Characteristics Of Aqueous Solutions Research Articles

Crystallization Features of Aqueous Solutions in Their Droplets Evaporated by Nanosecond Spark Discharge Treatment

Crystallization processes that occur during the drying of droplets of solutions by treating with nanosecond spark discharges have been experimentally investigated. It has been shown that crystallization in the droplets under plasma treatment proceeds in a different way than in identical droplets dried in the conventional mode.

Behaviorial Features of Aqueous Solutions of Thermoresponsive and pH-Sensitive Polymers with complicated architectures

Research on self-organization and aggregation in solutions of thermoresponsive and pH-sensitive polymers with complicated architectures such as star-shaped polyoxazolines and grafted copolymers with a polyimide spine and polydimethylaminoethylmethacrylate side chains was reviewed. A statistical N-isopropylacrylamide—maleic-acid copolymer was studied for comparison. Hydrophobic blocks in the macromolecules reduced the phase-stratification temperature and changed the set of scattering species by forming monomolecular micelles. An increased intramolecular density led to slower aggregate formation in solutions of polymers with complicated architectures.

Partial molar volume of methanol in water: Effect of polarizability

The available pairwise additive intermolecular interaction models used so far in simulations in combination with common combining rules do not seem to be able to reproduce the most distinct feature of aqueous solutions of alcohols, the minimum of the partial molar volume at low alcohol concentrations. Nonetheless, this fundamental failure seems to have been paid little attention to, partly because of very high requirements for accuracy and, hence, CPU time of simulations. As an attempt to go beyond empirical combining rules and account in a more physical and yet simple way for the cross interactions, a feasibility study has been undertaken using a polarizable model of water in molecular simulations of the water–methanol mixture at ambient conditions. It turns out that the inclusion of polarizability may qualitatively change the behavior of the mixture bringing the result in agreement with experiment.

Rheological properties of aqueous solutions of sodium carboxymethylcellulose and methylhydroxypropylcellulose blends

It was found that a specific feature of aqueous solutions of Na-CMC and MHPC is the presence of a viscosity extremum for a polymer ratio of 80:20 wt. % and in treating the MHPC solution in a rotary-pulsed activator at the rate of 300 rpm. It was hypothesized that an increase in the size of the coils of the MHPC macromolecules as a result of improvement of the thermodynamic quality of the solvent in the first case and their stretching in the second case is the cause of the increase in the viscosity of the solutions. Films spun from solutions, characterized by anomalous high viscosity values, have high strength and elasticity.

Physical aspects of vitrification in aqueous solutions

Vitrification is the process by which a liquid solidifies at temperatures usually far below the normal freezing point, but without the formation of any crystalline phase. The liquid has formed a glass. Occasionally, when the liquid consists of a solution, one of the components freezes to form a crystalline phase during cooling, but the remainder of the solution vitrifies. The product is then a partially crystallized glass. Glass formation, as a feature of aqueous solutions, either of the whole solution or of the remaining fraction after crystallization of ice, is discussed. We focus on the general principles involved in glass formation and also discuss in detail the effect of pressure on the nucleation and vitrification of the solution. In particular we look at the physical processes involved as well as the chemical aspects of the solutes which can be used in vitrifiable aqueous solutions. In any application of vitrification of aqueous solutions the material properties of the resultant glass are also important; these are also briefly considered. Recent work concerning the nature of the devitrification (crystallization during warming) event at high pressures is detailed.

Study of the characteristic structural features of aqueous solutions of butyric acid at 15?50�C from data on the solubility of the noble gases and the velocity of ultrasonic waves

The solubility of helium, neon, and argon in butyric acid and its mixtures with water has been studied throughout the entire range of concentrations, and the velocity of ultrasonic waves and the adiabatic compressibility at t = 25~ have been determined. It has been found that the dependence of these properties on the composition of the mixed solvent and temperature is characterized hy the presence of extremal points. From these it has been concluded that the structure of water is stabilized by the addition of butyric acid at Nacid 0.05. From the results obtained it follows that the dissolution of the noble gases increases the strength of the structure of the solvent. These regular features are confirmed by the nature of the change in the thermodynamic characteristics of the dissolution of the noble gases in aqueous solutions of butyric acid with change in composition.

Heats of solution of KCl and structural features of aqueous solutions of n-propanol at 10 to 60�

oO ~ 0.3%. The AHsoln values were extrapolated graphically to infinite dilution (AHs~ln). The values of AHsoln are given in Table 1. The materials used for the investigation were a "chemically pure" grade of potassium chloride, recrystallized by the procedure given in [4], and a "chemically pure" n-propanol, which was distilled before preparing the water -alcohol mixtures. The concentration range studied of the aqueous n-propanol solutions was determined by the solubility and solution kinetics of the KC1. Figure 1 shows graphically the dependence of/%Fsoin on ~he composition of aqueous solutions of n-propanol, expressed as mole fractions of alcohol ~,, at all the temperatures studied.