DISSOCIATION QUOTIENTS OF SUCCINIC ACID IN AQUEOUS SODIUM-CHLORIDE MEDIA TO 225-DEGREES-C

The first and second molal dissociation quotients of succinic acid were measured potentiometrically with a hydrogen-electrode, concentration cell. These measurements were carried out from 0 to 225 degrees C over 25 degrees intervals at five ionic strengths ranging from 0.1 to 5.0 molal (NaCl). The dissociation quotients from this and two other studies were combined and treated with empirical equations to yield the following thermodynamic quantities for the first acid dissociation equilibrium at 25 degrees C: logK(1a) = -4.210+/-0.003; Delta H-1a(o) = 2.9+/-0.2 kJ-mol(-1); Delta S-1a(o) = -71+/-1 J-mol(-1)-K-1; and Delta C-p1a(o) = -98+/-3 J-mol(-1)-K-1; and for the second acid dissociation equilibrium at 25 degrees C: logK(2a) = -5.638+/-0.001; Delta H-2a(o) = -0.5+/-0.1 kJ-mol(-1); Delta S-2a(o) = -109.7+/-0.4 J-mol(-1)-K-1; and Delta C-p2a(o) = -215+/-8 J-mol(-1)-K-1.