Microwave Absorption and Molecular Structure in Liquids. LXV. A Precise Michelson Interferometer for Millimeter Wavelengths and the Dielectric Constants and Losses of Some Low-Loss Liquids at 2.1 mm

The theory and apparatus for a Michelson interferometer for the precise measurement of dielectric constant and loss of liquids at 2.1-mm wavelength are described. The probable error of the dielectric-constant measurements is 0.2%. The probable error of the loss measurements is 2% or ±0.0002, whichever is higher. The dielectric constants and losses of dilute solutions of chlorobenzene in benzene have been measured at 2.1-mm wavelength at 20° and compared in the light of existing lower-frequency data. The dielectric constants and losses of several nonpolar and slightly polar liquids have also been measured at 2.1-mm wavelength at 20°. The presence of appreciable losses in benzene and carbon tetrachloride has been confirmed. Measured losses in cyclohexane and n-heptane are considerably lower than those in benzene and carbon tetrachloride.