Polyprotic acids have more than one ionization. The determination of the equilibrium constants for each stepwise ionization of a triprotic acid can be complicated. However, if the ionizations constants differ by 105 to 106, the calculations can be broken down into a series of steps. Likewise the titration curves [local] can appear differently for citric acid having pKa1 of 3.10, pKa2 of 4.80, and pKa3 of 6.39 compared to phosphoric acid having a pKa1 of 2.12, pKa2 of 7.20. and pKa3 of 12.44. The citric acid curve mimics the shape of a monoprotic weak acid curve except for the fact that it takes more NaOH to reach equivalence point. Citric acid does not buffer as well owing to the fact that it has poor separation in its pKa values.
Potentiometric titrations can also be used to identify pKa values. If pKa values are separated by 10 then the titration will provide two peaks.
