calculation from literature values with standard SSA and SSD at ionic strength of 1M, log K for Aerosil in brackets for Cabosil content »Si-OH2<1+> + F<1-> = »Si-OH2-F logK = 3.1(2.5) »Si-OH + H<1+> = »Si-OH2<1+> - pK1 = logK = -1.4 sum »Si-OH + F<1->+ H<1+> = »Si-OH2-F logK= 3.1(2.5)-1.4 = 1.7(1.1)