original reaction equation in the study: »X(w)-OH + As(OH)3 = »X(w)-O-As(OH)2 + H2O with log K = 2.8±0.1, formation constant in aqueous solution: AsO3<3-> + 3H<1+> = H3AsO3 logK = 34.74 (Schecher, W. D.; McAvoy, D. C. MINEQL+, V. 4.5, Users Manual, Hallowell, ME, 1998)