Publications

Abstract Enthalpies of dissolution in water of dialkylsulphides: CH3(CH2)v{single bond}S{single bond}(CH2)vCH3, v = 0, 1, and 2, and dialkyldisulphides: CH3(CH2)v{single bond}S{single bond}S{single bond}(CH2)vCH3, v = 0 and 1, were determined by microcalorimetry at the temperatures (288.15, 298.15, 308.15, and 328.15) K. Molar enthalpies of solvation and partial molar heat capacities at 298.15 K were derived for the infinitely dilute solutions. The partial molar heat capacities are discussed in terms of an empirical group scheme.

Abstract Thermopile heat conduction calorimeters normally have high time constants. Multistep titration experiments involving fast processes may then require several hours to perform. It is demonstrated that such experiments can be conducted about 10 times faster, without loss of accuracy, by use of a "dynamic correction method". For a new small vessel thermopile conduction calorimeter, injections can be made at 1.5-min intervals.

Abstract Cis/trans isomers of ferulic and isoferulic acids and their corresponding coumarins, scopoletin and isoscopoletin, were separated by isocratic High Performance Liquid Chromatography using RP-8 (5-mu-m) as a stationary phase and aqueous methanol or aqueous acetonitrile as a mobile phase. The UV spectrum of cis-isoferulic acid was obtained by a photodiode array detector.

Abstract The standard (po = 0.1 MPa) molar enthalpies of formation were derived from the standard molar enthalpies of combustion, in oxygen, at 298.15 K, measured by static bomb calorimetry for 2-hydroxyquinoline (2HOQ), 4-methyl-2-hydroxyquinoline (4Me-2HOQ), 4-hydroxyquinoline (4HOQ), and 2-methyl-4-hydroxyquinoline (2Me-4HOQ); the vapour pressures of the crystals were measured as functions of temperature by the Knudsen-effusion technique, and the standard molar enthalpies of sublimation, at 298.15 K, were derived by the Clausius-Clapeyron equation. {A table is presented}. © 1990.

Abstract The standard (p0 = 0.1 MPa) molar enthalpy of formation, at 298.15 K, of crystalline dicarbonylbiscyclopentadienyltitanium(II), Ti(η-C5H5)2(CO)2, has been derived from the enthalpy of the oxidative reaction of Ti(η-C5H5)2(CO)2 with 9,10-phenanthraquinone in toluene determined by precision solution-reaction calorimetry) as ΔHf 0 {Ti(η-C5H5)2(CO)2, cr} = -371.5 ± 12.9 kJ mol-1. A re-evaluation of the TiCO bond enthalpy term and an estimate of the mean bond dissociation enthalpy are also described. © 1990.

Abstract Monocrystalline gold surfaces having five different crystallographic orientations have been characterized by means of cyclic voltammetry in aqueous 0.11 M NaOH in order to examine the electrochemistry of oxide formation and removal in comparison with the well-characterized behavior in acidic media. For the higher-index faces Au(210) and (311), these voltammetric features in 0.11 M NaOH are closely similar to those observed in acidic electrolytes, although the occurrence of substantial OH- adsorption is signaled by a broad reversible current-potential feature at less positive potentials. For the low-index faces Au(100) and (111), however, the voltammograms in 0.11 M NaOH differ substantially from those in acid. These differences are ascribed to the influence of potential-dependent OH- adsorption, which overlaps with oxide formation and especially reduction, and attendant potential-induced surface reconstruction. The behavior of Au(110) is intermediate between that of these other two low-index and the higher-index faces. As for the voltammetric features in acidic electrolytes, such crystal face-dependent voltammetry in 0.11 M NaOH can be employed as a sensitive (albeit empirical) check of the chemical and physical state of the interface prior to other electrochemical measurements. © 1990.

Abstract The construction of a new Knudsen effusion apparatus for measuring vapour pressures of organic and organometallic solids as a function of temperature and the subsequent calculation of enthalpies of sublimation are described. The new apparatus enables the simultaneous operation of three different effusion cells, reducing, considerably, the time necessary for the study of each compound. The performance of the apparatus was checked by measuring, as a function of temperature, the vapour pressure of benzoic acid (between 307.15 and 314.15 K) and ferrocene (between 292.27 and 300.01 K), from which their standard molar enthalpies of sublimation, at 298.15 K, were derived: benzoic acid, Δcr gH298.15 XXX = 89.25±0.85 kJ mol-1; ferrocene, Δcr gH298.15 XXX = 72.39 ± 1.00 kJ mol-1. © 1990.

Abstract The standard (p^{o = 0.1 MPa}) molar enthalpies of combustion at 298.15 K were measured by static-bomb calorimetry and the standard molar enthalpies of sublimation at 298.15 K were measured by microcalorimetry for phenazine, benzofurazan, and their corresponding N-oxides: {A table is presented}. From the standard molar enthalpies of formation of the gaseous compounds, the molar dissociation enthalpies of the (NO) bonds werederived: D(NO)/(kJ · mol^-1): phenazine N-oxide, 280.7 ± 5.6; benzofuroxan, 250.9 ± 3.0. © 1990.