilizing a Bi film, along with cadmium (Cd) and lead (Pb) as the plating mediators, has recently been adapted to determine zinc (Zn) concentrations in highly alkaline environments (30 % NaOH or 35 % M KOH). Successful analysis of Zn in alkaline relies on the ability of the hydroxide to form soluble metal anion species, such as Bi(OH)₄⁻ and Zn(OH)₄²⁻. Here, we look to extend this technique to detect and quantify copper (Cu) ions in these highly basic electrolytes. However, in general, the use of ASV to detect and quantify Cu ion concentrations is notoriously difficult as the Cu stripping peak potential overlays with that of Bi from the common Bi film electrode. Here, an ASV method for determining Cu concentration in alkaline solutions is developed utilizing Pb as a deposition mediator. As such, it was found that when analyzing Cu solutions in the presence of Pb, the stripping voltammetry curves present separate and defined Cu stripping peaks. Different analyzes were made to find the best stripping voltammetry performance conditions. As such, an accumulation time of 5 minutes, an accumulation potential of≤−1.45 V vs. Hg/HgO, and a concentration of 35 wt% KOH were determined to be the conditions that presented the best ASV results. Utilizing these conditions, calibration curves in the presence of 5.0 ppm Pb showed the best linear stripping signal correlation with an r‐squared value of 0.991 and a limit of detection (LOD) of 0.67 ppm. These results give way to evaluating Cu concentrations using ASV in aqueous alkaline solutions.     

Solid phase extraction and diffusive gradients in thin films techniques for determination of total and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) in Black Sea water

Total dissolved and labile concentrations of Cd(II), Cu(II), Ni(II) and Pb(II) were determined at six locations of the Bourgas Gulf of the Bulgarian Black Sea coast. Solid phase extraction procedure based on monodisperse, submicrometer silica spheres modified with 3-aminopropyltrimethoxysilane followed by the electrothermal atomic absorption spectrometry (ETAAS) was developed and applied to quantify the total dissolved metal concentrations in sea water. Quantitative sorption of Cd, Cu, Ni and Pb was achieved in the pH range 7.5–8, for 30?min, adsorbed elements were easily eluted with 2?mL 2?mol?L^?1 HNO₃. Since the optimal pH for quantitative sorption coincides with typical pH of Black Sea water (7.9–8.2), on-site pre-concentration of the analytes without any additional treatment was possible. Detection limits achieved for total dissolved metal quantification were: Cd 0.002?µg?L^?1, Cu 0.005?µg?L^?1, Ni 0.03?µg?L^?1, Pb 0.02?µg?L^?1 and relative standard deviations varied from 5–13% for all studied elements (for typical Cd, Cu, Ni and Pb concentrations in Black Sea water). Open pore diffusive gradients in thin films (DGT) technique was employed for in-situ sampling and pre-concentration of the sea water and in combination with ETAAS was used to determine the proportion of dynamic (mobile and kinetically labile) species of Cd(II), Cu(II), Ni(II) and Pb(II) in the sea water. Obtained results showed strong complexation for Cu and Pb with sea water dissolved organic matter. The ratios between DGT-labile and total dissolved concentrations found for Cu(II) and Pb(II) were in the range 0.2–0.4. For Cd and Ni, these ratios varied from 0.6 to 0.8, suggesting higher degree of free and kinetically labile species of these metals in sea water.     

Model peptides based on the binding loop of the copper metallochaperone Atx1: selectivity of the consensus sequence MxCxxC for metal ions Hg(II), Cu(I), Cd(II), Pb(II), and Zn(II)

The amino acid sequence MxCxxC is conserved in many soft-metal transporters that are involved in the control of the intracellular concentration of ions such as Cu(I), Hg(II), Zn(II), Cd(II), and Pb(II). A relevant task is thus the selectivity of the motif MxCxxC for these different metal ions. To analyze the coordination properties and the selectivity of this consensus sequence, we have designed two model peptides that mimic the binding loop of the copper chaperone Atx1: the cyclic peptide P(C) c(GMTCSGCSRP) and its linear analogue P(L) (Ac-MTCSGCSRPG-NH2). By using complementary analytical and spectroscopic methods, we have demonstrated that 1:1 complexes are obtained with Cu(I) and Hg(II), whereas 1:1 and 1:2 (M:P) species are successively formed with Zn(II), Cd(II), and Pb(II). The complexation properties of the cyclic and linear peptides are very close, but the cyclic compound provides systematically higher affinity constants than its unstructured analogue. The introduction of a xPGx motif that forms a type II beta turn in P(C) induces a preorganization of the binding loop of the peptide that enhances the stabilities of the complexes (up to 2 orders of magnitude difference for the Hg complexes). The affinity constants were measured in the absence of any reducing agent that would compete with the peptides and range in the order Hg(II) > Cu(I) > Cd(II) > Pb(II) > Zn(II). This sequence is thus highly selective for Cu(I) compared to the essential ion Zn(II) that could compete in vivo or compared to the toxic ions Cd(II) and Pb(II). Only Hg(II) may be an efficient competitor of Cu(I) for binding to the MxCxxC motif in metalloproteins.     

Preconcentration of trace metals from acidic solutions by coprecipitation with dithizone

Traces of Ag, Bi, Cd, Cu, Hg, Pb, Pd and Zn are separated by carrier precipitation with dithizone from diluted HNO₃ and HCl solutions. The separated trace elements are determined by flame AAS and/or by spectrophotometry. The preconcentration recovery is dependent on the acid concentration of the sample solution. The amount of dithizone precipitated is optimized. The detection limits (ng/ml) are 15.0 (Pb, Zn), 12.0 (Pd), 10.0 (Bi), 6.0 (Ag), 5.0 (Hg), 2.0 (Cu) and 1.0 (Cd). Aluminium, aluminium sulfate and gallium are analyzed with the method. The accuracy of the results was checked by differential pulse voltammetry.     

Complexes of dicamba with cadmium(II), copper(II), mercury(II), lead(II) and zinc(II)

New solid complexes of a herbicide known as dicamba (3,6-dichloro-2-methoxybenzoic acid) with Pb(II), Cd(II), Cu(II) and Hg(II) of the general formula M(dicamba)₂·xH₂O (M=metal, x=0-2) and Zn₂(OH)(dicamba)₃·2H₂O have been prepared and studied. The complexes have different crystal structures. The carboxylate groups in the lead, cadmium and copper complexes are bidentate, chelating, symmetrical, in Hg(dicamba)₂·2H₂O - unidentate, and in the zinc salt - bidentate, bridging, symmetrical. The anhydrous compounds decompose in three stages, except for the lead salt whose decomposition proceeds in four stages. The main gaseous decomposition products are CO₂, CH₃OH, HCl and H₂O. Trace amounts of compounds containing an aromatic ring were also detected. The final solid decomposition products are oxychlorides of metals and CuO. This revised version was published online in July 2006 with corrections to the Cover Date.