Fig. 14 in Chemical evolution of the colour systems generated by riccionidin A, 3-deoxyanthocyanidins and anthocyanins

Fig. 14. (a) Spectral variations of riccionidin A taken immediately after direct pH jumps from the flavylium cation equilibrated at pH = 1.0. The system behaves as a tetra-protic acid with pKa1 = 4.2; pKa2 = 6.6; pKa3 = 7.7; pKa4 = 10.7; (b) pH dependent mole fraction distribution of the several species.