background electrolyte: major ion seawater (0.49M Na, 0.0517M Mg, 0.00992M Ca,0.01M K, 0.52M Cl, 0.0267M SO4); double extrapolation technique [JDL78] for determination of log K: plotting the ionization term for 0.001, 0.005, and 0.01 M Ca solution and extrapolation to log c=0 (c=1)and fraction of ionized sites (alpha)=0