Determination des constantes d'acidite de diacides moyennement forts

Abstract

The proton concentration resulting from the dissociation of a moderately strong dibasic acid can be precisely determined by means of an acid-base indicator by differential spectrophotometry. The dissociation constants are then calculated by linear regression of the appropriate function. The method was tested on the first two dissociation constants of protonated O-phosphoserine in aqueous solution (25 degrees , KNO(3) 0.1M): the values found are pK(1) = 0.72 (3sigma = 0.08) and pK(2) = 2.14(6) (3sigma = 0.01).