The Liquid-Vapor Critical Point Data of Fluid Metals and Semiconductors

The Liquid-Vapor Critical Point Data of Fluid Metals and Semiconductors 

Note Values in italics are estimated from extrapolation of experimental data. 

The problem of temperature and pressure control, temperature stability, and temperature homogeneity becomes particularly important in studies close to the liquid-vapor critical point. The difficulties are directly related to the strong critical divergences of the isothermal compressibility, xt = = —V dVldp)j and the isobaric expan- 

The critical temperatures of most metals can only be estimated and most lie well above those of mercury and the alkali metals (7. 3000 K). Conventional measurements under static, equilibrium conditions are nearly impossible at such extreme temperatures and pressures. Transient methods such as shock waves, exploding wires, and laser heating have been developed to study at least a few properties of the high critical-point metals. These include the equation of state and the velocity of sound. But these techniques are less accurate than static measurements and it has not been possible to obtain measurements very close to the critical point, or indeed, even to determine with any reasonable level of precision the location of the critical points of most of the metallic elements. 

Thus we must view with caution critical data derived from experiments that have not actually approached the immediate critical region. This includes much of the information in the lower pxjrtion of Table 1.1. Note that even some of the data for the lighter alkali metals lithium and sodium involve extrapolation from experiment. Extrapolation of experimental results using rules and methods obeyed for insulating liquids, such as the law of corresponding states or the law of rectilinear diameters, may lead to conclusions that are seriously in error. The reasons for the failure of these empirical rules in electronically conducting fluids forms a central theme of this book. 

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