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  • 1
    ISSN: 1572-8927
    Keywords: Electrochemical thermodynamics ; standard emfs ; standard potentials ; activity coefficients ; nonaqueous solvents ; mixed solvents ; aqueous-organic solvent mixtures ; hydration numbers ; amalgam electrode
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electromotive force of the amalgam cell {NaxHg1-x‖NaCl(m)‖AgCl‖Ag} has been measured at 25°C as a function of the mole fraction x of Na in amalgams and of the molality m of NaCl in (ethylene glycol + water), (acetonitrile + water), and (1,4-dioxane + water) mixed solvents, containing up to 0.8 mass fraction of the organic component, with relative permittivities ε ≥ 27. The relevant standard molal electromotive forces $$E_{\text{m}}^ \circ $$ have been determined, together with the mean molal activity coefficient γ± of NaCl as a function of its molality. In the case of (ethylene glycol + water) mixtures, a linear dependence of $$E_{\text{m}}^ \circ $$ on the mass fraction of ethylene glycol is observed, which is quite unusual, The Debye-Hückel equation is applicable successfully over the whole range of molalities explored, which extends to the vicinity of the solubility limit of NaCl in each solvent. The dependence of the standard emf on the logarithm of the volume fraction of water in the aqueous-organic solvent mixtures have been analyzed in terms of Feakins and French's theory, leading to a primary hydration number 7.2 for NaCl, in good agreement with previous results employing different methods.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8927
    Keywords: pH standards ; aqueous—organic solvents ; medium effects ; ionization constants
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Determination of primary standards for pH measurements in glycerol + water solventmixtures has been carried out based on reversible emf measurements of the cellPt|H2|KHPh (m PS) + KCl (m Cl)|AgCl|Ag|Ptwhere KHPh denotes the potassium hydrogen phthalate buffer solution of molalitym PS = 0.05 mol-kg−1, at glycerol mass fractions w G = 0.2 and 0.4, within thetemperature range −10 to 40°C. A multilinear regression procedure as a functionof electrolyte molality, glycerol mass fraction w G, and temperature T has beenapplied for the data processing leading to the values of primary standards pHPS.These can be represented by the following regression equationpHPS = (4.007037±0.001113) + (3.55844±0.01776)x G+(0.39622±0.01410)z + (4.3084±0.3377)z 2− (50.66±10.53)x G z 2 + (457.10±78.48)x G 2 z 2where z = (T − 298.15)/298.15. Parallel values of the first ionization constantof o-phthalic acid (H2Ph; benzene-1,2-dicarboxylic acid, the parent acid of KHPh),which are essential for the above calculations, have been determined fromreversible emf measurements of the cellPt|H2|H2Ph (m 1) + KHPh (m 2) + KCl (m 3)|AgCl|Ag|Ptover the range of solvent composition and temperatures mentioned above.
    Type of Medium: Electronic Resource
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