Equations baaed on the TTG model, and binary solution data, are given for the density and dynamic viscosity of seawater and concentrates. These equations may be applied to other multicomponent solutions, in particular modified seawater. The density and viscosity were calculated for salinities up to X07&, at 20°C and compared with the experimental data. The calculated densities agreed with the experimental values to within the experimental uncertainties (to 0.003% for salinities up to 565?& and better than 0.03% up to 150%+ The calculated viscosities were in good agreement with the most accurate experimental data (< 0.2% for salinities to 60% and < 0.3% for higher concentrations). SYMBOLS S -Salinity [l, 131, ppt by weight (g/kg solution) C -10m3S, g/g solution x -concentration, g/g solution mmolality, mol/kg water x -total moles of salts, mol/kg water -relative molality of salt, i, (mi/m,) Mimolecular mass of salt i, g Mt -XfiMi, g M; -Mt corrected for difference between defined salinity [l, 131 and the total solute mass per kg of solution, g ddensity, g/cm3 ( lo3 kg/m3 ) V specific volume, cm3 /g (m3 /103kg) JI -apparent volume (TTG), cm3 /g (m3 /103kg) t temperature, OC T temperature, "K P -pressure, bars Pe -effective pressure of binary solution, bars Pe -effective pressure of multicomponent solution, bars BT-Tait parameter, bars -2.