Behavior of Sodium near Melting Point Found by Measurement of Sound Velocity

The sound velocity of sodium was measured in the solid phase and the liquid phase near the melting point by ultrasonic pulse transmission method. The temperature range of the experiment was from 19°C to 160°C, and the frequency of sound used was 1 MHz. The sound velocity and its temperature coefficient in the solid phase just below the melting point (97.8°C) were 3180 m/s and -1.23 m/s·deg, respectively ; and those in the liquid phase just above the melting point were 2515 m/s and -0.52 m/s·deg, respectively. By combining the present results with the existing data of thermal expansivity and specific heat, the elastic properties of sodium at and around the melting temperature were presented and discussed.