In the sample data set, pKa1 = 4 and pKa2 = 8, and thus Ka1 = 1 ´ 10-4 and Ka2 = 1 ´ 10-8. Notice that the points on the titration curve corresponding to pKa1 and pKa2 are circled in red. For diprotic acids that have well-separated dissociation constants and thus well defined equivalence points,