Computer calculation of equilibrium constants of species present in mixtures of metal ions and complexing agents

A general computer program is described for the interpretation of pH titration data for mixtures containing the ions of up to two metals and up to two ligands. The program, which employs the non-linear least-squares method, may be used to calculate equilibrium constants for hydrolysed metal ions, protonated ligands, and simple, protonated, hydrolysed, polynuclear, and mixed complexes.     

Structural relaxation of SiO2 at elevated temperatures monitored by in situ Raman scattering

Raman scattering spectra of high-purity synthetic silica glass were measured in situ in the temperature range from 950 to 1200 °C by means of an experimental approach which gives very low thermal background. The temperature dependence of the scattering permits an analysis of the spectra into the first-order and overtone contributions in a consistent manner. For low-OH content the dynamics of relaxation of the D₂ defect follow a single exponential decay, but more complex relaxation is found when OH content is high. In the latter case a double-exponential fit describes the observed relaxation well. The activation energies found are: for creation of D₂ defects 0.53 ± 0.07 eV; for single exponential relaxation in low-OH material, 6.0 ± 0.3 eV; for high-OH material, primary relaxation 5.1–5.2 ± 0.3 eV, secondary relaxation 2.4–2.5 ± 0.5 eV.     

Electromagnetic scattering by a homogeneous chiral obstacle in a chiral environment

Time-harmonic electromagnetic waves are scattered by a homogeneouschiral obstacle embedded in a chiral environment. The correspondingtransmission problem is reduced, via Bohren's decomposition,to an integral equation over the interface between the obstacleand the surrounding medium. This integral equation is shownto be uniquely solvable except for a discrete set of electromagneticparameters of the obstacle.     

Computer calculation of equilibrium concentrations in mixtures of metal ions and complexing species

A method is described for calculating equilibrium concentrations of all species in multi-metal-multi-ligand mixtures from the pH of the solution, the total concentration of each metal and each complexing agent, and the relevant equilibrium constants (pK(a) values and stability constants). No restriction is imposed on types of possible complexes, which can include mixed, hydrolysed, protonated and polynuclear species. Two examples are given. One of these comprises a 10-metal-10-ligand system (195 equilibrium constants). In the second system, mixed complex formation is important. The computer program is given.