Volume 214, Issue 3 - 3

Using the four-photon polarization spectroscopy we have studied the Rayleigh wing spectral patterns of several aqueous salt solutions within the 0-50 cm -1 frequency range. Within the framework of an approach allowing a representation of the Rayleigh wing spectrum as two Lorentzian functions, characterized by the long and the short times of relaxation of an anisotropic mode, we obtained that the short relaxation time does depend on the concentration of electrolyte and its type, whereas the long relaxation time does not. The effect can be qualitatively interpreted supposing that the fluctuations of ionic concentration give rise to the fluctuations of local electric field. An instantaneous magnitude of this field is about 10 4 V/cm and its time of changing is about 10 -12 s. This electric field initiates local microscale Kerr-effects thus contributing to the fluctuations of optical anisotropy, which accounts for an additional depolarized scattering.

The solubilities of amino acids (Glycine, α-alanine, L-asparagine, L-methionine, L-proline, L-valine, L-leucine, L-phenylalanine, L-glutamine) in dioxane-water mixtures (0-100%) have been determined colorimetrically as well as pH metrically using acid-free formaldehyde solution. The solubility decreases enormously with increase in percentage of dioxane. The results have been interpreted in terms of specific solvation and hydrophobic effects. In order to comprehend the results better, the scaled particle theory has been applied to determine the transfer free energy changes for interaction from water to aquo-organic solvent mixtures and the results are qualitatively in agreement. An estimate of the hydrophobic interactions due to constituent groups in different aquo-organic mixtures has been attempted.

The dynamic behaviour of calcium pyruvate, Ca(pyr) 2 , were studied by light scattering and rheology measurements at dilute and semi-dilute concentrations in aqueous solutions at 20°C. The formation of a stabilized film of Ca(pyr) 2 were studied and the rheological properties of the films have been measured above the overlap weight concentration, Φ* = 0.9% (w/w), where viscoelastic properties were found to develop. SCEM and Brewster-Angle-Microscopy images indicate that the aggregates of Ca(pyr) 2 are elongated in shape with an average length scale of 20 μm. However these particles are in close contact and form fractal clusters with d f = 1.75. The determined radii of gyration and the rheology measurements are consistent with a network of cross-linked aggregates with elastic properties even under biochemical relevant concentrations (5-10 mM). Considering the low overlap weight fraction Φ*, and the radius of gyration (R g = 21.0 nm) of the individual clusters for Φ < Φ*, the observed large clusters of 20-30 μm of Ca(pyr) 2 in solution for Φ > Φ* seem to be rather elongated than spherical.

Literature data for the solubility of mercury(II)-chloride in the quinary system Na-K-Mg-Ca-Cl-H 2 O are compiled. Solubilities of mercury(II)-chloride could be modeled mainly for solutions containing no mixed salts by application of the Pitzer theory. Pertinent coefficients are given. The calculated set of Pitzer coefficients applies only to solutions without sulfate and at a pH not higher than 3.

Apparent molar volumes, V 2,Φ , at 298.15 K have been obtained for the following α-amino acids in aqueous sodium acetate solutions from measurements of density: glycine, DL-α-alanine, DL-α-amino-n-butyric acid, DL-valine and DL-leucine. The infinite dilution apparent molar volumes, V 0 2,Φ , were calculated by linear extrapolations using the least-squares method. These data were used to derive the standard volumes of transfer, Δ t V 0 , of the amino acids from water to aqueous sodium acetate solutions. It was shown that both V 0 2,Φ, and Δ t V 0 vary linearly with increasing number of carbon atoms in the alkyl chain of the amino acids. These linear correlations have been used to estimate the contributions of the charged end group (NH + 3 , COO - ) and CH 2 group of the amino acids to V 0 2,Φ, and Δ t V 0 . An increase in the transfer volume and a decrease in hydration number of the amino acids with increasing electrolyte concentrations have been explained due to strong interactions of sodium acetate with the charged center of zwitterion for the amino acids compared to sodium acetate-nonpolar group interactions. The volumetric interaction parameters of the amino acids with sodium acetate were calculated in water. The pair interaction parameters are found to be positive and decrease with increasing alkyl chain of the amino acids, indicating that more hydrophobic amino acids undergo more dehydration effect of sodium acetate. A comparison of the pair interaction parameters of the amino acids with different electrolytes has shown that acetate ion has stronger interactions than chloride and thiocyanate ions. These interactions have been rationalized in terms of the cosphere overlap model.

We consider a photon gas, which is enclosed in a cavity and is in thermal equilibrium at temperature T. Each photon has a particle entropy σ = ka and a particle energy ε = hv = cp. The particle entropy σ is measured by the dimensionless number a in multiples of the Boltzmann constant k, which serves as an atomic entropy unit. The particle energy ε is related to the frequency Þgn and the momentum p of the relativistic photons, c velocity of light. Particle entropy and particle energy are connected by the temperature, ε = σT. Applying statistical thermodynamics we obtain the thermodynamics of the photon gas, written in particle entropies a. We also get the Planck distribution, and the Planck, Stefan-Boltzmann, and Wien radiation law. - The total entropy S of the photon gas is composed of two parts S 1 , S 2 . They can be traced back to the corresponding properties of the single photons: 1) the particle entropy σ, and 2) the Boltzmann constant k, which represent the entropy quantum. The close relation between the photon gas and the ideal gas of monatomic particles is discussed.

The surface energy, the electric double layer capacity and the "estance´´ (the charge derivative of the surface tension) were analyzed as a function of the electric potential across copper, gold and nickel solid electrodes in the eutectic melt 62 mol% Li 2 CO 3 + 38 mol% K 2 CO 3 in a reducing atmosphere (80% H2 + 20% CO 2 ) at the temperature of 923 K. The metals were found to behave differently in a polarization interval that is positive with respect to the stationary potentials of the electrodes. The density of the positive electric charge at the copper electrode increased monotonically as the potential was shifted toward positive values. The density of the positive charge at the gold and nickel electrodes decreased in the potential interval more positive than the zero potential charge. The charge even acquired the negative sign at the gold electrode. This phenomenon is explained by the fact that adsorption of the salt phase anions at the interface is ''specific´´ rather than electrostatic. The specific adsorption is accompanied by the charge transfer through the interface. This may be followed by formation of covalent bonds between the adsorbent and the adsorbate.

The order-disorder phase transition in solid phenanthrene was studied with differential scanning calorimetry and X-ray powder diffraction. This fully reversible transformation can be influenced by doping phenanthrene with structurally similar polycyclic aromatic hydrocarbons or heterocyclic aromatics. So far, four dopants have been used: benzo[c]cinnoline, phenanthridine, anthracene and carbazole. It was found that the transformation is not influenced by dopants that form eutectic phase diagrams with phenanthrene (benzo[c]cinnoline, phenanthridine). However, if the dopant is incorporated into the phenanthrene lattice to form a mixed crystal, the transition is inhibited above 3.7 mol% anthracene and 6.1 mol% carbazole, respectively. By X-ray diffraction, it is shown that these dopants induce the formation of the high-temperature phase already at room temperature.