EVALUATION OF A 4 MHZ INTEGRATED-CIRCUIT OSCILLATOR FOR THE MEASUREMENT OF SOLUTE DIPOLE-MOMENTS IN DILUTE-SOLUTION

A simple device for the measurement of solute dipole moments in dilute solutions of nonpolar solvents is described and evaluated. The device is ba;ed on an integrated circuit radio frequency oscillator and is d emonstrated to be capable of measuring changes in solution dielectric constant of less than one part in 10 000. This allows the measurement of solute dipole moments using solutions in the 0.0001-0.005 molar ran ge. Solute-solute interactions are shown to be minimized within this c oncentration range, and a simple means of extracting the solute dipole moment from concentration-dependent dielectric constant measurements is described. Dipole moments of para-(dimethylamino)benzonitrile, nitr obenzene, para-(nitro)anisole, and para-(nitro)aniline are measured, a nd are shown to compare favorably with previously reported values. The device is demonstrated to be capable of distinguishing solution diele ctric constant changes associated with solute concentration changes as low as 3x10(-5) M. It is therefore well suited to the measurement of dipole moments of polar compounds whose solubility in nonpolar solvent is low. (C) 1996 American Institute of Physics.