草酸
A calculated titration curve for oxalic acid is shown at the right. Oxalic acid has p"K"a values of 1.27 and 4.27. Therefore, the buffer regions will be centered at about pH 1.3 and pH 4.3. The buffer regions carry the information necessary to get the p"K"a values as the concentrations of acid and conjugate base change along a buffer region.