Determination of dissociation parameters of weak acids in different media according to the isohydric method

Tadeusz Michałowski; Bogusław Pilarski; Agustin G Asuero; Agnieszka Dobkowska; Sławomir Wybraniec

doi:10.1016/j.talanta.2011.09.002

Determination of dissociation parameters of weak acids in different media according to the isohydric method

Talanta. 2011 Oct 30:86:447-51. doi: 10.1016/j.talanta.2011.09.002. Epub 2011 Sep 7.

Authors

Tadeusz Michałowski¹, Bogusław Pilarski, Agustin G Asuero, Agnieszka Dobkowska, Sławomir Wybraniec

Affiliation

¹ Faculty of Engineering and Chemical Technology, Cracow University of Technology, 31-155 Cracow, Poland. michalot@o2.pl

PMID: 22063565
DOI: 10.1016/j.talanta.2011.09.002

Abstract

The isohydricity (pH constancy) principle is referred to the pair of solutions: weak acid (HL, C(0)mol/L) and strong acid (HB, C mol/L) when mixed e.g., according to titrimetric mode. Such a case takes place if the relation C(0)=C+C(2) × 10(pK(1)) is valid, where pK(1)=-log K(1), K(1) - dissociation constant for a weak monoprotic acid HL. This principle, outlined and formulated in earlier paper (Michałowski et al., Talanta 82 (2010) 1965), is the basis for a sensitive method of pK(1) determination, confirmed for a series of weak acids in presence of basal electrolytes or in water+organic solvent (dimethyl sulphoxide, methanol, isopropanol) media. The results of titrations were elaborated according to principles of regression analysis, with use of least squares method. A new criterion for precision of the results obtained according to this method is formulated. The pK(1) values obtained are comparable with ones found in literature.