The density, kinematic viscosity, and refractive index of aqueous solutions of poly(ethylene glycol) (PEG) have been measured at (298.15, 303.15, 308.15, 313.15, 318.15, 323.15, and 328.15) K. The PEG samples had an average molecular mass (1000 and 10000). The density and refractive index results were correlated to a first-order polynomial with respect to PEG mass fraction at each temperature. It was shown that from the refractive index results the density of the aqueous PEG mixtures can be predicted accurately. The kinematic viscosity results were correlated by a newly modified Eyring's viscosity model. The parameters of the model were determined and presented.
The cloud-point temperatures and phase separation of (water + poly(ethylene glycol) + salt) ternary systems were studied by the refractometry method. The salts were K 3 PO 4 , K 2 HPO 4 , Na 2 HPO 4 , or Na 2 CO 3 . The phase separation was also observed by visual inspection. Differences between the measured cloud point using the refractometry method, and visual inspection was up to (1 °C. The measured cloud-point temperatures are compared with those obtained by viscometry and laser beam scattering methods. These comparisons indicate complete agreement between the different methods for cloud-point temperature measurements for the (water + poly(ethylene glycol) + salt) ternary system. The salt-included liquid-liquid separation is studied by using the Flory-Huggins polymer solution theory. A simple linear temperature composition-dependent interaction parameter (χ) was applied for correlation of the measured cloud-point temperatures. The comparison between measured and correlated cloudpoint temperatures indicates that average absolute deviation is less than 0.61 °C. Therefore, the Flory-Huggins model was successfully applied to determine the phase separation conditions of the (water + poly(ethylene glycol) + salt) ternary systems.
Reactive oxygen species (ROS) are reactive molecules which are produced normally by metabolic reactions. 2,7-Dichlorofluorescein diacetate (DCHF-DA) assay is used to determine intracellular levels of ROS in cancer cells. In the present study, the mechanism and kinetic parameters of this determination are obtained by kinetic Monte Carlo simulation. The values of the rate constants for the suggested mechanism were obtained by simulation. Then, the effect of DCHF-DA concentration on the rate of reaction was studied. According to the results, the product concentration should increase on increasing the DCHF-DA concentration. In addition, the effect of ROS concentration on the rate of reaction was determined.
LiquidÀliquid equilibrium (LLE) results for ternary mixtures of {methanol (1) þ methylbenzene (2) þ decane (3)} at different temperatures from (298.15 to 313.15) K are reported. The compositions of the liquid phases at equilibrium were determined by gasÀliquid chromatography. The data were correlated with the NRTL and UNIQUAC equations. Also, the selectivity and distribution coefficient of methanol for the extraction of methylbenzene from decane at different temperatures are compared. The phase diagrams for the ternary mixtures are presented, and the correlated tie line results are compared with the experimental data. The comparison indicates the applicability of the NRTL and UNIQUAC activity coefficient models for LLE calculations on the studied mixtures.
The compositions of coexisting phases have been determined for aqueous two-phase systems containing poly(ethylene glycol) of nominal molecular weight 20000 and copper sulfate at (290.15, 299.15, 308.15, and 317.15) K. The effect of temperature on the liquid–liquid equilibrium was discussed. The experimental compositions of coexisting phases of the systems were used to obtain interaction parameters in universal quasichemical theory (UNIQUAC) activity coefficient models. The experimental tie line data were compared with those obtained using the UNIQUAC model. The results of comparison were indicated by calculation of the root-mean-square deviations (rmsd). The calculated results show good agreement with the experimental data.
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