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  • 1
    ISSN: 1520-5134
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1520-6882
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Amsterdam : Elsevier
    Biochemical and Biophysical Research Communications 188 (1992), S. 252-256 
    ISSN: 0006-291X
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Springer
    Journal of solution chemistry 28 (1999), S. 1329-1340 
    ISSN: 1572-8927
    Keywords: Transference cells ; transference numbers ; salt bridges ; mixed solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The electromotive forces (emf) E A and E C of the following concentration cells with transference: $${\text{Ag}}\left| {{\text{AgCl}}} \right|{\text{KCl (}}m_2 {\text{)}}\left\| {{\text{KCl(}}m_1 {\text{)}}\left| {{\text{AgCl}}} \right|{\text{Ag and K}}_{\text{x}} {\text{Hg}}_{{\text{1}} - {\text{x}}} |{\text{KCl(}}m_1 {\text{)}}} \right\|{\text{KCl(}}m_2 {\text{)|K}}_{\text{x}} {\text{Hg}}_{{\text{1}} - {\text{x}}} ,$$ respectively, together with the emfs E MAX of the corresponding double cell without transference: $${\text{K}}_{\text{x}} {\text{Hg}}_{{\text{1}} - {\text{x}}} \left| {{\text{KCl(}}m_1 {\text{)}}} \right|{\text{AgCl}}\left| {{\text{Ag}} - {\text{Ag}}} \right|{\text{AgCl}}\left| {{\text{KCl(}}m_2 {\text{)}}} \right|{\text{K}}_{\text{x}} {\text{Hg}}_{{\text{1}} - {\text{x}}} $$ have been measured at KCl molalities m (m 1 fixed and m 2 varied, with m 2〉m 1) approximately up to the KCl solubility limit in 12 solvent mixtures for the three aqueous–organic solvent systems (ethylene glycol+water), (acetonitrile + water), and (1,4-dioxane + water) up to 0.8 mass fraction of organic component. For all the cases explored, the E A vs. E MAX relation is linear over the whole KCl molality range. The ionic transference numbers t of KCl determined therefrom show a curvilinear dependence on the mass fraction of the organic component of the relevant solvent mixture and are found to fall in the range 0.52–0.48, viz., within ±4% of exact equitransference (t + = t − = 0.5). In particular, KCl becomes exactly equitransferent (i.e., an ideal salt bridge) in aqueous mixtures with the following mass fractions of organic component: 0.4 ethylene glycol and 0.09 acetonitrile, as well as 0.12 methanol, and 0.08 and 0.34 ethanol from our recent work. Even if use of KCl as a salt bridge would be somewhat restricted by its limited solubility in high mass fractions of dioxane and acetonitrile and pending extension of investigation to other mixed-solvent systems, the above figures characterize KCl as a fairly good “intersolvental” salt bridge in electrochemistry, electroanalysis, and corrosion science.
    Type of Medium: Electronic Resource
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  • 5
    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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  • 6
    ISSN: 1572-8927
    Keywords: Transference numbers ; concentrated electrolyte ; hydrochloric acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ion-transfer parameters of aqueous hydrochloric acid over a wide molality range have been re-investigated taking the concurrent solventtransfer into due account. In this context, the transference numbers for the hydrogen ion τH and for water τw have been determined from 10−2 to 15 mol-kg−1, together with the corresponding infinite-dilution values τ H o and τ w o , by processing a set of nearly a hundred emf measurements (some twenty of them new for this work) on HCl concentration cells with transference with both cation-reversible and anion-reversible electrode pairs.
    Type of Medium: Electronic Resource
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  • 7
    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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  • 8
    ISSN: 1572-8927
    Keywords: Transference cells ; transference numbers ; salt bridges ; mixed solvents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Electromotive forces (emf) were measured in the transference cells: Ag∣AgCl∣- Nacl (m2) in Z∥ NaCl (m1) in Z∣AgCl∣Ag and NaxHg1-x∣NaCl (m1) in Z∥ NaCl (m2) in Z∣NaxHg1-x (where NaxHg1-x denotes a flowing Na–amalgam electrode and Z an aqueous-organic solvent mixture) at various molalities m 2 〉 m1 of NaCl in Z = (ethylene glycol + water), (acetonitrile + water) and (1,4-dioxane + water), with mass fractions of the organic components ≤0.8. The transference number of Na+ in (ethylene glycol + water) and (1,4-dioxane + water) varies little with respect to that in pure water medium, whereas in (acetonitrile + water) it increases remarkably with increasing proportion of acetonitrile so as to approach equitransference, behavior similar to that previously found in (methanol + water) and in (ethanol + water). At acetonitrile mass fraction 0.6 NaCl is sufficiently close to equitransference to emerge as a useful salt bridge, nearly at the same level as the popular aqueous KCl.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1618-2650
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary One of the most complex establishments of standards in quality control is that for the measurement of acidity, the pH. Not only is this complexity linked with the environment or the matrix considered (solutions from chemical laboratories or industries, biophysiological fluids, sea waters, estuarine waters, freshwaters, acid rains, etc.) but also with the solvent type (water, nonaqueous solvents, aqueous-organic solvent mixtures). The results are distinct pH scales which, for each solvent considered, are articulated on one reference value standard (pHRVS) plus a group of primary standards (pHPS) and/or operational standards (pHos), as specified in recent IUPAC recommendations. Such specifications ensure that the above standards be determined according to the same electrochemical principles and procedures and be accurate typically to ±0.002 in pH. However, the acquisition and availability of such standards, though rapidly expanding, are hitherto limited to a few nonaqueous solvents or aqueous-organic solvent mixtures. Within this context, the determination of pHRVS in ethylene glycol/water mixtures, based on electromotive force measurements of the cell Pt|H2|RVS Buffer + KCl|AgCl|Ag|Pt over a range of temperatures and solvent compositions is here described. Anyway, the comparability of pH scales in different solvent media (and even in different environments) depends on the uncertain determinability of the primary medium effect upon the H+ ion. Finally, the predictability of the above standards, whithin acceptable reliability limits, for hitherto unexplored solvent media has been recently assessed in terms of such qualifying physicochemical quantities as solvent composition, dielectric constant and temperature. Status, applications and problems related to the above points are here analysed.
    Type of Medium: Electronic Resource
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