Appendix—Derivation of equations
J. N. Phillips · Biochemical Journal · 1952
AVIDITY OF NATURAL SUBSTANCES FOR TRACE METALS 697 occurred (pH 2.7).Small as this depression is, it corresponds to logK'=11-0 at this part of!the titration.Glutamic acid gave a depression of only 0-07 pH unit.It is becoming clear that the avidity of substances for ferric salts can be measured only if there is no interfering pKa between 1-5 and 3, or if the avidity is so great that basic ferric salts are not precipitated at pH 3.