Václav Svoboda

Comparison of methods employing gas chromatography retention data to determine vapour pressures at 298 K

Validity of five models suggested for expressing the relationship between vapour pressures and GC retention times measured on a non-polar capillary column were tested on a common set of compounds [five homologous series of the type H-(CH2)n-Y, where Y denotes Cl, Br, CHO, OCOCH3 and COOCH3, and n varies from 6 to 14]. Standard methods of statistical analysis, as well as vapour pressure values obtained independently from direct vapour pressure measurements were used as validity criteria. For the 40-compound data set examined, the methods provided vapour pressures agreeing within 9.2-24.7% (average absolute percent error) with direct experimental data.

Enthalpies of vaporization and cohesive energies for six monochlorinated alkanes

Abstract Enthalpies of vaporization were determined for six monochlorinated alkanes in the temperature range from 298 to 368 K. Measurements were performed on an adiabatic isothermal calorimeter with an estimated accuracy of 0.3 per cent. Cohesive energies were calculated from the experimental results.

Enthalpies of vaporization and cohesive energies for a group of aliphatic ethers

Abstract The temperature dependence of the enthalpy of vaporization for a group of 11 aliphatic ethers is reported. Measurements have been performed on an adiabatic isothermal calorimeter with an accuracy of 0.25 per cent. The experimental values are exploited for calculating cohesive energies.

Enthalpies of vaporization and cohesive energies for seven aliphatic ketones

Abstract Enthalpies of vaporization were determined for seven aliphatic ketones with an adiabatic isothermal calorimeter in the temperature range from 298 up to 368 K. Cohesive energies were evaluated from experimental results and correlated with temperature.

Enthalpies of vaporization and cohesive energies of eight C9 to C11 alkanes

Abstract Enthalpies of vaporization of nonane, 2-methylnonane, 3-methylnonane, 5-methylnonane, 2,4-dimethyloctane, 2-methyldecane, 4-methyldecane, and 2,4,7-trimethyloctane were measured over the temperature range from 328 to 368 K using an adiabatic vaporization calorimeter. The accuracy of the results was better than 0.2 per cent. Smoothed values were extrapolated to obtain enthalpies of vaporization at 298.15 K and normal boiling temperatures. Cohesive energies were calculated from the results and correlated with temperature.

Enthalpies of vaporization at high pressures for methanol, ethanol, propan-1-ol, propan-2-ol, hexane, and cyclohexane

Abstract An isothermal vaporization calorimeter of a new design was used to measure enthalpies of vaporization of methanol, ethanol, propan-1-ol, propan-2-ol, hexane, and cyclohexane over the temperature range 343 to 438 K and the corresponding vapour pressures up to 1.9 MPa. The estimated maximum error of measurement is smaller than 1 per cent. The maximum standard deviation is 0.6 per cent.

On the enthalpy of vaporization of isomeric butanols

Abstract The paper reports new experimental enthalpies of vaporization for 2-methylpropanol in the range from 298.15 to 358.2 K, and for 2,2-dimethylethanol in the range from 303.15 to 368.2 K. All available experimental enthalpies of vaporization for four isomeric butanols have been collected, their accuracies have been assessed, and parameters of a correlating equation for Δ l g H m as a function of temperature have been evaluated. The correlations apply to the temperature ranges from 298 to 440 K for 2,2-dimethylethanol, and from 298 to 500 K for the other alcohols. The reliability of the various sources of experimental values is assessed, and anomalous variation in Δ l g H m with temperature is discussed.

A calorimeter for the determination of enthalpies of vaporization at high temperatures and pressures

Abstract A new calorimeter has been designed for the determination of the temperature dependence of the enthalpy of vaporization of pure substances at high temperatures and pressures. The instrument works on the principle of isothermal calorimetry and consists of a closed system with controlled heat flow and vapour withdrawal. It has been designed for measurements over the temperature and pressure ranges 298 to 600 K and several kPa to 3 MPa, respectively. The calorimeter has been tested by measuring the temperature dependence of the enthalpy of vaporization of benzene.

Enthalpies of vaporization and cohesive energies of 2-chloro- 1,1,2-trifluoroethyl ethyl ether, 2-chloro-1,1,2-trifluoroethyl propyl ether, 2-chloro-1,1,2-trifluoroethyl chloromethyl ether, and 2-chloro-1,1,2-trifluoroethyl difluoromethyl ether

Abstract The temperature dependences of molar enthalpies of vaporization of four chlorofluoroethers were measured calorimetrically with an accuracy of 0.3 per cent. The compounds and the temperature ranges of measurement were: 2-chloro-1,1,2-trifluoroethyl methyl ether, 298.15 to 343.15 K; 2-chloro-1,1,2-trifluoroethyl isopropyl ether, 298.15 to 328.15 K; 2-chloro-1,1,2-trifluoroethyl butyl ether, 298.15 to 368.15 K; 2-chloro-1,1,2-trifluoroethyl chlorofluoromethyl ether, 298.15 to 368.15 K. The results were correlated as a function of temperature, and molar cohesive energies were evaluated.

Dependence of molar heat capacity of liquid alkanols C3–C5 on their structure

Abstract The dependence of molar heat capacities upon the molecular structure of isomeric alcohols C3–C5 is discussed in the liquid and ideal gas states. In general, the differences of the heat capacities for the ideal gas state are small in comparison to those for the liquid state. The larger differences for the liquid state are due to steric effects which occur during the formation of hydrogen bonds between molecules.