Sodium dithionite as a selective demasking agent for the complexometric determination of thallium

• Main Authors: PRAKASH SHETTY, NITYANANDA SHETTY
• Format: Article
• Language: English
• Published: Serbian Chemical Society 2005-11-01
• Series: Journal of the Serbian Chemical Society
• Subjects: complexometry; demasking agent; EDTA method; sodium dithionite; thallium
• Online Access: http://www.shd.org.yu/HtDocs/SHD/vol70/No11/JSCS_V70_No11-13.pdf

Sodium dithionite is proposed as a new demasking agent for the rapid and selective complexometric determination of thallium(III). In the presence of diverse metal ions, thallium (III) was first complexed with excess EDTA and the surplus EDTAwas then titrated with a standard zinc sulphate solution at pH 5–6 (hexamine buffer) using Xylenol Orange as the indicator. The EDTAequivalent to thallium was then released selectively with sodium dithionite and back titrated with a standard zinc sulphate solution as before. Reproducible and accurate results were obtained in the range 4–100 mg of thallium with a relative error of ±27 % and a coefficient of variation (n = 6) of not more than 0.30 %. The effects of various diverse ions were studied. The method was applied to the determination of thallium in its complexes and in alloys.