CONSISTENCY OF PH STANDARD VALUES WITH THE CORRESPONDING THERMODYNAMIC ACID DISSOCIATION-CONSTANTS (TECHNICAL REPORT)

With the simplest possible assumptions on the ion activity coefficient s, namely a Debye-Huckel approach, pH values of eleven standard buffer solutions have been calculated from the corresponding thermodynamic a cidity constants, K(I-->0), and compared to the electrometrically assi gned pH(S) values (by Hamed cell method). Agreement is within +/-0.01 in the temperature range 10-40 degrees C for all standards, except car bonate. The results for the phthalate, acetate, phosphate and carbonat e systems at 25 degrees C indicate that this consistency is improved i f specific ion interactions are taken into account, according to the P itzer theory.