COMPARATIVE ANALYTICAL DETERMINATION OF THALLIUM IN DIFFERENT GRADE MINERALS AND ORES USING SEMIMETHYLTHYMOL BLUE

The composition, overall stability constant and molar absorptivity of the chelate of thallium(III) ion with Semimethylthymol Blue (SMTB) wer e determined spectrophotometrically in a medium of perchloric acid and sodium perchlorate solution (pH 2.5). In the thallium(III)-SMTB syste m, a violet, Tl(SMTB) chelate was formed with log beta(1:1) = 22.1 +/- 0.1 and molar absorptivity of 4.11 x 10(4) mol l cm(-1) (570 nm). SMT B was proposed as a new reagent for the spectrophotometric determinati on of micro-molar amounts of thallium(III) at lambda(max) 570 nm. The colour development depends on time, temperature, pH and buffer species . The interferences of different cations, anions and organic acids on thallium(III) determination were also investigated. Beer's law is obey ed for 0.4-3.7 mu g ml(-1) Tl(III) (0.41-3.68 ppm). Spectrophotometric determination of thallium in different grade minerals and ores were r eproducible and satisfactory. Comparative study including different st atistical tests between the spectrophotometric and complexometric dete rminations of thallium(III) using SMTB in its minerals and ores has be en carried out.