For the use of a mercury column for precise pressure measurements—such as the pressurized 30 meter mercury‐in‐steel column used at the Van der Waals–Zeeman Laboratory for the calibration of piston gauges up to nearly 300 MPa—it is highly important to have accurate knowledge of such properties of mercury as density, isobaric secant and tangent volume thermal expansion coefficients, and isothermal secant and tangent compressibilities as functions of temperature and pressure. In this paper we present a critical assessment of the available information on these properties. Recommended values are given for the properties mentioned and, in addition, for properties derived from theses such as entropy, enthalpy, internal energy, and the specific heat capacities.