(p,ρ,T) Properties of seawater at brackish salinities: Extensions to high temperatures and pressures

- (p,ρ,T) Data of seawater at brackish salinities are estimated.
- The measurements were carried out with a vibration tube densimeter.
- The thermomechanical coefficients were calculated.

The (p,ρ,T) values of certified IAPSO standard seawater (SSW) samples [SP=34.993, k15=0.99982 (2008); SR=34.994, k15=0.99984 (2009)] and of diluted/evaporated SSW samples at SA=(2.536, 2.715, 3.531, 5.111, 6.326, 7.613, 9.153, 10.977, 12.202, 13.588, 15.423, 17.047, 18.095, 20.269, 22.173, 23.930, 25.731, 27.295, 28.893, 29.680, 31.684, 33.507, 35.159, 37.372, 37.969, 40.163, 41.825, 44.811, 46.118, 48.600, 50.232, 52.449, 55.529) g kg−1, temperatures T=(273.15-468.15) K, and pressures up to p=140 MPa are examined with more than 7616 experimental density results that have been obtained since 2008. The density interval of all obtained values is between ρ=(870.4-1099.5) kg m−3. The temperature and pressure intervals of experiments are approximately ΔT=(5-20) K and Δp=(5-10) MPa, respectively.A part from these measurements [SA=35.159 g kg−1 and SA=(31.684-55.529) g kg−1] is already published earlier by Safarov et al. (2009, 2012). In this publication now, the final portion of experimental (p,ρ,T) values of seawater for SA=(2.536-29.680) g kg−1 and a discussion of literature comparison using the constructed equation of state (EOS) for all obtained (p,ρ,T) results at SA=(2.536-55.529) g kg−1, temperatures T=(273.15-468.15) K, and pressures up to p=140 MPa are presented.The reproducibility of the density measurements is observed to be in the average percent deviation range of Δρ/ρ=±(0.01-0.03) %. Based on these measurements, an empirical expression for the density of seawater has been developed as a function of salinity, pressure and temperature. The results can be used with care to extend the present equation of state (EOS) of seawater to higher temperatures for pressure up to 140 MPa.