Excess molar enthalpy of binary mixtures of hexane+ethyl benzene, <Emphasis Type="Italic">o</Emphasis>-xylene, <Emphasis Type="Italic">m</Emphasis>-xylene and <Emphasis Type="Italic">p</Emphasis>-xylene at 298.15 K

Summary This paper reports excess molar enthalpies of the binary systems hexane+ethyl benzene, hexane+o-xylene, hexane+m-xylene and hexane+p-xylene at 298.15 K and atmospheric pressure, over the whole composition range. The data was measured directly using a Calvet microcalorimeter. The excess magnitude was correlated to a Redlich-Kister type equation for each mixture. Also, we will discuss the results for the four mixtures studied here and by comparison with the same binary systems but containing propyl propanoate as first component. Finally, we will correlate our results with the Nitta-Chao and the three UNIFAC theoretical approximations.     

SYNTHESIS AND DESULFURATION OF THIANAPHTHEN-3-CARBOXYLIC ACID DERIVATIVES

Abstract

Bis(trimethylsilyl)peroxide (BSPO) can be used for chemo- and stereoselective generation of P=O group by oxygenation of P(III) centre and transformation of P=S and P=Se groups.     

Viscosities and Densities of Solutions of n-Decane, or n-Tetradecane with Several Esters at 25°C

Viscosity and density data are reported for n-decane + propyl ethanoate, propyl propanoate, propyl butyrate, and n-tetradecane + propyl ethanoate, propyl propanoate, and propyl butyrate at 25°C and atmospheric pressure. Kinematic viscosities were determined using a capillary viscosimeter and densities were measured using vibrating-tube densimetry. The equations of Grunberg–Nissan, McAllister, Auslander, and Teja were fitted to the viscosity data. Excess molar Gibbs free energies of activation for flow were also evaluated. The experimental values obtained for excess volumes were compared with the Nitta et al. group contribution model.     

Excess molar volumes and enthalpies for the binary systems propyl propanoate + o-xylene, m-xylene, and p-xylene at 298.15 K

This paper reports excess molar enthalpies, H_m^E, and excess molar volumes, V_m^E, of the binary systems {propyl propanoate + o-xylene}, {propyl propanoate + m-xylene} and {propyl propanoate + p-xylene} at the temperature 298.15 K and atmospheric pressure, over the whole composition range. V_m^E was calculated from the experimental measurement of the corresponding densities, while H_m^E was measured directly. The excess magnitudes were correlated to a Redlich-Kister type equation. Finally, we will discuss the results of the three mixtures studied here and by comparison with other binary systems containing propyl propanoate and a benzene-based compound previously published.     

The determination of sulfonamides in honey by high performance liquid chromatography--mass spectrometry method (LC/MS)

The sulfonamides (SAs) are stable chemotherapeutics used against the bacterial disease affecting bees, known as American foulbrood (Bacillus larvae), so their residues could appear in the honey of treated bees. Their presence at a concentration above the limit value could be a potential danger to human health. Therefore, a simple, rapid, and reliable method for determination of 11 available SAs in honey was optimized. The samples were homogenized and cleaned with extraction on solid phase by means of Chromabond C18 end-capped cartridge followed by LC/MS analyses. A detection limit of 25 microg/kg was achieved for all analytes. The repeatability of the method was proven and the optimal parameters for temperature and pH of the mobile phase and acetic buffer, respectively, were determined. In this study, 20 samples of domestic honey were included. Six of the analyzed samples were positive, but all results were below the Croatian permissible limit value (100 microg/kg).     

Nonmesonic Weak Decay Spectra of Light Hypernuclei

The nonmesonic weak decay spectra of light hypernuclei have been evaluated in a systematic way. As theoretical framework we adopt the independent particle shell model with three different one-meson-exchange transition potentials. Good agreement with data is obtained for proton and neutron kinetic energy spectra of ${^4_\Lambda}$ He, and ${^5_\Lambda}$ He, when the recoil effect is considered. The coincidence spectra of proton-neutron pairs are also accounted for quite reasonably, but it was not possible to reproduce the data for the neutron–neutron pair spectra. It is suggested that the π + K meson-exchange model with soft monopole form factors could be a good starting point for describing the dynamics responsible for the decays of these two hypernuclei. The ${^4_\Lambda}$ H spectra are also presented.     

Viscosities and Densities for the 1-Propanol + n-Heptane System at Several Temperatures

Viscosities and densities have been measured for 1-propanol + n-heptane at 20, 25, 30, and 35°C and atmospheric pressure. Kinematic viscosities were determined using a capillary viscosimeter; densities were measured using vibrating-tube densimetry. The viscosity deviations were evaluated. Viscosity results were fitted to the equations of Grunberg–Nissan, McAllister, Auslander, and Teja. The experimental excess molar volumes were compared with the results obtained with the Nitta–Chao model.