The effects of high CO2 molality on carbon dioxide equilibrium are important to studies related to the disposal of liquid CO2 into the oceans. Using the Pitzer method, terms that take into account the effect of dissolved CO2 on the solubility coefficient of CO2 and stoichiometric dissociation constants of acid-base equilibrium have been obtained in explicit form. Using available thermodynamic data for liquid CO2 and CO2 gas solubility in seawater, we developed an equation for the solubility of liquid CO2 in seawater as a function of temperature, pressure, and salinity. It was established that the effect of high CO2 molality on carbon dioxide system constants shifts the stoichiometric carbonate equilibrium of seawater by an increased pH level of more than 0.3 pH units.