Indirect complexometric determination of thorium(IV) using tartaric acid as masking agent

Department of Chemistry, Srinivas Institute of Technology, Valachil, Mangalore-574 143, Karnataka, India E-mail : shreedakumar@yahoo.co.in Manuscript received 05 October 2009, revised 07 July 2011, accepted 21 July 2011 A complexometric method for the determination of thorium(IV) in presence of other metal ions based on the selective masking ability of tartaric acid towards thorium is described. Thorium(IV) present in a given sample solution is first complexed with a known excess of EDTA and the surplus EDTA is titrated against bismuth nitrate solution at pH 2-3 using xylenol orange as indicator. A known excess of tartaric acid (10%) is then added and the EDTA released from the Th-EDTA complex is titrated against standard bismuth nitrate solution. Reproducible accurate results are obtained for 9.36 to 46.8 mg of thorium with relative errors ±0.21% and standard deviations s; 0.06 mg. The interference of various ions were studied. The method is applied for the determination of thorium in alloy solutions