The same procedure that was used in the case of two weak acids (taking into account the contribution of H 3 O + and OH -, see section 3.2.2) allows performing just such a task. To exemplify that point, figure .a displays the roots landscape in the case where pK a2 = 7 and for r ∆pKa = 1 and 1.1, with or without optimization of r l and r h . A first situation is simply the one obtained for pK a = 7 and r = 1.5 (and, here, r ∆pKa = 1 and r l = r h ) in section 4.1. Then the roots evolve in an asymmetrical manner when r ∆pKa = 1.1 is imposed with r l = r h , leading to a skewed plateau of the buffer index. Finally, by optimizing r h , it is possible to recover a single multiple roots and the corresponding β curve appears as flat as the first one. The difference in height is due to the fact that the optimization was obtained by increasing C h , leaving the other two unchanged, hence the overall buffer index increases.