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On the use of dimensionless parameters in acid‐base theory: VI. The buffer capacities of equimolar binary mixtures of monovalent weak protolytes as compared to that of bivalent protolytes
Author(s) -
Rilbe Harry
Publication year - 1994
Publication title -
electrophoresis
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.666
H-Index - 158
eISSN - 1522-2683
pISSN - 0173-0835
DOI - 10.1002/elps.1150150180
Subject(s) - chemistry , bivalent (engine) , dimensionless quantity , titration , binary number , dissociation constant , dissociation (chemistry) , valence (chemistry) , thermodynamics , crystallography , analytical chemistry (journal) , chromatography , physics , mathematics , organic chemistry , biochemistry , receptor , arithmetic , metal
The general equation for the relative molar buffer capacity, earlier shown to be valid for bivalent acids, bases, and ampholytes, is shown to hold also for equi‐molar, binary mixtures of monovalent protolytes if only the parameter s = \documentclass{article}\pagestyle{empty}\begin{document}$ {\rm}\sqrt {K_{\rm 1} ^\prime {\rm /4}K_{\rm 2} ^\prime} $\end{document} is exchanged for t = s + 1/4 s. The same applies to the equations for the mean valence of the two classes of protolytes. As a consequence thereof, the titration and buffer capacity curves of a bivalent protolyte are identical with those of a monovalent protolyte with a p K ′ value equal to \documentclass{article}\pagestyle{empty}\begin{document}${\rm}\sqrt {K_{\rm 1} ^\prime {\rm}K_{\rm 2} ^\prime} $\end{document} of the bivalent one (the isoprotic point of an ampholyte). For a hypothetical bivalent acid, base, or ampholyte with s = 1, Δp K ′ = log 4, this implies that the intrinsic rather than the hybrid dissociation constants are responsible for the titration and buffer capacity curves.