Stepwise Co-ordination and Thermodynamics of Uranyl(lI) and Thorium(IV) Ions with lsopropylmercaptan

Department of Chemistry, Malaviya Regional Engineering College, Jaipur Manuscript received 19 July 1977, revised 22 April 1980, accepted 9 July 1980 The complexation of uranyl (\(UO^{+2}_2\)) and thorium (Th+4) ions with isopropylmercaptan [(CH3)2 CH.SH] has been studied by potentiometric and conductometric titration techniques in aqueous 10% ethanolic (v/v) medium. Uranyl ions form 1 : 1 and 1 : 2 complexes in the pH-range 4.0-5.4 and thorium ions form 1 : 1, 1: 2, 1 : 3 and 1 : 4 complexes in the pH-range 2.8-4.9 with stepwise considerable overlapping.Their log Kstab values are determined at 15, 25 and 35o at constant ionic strength,\(\mu \)=0.1 M (NaCIO4 ), by applying Calvin and Melchior's extension of Bjerrum method. The overall changes in thermodynamic functions \(\bigtriangleup\)H,\(\bigtriangleup\)G and \(\bigtriangleup\)S accompanying complexation have been determined at 25o with the help of an isobar and Gibb's Helmholtz equation