Dispersion of the high-frequency sound velocity in the aqueous solution of 4-methylpyridine

Dispersion of the high-frequency sound velocity in the aqueous solution of 4-methylpyridine with the concentration 0.06 mole fraction corresponding to the singular point in the temperature-concentration phase diagram is studied. Along with observation of positive dispersion of the speed of sound in going over from ultrasound to hypersound frequencies (5.4 MHz to 4.8 GHz), negative dispersion (a decrease in velocity with increasing frequency) was also observed in a narrow interval of hypersound frequencies from 4.8 to 6.1 GHz.