The special features of the thermodynamic characteristics of hydration of univalent ions according to the reference interaction site model

The dependence of the Gibbs energy of hydration of univalent ions was calculated on the basis of integral equations for a molecular liquid. Calculations were performed in the approximation of the reference interaction site model (RISM). The relation between the energy of hydration of ions and local electrostatic field microinhomogeneities in solution was studied. It was shown that the best variant was the RISM with the hypernetted chain closure, partial inclusion of orientation effects, and semiempirical corrections for the excluded volume and the presence of H-bonds with solutes. Predictions based on the selected variant of the model were in close agreement with the experimental data. The analysis performed indicated directions for the improvement of the RISM method.     

Calculations of the thermodynamic properties of dimethylsulfoxide-water solutions on the basis of the cluster solvation model

The thermodynamic functions of dimethylsulfoxide mixtures with water were analyzed over the whole composition range using the cluster solvation model taking into account the distribution of clusters over solvation numbers. The equations of the model were shown to correctly describe the concentration dependences of saturated vapor pressure and excess enthalpy and volume on the assumption of dimethylsulfoxide hydration. The hydration numbers of dimethylsulfoxide and the variance of the distribution of hydrates over stoichiometric numbers were shown to increase as the temperature decreased.     

On the interrelation between the methodologies of chemistry and physics

Aspects of the methodology and language of chemistry and physics are discussed. Chemistry defines the chemical properties of any substance from the results of its interaction with other substances using the logic of relations. Therefore, describing the properties of substances means using sets of different ideas, including ones that are opposite in meaning. Consequently, depending on the nature of reagents with respect to which properties are established, substances show chemical dualism. This dualism was established in chemistry long before the discovery of wave–particle dualism, to understand which N. Bohr proposed the complementarity principle in 1927. The methodology of natural sciences corresponds to the principle of complementarity and the need to use it to understand the world and record the results in the linguistic reality of several languages.     

4-Aminofurazan-3-carboxylic Acid Iminoester in Reactions with N,O-Nucleophiles

Reactions of 4-aminofurazan-3-carboxylic acid iminoester with o-aminophenol and ethylenediamine give rise respectively to 4-(1,3-benzoxazol-2-yl)- and 1-(4,5-dihydro-1H-imidazol-2-yl)-1,2,5-oxadiazol-3-amines, with aminoethanol arises 2-[(Z)-1-amino-1-(4-amino-1,2,5-oxadiazol-3-yl)methylideneamino]-1-ethanol. Treating of 3-amino-4-(1H-benzo[d]imidazol-2-yl)-1,2,5-oxadiazole with triethyl orthoformate in acetic anhydride yielded benzo[4,5]imidazo[1,2-c][1,2,5]oxadiazolo[3,4-e]pyrimidine, and alkylation with haloalkanes furnished 3-amino-4-(1-R-benzo[d]imidazol-2-yl)-1,2,5-oxadiazoles.     

The dependence of the osmotic coefficient on the composition of multicomponent solutions

The thermodynamic theory of binary aqueous solutions of electrolytes taking into account the electrostatic interaction of ions and their hydration and association was extended to multicomponent solutions. Equations for calculating the osmotic coefficient of multicomponent solutions from parameter estimates (hydration and association numbers under standard conditions) determined for the corresponding binary subsystems were substantiated. Interval parameter estimates were used to calculate the osmotic coefficients for several three-five-component aqueous solutions containing both nonelectrolytes and electrolytes. A comparison of the results with the literature data showed that cross interactions between components could be ignored for the multicomponent solutions studied.     

Crystallization of calcium carbonate with the filtration of aqueous solutions through a microporous membrane

It is established that the filtration of water through a microporous membrane does not change the hardness of the water; it does, however, reduce the amount of scale deposit, due to the crystallization of salts in water in the form of aragonite. The effect is consistently observed in water with a hardness of more than 7.0 H, a content of hydrocarbonate ions of more than 500 mg/L, and a pH ≥ 7.3. It is shown that introducing the seeds of calcite crystals into a filtrate results in the precipitation of calcite rather than aragonite. It is concluded that quasi-softening in the case of hard water microfiltration is caused by the removal of calcite micronuclei, and thus by conditions being created for the crystallization of aragonite as a thermodynamically less stable form.