experiments at I = 0.006, 0.05 and 0.5 M NaClO4, log K determined for I =0; 25+-0.1°C; original reaction equation in the study: »Fe-OH + H2CO3 = »Fe-CO3<1-> + H2O + H<1+> with logK = -3.3, formation constants: logK1 = -6.366 for the reaction H2CO3 = H<1+> + HCO3<1->[FNK96], logK2 = -10.329 for HCO3<1-> = H<1+> + CO3<2-> [GFFGN03] --> so for H2CO3 = 2H<1+> + CO3<2-> the logK = -16.695