Density and derived properties of standard seawater up to high pressure in stable and metastable states

In this work, a consolidated experimental apparatus for measuring the density of liquids, such as high pressure and metastable states, based on the isochoric method, was exploited to measure thermal properties of seawater. Density of standard seawater was measured in a wide range of temperature and pressure, specifically from (261.15 to 313.15) K and up to 110 MPa. All terms contributing to the uncertainty in determining the volume and the mass of the specimen were evaluated, obtaining a relative expanded uncertainty of seawater density around 0.03% (k = 2). Experimental results were fitted by using a 8-parameters function of specific volume as a function of temperature and pressure. Using the obtained expression, density, isobaric thermal expansion, and isothermal compressibility of seawater were calculated from (263.15 to 313.15) K and for pressures between (1 and 105) MPa. A comparison with the predictions obtained by the Thermodynamic Equation of Seawater 2010 (TEOS-10) shows a general good agreement that worsens when metastable states are considered.