Study of solvent-solvent interaction by paper chromatography. I. Dimethyl sulphoxide-water system

Summary The interaction between dimethyl sulphoxide (DMSO) and water, occurring when the two liquids are mixed together, has been studied: 1. by the measurement of the rate of migration of the different solvent mixtures, over the whole concentration range, on paper chromatograms, and 2. by observing the paper chromatographic behaviour of hexacyanoferrate II anions when these mixtures are used as mobile phases. The rate of migration gives a very pronounced maximum at the solvent concentration which corresponds to the composition DMSO·H₂O. The chromatographic behaviour of the hexacyanoferrate II ion besides confirming this conclusion shows the existence of three distinct zones of differing solvent structure and solvating behaviour.     

Dielectric studies in dilute solutions

Dielectric studies in dilute solutions of cyclohexane and benzene have been carried out in the temperature range 294–318°K. The observed data have been utilized to evaluate the relaxation times and thermodynamic parameters of these molecules. The high values ofα for 2-acetyl pyridine indicate the occurrence of more than one relaxation time. In the remaining systems, the observed lowα values indicate their rigid behaviour. The variation in the dielectric relaxation time is mostly correlated with the change in the heterocyclic configuration of the system.     

Evaluation of the thermodynamic parameters for association process of hydrogen bond complexes from the dielectric relaxation measurements.

A relation between the free energy for dipole relaxation process and that for the association process has been proposed. Using this relation, an equation has been defined for evaluating the association equilibrium constant from the dielectric relaxation measurements. These equations have been applied to study the association of dimethyl sulphoxide and p-tolyl sulphoxide with proton donors (phenol and O-cresol) in an inert solvent carbon-tetra-chloride in the temperature range 298–322K. The calculation of the association equilibrium constant and hence the thermodynamic parameters have shown the wide scope, the proposed relations can be put to in the study of the association process of hydrogen bond complexes.     

Transonic whistler solitons

We consider the coupling of ion-acoustic perturbations with large amplitude electron whistler waves. Transonic envelope whistler solitons having a group velocity near the ion-acoustic speed are found.     

Comparison of methods for numerical differentiation

Numerical differentiation can uncover hidden features in chemical data, but the limitations of the technique used should be understood. A method based on fitting data to a quadratic polynomial gives good signal-to-noise ratios, but systematically low derivative intensities. Central difference methods are more accurate but less tolerant of noise.     

On the equivalence of angular force for lattice dynamics of b.c.c. metals

All angular force models developed for the study of lattice dynamics of b.c.c. metals are bound to give identical results. The recent model of Rani and Gupta is not an exception from this rule.