Determination of Relative pK Values of Dibasic Protolytes by Regression Analysis of Absorbance Diagrams

Friedrich Göbber, Jürgen Polster

Research output: Contribution to journalArticlepeer-review

3 Scopus citations

Abstract

The absorbances of a dibasic acid measured at two distinct wavelengths with varying pH as the parameter form a conic section which can be determined by an appropriate leastsquares method. The conic section and the absorbances of the acid in its nondissociated form and its completely dissociated form allow for the determination of the difference of the pK values (ΔpK) and the absorbances of the ampholyte without using pH values. If data from more than two wavelengths are available, one ΔpK value can be computed for each pair of wavelengths. Because the reliabilities of the particular results are considerably different, an extensive error analysis is necessary to obtain an averaged ΔpK value together with an estimated standard deviation. The results for o-phthalic acid are given as an example.

Original languageEnglish
Pages (from-to)1546-1550
Number of pages5
JournalAnalytical Chemistry
Volume48
Issue number11
DOIs
StatePublished - 1 Sep 1976
Externally publishedYes

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