On the reaction between iodide and mercury(II)

A survey on the iodide-mercury(II) reaction and its analytical uses is given. Titrations of iodide with mercury(II) in various acidities, using nitrate, acetate, and chloride as titrants and silver or platinum amalgam as the indicator electrode, showed that mercury(II) nitrate is the best titrant giving 0.46 V/0.1 ml potential break in comparison with 0.14 V/0.1 ml of mercury(II) chloride and 0.35V/0.1 ml of mercury(II) acetate, all titrants being 0.05 M in mercury(II).     

Radiation chemistry of Cu(II) tetrasulfophthalocyanine in water-methanol system

The effect of ionising radiation on copper(II) phthalocyanine 3,4′,4′′,4′′′ tetrasulfonic acid, tetrasodium salt (Cu(II)tspc^4-) in aqueous as well as in water-methanol solutions has been studied. The determined yields of complex decomposition (measured on the basis of absorption decay) depend on the composition of matrices and the dose applied. The rate constant of electron scavenging by Cu(II)tspc^4-, k = (1.3 ± 0.1) × 10¹⁰ M^-1 s^-1 in methanol-water (2:8 v/v) solutions has been determined using the pulse radiolysis technique. The rate constant k = (1.16 ± 0.1) × 10¹⁰ M^-1 s^-1 of scavenging of OH radicals applying the competion method with p-nitrosodimethylaniline (pNDA) has been determined in aqueous solutions.     

The investigation of the adsorptive behaviour of electroactive species by means of admittance analysis: Part II. Anion-induced adsorption of cadmium(II) from bromide and iodide solutions at the dropping mercury electrode

The adsorption of Cd(II) has been studied by measuring the interfacial admittance spectra at different dc potentials of the dropping mercury electrode (DME) in solutions of: (a) 1 M KBr+0.48 mM Cd(NO₃)₂,(b) 1 M KI+0.105 mM CdI₂ and (c) 0.1 M NaI+0.9 M NaClO₄ +0.116 mM CdI₂ The experimental data were analysed using the procedures described in Part I of this series. The frequency dependence of the admittance corresponds to that of a reversible electrode reaction with reactant adsorption. The potential dependence of the resulting adsorption parameters can be mathematically described by a Langmuir isotherm for adsorption of Cd(II) with the adsorption energy being at least a quadratic function of potential. Detailed checks on the consistency of this model have been applied and were found to be satisfactory.     

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.     

Electrometric study of uranyl(II) and beryllium(II) complexes of 2,2′-dimercapto diethyl ether

Complexation of uranyl(II) and beryllium(II) ions with 2,2′-dimercaptodiethyl ether has been studied in 40% ethanolic media by potentiometric and conductometric titration techniques revealing the formation of an 1∶1 complex in either case. The stability constants of the complexes have been determined at ionic strength μ=0.1M (NaClO₄) by applyingCalvin andMelchior's extension ofBjerrum's method. LogK _stab values are found to be 12.60, 11.96 at 25 °C and 12.55, 11.90 at 35 °C respectively. The values of ΔG, ΔH and ΔS for the complexation reactions determined at 25 °C are also reported.     

Etude des complexes sulfosalicylate de cuivre(III), nickel(II), cobalt(II) et uranyle(II) a l'aide d'une resine echangeuse de cations: Study of the sulphosalicylate complexes ofcopper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.

Study of the sulphosalicylate complexes of copper(II), nickel(II), cobalt(II) and uranyl(II) by means of cation-exchange resins.The conditional stability constants of the 1:1 complexes of the sulphosalicylate ions (L^3-) with copper(II), nickel(II), cobalt(II) and uranyl ions have been determined in a sodium perchlorate solution (0.1 M) and at various pH values by a cation-exchange method based on Schubert's procedure. The limits of application of the method are discussed. The variation with pH of the conditional stability constants can be explained by the existence of the complexes: CuH₂L, CuHL, CuL^-; NiH₂L⁺, NiHL, NiL^-; CoHL, CoL^-; UO₂H₂L⁺, UO₂HL, UO₂L^-, UO₂LOH^2-. The stability constants of these complexes are reported. Distribution diagrams of the various complexes of each element with pH and total concentration of sulphosalicylate parameters are given.     

THE INTERACTION OF 2-AMINO-2-HYDROXYMETHYL-1,3-PROPANEDIOL WITH COBALT(II) AND MANGANESE(II) IONS

Abstract

The stepwise complex formation between 2-amino-2-hydroxymethyl-1,3-propanediol (TRIS) with Co(II) and Mn(II) was studied by potentiometry at constant ionic strength 2.0 M (NaClO₄) and T = (25.0 ± 0.1)°C, from pH measurements. Data of average ligand number (Bjerrum's function) were obtained from such measurements followed by integration to obtain Leden's function, F ₀(L). Graphical treatment and matrix solution of simultaneous equations have shown two overall stability constants of mononuclear stepwise complexes for the Mn(II)/TRIS system (β₁ = (5.04 ± 0.02) M^?1 and β₂ = (5.4 ± 0.5) M^?2) and three for the Co(II)/TRIS system (β₁ = (1.67 ± 0.02) × 10² M^?1, β₂ = (7.01 ± 0.05) × 10³ M^?2 and β₃ = (2.4 ± 0.4) × 10⁴ M^?3). Slow spontaneous oxidation of Co(II) solutions by dissolved oxygen, accelerated by S(IV), occurs in a buffer solution TRIS/HTRIS⁺ 0.010/0.030 M, with a synergistic effect of Mn(II).     

Binding studies on substituted benzoic acids: Part I. 3,5-dinitrosalicylic acid—acid dissociation and complexation with nickel(II) and cobalt(II)

The values of pK₁ and pK₂ for 3,5-dinitrosalicylic acid (DNSA, H₂L) have been determined at 25.0°C and 0.1 M ionic strength (sodium perchlorate) as 0.25 and 7.20. respectively. The binding of nickel(II) and cobalt(II) has been investigated over the pH range 1.0–7.0 at the same temperature and ionic strength. Values of log K_ML for the formation of the unprotonated complexes are 4.05±01 and 3.82±01 for nickel(II) and coball(ll) respectively. Values for log K_MHL are close to 11 mol^-1 for both metals; it seems probable that these species are not inner-sphere complexes, and possible reasons for this are suggested. The stability constants obtained are compared with others in the literature, and the possibility of using DNSA as a metal-ion indicator is discussed briefly.     

Characteristics of a new catalytic hydrogen current observed with albumin in the presence of cobalt(III) or (II) at the hanging mercury drop electrode

When the hanging mercury drop electrode (HMDE) is placed in a solution which is 0.1 M in ammonia and 0.1 M in ammonium chloride and about 5 to 10×10^?4M in cobalt(III)-hexamine or cobalt(II) chloride and in very small concentrations of bovine serum albumin (BSA), the protein is slowly adsorbed. When the adsorption is highly incomplete and the HMDE is kept for 30 s at about ?1.05 V vs. SCE, “active cobalt’ is deposited as a complex (Co(0)BSA). This is anodically oxidized at about 0.0 V to unstable Co(I)BSA). When the electrode is then rapidly (500 mV s^?1) cathodized, a catalytic hydrogen current (i_c) with peak at circa ?1.45 V is observed. In this way it is even possible to detect and estimate BSA in concentrations of the order of 10^?12M. A detailed study has been made of the characteristics of i_c under several conditions. “Active cobalt” on the HMDE does not affect Brdi?ka currents. Cystine and cysteine also yield the catalytic hydrogen current i_c under the same conditions as does BSA.     

Functionalized di- and tetrathia-crowns and their use to quantitatively separate and recover gold(III), palladium(II), silver(I) and mercury(II) Ions

Two new dithia-crowns containing a hydroxy group and 1,4,7,10-tetrathia-18-crown-6 containing an allyl-oxymethyl substituent were prepared in good yields. Two of these crowns were covalently attached to silica gel. The silica gel-bound thia-crowns were used to separate gold( III ), palladium( II ), silver( I ) and mercury( II ) ions from an aqueous 0.1 M nitric acid solution which also contained 1.0 M ferric chloride.     

Influence of cyanide and sulphide ions on the reduction and reoxidation of cobalt(II) in thiocyanate solution at mercury electrodes

The process of reduction and reoxidation of cobalt(II) in thiocyanate solution at hanging mercury drop electrode has been investigated by cyclic voltammetric, chronoamperometric and anodic stripping methods. In 0.1 M NaSCN and 0.4 M NaClO₄ solution containing 1×10^?3M cobalt(II), the voltammogram on the first cycle at 0.05 V s^?1 gives a cathodic peak at ?1.06 V with hysteresis on reversal, and an anodic wave with a peak potential of ?0.28 V and with two shoulders near ?0.38 and ?0.45 V, respectively. Multicyclic voltammograms under the same conditions give a cathodic peak at ?0.90 V and an anodic peak at ?0.45 V. The reduction and reoxidation of cobalt(II) in thiocyanate solution is accelerated by the reduction products of thiocyanate ion, cyanide and sulphide ions, which are produced during the electroreduction of cobalt(II).A mechanism of reduction and reoxidation of cobalt(II) which involves a chemical reduction of thiocyanate ion by electroreduced metallic cobalt and takes into account cyanide and sulphide ions is proposed. The hysteresis on the cathodic wave is caused by the difference in reduction potentials of cobalt(II)-thiocyanate and-cyanide complexes. Cyclic voltammetric study of cobalt(II) in perchlorate solution containing trace amounts of cyanide and sulphide ions supports these conclusions.     

1,8-dihydroxyanthraquinone-Mg(II) complex: II. Spectrophotometric study. Determination of Mg(II)

The 1,8-dihydroxyanthraquinone (1,8-DHAn) shows a colored and fluorescent reaction with the ion Mg(II) in a hydroalcoholic and ammonical medium.In the present work we have studied spectrophotometrically the 1,8-DHAn-Mg(II) complex in a hydroethanolic and ammonical, 8 × 10^?4M medium. We found that the complex shows a maximum absorbance at 510 nm, and obeys a 1:1 stoichiometry with log K of 4.08.We propose a new method for the spectrophotometric determination of Mg(II) which is valid for concentrations between 0.25 and 2.00 ppm, and yields an error of 1.32%.     

Potentiometric and spectrometric study: Copper(II), nickel(II) and zinc(II) complexes with potentially tridentate and monodentate ligands

Equilibrium and solution structural study of mixed-metal-mixed-ligand complexes of Cu(II), Ni(II) and Zn(II) with L-cysteine, L-threonine and imidazole are conducted in aqueous solution by potentiometry and spectrophotometry. Stability constants of the binary, ternary and quaternary complexes are determined at 25 ±1°C and in I= 0.1 M NaClO₄. The results of these two methods are made selfconsistent, then rationalized assuming an equilibrium model including the species H₃A, H₂A, A, BH, B, M(OH), M(OH)₂, M(A), MA(OH), M(B), M(A)(B), M₂(A)₂(B), M₂(A)₂(B-H), M¹M²(A)₂(B) and M¹M²(A)₂(B-H) (where the charges of the species have been ignored for the sake of simplicity) (A = L-cysteine, L-threonine, salicylglycine, salicylvaline and BH = imidazole). Evidence of the deprotonation of BH ligand is available at alkalinepH. N₁H deprotonation of the bidentate coordinated imidazole ligand in the binuclear species atpH > 70 is evident from spectral measurements. Stability constants of binary M(A), M(B) and ternary M(A)(B) complexes follow the Irving-Williams order.     

Synthesis and spectroscopic,magnetic and cyclic voltammetric characterization of some metal complexes of methionine: [(C5H10NO2S)2MII]; MII = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II)

Some metal complexes of DL–methionine were prepared in aqueous medium and characterized by different physico-chemical methods. Methionine forms 1:2 complexes with metal, M(II). The general empirical formula of the complexes is proposed as [(C₅H₁₀NO₂S)₂M^II]; where M^II = Mn(II), Co(II), Ni(II), Cu(II), Zn(II), Cd(II) and Hg(II). All the complexes are extremely stable in light and air and optically inactive. Magnetic susceptibility data of the complexes demonstrate that they are high spin paramagnetic complex except Zn(II), Cd(II) and Hg(II) complexes. The bonding pattern in the complexes are similar to each other as indicated by electronic absorption spectra and FTIR spectral analysis. The current potential data, peak separation (AE) and the peak current ratio (i_pa/i_pc) of the (Mn, Cu and Cd) complexes indicate that the charge transfer processes are irreversible, the systems are diffusion controlled and also adsorptive controlled. The charge transfer rate constant of metals in their complexes are less than those in their metal salts at identical experimental conditions due to the coordination of metal with methionine.     

An interpretation of the polarized crystal spectra of Mn(II) and Co(II) in D2h symmetry

Crystals of TMAM_xM′_1?xCl₃ · 2H₂O where TMA = (CH₃)₃NH⁺ and M = Mn²⁺, M′ = Co²⁺ are strikingly pleochroic. The polarized spectra of these highly colored orthorhombic salts are reported and transition assignments are made based on D_2h symmetry. Peaks in the Mn(II) spectra are explained as electric dipole transitions while peaks in the Co(II) spectra are explained as magnetic dipole transitions.     

Effect of halides and alkali cations on the Zn(Hg)/Zn(II) electrode reactions

The title subject has been studied by galvanostatic single-pulse, chronopotentiometric and equilibrium measurements on the Zn(Hg)/Zn(II) electrode in x M KI+(1?x) M KCl (x from 0 to 1), 1 M KBr and 1 M MeCl (Me=Li, Na, K and Cs) solutions of pH 3 at 25°C. Quantitative information about the effect of specifically adsorbed halides on the rates of the Zn(II)/Zn(I) and the Zn(I)/Zn(Hg) steps is obtained separately (for the latter step mainly at potentials near ?1.0 V(SCE)), and the latter step seems to be more influenced than the former by the adsorption. An attempt is made to correlate the adsorption effect on the rate of the Zn(II)/Zn(I) step to double-layer parameters according to recent models for such effects. The extra current observed at potentials where the halides are adsorbed, seems to vary with the surface activity of the specifically adsorbed ion. The lack of any observed kinetic effect of Cs⁺, which is specifically adsorbed at these potentials, is possibly due to the Cs⁺ specific adsorption enhancing the Cl^? specific adsorption and vice versa, so that the decelerating and accelerating effects by these ions may cancel each other.     

Maleates of Mn(II), Fe(II), Co(II), and Ni(II) as precursors for synthesis of metal-polymer composites

Comparison was made for the structural, IR spectral, and thermoanalytical characteristics of normal [M₁(H₂O)₂(C₄H₂O₄)](H₂O) (M₁ = Co(II) and Ni(II)) and acid maleates [M₂(H₂O)₄(C₄H₃O₄)₂] (M₂ = Mn(II), Fe(II), Co(II) and Ni(II)). Only structures of acid maleates contain intramolecular asymmetric hydrogen bond whose asymmetry increases in the series of transition metal salts. Thermal decomposition of Co(II), Ni(II) normal maleates, and Mn(II), Fe(II), Co(II), Ni(II) acid maleates proceeds in three stages. Onset decomposition temperatures for the first and second stages decreases in the series of normal maleates Co(II) ≥ Ni(II) and increases in the series of acid maleates Fe(II) < Co(II) < Ni(II) ≈ Mn(II). Onset temperature of the third stage decreases in the series of both normal maleates Co(II) > Ni(II) and acid maleates Mn(II) > Fe(II) > Co(II) > Ni(II).     

Equilibrium study on Cd(II) and Zn(II) chelates of mercapto carboxylic acids

Cadmium(II) and zinc(II) complexes with the chelating agents meso-2,3-dimercapto succinic acid, meso-monomethyl dimercapto succinate, meso-dimethyl dimercapto succinate and the related methylmercapto acetate and mercapto succinic acid were studied potentiometrically in 0.1 M KCl at 25 °C. Models and hypotheses of coordination for the solution complexes are proposed. IR characterisation and stoichiometry of the solid state compounds evaluated by elemental analysis are presented. The obtained formation constants, together with the previously measured ionisation constants of the ligands, were used to compute pCd and pZn values and then to evaluate the effectiveness of the studied chelating agents in binding Cd(II) and Zn(II) in intoxication treatments.     

Single-ion activities and Mn(Hg)/Mn(II) reactions in aqueous solutions of alkaline-earth chlorides

Combined thermodynamic and kinetic studies have yielded convenient single-ion activity coefficients for manganese(II), alkaline-earth, and chloride ions and standard exchange currents for the two steps of the Mn(Hg)/Mn(II) electrode in 0.005 M MnCl₂+0.495 M MeCl₂ (for Me=Mg, Ca, Sr, Ba, and Mn) at 25°C. The results indicate that the fall in mean ionic activity coefficient for the alkaline-earth chlorides along the sequence from magnesium to barium is carried to a larger extent by the cation than by the anion, that also the activity coefficient for the minority cation Mn(II) falls along this sequence, and that other than activity-coefficient effects on the Mn(Hg)/Mn(II) reactions appear only with barium ions, which retard the reactions additionally. The results are discussed with emphasis on ionic interactions and double-layer effects.     

Complexation of [S,S,S]- and [R,S,R]-isomers of N-bis [2-(1,2-dicarboxyethoxy)ethyl] aspartic acid with Mg(II), Ca(II), Mn(II), Fe(III), Cu(II) and Zn(II) ions in aqueous solution

In a search for environmentally friendly metal chelating ligands for industrial applications, the protonation and complex formation equilibria of [S,S,S]- and [R,S,R]-isomers of N-bis[2-(1,2-dicarboxyethoxy)ethyl] aspartic acid (BCA6) with Mg(II), Ca(II), Mn(II), Fe(III), Cu(II) and Zn(II) ions in aqueous 0.1 M NaCl solution were studied at 25°C by potentiometric titration. The model for complexation and the stability constants of the different complexes were determined for each metal ion using the computer program SUPERQUAD. With all metal ions (M ⁿ⁺), stable ML ^n?6 complexes dominated complex formation for both isomers. Differences in complexation models were found for binuclear species.