Formation Of Complex Anions Research Articles

Effect of Ultrasound on the Kinetics of the Dissolution of Crystalline Iodine in Ethanol

The effect ultrasound has on the kinetics of crystalline iodine solvation in ethanol is studied using data from UV absorption spectra. It is shown that treatment with ultrasound greatly accelerates the chemical reaction associated with the formation of complex anions $${\text{I}}_{3}^{ - }$$ .

Calorimetric study of melts in the system KF - K2TaF7

Abstract Enthalpy increment measurements on melts in the system KF-K2TaF7 were carried out by drop calorimetry at temperatures between 298 K and 1063, 1103 and 1143 K for selected compositions. Heat capacities of the melted mixtures and enthalpies of mixing have been determined. Careful calorimetric experiments showed small but distinct non-ideality of the melt. The molar heat capacity of melt exhibits small positive divergence from additivity. The molar enthalpy of mixing shows negative deviation from ideality which decreases with increasing temperature. The thermal effect at mixing was assigned predominantly to association reactions producing more complex fluorotantalate anions. The formation of complex anions with lower coordination number of Ta may not be excluded.

Influence of solution pH and background electrolytes on heavy metals ion adsorption by activated carbons from aqueous solutions

The adsorption of cadmium and zinc ions, IIb family heavy metals, from aqueous solutions onto the two activated carbons of different surface nature, one with acidic functional groups prepared by 95°C concentrated nitric acid oxidation (oxidized carbon) and the other with no acidic functional group treated at 1000°C in helium flow (out-gassed carbon), was investigated to clarify the influence of background electrolyte on the adsorption performance. The cadmium uptake onto oxidized carbon was found to be decreased under the coexistence of NaCl, because Na+ occupied adsorption sites for cadmium. For the out-gassed carbon, the cadmium uptake was increased at low pH due to the formation of complex anions of CdCl3− and CdCl42−, but zinc uptake was not changed any PH, because chloride anions could not make complex with zinc ions. Under the coexistence of NaNO3, the increase in cadmium uptake to the out-gassed carbon was not observed because the complex is no longer formed with nitrate anions for cadmium. At simultaneous adsorption of cadmium and zinc ions to the outgassed carbon under the coexistence of NaCl, only cadmium could be adsorbed at low pH as expected. The results suggest that the separation of these IIb family ions may be achieved using out-gassed carbon.

Density and Surface Tension of the System KF–K2TaF7–Ta2O5

The density of the system KF–K2TaF7–Ta2O5 was measured by the Archimedean method and the surface tension by the maximum bubble pressure method in the composition range up to 20 mol% Ta2O5. The density in the system KF–K2TaF7–Ta2O5 increases from KF through K2TaF7 to Ta2O5 and the surface tension increases from K2TaF7 through KF to Ta2O5. Based on the measured density values, the molar volumes of the binary and ternary melts at 860 °C, 900 °C and 950 °C were calculated as well as the partial molar volumes of particular components in different binaries. The small negative deviation from ideal behaviour in the binary system KF–K2TaF7 was identified by the calculation of the molar excess volume. The formation of complex anions [TaF8]3− is expected in this binary system. The surface tension decreases monotonically from KF to K2TaF7 in the binary system KF–K2TaF7. In the next two binaries KF–Ta2O5 and K2TaF7–Ta2O5 decrease of the surface tension was observed with the initial addition of Ta2O5 followed by the increase of the surface tension by further addition of Ta2O5. Based on measured data it was concluded that in binaries KF–Ta2O5 and K2TaF7–Ta2O5 the surface active component is Ta2O5 and in the binary KF–K2TaF7 the surface active component is K2TaF7. Mathematical description of the concentration dependence of the molar volume and surface tension of the measured ternary system was done by the polynomial function at 860°C, 900°C, and at 950°C.

Complex formation in electrolyte solutions in the course of plating protective coatings on titanium

Conditions for complex formation in aqueous electrolyte solutions containing salts of aluminum and hydroxy carboxylic acids were studied by 2 7Al and 1 9F NMR spectroscopy. The formation of complex anions in the electrolytes at various pH and their discharge on the anode under conditions of a microplasma process allowed preparation of surface layers containing α-Al2O3 on VT1-0 titanium. The interrelation between the composition and properties of the coatings was studied.

Thermodynamic and structural aspects of electrochemical deposition of metals and binary compounds in molten salts

The influence of the ionic structure of electrolytes used in the electrodeposition of molybdenum, titanium and aluminium on the mechanism and kinetics of metal deposition is discussed. Using electrochemical methods of study and a complex thermodynamic and physico-chemical analysis it was determined that in all the electrolytes investigated the electro-deposition process is significantly facilitated by the formation of complex anions with lower symmetry of the co-ordination sphere. In the case of molybdenum deposition, complex heteropolyanions are probably created in the melt by the addition of B 2O 3 or SiO 2 to the K 2MoO 4-based electrolytes. The electrodeposition of titanium from the K 2TiF 6-based electrolytes is enhanced by the formation of the less stable TiF 7 3−, resp. TiF 6Cl 3− anions. In the electrolysis of aluminium from cryolite-alumina melts the creation of oxyfluoroaluminate anions facilitates the electrodeposition of aluminium.

Formation of smectic mesophases in binary systems of short chain alkanoic acid salts

Abstract The formation of thermotropic ionic smectic liquid crystals in binary systems of lithium and caesium acetates, propionates and butyrates has been discovered. Mesomorphism of mixed melts of non-mesogenic components results from the formation of complex anions. Correlations between anion mesogenic properties and its size, shape, anisotropy in the Coulomb charge distribution as well as the nature of the surrounding cations are discussed.

Quantum-chemical analysis of silicon atom pentacoordination

The energy characteristics and dynamics of charge redistribution in the X ax(H 3) eq Si…Y group in changing the Si ← Y coordination bond length and rehybridization of the silicon atom valence shell have been calculated in MNDO approximation. The calculations are carried out with a complete optimization of molecular geometry of C 3y symmetry. The formation of complex anions X = H, F, Cl; Y = H − (I) and molecular complex F ax(H 3) eqSi ← OCHOH (II) is discussed. The main difference between pentacoordinate structures I and II is a weaker perturbation of the FSiH 3 molecule caused by the OCHOH ligand as compared to that of H −. When tetrahedral silicon is involved in the formation of an additional donor-acceptor Si ← Y bond, this atom acquires a higher positive charge as compared with the tetracoordinate state of its valence shell. In this case, the electronic density is transferred to the axial and equatorial atoms attached to silicon, affecting predominantly the substituent X ax charge. The complexing energies calculated are as follows, kJ/mol: −253.9 (X = H), −273.2 (X = F), −398.7 (X = Cl) for I and 72.4 for II.

A Complex Ion Model for Molten Halides

The formation of complex anions in molten halide systems is treated semi-quantitatively by a discrete complex anion model. The treatment is a more general application and extension of an approach reported previously by the author. By assuming the existence of discrete MY42− tetrahalo complex anions, the model gives good agreement to experimental enthalpies and entropies of mixing and electrical conductivities in a large number of different halide systems of the general formula MY2–AY, where M is a divalent metal, and A is an alkali. Very few adjustable parameters are required. The parameters provide semi-quantitative basicity (or acidity) scales by which molten salts and slags may be classified. The relationships of these basicity scales to ionic radii, ligand field stabilization energies, etc. are shown. General thermodynamic and mathematical aspects of the problem of complexing are discussed, particularly as regards the proper method of calculating the degree of dissociation of the complexes.

Adsorption of mercuric chloride by colloids—Part I

The adsorption of the HgCl2 of different concentrations by colloids such as dry gels of ferric hydroxide, silica gel, aluminium hydroxide and acticarbon was investigated in order to study the nature of the adsorption of HgCl2. It is found that at dilute concentrations of HgCl2 the adsorption tends to be apolar, while at higher concentrations the adsorption is polar. The addition of a strong electrolyte such as sodium chloride retards the adsorption of HgCl2 due to the formation of complex anions of mercury.