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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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Abstract  

Enthalpies of solution of 15-crown-5 (15C5) in the mixtures of water with acetonitrile (AN) or propan-1-ol (PrOH) and benzo-15-crown-5 ether (B15C5) in the PrOH-water mixtures have been measured at 298.15 K. The values of standard enthalpies of solution of 15C5 are negative in the mixtures of water with AN within the whole range of mixture composition and in the mixtures water-PrOH for water content x w>0.1 and those of B15C5 are positive (except the standard enthalpy of B15C5 in pure water) in the system water-PrOH. The results of the calorimetric measurements together with the earlier data for B15C5 in water-acetonitrile mixtures are discussed with regard to the intermolecular interactions that occur in these systems.

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Enthalpic pair interaction coefficients in DMF solution

3. Thermochemistry of NaI solutions in mixtures of N,N-dimethyIformamide with urea, formamide, acetamide and N,N-dimethylacetamide at 298.15 K

Journal of Thermal Analysis and Calorimetry
Authors:
H. Piekarski
and
D. Waliszewski

Dissolution enthalpies of NaI in mixtures of N,N-dimethylformamide with urea, formamide, acetamide and N,N-dimethylacetamide were measured. The results were compared with data measured earlier for other DMF — non-electrolyte mixtures. The enthalpic pair interaction coefficients,h xy (Na+I — non-electrolyte) in DMF were calculated and analysed together with the appropriate data concerning other Na+I — non-electrolyte pairs in DMF. The group interaction coefficients illustrating the interactions of Na+I with the CH2, OH, O, CO, ‘Pep’ and ‘iPep’ groups were determined and discussed.

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Enthalpies of dissolution of benzo-15-crown-5 ether (B15C5) in mixtures of acetonitrile with water and in solutions of NaI and NaBPh4 (I=0.05 mol dm−3) in these mixtures were measured at 298.15 K. From the obtained results and appropriate literature data, the thermodynamic functions of B15C5/Na+ complex formation in acetonitrile-water mixtures were determined. The enthalpies of transfer of the complex B15C5/Na+ from pure acetonitrile to the examined mixtures were calculated and are discussed.

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The enthalpies of crystallization of NaCl, KCl, LiCl·H2O, MgCl2·6H2O, CaCl2·6H2O and BaCl2·2H2O from aqueous solution were determined by means of different calculation methods on the basis of the earlier-measured differential and integral enthalpies of solution of the above salts. The obtained crystallization enthalpies are discussed and compared with the appropriate literature data.

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Abstract  

For the equilibrium solid phases occurring in the systems: KCl−KBr−H2O, K2SO4−(NH4)2SO4−H2O and KNO3−NH4NO3−H2O, the concentration dependencies of differential solution enthalpies, Δsol H 2 for several crystallization paths, were measured. The limiting differential solution enthalpies, Δsol H 2 0 , were determined by extrapolation of the above dependencies to the ionic strength,I m 0 , corresponding to the appropriate binary solutions. For KCl−KBr−H2O system only, the clear dependence between Δsol H 2 0 andI m 0 values was found and discussed.

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Heat capacity of aqueous 2-(2-hexyloxyethoxy)ethanol solutions by DSC

Application of two-point scaling to pseudophases coexistence

Journal of Thermal Analysis and Calorimetry
Authors:
H. Piekarski
,
M. Tkaczyk
, and
M. Wasiak

Summary  

The specific heat capacities of aqueous solutions of 2-(hexyloxyethoxy)ethanol (C6E2) have been measured from 2 to 55C within the whole available composition range by DSC. Changes of specific, partial and apparent molar heat capacities of investigated system were analysed and considered as an effect of structural transformations. The two-point scaling theory was applied to the description of the binary mixtures properties in the pseudophases coexistence region.

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