Showing papers by "National Institute of Technology, Karnataka published in 2000"

Indirect complexometric determination of thallium(III) using thioglycolic acid as masking agent

Abstract: A simple and selective complexo metri c method for th e determination of th allium(III ) is proposed by using thioglyco li c acid as a mask in g agent. In th e presence of diverse metal ions th allium(lll ) is complexed with excess EDTA and the surplus EDTA is back titrated (pH 5 - 6, hexamine) with standard zinc sulphate soluti on using xylenol orange indicator. A fr es hly prepared I % aqueous so luti on of thi oglycoli e ac id is th en add ed to displace EDTA from TI (III)- EDTA complex and th e re­ leased EDTA is titrated wi th stand ard zinc sulph ate soluti on. The results for the determi natio n of 4- 87 mg of th allium are obtain ed wit h a relative error of 0.3% and coefticient of vari ation 0.46%. The effect of diverse ions are studied . The method is appli ed to th e determination of th allium in its compl exes and sy ntheti c mixtures. Recently, complexometric titrations, particularly those involving masking and demasking technique are rece ivin g considerable attention since they provide simple, rapid and accurate methods for th e determi­ nation of the desi red metal ion in th e presence of as­ sociated metal ions. A search in th e literature di s­ closes that a number of sulphur - nitrogen donor li g­ ands such as thi osemicarbazide 1 , hydrazin e su lphate 2 , 4-amino-5-mercapto-3-propyl-1 ,2,4-triazole 3 , 2-mer­ captoethanol4, ascorbic acid 5 , ethyle ne thiourea 6 , 3mercapto-1 ,2-propanediol 7 , hydroxylamine hydro­ chloride8, 2-thiazoline-2-thi ol 9 have been used as se­ lective re leasin g agents in the complexometric deter­ mination of thallium(III). Some of th ese methods e i­ ther require heating or readjustment of pH for th e quantitaii ve release of EDT A from TI-EDT A com­ plex. In thi s paper, th e application of thiog ly colic acid as a selective rel easin g agent in th e indirect complex­ ometric determination of thallium(III) has been reported .