Superheated dielectric constant

The static dielectric constant of superheated water was measured by the relative noncontact bridge method. " The glass measuring cell was relieved of pressure. Measurements were made in the range from 423 to 573 K along isotherms with an interval of 10 K. Within the measurement error the static dielectric constant of superheated water remains unchanged along the isotherms. 

Chukanov, V. N. (1971) Dielectric Constant of Superheated Liquid Water. Teplofizika vysokikh temperatur 9, 1071-1073. 

GC is the most commonly used separation method in the analysis of BTEX from environmental samples. Liquid chromatography (LC) analysis with superheated water or water-dimethylsulfoxide (DMSO) mixmres has also been reported. In both cases a reduction in the dielectric constant of the mobile phase for the separation of nonpolar analytes was studied. The results showed how the rise in temperamre required a decrease in DMSO in order to achieve the same retention time. 

This table gives properties of compressed water and superheated steam at selected pressures and temperatures. The properties included are density p, enthalpy//, entropy S, heat capacity at constant pressure C, and static dielectric constant (relative permittivity). The table was generated from the formulation approved by the International Association for the Properties of Water and Steam for general and scientific use. The reference state for this table is the liquid at the triple point, at which the internal energy and entropy are taken as zero. A duplicate entry in the temperature column indicates a phase transition (liquid-vapor) at that temperature property values are then given for both phases. In the 100 MPa section of the table, an entry is given at the critical temperature, 647.10 K. Temperatures refer to the ITS-90 scale, on which the normal boiling point of water is 373.12 K (99.97°C). 

The average relaxation time is of course temperature dependent and maybe related to a rate constant k for the relaxation process of the molecules in solution. Table 1.3 gives some representative data for EtOH and illustrates the extent to which the relaxation time decreases with temperature. It is noteworthy that the relaxation time decreases from 270 to 49 ps as the temperature rises from 10 to 70°C, and therefore, as the temperature increases the alcohol couples more effectively with the microwave source at 2.45 GHz. Such a situation is ripe for superheating the solvent, since the extent of conversion increases as the temperature rises. It also follows that some organic solvents with very long relaxation times at room temperature may appear to be unsuitable candidates for dielectric heating, but since the match becomes more favourable with temperature then they may behave as effective couplers as the temperature rises, that is, after a slow start they may very well heat very rapidly. 

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