Comments on “Solubility of Liquid CO2 in Synthetic Sea Water at Temperatures from 278 K to 293 K and Pressures from 6.44 MPa to 29.49 MPa, and Densities of the Corresponding Aqueous Solutions” (Teng, H.; Yamasaki, A. J. Chem. Eng. Data 1998, 43, 2−5)

Teng and Yamasaki (1998) recently reported measurements of the CO 2 solubility in seawater and the density of CO 2 -saturated seawater under high pressures.They provided a set of solubility/density data, which may contribute to the research and development of the technology of CO 2 disposal in the ocean.However, there is an ambiguity as to what the solubility they measured was.This issue is discussed below.The pressure/temperature region covered by Teng and Yamasaki's measurements partially falls in the hydrateformation region.In fact, the authors wrote that they observed CO 2 hydrate formation in some of their experiments.It is now well acknowledged that, in the hydrateformation pressure/temperature region for any hydrateforming substance (CO 2 in the present case), the concentration of the substance in a water-rich liquid phase in equilibrium with the hydrate, x gh , is different from x g , the solubility of the same substance in the water-rich liquid phase in the metastable state in the absence of the hydrate.Under a constant pressure, x gh decreases and x g increases as the temperature decreases beyond T tri , the critical temperature at which the three phasessa water-rich liquid phase, a hydrate phase, and a hydrate-former-rich fluid phasescan be equilibrated.This fact has been confirmed both experimentally (Kimuro et al., 1994;