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+> + NO3<1-> = »Fe-OH2-NO3 logK = 2.9(2.4) »Fe-OH + H<1+> = »Fe-OH2<1+> -pK1 = logK = 6.8 sum »Fe-OH + NO3<1-> + H<1+> = »Fe-OH2-NO3 logK = 2.9(2.4)+6.8 = 9.7(9.2)