The Infona portal uses cookies, i.e. strings of text saved by a browser on the user's device. The portal can access those files and use them to remember the user's data, such as their chosen settings (screen view, interface language, etc.), or their login data. By using the Infona portal the user accepts automatic saving and using this information for portal operation purposes. More information on the subject can be found in the Privacy Policy and Terms of Service. By closing this window the user confirms that they have read the information on cookie usage, and they accept the privacy policy and the way cookies are used by the portal. You can change the cookie settings in your browser.
Paralleling the increasing availability of oscillators, harmonic generators, detectors, and other microwave components that operate at wavelengths extending into the millimeter range, there has been a gradual evolution of techniques for the determination of the dielectric properties of liquids at these frequencies. The present paper aims to provide a general description of the interferometric method...
This study was undertaken because many careful dielectric constant measurements at radio frequencies have indicated the possession of small but appreciable dipole moments for supposedly symmetrical molecules1,2.
The physical properties of succinonitril, NCCH2CH2CN, have made it suitable for inclusion in a program of research at microwave frequencies on solids possessing high dielectric constants because of the rotational freedom of their polar molecules. At radio frequencies, White and Morgan found no drop in the high dielectric constant when liquid, succinonitrile solidified at 54.2°C. Below the freezing...
For the investigation of the relations between dielectric properties and molecular characteristics, the tetrahalogenated methanes provide a series of molecules which deviate in shape only a little from that of a sphere and in dipole moment only a little from zero. The dielectric constants of many of them have been measured in the liquid and solid states over a wide range of temperature at a frequency...
Previous measurements made in this laboratory have shown that elongated and flat molecules, and in general, non-spherical molecules, have a viscosity-dependent relaxation time, whereas the nearly spherical molecules exhibit relaxation times which are virtually independent of the viscosity of the medium. This paper will present some data which substantiates the viscosity independence of the relaxation...
By an adaptation of the Roberts and von Hippie “short circuit-line” method the dielectric constant and loss at 3.20 cm. wavelength of dl-camphor, d-camphor and isoborneol have been measured in the solid state over a wide range of temperatures and in the liquid phase just above the melting point. The values here obtained are compared with the radio-frequency values found in the literature. At 3.20...
Further measurements of dielectric constant and loss, in the microwave region have been carried out upon pure polar liquids and upon solutions of polar molecules in non-polar liquids of widely varying viscosities. Earlier measurements showed that the wavelength at which the loss was a maximum, that is, the critical wavelength, increased with increasing viscosity of the liquid and size of the molecule,...
The low frequency dielectric properties of 1-monopalmitin, 1-monostearin, 1,3-dipalmitin, 1,3-distearin and a number of long-chain triglycerides have been investigated in the solid state over a wide range of temperature, The measurements were made with the aid of an impedance bridge operating in the frequency range from 0.5 to 100 kilocycles.
Previous work carried out in this laboratory has indicated the desirability of further studies of the correlation between dielectric relaxation phenomena, molecular structure and viscosity. Measurements have been carried out on solutions of the nearly spherical t-butyl chloride and methyl chloroform molecules and the long n-tetradecyl bromide molecule in two non-polar solvents, n-heptane and a viscous...
The dielectric constant and cooling curves of highly purified n-hexade-cane, n-dodecyl, n-hexadecyl, n-octadecyl, and n-docosyl bromide have been measured over a large temperature range and at audio frequencies. These compounds will be designated hereafter as C16, C12-Br, C16-Br, C18-Br, and C22-Br respectively. C12-Br, C16-Br, and C18-Br showed a gradual rise in dielectric constant (prestation) beginning...
The dielectric constant is a very useful tool for studying molecular freedom and phase changes in organic polar compounds. Its magnitude can be used as an indication of the degree of orientational freedom of molecules in both liquid and solid phases. Thermal behavior is another useful tool, which, when combined with dielectric constant data, can often be helpful in describing phase changes in terms...
A method of measuring at microwave frequencies both the real (ε') and imaginary (ε″) part of the complex dielectric constant of liquids with a loss tangent less than 0,05 is described. The method uses a vertical section of rectangular waveguide for both propagation and for the liquid cell, which is sealed from the rest of the waveguide by a thin mica window. The waveguide cell is terminated by a micrometer...
The dielectric constants of pure samples of four normal long-chain bromides and four normal long-chain alcohols were measured as a function of temperature at 0.25, 0.5,5.0, 50 and, in one case, at 525 kc. to obtain information on the relationship between the molecular structure of solids and their dielectric properties. Long-chain molecules present the interesting possibility of rotation about the...
Set the date range to filter the displayed results. You can set a starting date, ending date or both. You can enter the dates manually or choose them from the calendar.