Vapor Pressure Osmometry and Its Applications in the Osmotic Coefficients Determination of the Aqueous Monomer Glycol and Polymer Polyethylene Glycol Solutions at Various Temperature

Based on the principle and calibration of vapor pressure os-mometer and itsapplication in the thermodynamics of the aqueous solutions, the results on aqueous solutions ofmonomer glycol, PEG_(200), PEG_(400), PEG_(1500) and PEG_(2000) over the different concentrationrange at various temperatures were reported. Using a linear least-square fitting routing, theosmotic coefficients were fitted by a simple polynomial equation. It was found that the relationshipbetween the molar osmotic coefficients (Φ) and the molar concentration (c) of the solutions are ina quite good agreement with the fitted polynomial equation at various temperatures over thedifferent concentration range. The experimental results also show that over the studiedconcentration range and at various temperatures, the concentration dependence of the molar osmoticcoefficients of the aqueous solution systems with the solutes of PEG_(200), PEG_(400), PEG_(1500)and PEG_(2000) are totally presented in a rising trend, and their temperature dependence of theosmotic coefficients of the aqueous solution systems of the molar concentration exhibits their ownregularities, respectively. The aqueous glycol solution system exhibits the properties of the dilutesolution.

Correlation of the mean activity coefficient of aqueous electrolyte solutions using an equation of state

Accurate calculation of thermodynamic properties of electrolyte solution is essential in the design and optimization of many processes in chemical industries. A new electrolyte equation of state is developed for aqueous electrolyte solutions. The Carnahan-Starling repulsive model and an attractive term based on square-well potential are adopted to represent the short range interaction of ionic and molecular species in the new electrolyte EOS. The long range interaction of ionic species is expressed by a simplified version of Mean Spherical Approximation theory （MSA）. The new equation of state also contains a Born term for charging free energy of ions. Three adjustable parameters of new eEOS per each electrolyte solution are size parameter, square-well potential depth and square-well potential interaction range. The new eEOS is applied for correlation of mean activity coefficient and prediction of osmotic coefficient of various strong aqueous electrolyte solutions at 25℃ and 0.1 MPa. In addition, the extension of the new eEOS for correlation of mean activity coefficient and solution density of a few aqueous electrolytes at temperature range of 0 to 100℃ is carried out.

RELATIONSHIPS BETWEEN IONIC RADII AND PITZER'S PARAMETERS IN 1:1 TYPE ELECTROLYTE SOLUTIONS

A new expression for the osmotic and activity coefficients in single electrolyte solution is developed by reforming the Pitzer's osmotic equation.As a result,the correlations between the oMX,the sum of the"hard core"radii of ionsβ^(0)_(MX)andβ^(1)X_(MX),and the second virial coefficients/jjJx and'n Pitzer's equations are obtained.Furthermore,an"ionic overlap"model and its relevant equation are suggested.The relationships between the thermodynamic properties of aqueous electrolytes and the characteristic of their ions(ionic radii and ionic hydration)are discussed quantitatively.

Molecular Thermodynamic Model for Polyelectrolyte Solutions with Added Salts

A molecular thermodynamic model of polyelectrolyte developed previously was extended to polyelectrolyte solutions with added salts.Thermodynamic properties,such as activity coefficients of polyelectrolytes or added salts and osmotic coefficients of solvent, of a number of aqueous mixtures of polyelectrolytes and salts are analyzed with the proposed model.Successful correlation is obtained in the range of moderate or higher polyion concentration.For the same sample,thermodynamic properties of polyelectrolytes with and without simple electrolytes can be predicted mutually using parameters from regression data.

Application of the quasi-random lattice model to rare-earth halide solutions for the computation of their osmotic and mean activity coefficients

This work dealt with the computation of the mean activity coefficients of rare-earth halide aqueous solutions at 25℃, by means of the Quasi Random Lattice（QRL） model. The osmotic coefficients were then calculated consistently, through the integration of the Gibbs-Duhem equation. Using of QRL was mainly motivated by its dependence on one parameter, given in the form of an electrolyte-dependent concentration, which was also the highest concentration at which the model could be applied. For all the electrolyte solutions here considered, this parameter was experimentally known and ranged from 1.5 to 2.2 mol/kg, at 25 ℃.Accordingly, rare- earth halide concentrations from strong dilution up to 2 mol/kg about could be considered without need for best-fit treatment in order to compute their osmotic and mean activity coefficients. The experimental knowledge about the parameter was an advantageous feature of QRL compared to existing literature models. Following a trend already observed with low charge electrolytes,a satisfactory agreement was obtained with the experimental values for all the investigated rare-earth chlorides and bromides. For the sake of compactness, in this work the considered rare-earth halides were all belonging to the P63/m space group in their crystalline（anhydrous） form.