Velocity of Sound and Equations of State for Methanol and Ethanol in a Diamond-Anvil Cell

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Abstract
The adaptability of laser-induced phonon spectroscopy to the determination of acoustic velocity and the equation of state in the diamond-anvil high-pressure cell is demonstrated. The technique provides a robust method for measurements at high pressure in both solids and liquids so that important problems in high-pressure elasticity and the earth sciences are now tractable. The velocity of sound and the density of methanol at 25°C have been measured up to a pressure of 6.8 gigapascals. These results imply a higher density (by approximately 5 percent) for liquid methanol above 2.5 gigapascals than that given in existing compilations. The adiabatic bulk modulus increases by a factor of 50 at a maximum compression of 1.8. The thermodynamic Grüneisen parameters of methanol and ethanol both increase with increasing pressure, in contrast to the behavior of most solids.