[en] The condensed phase standard (p° = 0.1 MPa) molar enthalpy of formation of ethyl-2-thiophenecarboxylate was derived from the remeasured standard molar energy of combustion, in oxygen, at T = 298.15 K, by rotating bomb combustion calorimetry and the standard molar enthalpy of vaporization, at T = 298.15 K, remeasured by Calvet microcalorimetry. Combining these two values, the following enthalpy of formation in the gas phase, at T = 298.15 K, was then derived for ethyl-2-thiophenecarboxylate: −(277.7 ± 2.9) kJ · mol⁻¹. The calculated gas-phase enthalpy of formation of the title compound, through the G3(MP2)//B3LYP approach was found to be 278.9 kJ · mol⁻¹, in excellent agreement with the experimental measured value

[en] In our previous publications it has been shown that the method of Benson's group permits the estimation of the enthalpies of vaporization of organic compounds. In the present paper we have applied this method for unsaturated hydrocarbons, thus completing our previous work on acyclic alkenes. For the alkylbenzenes we have changed the values of the groups C-(Csub(b))(C)(H)₂ and C-(Csub(b))(C)₂(H) previously determined. A more accurate value for the enthalpies of vaporization of the alkylbenzenes of higher molecular weight is obtained. (orig.)

No abstract available

[en] Studies made under conditions of complete isothermal evaporation at mass-spectrometric vapour analysis permitted determining atomization enthalpy of rareearth metal monochalcogenides. These values were also determined from temperature dependences in intensities of ionic currents of main vapour components. The results obtained showed that mearurements made with oxygen either above 0.2% (by mass) or with the ionic current intensity ration Isub(LnOsup(+))/Isub(Lnsup(+))0.2 lead to enhanced values of atomization enthalpies of REM chalgogenides. The level γ=0.1 is recommended (γ=Isub(LnO)/Lnsup(+)) which may be considered necessary and sufficient for reliability of atomization enthalpy values of REM chalgogenides

[en] In this work, modifications are made to a fairly simple laboratory experiment to experimentally determine the latent heat of vaporization with a substantially lower error than those previously reported. A new experimental technique of using an asynchronous data capture method is proposed for use with an adiabatic calorimeter for measurement as it isolates the measurement vessel from changes in the surroundings affecting the measured quantity. Further modifications are made to the experiment to determine the power at each instant the rate of mass drop is measured within the measurement range to ensure the errors associated with varying power resulting from resistance fluctuations are also minimized. The asynchronous data capture method proposes the use of computer control for the entire experiment, which again reduces the error in terms of delays in human reaction time. Applying these three new techniques to the experiment enables the latent heat of L_N2 to be determined experimentally and results in a substantially lower error bar attached to the final value for the latent heat of vaporization of liquid nitrogen. The value of L_v = 201.2 ± 0.194 J/g differs by approximately 1% from the accepted value of 199.0 J/g (G.W.C. Kaye and T.H. Laby. Tables of physical and chemical constants, fifteenth edition. Longman, London. 1995). Sources of systematic (experimental) error are suggested and estimated for in this experiment and thus this small discrepancy is accounted for. (author)

[en] 'Carabao' mango fruits subjected to gamma radiation at 100, 150 or 250 Gy resulted in fruits of an acceptable quality. In contrast to the vapor heat treatment, no internal breakdown was observed even in fruits irradiated at 350 Gy. At this dose a low but significant incidence of pulp discoloration was found, albeit in only one trial. Both the vapor heat treatment and gamma radiation need to be supplemented with hot water treatment for effective and more consistent disease control. Although irradiation appears to delay ripening, its effect seems to be largely on peel color development. The results of this study indicate that irradiation might be an appropriate quarantine treatment for the 'Carabao' mango. (Auth.). 7 tabs., 3 figs

[en] Vapour pressures and the molar enthalpies of vapourization of the γ-lactones (γ-valerolactone, γ-hexanolactone, γ-heptanolactone, γ-nonanolactone, and γ-decanolactone) have been determined by the transpiration method. These results together with a large number of experimental data from the literature have been checked for internal consistency. This collection has been used for development of group-additivity procedure for prediction of vapourization enthalpies of lactones

[en] This paper reports an experimental investigation of the latent heat of vaporization (h_fg) in nanofluids. Two different types of nanoparticles, graphite and silver, suspended in deionized water were exposed to a continuous laser beam (130 mW, 532 nm) to generate boiling. The latent heat of vaporization in the nanofluids was determined by the measured vapor mass generation and the heat input. To ensure that the measured h_fg values are independent of heating method, the experiments were repeated with an electrically heated hot wire as a primary heat input. These experiments show considerable variation in the h_fg of nanofluids. That is, graphite nanofluid exhibits an increased h_fg and silver nanofluid shows a decrease in h_fg compared to the value for pure water. As such, these results indicate that relatively low mass fractions of nanoparticles can apparently create large changes in h_fg

No abstract available

[en] Vapour pressures and the molar enthalpies of vaporization Δ_l^gH_m of the linear alkyl-benzenes C₆H₅C_nH_2n+1 with the alkyl chain length n=5, 7, 10, and 11 have been determined by the transpiration method. Kovat's indices of the linear and branched alkyl-benzenes C₁ to C₁₆ were collected from the available literature. A linear correlation of enthalpies of vaporization Δ_l^gH_m at T=298.15K of the alkyl-benzenes with the number of carbon atoms, as well as with the Kovat's indices on the non-polar GC columns has been found. A simple GC-correlation approach for correlation and accurate predictions of vapour pressures and vaporization enthalpies of mono- and poly-alkyl-substituted benzenes has been suggested