A new flow vibrating-tube densimeter with a photoelectric pick-up system and a new concept of an electromagnetic drive system is described. The apparatus is designed for measurements in the temperature and pressure ranges from 298 K to 573 K and up to 35 MPa, respectively. The density data for dilute aqueous solutions of phenol obtained in the temperature range from 298.15 K to 573.15 K and partial molar volumes of phenol calculated from measured data are presented.