When more equilibrations are in effect, that is, when pKI pK2, pK3,... etc are contributing at the same time to the proton concentration HI the pl can not be calculated by the sum average. In general, pKI, pK2, and pk3 should be separated from each other by at least one unit, that is, the corresponding equilibrium constants differ by one order of magnitude (10 times more or 10 times lessWhen more equilibrations are in effect, that is, when pK1, pK2, pK3, …etc are contributing at the same time to the proton concentration [H+ ], the pI can not be calculated by the sum average. In general, pK1, pK2, and pK3 should be separated from each other by at least one unit, that is, the corresponding equilibrium constants differ by one order of magnitude (10 times more or 10 times less)