Snigur D. The use of tristimulus colorimetry functions in the study of the acid-base equilibria in solutions of organic compounds

Thesis is concerned with application possibility of tristimulus colorimetry method and argumentation of theoretical basis, and experimental approach of tristimulus colorimetry functions values use as analytical response in studies of acid-base equilibria in solutions of multifunctional organic compounds. A conceptual model is proposed, it is based on the change in tristimulus colorimetry function values in the ionization of functional groups of multifunctional compounds. The definitions of the corresponding terms are described. It has been established that use tristimulus colorimetry functions value as analytical response allows differentiating similar in acid-base characteristics functional groups, to determine the corresponding values of the ionization constants and to build a holistic picture about existing acid-base equilibria in a wide range of acidity of the medium. The values of tristimulus colorimetry functions of the specific and total color difference, the yellowness index, as well as the principles of their calculation within different color spaces by the example of multifunctional compounds (about 50), namely different classes of dyes (azo-, triphenylmethane, xanthene, anthraquinone and pyrilium derivatives). It is established that all specified functions are suitable for the determination of pKа, and the use of functions of full color difference makes it possible to simplify the mathematical apparatus for processing experimental data. The advantages of tristimulus colorimetry method before classical instrumental methods (spectrophotometry, potentiometry, conductometry) of studying acid-base equilibria in solutions of polyfunctional compounds are shown.