Showing: 10 from total: 1718 publications
1701. THERMODYNAMIC PROPERTIES OF GLYCEROL ENTHALPIES OF COMBUSTION AND VAPORIZATION AND THE HEAT-CAPACITY AT 298.15-K - ENTHALPIES OF SOLUTION IN WATER AT 288.15, 298.15, AND 308.15-K
BASTOS, M ; NILSSON, SO ; DASILVA, MDMCR ; DASILVA, MAVR ; WADSO, I
in JOURNAL OF CHEMICAL THERMODYNAMICS, 1988, ISSN: 0021-9614,  Volume: 20, 
Article,  Indexed in: crossref, scopus, wos 
Abstract Enthalpies of combustion and vaporization and the heat capacity have been determined for glycerol at 298.15 K. Using microcalorimeter techniques, enthalpies of solution at infinite dilution have been determined for glycerol in water (288.15, 298.15, and 308.15 K). The partial molar heat capacity of glycerol in infinitely dilute aqueous solution was derived: Cp,2 ∞ = (239 ± 3) J · K-1 · mol-1. This value confirms the view that the special type of interaction with water found in higher polyhydroxyl compounds is still absent for glycerol. © 1988.

1702. The temperature dependence of the double-layer properties of gold faces in perchloric acid solutions. Part II. The (110) gold face
Hamelin, A ; Stoicoviciu, L ; Silva, F
in Journal of Electroanalytical Chemistry, 1987, ISSN: 0022-0728,  Volume: 236, 
Article,  Indexed in: scopus 
Abstract The gold (110)/perchloric acid interface was studied at temperatures ranging from 0.5 to 41° C by differential capacity-potential curves. The temperature coefficient of the Galvani potential drop was found to vary with the concentration of the solution, in contrast to what was observed for the (210) gold face. The azimuthal anisotropy and reconstruction of the gold (110) face make difficult interpretation in terms of a model of the variations of the entropy of formation of this interface. C1 (σ) curves with two round maxima were found. Comparison to result obtained with this gold face in KPF6 and the silver (110) face is discussed. The inner-layer capacity, at zero charge, for Au (110) in HClO4 is also discussed and the sign of its temperature coefficient is deduced from modified Parsons-Zobel plots. © 1987.

1703. ARE THE REACTIONS LI+NA2 AND NA+K2 DIRECT OR INDIRECT - A DYNAMICS STUDY OF SEMIEMPIRICAL VALENCE-BOND POTENTIAL-ENERGY SURFACES
MORAIS, VMF ; VARANDAS, AJC
in JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS II, 1987, ISSN: 0300-9238,  Volume: 83, 
Article,  Indexed in: scopus, wos 
Abstract Quasiclassical trajectory calculations have been carried out for the Li + Na2 (ν = 0, J = 10) → LiNa + Na and Na + K2 (ν = 0, J = 10) → NaK + K reactions at collision energies of 3.5 and 2.3 kcal mol-1, respectively, using realistic potentials based on an extended-LEPS method. Most dynamics features suggest that those reactions proceed at such energies via an indirect mechanism. However, the analysis of the product internal state vibrational distributions show, particularly in the case of Na + K2, that it is not possible to assign a vibrational temperature to such distributions. The result from LIF experiments, which suggest a direct mechanism for Li + Na2 but are less conclusive for Na + K2, are thus only partly corroborated by the present calculations.

1704. THE TEMPERATURE-DEPENDENCE OF THE DOUBLE-LAYER PROPERTIES OF GOLD FACES IN PERCHLORIC-ACID SOLUTIONS .1. THE (210) GOLD FACE
HAMELIN, A ; STOICOVICIU, L ; SILVA, F
in JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 1987, ISSN: 0022-0728,  Volume: 229, 
Article,  Indexed in: crossref, scopus, wos 
Abstract The temperature dependence of the differential capacity curves for the (210) gold face in perchloric acid solutions of concentrations ranging from 10 mM to 2 M has been examined. The temperature coefficients of the Galvani potential drops are almost the same as that of mercury in sodium fluoride. The variations of the inner layer capacity, as a function of the charge density, are discussed tentatively. The entropies of formation of the interface and of the inner part of the double layer, as a function of the charge density, are reported. © 1987.

1705. ON THE 2 MODES OF CONDENSATION DISPLAYED BY THIOUREA AT THE MERCURY WATER INTERFACE
BUESSHERMAN, C ; GIERST, L ; GONZE, M ; SILVA, F
in JOURNAL OF ELECTROANALYTICAL CHEMISTRY, 1987, ISSN: 1572-6657,  Volume: 226, 
Article,  Indexed in: crossref, scopus, wos 
Abstract In the presence of "inert" electrolytes (sodium fluoride, sulfate, carbonate, phosphate) there exists a range of temperatures and thiourea (TU) concentrations (low and high respectively) where two distinct condensed TU monolayers, totally devoid of anions, are observed. The two relevant molecular structures which are suggested rest on the analysis of the following data: (1) E-T-[TU] phase diagrams derived from capacitance measurements, (2) superficial excesses and molecular areas, (3) charge densities, (4) inhibition power, and (5) kinetics displayed by the various phase transitions involved. Anions like ClO- 4, NO- 3, ClO- 3 are only coadsorbed within the gas-like film of TU, with the result that the pure TU condensed regions are squeezed detectably. On the other hand, anions known to interact strongly with Hg (Cl-, Br-, I-, SCN-)_do coadsorb significantly at all potentials. However, pure TU films tend to reappear if the concentration of these anions is lowered sufficiently with respect to that of the surfactant. © 1987.

1706. ENTHALPIES OF COMBUSTION OF THE 3 TRIHYDROXYBENZENES AND OF 3-METHOXYCATECHOL AND 4-NITROCATECHOL
DASILVA, MDMCR ; DASILVA, MAVR ; PILCHER, G
in JOURNAL OF CHEMICAL THERMODYNAMICS, 1986, ISSN: 0021-9614,  Volume: 18, 
Article,  Indexed in: scopus, wos 
P-001-VXK
Abstract The standard (po = 101.325 kPa) molar enthalpies of combustion in oxygen 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 each of the three trihydroxybenzenes, 3-methoxycatechol, and 4-nitrocatechol: {A table is presented}. The derived standard molar enthalpies of formation of the gaseous compounds were compared with values estimated assuming that each group, when substituted into the benzene ring, produces a characteristic increment in the enthalpy of formation, with additional corrections for adjacent substituents. © 1986.

1707. Enthalpies of combustion of the three trihydroxybenzenes and of 3-methoxycatechol and 4-nitrocatechol
Ribeiro da Silva, MD ; Ribeiro da Silva, MA ; Pilcher, G
in The Journal of Chemical Thermodynamics, 1986, ISSN: 0021-9614,  Volume: 18, 
Article,  Indexed in: crossref 

1708. On the third virial coefficient for the alkali metal vapours
Morais, VMF ; Varandas, AJC
in Chemical Physics Letters, 1985, ISSN: 0009-2614,  Volume: 113, 
Article,  Indexed in: scopus 
P-007-MH1
Abstract Theoretical calculations of the third virial coefficient for the pure components of all alkali metal vapours have been carried out using recently reported potential energy surfaces for the doublet and quartet states in which the interaction of three 2S ground-state atoms may evolve. The discrepancy between the theoretical and available experimental estimates for those coefficients is pointed out. © 1985.

1709. STANDARD ENTHALPIES OF FORMATION OF BIS(PENTANE-2,4-DIONATO)CU(II) AND OF 4 BIS(METHYL-SUBSTITUTED HEPTANE-3,5-DIONATO)CU(II) COMPLEXES - THE MEAN (CU-O) BOND-DISSOCIATION ENTHALPIES
DASILVA, MAVR ; DASILVA, MDMCR ; CARVALHO, APSMC ; AKELLO, MJ ; PILCHER, G
in JOURNAL OF CHEMICAL THERMODYNAMICS, 1984, ISSN: 0021-9614,  Volume: 16, 
Article,  Indexed in: scopus, wos 
P-001-WX5
Abstract At 298.15 K, the following standard molar enthalpies of formation of the crystalline solids were determined by solution-reaction calorimetry, and the enthalpies of sublimation were measured by microcalorimetry. {A table is presented} (PD, pentan-2,4-dionato; piprm, 2,2-dimethylheptan-3,5-dionato; dibm, 2,6-dimethylheptan-3,5-dionato; ibpm, 2,2,6-trimethylheptan-3,5-dionato; dpm, 2,2,6,6-tetramethylheptan-3,5-dionato.) The mean molar bon-dissociation enthalpy <D>(CuO) was related to D(OH) in the enol form of the diketone, and {<D>(CuO)-0.5D(OH), Hl, enol} was found to equal -(41.8 ± 2.0) kJ · mol-1, constant to within experimental error for all these complexes. Accepting {D(OH), Hl, enol} = (400 ± 20) kJ · mol-1, then <D>(CuO) = (158 ± 10) kJ · mol-1 showing a negligible effect of methyl substitution in the ligand l upon <D>(CuO). © 1984.

1710. ENTHALPIES OF COMBUSTION OF 1,2-DIHYDROXYBENZENE AND OF 6-ALKYLSUBSTITUTED 1,2-DIHYDROXYBENZENES
DASILVA, MDMCR ; DASILVA, MAVR ; PILCHER, G
in JOURNAL OF CHEMICAL THERMODYNAMICS, 1984, ISSN: 0021-9614,  Volume: 16, 
Article,  Indexed in: scopus, wos 
P-001-WX6
Abstract The standard (po = 101.325 kPa) molar enthalpies of combustion in oxygen 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 1,2-dihydroxybenzene (catechol) and six alkylsubstituted catechols: {A table is presented}. The increment in the molar enthalpy of formation of the gaseous compound for substitution of alkyl-groups into catechol was found to be approximately the same as the corresponding increment for substitution into benzene. © 1984.