Thermodynamic properties of 2,2,4-trimethylpentane

p, V, T data for 2,2,4-trimethylpentane (TMP) have been obtained in the form of volume ratios for six temperatures in the range 278.15 to 338.15 K for pressures up to 280 MPa. Isothermal compressibilities, isobaric expansivities, and internal pressures have been evaluated from the volumetric data. There are strong indications that the combination of the present results with literature data at 348 and 373 K enable accurate extrapolations in the liquid range up to 473 K, and possibly to as low as 170 K, for pressures up to 980 MPa; use of only the present results with the requirement that the B coefficient of the Tait equation should become equal to the negative of the critical pressure at the critical temperature provides interpolations and extrapolations of comparable accuracy. It is suggested that 2,2,4-trimethylpentane is a suitable secondary reference material (because of its large liquid range at atmospheric pressure and the similarity of its volumetric properties to a wide range of fluids) for calibration of measuring cells used for determining volumes of fluids under pressure.