Precise determination of the isothermal compressibility of mercury at 20 " C and 192 bar

The isothermal compressibility of mercury at 20 "C and 192 bar has been determined with an accuracy estimated at k 0.4 %, which represents a considerable increase in accuracy over previous determinations. The value obtained is within 0.3% of that derived from the velocity of sound by Davis and Gordon, although the accuracy claimed for the latter was only k 0.8 %. 1. Introduction In a companion paper (Hayward 1971) the principles underlying the accurate measurement of the isothermal compressibility of liquids have been analysed. By taking account of these principles, in particular by employing an iron substitution method to eliminate errors due to pressure vessel deformation, and by employing the parallel secant method of analysing the test results, the isothermal compressibility of mercury has been determined with greater precision than ever before.