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  • entropy  (2)
  • hydrochloric acid  (2)
  • 5'-O-demethyl-8-O-methyl-dioncophylline A
  • 1
    ISSN: 1572-8927
    Keywords: Deuterium chloride ; deuterium oxide ; electrochemical cell ; emf ; enthalpy ; entropy ; free energy ; heat capacity ; isotope effect ; standard potential ; thermodynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The themodynamic properties of solutions of deuterium chloride (DCl) in deuterium oxide (D2O) have been determined from emf measurements of the electrochemical cell without transference from 5 to 50°C, and from 0.002 to 1.0 mol-kg−1. The standard potential of the silver/silver chloride electrode relative to the platinum/deuterium electrode has been determined. An equation for the Gibbs energy as a function of temperature has been derived from which the enthalpy, entropy, and heat capacity have been computed. Equations for the activity coefficient and the osmotic coefficient of DCl in D2O have been developed. The excess Gibbs energy of the solution and the excess partial molar free energy as a function of temperature have been calculated, from which the other excess thermodynamic properties have been computed. The values for the heat capacity and the apparent molar heat capacity have been compared with calorimetric data in the literature. The relative partial molar enthalpy has been calculated. The solvent isotope effect on the excess thermodynamic functions is discussed.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1572-8927
    Keywords: Activity coefficient ; amino acid ; EMF ; first dissociation constant ; HEPES ; glycine ; MOPSO ; ionic interaction ; hydrochloric acid
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Ionic interaction in the three systems Hcl-HEPES (N-2-hydroxyethylpiperazine-N′-2-ethanesulfonic acid), HCl-MOPSO (3-(N-Morpholino)-2-hydroxypropanesulfonic acid), and HCl-glycine have been studied in terms of their mutual influence on the respective activity coefficients of each component. Activity coefficients for each component of the three systems are calculated from emf measurements of solutions containing HCl and the amino acid in a H2/solution/AgCl,Ag cell at 25°C. The first dissociation constant of HEPES at 25°C has also been determined using emf and pH titration measurements.
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  • 3
    ISSN: 1572-8927
    Keywords: Electrolytic conductance ; hydrochloric acid ; ionic mobility ; magnesium chloride ; and mixture effect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The Onsager-Fuoss-Chen theory of conductance for mixtures has been explored and compared with experimental results for the system HCl−MgCl2−H2O from 5×10−5 to 0.02 mol-kg−1 of water. In the theory, the higher order term O(ka) which involves the ion size parameter has been replaced by a linear term with an empirical constant. The theory including the additional linear term agrees well with the experimental results. The mixture effect on the equivalent conductance is small, but on the individual ionic mobilities is substantial.
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  • 4
    ISSN: 1572-8927
    Keywords: Dissociation constant ; buffers ; NaMOPS ; temperature dependence ; emf ; Gibbs energy ; enthalpy ; entropy ; heat capacity ; zwitterion ; liquid junction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The second dissociation constant pK2 of 3-(N-morpholino)propanesulfonic acid (MOPS) has been determined at eight temperatures from 5 to 55°C by measurements of the emf of cells without liquid junction, utilizing hydrogen electrodes and silver–silver chloride electrodes. The pK2 has a value of 7.18 ± 0.001 at 25°C and 7.044 ± 0.002 at 37°C. The thermodynamic quantities ΔG°, ΔH°, ΔS°, and ΔC p o have been derived from the temperature coefficients of the pK 2. This buffer at ionic strength I = 0.16 mol-kg−1 close to that of blood serum, has been recommended as a useful secondary pH standard for measurements of physiological fluids. Five buffer solutions with the following compositions were prepared: (a) equimolal mixture of MOPS (0.05 mol-kg−1) + NaMOPS, (0.05 mol-kg−1); (b( MOPS (0.05 mol-kg−1) + NaMOPS (0.05 mol-kg−1) + NaCl (0.05 mol-kg−1); (c) MOPS (0.05 mol-kg−1) + NaMOPS (0.05 mol-kg−1); + NaCl (0.11mol-kg−1); (d) MOPS (0.08 mol-kg−1) + NaMOPS (0.08 mol-kg−1); and (e)MOPS (0.08 mol-kg−1) + NaMOPS (0.08 mol-kg−1) + NaCl (0.08 mol-kg−1).The pH values obtained by using the pH meter + glass electrode assembly are compared with those measured from a flow–junction calomel cell saturated with KCl (cell B), as well as those obtained from cell (A) without liquid junction at 25 and 37°C. The conventional values of the liquid junction potentials E j have been obtained at 25 and 37°C for the physiological phosphate reference solution as well as for the MOPS buffers (d) and (e) mentioned above.
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  • 5
    ISSN: 0031-9422
    Keywords: 5'-O-demethyl-8-O-methyl-7-epi-dioncophylline A ; 5'-O-demethyl-8-O-methyl-dioncophylline A ; Dioncophyllaceae ; Triphyophyllum peltatum ; atropisomerism. ; biaryls ; naphthylisoquinoline alkaloids ; stem bark
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Biology , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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