We do not know of any detailed study dealing with mixtures of three weak acids in detail. The closer situation we found was that of trivalent species. In his study of the buffer capacity of trivalent protolytes, Rilbe found no value of ∆pK a that allowed a flat dependency of the buffer index . As a matter of fact, this is only possible if the three pK a correspond to monovalent species of different concentrations, as we are about to see, and this is obviously impossible for trivalent species.