SEQUENTIAL TITRIMETRIC AND SPECTROPHOTOMETRIC DETERMINATIONS OF TRACEAMOUNTS OF TIN(II) AND TIN(IV) BY AMPLIFICATION REACTIONS

Two simple and accurate titrimetric and spectrophotmetric methods have been developed for the determination of tin. The methods were based u pon the oxidation of tin to tetravalent tin with sodium periodate at p H 2.2-3.5; excess periodate ions were then masked with 5% sodium molyb date at the same pH. The released iodate ions were determined spectrop hotometry (at 350 nm) as triiodide after the addition of KI. This prop osed procedure offered a six-fold amplification for each tin(II) ion. Alternatively, the released iodine was extracted with chloroform and s haken with an aqueous solution of 1% (w/v) sodium sulfite. The iodide ions produced in the aqueous phase were then oxidized with sodium peri odate after removing the unreacted sodium sulfite by boiling with H2SO 4 (2 M). The released iodate was finally determined by iodometry or sp ectrophotometry. This procedure offered 144-fold amplification per tin (II) ion. The determination of tin(IV) after prior reduction to tin(lI ) with sulfur dioxide was also found to be suitable. Analyses of the b inary mixtures of tin(II)-tin(IV) in an aqueous solution, tin in organ otin compounds and tin(II) and tin(IV) in artificial sea-waters were s uccessfully carried out.