Complex permittivity of low-concentration aqueous solutions of acetone

The spectra of complex permittivity (epsilon' and epsilon ") of aqueous sol utions of acetone were studied in the millimeter and centimeter band region s at 10-120 GHz frequencies. The quasi-optical method was modified and used to study absorption, reflection, and complex permittivity of aqueous solut ions of nonelectrolytes in the high-frequency region of the millimeter band (80-120 GHz). In low-concentration (<14 mol %) solutions of acetone, and i n the whole frequency range, a single Debye-type relaxation process occurs. To within the accuracy of measurements, additional absorption and addition al molecular relaxation processes in the high-frequency region of the milli meter band were not detected. The obtained dielectric relaxation times in s olutions of acetone were substantially longer than in water at all temperat ures (288-308 K). Such changes are determined by stabilizing hydrophobic hy dration effects. It appears that acetone molecules in voids of the pseudocl athrate structure built of water molecules do not experience free rotation, as was earlier believed.