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is necessary for determining such an important thermodynamic quantity as —the partial molar heat capacity at infinite dilution by means of the integral solution enthalpy method. Another way of obtaining the values is the extrapolation of apparent

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Abstract  

The heat capacities of binary aqueous solutions of 1,2-ethanediol, 1,2-propanediol and 1,2-butanediol were measured at temperatures ranging from 283.15 to 338.15 K by differential scanning calorimetry. The partial molar heat capacities at the infinite dilution were then calculated for the respective alkanediols. For 1,2-ethanediol or 1,2-propanediol, the partial molar heat capacities at the infinite dilution of increased with increasing temperature. In contrast, the partial molar heat capacities of 1,2-butanediol at the infinite dilution decreased with increasing temperature. Heat capacity changes by dissolution of the alkanediols were also determined. Heat capacity changes caused by the dissolution of 1,2-ethanediol or 1,2-propanediol were increase with increasing temperature. On the other hand, heat capacity changes caused by the dissolution of 1,2-butanediol are decrease with increasing temperature. Thus our results indicated that the structural changes of water caused by the dissolution of 1,2-butanediol differed from that of the two other alkanediols.

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Abstract  

Enthalpy of solution, ΔH sol o , enthalpy of sublimation, ΔH subl o , apparent partial molar volume and heat capacities,V 2 o andC p,2 o were determined for aqueous solutions of thirty alkylated derivatives of uracyl and adenine, eight derivatives of cytosine and guanine. Calculated accessible surface areas and molar volumes are presented, too. The values of enthalpy of solution, enthalpy of sublimation can be useful in the studies on the nature of interaction between these compounds and water molecules. Apparent partial molar volume and heat capacity give a new aspect on hydrophob properties of the examined nucleic acid base derivatives.

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Abstract  

The specific heat capacities of {2-(hexyloxytriethoxy)ethanol (C6E4)+water} system have been measured from 280 to 333 K within the whole composition range by DSC. Changes of specific, apparent and partial molar heat capacities of investigated aqueous solution vs. composition and temperature, considered as an effect of structural transformations were analyzed in order to draw boundary between region where amphiphile molecules occur as monomers and small aggregates and the area in which the first micelles appear. For each solution, the temperature dependences of the differential heat flow were analyzed in order to find the curve of phase coexistence, i.e. the boundary between one- and two-phase areas for the examined system.

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Densities, heat capacities, enthalpies of dilution at 298 K and osmotic coefficients at 310 K of octyltrimethylammonium chloride were measured as functions of concentration. From the experimental data, the partial molar volumes, heat capacities, relative enthalpies, nonideal free energies and entropies at 298 K were derived as functions of concentration. A comparison between the above data and those of dodecyltrimethylammonium chloride reported in the literature shows that the increase of the alkyl chain length shifts the apparent molar volumevs. concentration curves towards greater values and the heat capacity, relative enthalpy and free energyvs. concentration curves towards smaller values. By assuming the pseudo-phase transition model the properties of micellization (ΔYm) were graphically evaluated. TheΔYm values of OTAC compared with those of DTAC are consistent with the increase of the hydrophobicity by increasing the alkyl chain length.

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liquid crystals, plastic crystals and ionic liquids, and molten salts. There is a discussion of heat capacities in the critical region, of computer simulation studies of heat capacity effects associated with hydrophobic effects and of partial molar heat

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When discussing solutions and solubility, say, the solubility of a gas in a liquid at a given temperature T and pressure P , one is either interested in single - phase properties , such as partial molar volume or partial molar heat capacity, or in

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enthalpies of the solvent and solute of the studied solution; ν is the number of ions of K_DC ( ν = 2); M 1 is the molar weight of the water; and are the partial molar heat capacities of the water and K_DC in the solution at the concentration m

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also on temperature [ 13 ]. The systems that tend to form stable micellar aggregates show characteristic changes in the course of concentration dependencies amongst others of partial molar volume and partial molar heat capacity. These values

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. 26. Spink , CH , Wadsö , I . Thermochemistry of solutions of biochemical model compounds. 4. The partial molar heat capacities of some amino acids in aqueous solution . J Chem Thermodyn . 1975 ; 7 : 561 – 572 . 10

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