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  • 1
    ISSN: 1572-8927
    Schlagwort(e): Heat capacity ; high temperature ; mixed electrolytes solution ; sodium chloride ; potassium chloride ; sodium sulphate ; potassium sulphate
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Specific heats at constant pressure for the mixed system K/Na/Cl/SO4 in H2O have been obtained from heat content measurements by means of a drop calorimeter between 60 and 220°C over the salt concentration range 0.5–5m, with ionic strengths up to 7.5. Measurements have also been made on aqueous K2SO4 solutions in the same temperature range between 0.3 and 1.6m. The heat capacities of the quaternary system were represented using the semiempirical Pitzer equations neglecting the mixed interaction terms as a first approximation. A comparison of experimental with calculated data shows that the ability of this method to describe the system is satisfactory even at rather high concentrations, but only for solutions of low sulphate ion content.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 17 (1988), S. 481-497 
    ISSN: 1572-8927
    Schlagwort(e): Heat capacity ; enthalpy of dilution ; aqueous NaOH ; aqueous Na2SO4 ; high temperature ; flow calorimeter
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The apparent molar heat capacity, C p,ϕ, of aqueous NaOH has been measured at temperatures between 50 and 250°C and molalities from 0.05 to 1.5 mol-kg−1. Enthalpies of dilution ΔLϕ were also determined at 99°C and apparent molar relative enthalpies Lϕ were calculated up to 1.9 m. Measurements were performed by means of a flow calorimetric apparatus constructed in our laboratory and standardized for C p,ϕ and ΔLϕ with aqueous Na2SO4 and with the formation of water from its ions, respectively. Characteristics and performance of this calorimeter are described in detail. Pitzer's semiempirical equations are used for the representation of the results and a general fitting of C p,ϕ data is reported using also recent literature values measured between 4 and 55°C. The fitted parameters are finally utilized, through an integration procedure, to derive a general equation to calculate Lϕ at any temperature between 4 and 250°C.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    Journal of solution chemistry 18 (1989), S. 447-461 
    ISSN: 1572-8927
    Schlagwort(e): Heat capacity ; enthalpy of dilution ; aqueous NaAl(OH)4 ; high temperature ; flow calorimeter ; aluminum ion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The apparent molar heat capacities, Cp,ϕ, of alkaline aqueous solutions of aluminum ion in excess NaOH have been measured at temperatures between 50 and 250°C in the overall molality range 0.3–1.7 mol-kg−1. Enthalpies of dilution, ΔLϕ, have also been determined at 99°C and apparent molar relative enthalpies, Lϕ, were calculated starting from 2.16 mol-kg−1 as the maximum concentration. Measurements of the above quantities have been performed by means of a differential flow calorimeter built in our laboratory and already described. The thermodynamic data obtained and the corresponding quantities for aqueous NaOH previously determined have been fitted to the equations of the Pitzer ionic interaction model to obtain parameters relative to aqueous NaAl(OH)4. These parameters permit the calculation of Cp,ϕ, and Lϕ for this species over the examined range of temperatures and concentrations.
    Materialart: Digitale Medien
    Bibliothek Standort Signatur Band/Heft/Jahr Verfügbarkeit
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