The Dielectric Properties of Some Long-Chain Fatty Acids and Their Methyl Esters in the Microwave Region

Abstract

Measurements were made of the dielectric constant and loss of stearic, palmitic, and some other acids in the solid and liquid states between wavelengths of 1 and 50 cm. The loss was small in the solid state, and there was no absorption peak in the wavelength range covered; in the liquid state the loss was greater with evidence of a small absorption peak near 3 cm. The methyl esters show an absorption peak in the microwave region in both the solid and liquid states. The measurements on the liquid methyl esters indicate that resonance absorption is occurring at a frequency of about 6000 Mc/sec. Some ethyl esters were measured and were found to show a relaxation loss in the microwave region of the same order as the relaxation loss of the methyl esters but they showed no sign of resonance absorption loss. An attempt is made to explain both the relaxation loss and the resonance loss on the basis of a model which has already been used by Hoffman and Smyth.