Solubility of Co(OH)(2), CoCO3 and Ni(OH)(2) in seawater and dilution
solutions of NaNO3 was studed. This dates was used for determine of to
tal activity coefficients and free ion fraction cobalt and nickel in s
eawater. Free ion fraction of Co and Ni at pH less than or equal to 8
approximately is equal 50 and 35% respectively.