<Original Papers>The Velocities of Ultrasound in Molten Iron, Cobalt and Nickel

The velocities of ultrasound at 10,30 and 50MHz were measured in molten iron, cobalt and nickel at temperatures from their melting points to about 1,900K by using a pulse-transmitting method. The relation between velocities and experimental tempeatures in these molten metals could be represented by straight lines having negative temperature coefficients. The adiabatic and isothermal compressibilities were calculated at the melting points from the experimental results combining with other thermodynamic data. The isothermal compressibilities of these molten metals were compared with those of other molten metals and discussed by simple models. In comparisons of the isothermal compressibilities calculated by simple models with experimental values, it was found that the results obtained by Ascarelli\u27s model agreed well with the experimental ones except for Ag and Cu, while the hard sphere model did not yield satisfactory results. From this fact, it may be concluded that the contribution of free electron gas cannot be neglected in the explanation of the compressibility of molten metals