Spectral and thermal studies of uranyl-pyrocatechol complexes and their application for determination of uranyl ions

The information and stability of uranyl ion complexes with pyrocatechol [P.C.] were studied spectrophotometrically, through the effect of pH and time on the coloured complexes formed, the determination of their stoichiometry and the calculation of their stability constants. Based on these studies, general conclusions on the stability, structure and optical properties of UO[2] -P.C. complexes were derived and their significance and the sensitivity for spectrophotometric determination of UO[2++] in aqueous solution were outlined. The solid UO[2]-P.C. complexes were isolated in two ratios 1:2 and 1:3 and characterized using elemental analysis, IR spectra and thermal analysis [DTA and TG] in order to investigate their structures and thermal stability

Studies on spectral characteristics of o,p-,m- aminophenols in comparison with catechol and pyrogallol in solutions of sodium hydroxide

The absorption spectra of 5 phenol derivatives indicators in alcohol water mixture disclose absorption peaks whose position is dependent on alkali concentration and alcohol content of the medium. The peaks are slightly shifted towards higher wave lengths with rise in alkali concentrations. Indicators with OH ions are ionized in the solution by proton loss rather than by hydroxide addition. The molar extinction coefficient epsilon, epsilon a and epsilon HA of the partially ionized, completely ionized and non-ionized forms of each indicator are calculated. The values of these coefficients are then used for the computation of the indicator ratios [I] of the different indicators in the various solutions. In addition, the pKa-values of the indicators are obtained by plotting [log I-log COH] against COH and extrapolating to zero concentration. These values of I and pKa are of importance in the evaluation of the acidity function H of the different solutions