Protolytic properties of methyl yellow both in water-ethanol medium and in hardened gelatin gel with the presence of sodium dodecylsulphate and tetrabutylammonium chloride

Abstract

This paper presents the results of studying the acid-base properties of the indicator dye methyl yellow in water–ethanol solutions with a volume fraction of alcohol of 10 % and 50 %. The influence of the addition of NaCl salts and tetrabutylammonium chloride, as well as the anionic surfactant sodium dodecylsulfate (SDS) on the acidity constant of the indicator, was evaluated. Under the chosen conditions, ethanol additives have a more significant effect on the pKa value. For the first time, using the dynamic light scattering method, the particle sizes, polydispersity index, and ζ-potential of colloidal particles in pure aqueous and mixed water–ethanol solutions of methyl yellow (φalcohol from 0.2 % to 50 %) in the presence of NaCl and SDS were estimated. In solutions with φalcohol = 50 % colloidal particles were not found. It has been shown that the hardened gelatin gel of photographic film can be used as a convenient sorbent for methyl yellow. In the process of dye extraction into a gelatin film from water-alcohol solutions containing SDS and NaCl, the acid-base properties of the methyl yellow remained almost unchanged. The difference between the pKa values obtained for the indicator both in solution and in the film did not exceed the measurement error.