Formation Enthalpies of Water–n-octane–1-propanol–sodium Dodecyl Sulfate Microemulsions at 298.15 K

The solution enthalpies of water–n-octane–1-pentanol (PeⁿOH)–sodium dodecyl sulfate (SDS) microemulsions and their components in 2-propanol at 298.15 K were determined by the thermochemical method at fixed mass fractions of PeⁿOH (0.1450) and SDS (0.0775). The formation enthalpies of microemulsions were calculated using the thermochemical cycle, and it was shown that their values are positive. The results obtained indicate that the intercomponent interactions in the investigated systems are rather weak. The formation of thermodynamically stable microemulsions is determined by entropy changes associated with the disintegration of water and 1-pentanol homoassociates.     

On interrelation between the internal pressure and the cohesion energy density

The question about the definition of the “internal pressure” concept is being discussed. It is shown that the previously found differential relation between the cohesion energy density and the internal pressure is one of the examples of an absolutely general interrelation between definitely connected differential functions. It is ascertained that the ratio (the internal pressure divided by the cohesion energy density) is a structuresensitive parameter inherent to the calorific (thermal) equation of a liquid state.     

Calorimetric study of the solvation of benzene and its chloro-, nitro-, and aminoderivatives by n-hexane, 1-butanol, and mixed solvent n-hexane-1-butanol

The heats of dissolution of benzene, chlorobenzene, ortho-dichlorobenzene, nitrobenzene, and aniline in n-hexane and 1-butanol and those of benzene, chlorobenzene, nitrobenzene, and aniline in a mixture of n-hexane and 1-butanol were measured by calorimetry at 25°C. The enthalpies of solvation of the compounds were calculated. The correlation between the enthalpies of solvation of the compounds and their molar refraction was studied. The enthalpies of solvation of the compounds and their functional groups by the mixture of n-hexane and 1-butanol were considered.     

Effect of temperature on the enthalpies of formation of water-o-xylene-Triton X-100 microemulsions

Enthalpies of solution for water-o-xylene-Triton X-100 (TX-100) microemulsions and their components in 2-propanol are determined thermochemically at 288.15, 298.15, and 313.15 K. Enthalpies of formation for the microemulsions are calculated using a thermochemical cycle. It is shown that the enthalpies of formation are negative and fall in moving from water/oil microemulsions to oil/water microemulsions. The obtained data show that strong molecular interactions between components in the investigated systems favor the formation of thermodynamically stable microemulsions. It is concluded that the spontaneous formation of the microemulsions can be due to both the entropy and enthalpy contributions to the change in free energy.     

The thermochemical characteristics of solution of phenol and benzoic acid in water-dimethylsulfoxide and water-acetonitrile mixtures

The solution of phenol and benzoic acid in water-dimethylsulfoxide (DMSO) and water-acetonitrile (AN) mixtures was studied. As distinct from benzoic acid, the thermodynamic characteristics of solution of phenol sharply change at concentrations corresponding to a change in the character of cluster formation in water-DMSO and water-AN mixtures. Differences in the solvation of phenol and benzoic acid are explained by different mechanisms of the interaction of the solutes with clusters existing in binary mixtures.     

Critical current in planar SNS Josephson junctions

Specific features of the proximity effect and Josephson behavior of submicron planar SNS junctions fabricated by electron beam lithography and shadow evaporation have been studied experimentally and theoretically. The critical current of the junctions has been found to drastically increase with a decrease in temperature, which is associated with a change in the effective size of the weak link owing to the additional SN interface.     

A Simple Method for Estimating the Solubility Parameter of Small Molecules and Polymeric Materials

Russian Journal of Applied Chemistry - The study relates to the problem of selecting a solvent for organic polymers during their chemical processing. Based on the method of Askadsky, simple schemes...     

Group Contributions to the Enthalpy Characteristics of Solutions of Formic and Acetic Acid Amides in Water-1,2-Propanediol Mixtures

Enthalpies of solution of formamide and of dimethyl and diethyl derivatives of formamide and acetamide in mixtures of water with 1,2-propanediol at 298.15 K were determined thermochemically. The contributions of hydrocarbon radicals and polar groups to the enthalpies of solution, vaporization, and solvation of the amides were determined. The influence exerted by the structure of molecules and the composition of mixtures on the enthalpy characteristics was considered.     

Dissolution of Polyethylene in a Hydrocarbon Medium for the Subsequent Reprocessing by Hydroconversion

Factors influencing the dissolution of high-density polyethylene in petroleum tar to obtain a homogenized solution for the subsequent hydrogenation in the presence of a nanosized catalyst synthesized in situ under the hydroconversion conditions were studied. The calculation of the solubility indices shows that the best solvents for high-density polyethylene are low-molecular-mass alkanes and alkenes present in the paraffin–naphthene fraction of the tar. Because high-density polyethylene has crystalline structure, the dissolution occurs via swelling with the formation of a true solution depending on the ratio of high-density polyethylene to the tar. A conclusion was made that, to reach the best dissolution, the ratio of high-density polyethylene to the tar should be decreased, or the paraffin–naphthene fraction should be additionally introduced.