Thermal decomposition of Tl(III) oxine chelate

Abstract

Precipitation of Tl(III) from aqueous solution with 8-hydroxyquinoline is quantitative at pH above 5.5 and provides bases for the gravimetric determination of Tl(III). Not all the combined water, however, could be removed without decomposition of the compound at 110 to 120°C. The recommended procedure for accurate determination of Tl(III) is as follows. Dissolve Tl2O3 with dilute HNO3 and add 2% 8- hydroxyquinoline- acetic acid solution. Adjust the pH to 5.5 with ammonium acetate solution. Digest the solution for 1 hour at 50 to 60°C. Wash with dilute ammonium acetate solution and dry at 40 to 60°C for 2 hours, and finally at 95°C for 1 hour. The composition of the precipitate was Tl(C9H6-NO)3·2H2O. Tl(III) in the precipitate was reduced to Tl(I) at the temperature above 130° Cand was converted to Tl2O3 at the temperature above 420°.C Free 8-hydroxyquinoline was also sublimed at the temperature above 160°. These results were confirmed by thermogravimetry, polarography, spectrophotometry and elemental analysis. © 1970, The Japan Society for Analytical Chemistry. All rights reserved.