calculation from literature values with standard SSA and SSD at ionic strength of 1M, log K for pHzpc 8.4-8.6 in brackets for pHzpc 9-9.5 »Fe-OH2<1+> + OH<1-> = »Fe-OH2-OH logK = 12.2.0(11.1) »Fe-OH + H<1+> = »Fe-OH2<1+> -pK1 = logK = 6.8 sum »Fe-OH + OH<1-> + H<1+> = »Fe-OH2-OH logK= 12.2(11.1)+6.8 = 19.0(17.9)