As is shown by figure , the triple point is broken when the contributions of H 3 O + and OH -are taken into account even if C 1 = C 2 , as long as pK a = 7. This behaviour is symmetrical whether this parameter is above or below 7, and these curves appear very similar to the ones obtained for C 1 = C 2 when neglecting H 3 O + and OH -(see figure ). The further pK a is from 7, the stronger the divergence from the ∆pK a curve established in the absence of H 3 O + and OH - contributions. Moreover, these curves become dependent upon the concentration of the buffer solutions, as it cannot be factored out: the higher the dilution, the higher ∆pK c a , as in the case of solutions with higher differences in concentrations.