MEASUREMENT OF DENSITY, SOUND-VELOCITY, SURFACE-TENSION, AND VISCOSITY OF FREELY SUSPENDED SUPERCOOLED LIQUIDS

Noncontact methods have been implemented in conjunction with levitatio n techniques to carry out the measurement of the macroscopic propertie s of liquids significantly cooled below their nominal melting point. F ree suspension of the sample and remote methods allow the deep excursi on into the metastable liquid state and the determination of its therm ophysical properties. We used this approach to investigate common subs tances such as water, o-terphenyl, succinonitrile, as well as higher t emperature melts such as molten indium, aluminum, and other metals. Al though these techniques have thus far involved ultrasonic, electromagn etic, and more recently electrostatic levitation, we restrict our atte ntion to ultrasonic methods in this paper. The resulting magnitude of maximum thermal supercooling achieved has ranged between 10% and 15% o f the absolute temperature of the melting point for the materials ment ioned above. The methods for measuring the physical properties have be en mostly novel approaches, and the typical accuracy achieved has not yet matched the standard equivalent techniques involving contained sam ples and invasive probing. They are currently being refined, however, as the levitation techniques become more widespread and as we gain a b etter understanding of the physics of levitated liquid samples.