Publications

Abstract Concentration-dependent phase separation into two polymer-containing liquid phases has been studied for the polymer pair poly(ethylene glycol) and dextran. Below the point of phase separation, the light scattering of polymer mixtures was considerably greater than for single polymers in solution. Also the viscosity of polymer mixtures was larger than the sum of the viscosity increments of polymer solutions. On the other hand, both heat capacity and density were additive in the one-phase region. The possible solvent structure in mixed polymer solutions is discussed.

Abstract A classical intramolecular dynamics study for the ground electronic state of the sodium trimer has been carried out using a realistic potential energy surface previously reported by the authors. It is shown that the trajectories are exponentially diverging even for very low energies close to the bottom of the potential well. This fact is confirmed by the calculated maximum Lyapunov characteristic numbers, which suggest that the Na3 molecule possesses a small vibrational relaxation time. This result corroborates previous findings on atom-diatom reactive scattering for analogous systems, which have indicated a high degree of statistical behavior in the dynamics of these reactions.

Abstract A procedure for the estimation of the number and values of acidity constants from variations observed in aqueous Fourier transform infrared spectra of compounds containing carboxylic groups, including fulvic acids, with increasing pH, by using principal component analysis and evolving factor analysis, has been studied. The validation of the procedure was made by treating simulated data without and with random noise and data obtained in experiments with simple carboxylic compounds (acetic, shikimic, maleic, malonic and succinic acids) and binary mixtures of these compounds. The results for fulvic acids show two different types of carboxylic groups with pK(a) values of 2.8 and 4.6.

Abstract The standard (p° = 0.1 MPa) molar enthalpies of combustion at 298.15 K were measured by static-bomb calorimetry and the standard molar enthalpies of sublimation at 298.15 K were measured by microcalorimetry for the following aromatic nitriles and aromatic nitrile N-oxides: (2, 4, 6 - Trimethylbenzonitrile 5530.7 ± 0.9 82.9 ± 1.6; 2, 4, 6 - Trimethylbenzonitrile N -oxide 5563.1 ± 0.8 77.5 ± 3.7; 2, 4, 6 - Trimethoxybenzonitrile 5150.0 ± 0.9 112.6 ± 2.0; 2, 4, 6 - Trimethoxybenzonitrile N -oxide 5187.1 ± 1.6 91.9 ± 1.9; 2, 6 - Dimethylbenzonitrile 4890.1 ± 1.0 83.9 ± 2.8). From the standard molar enthalpies of formation of the gaseous compounds, the molar dissociation enthalpies of the (N{single bond}O) bonds were derived: D(N{single bond}O)/(kJ·mol-1) trimethylbenzonitrile N-oxide, (222.2 ± 4.6); trimethoxybenzonitrile N-oxide, (232.8 ± 3.8).

Abstract Enthalpies of dissolution in water of dialkylsulphides: CH3(CH2)v{single bond}S{single bond}(CH2)vCH3, v = 0, 1, and 2, and dialkyldisulphides: CH3(CH2)v{single bond}S{single bond}S{single bond}(CH2)vCH3, v = 0 and 1, were determined by microcalorimetry at the temperatures (288.15, 298.15, 308.15, and 328.15) K. Molar enthalpies of solvation and partial molar heat capacities at 298.15 K were derived for the infinitely dilute solutions. The partial molar heat capacities are discussed in terms of an empirical group scheme.

Abstract Thermopile heat conduction calorimeters normally have high time constants. Multistep titration experiments involving fast processes may then require several hours to perform. It is demonstrated that such experiments can be conducted about 10 times faster, without loss of accuracy, by use of a "dynamic correction method". For a new small vessel thermopile conduction calorimeter, injections can be made at 1.5-min intervals.