Quantitative Estimation of Ruthenium(III) Using Morpholine‐4‐Carbodithioate as a New Analytical Reagent

Abstract

Ruthenium(II1) has been precipitated gravimetrically in the pH range 7.0-8.5 with morpholine-4-carbodithioate and determined by weighing as a black complex {C,HaONSJ,Ru after drying at lOO-llO·C. The interference of the various metal ions has been avoided by using an ammonical mixture of EDTA and tartrate (1:1 molar ratio). The complex is thermally stable up to l&C.Very few methods are available in literature for the gravimetric determinations of ruthenium(III). Though reagents such as mepazine hydrochloride», 4-amino-S-nitro-2,6-pyrimi· dinediolv, 3-nitroso-4-hydroxy-S.6 benzocoumarin') and thiovoluric llcid u have been used to determine ruthenium(III) spectrophotome-trical1y. Bayer and Ottl) reported morpholine-4carbodithioate as a possible analytical reagent.Here we report, the results of quantitative estimarion, separation, thermogravimetric analysis and IR studies. MATERIALS AND METHODSThe potassium salt of the reagent was prepared by mixing potassium hydroxide, morpholine and earbondisulphide in ether at O'C in a ratio 1: 1: 1. The purity of the reagent was confirmed by elemental analysis and IR spectra.The stock solution of ruthenium was prepared by dissolving 1.0 gm. of ruthenium(III) chloride (J. M. Chemicals, London) in dilute hydrochloric acid. The ruthenium content was standardized gravimetrically by thioanilide method51.The thermogravimetric studies of the metal chelate was carried out on a stanticn-thermo gravimetric Balance at the heating rate of 3'CI minute. Procedure for the Determination of Ruthenium (ill)Aliquots of the standard solution of ruthe-nium{III) was diluted to about 100 ml, with distilled water and the pH was adjusted between 7.0-8.5. The 1% (wlv) reagent solution was added to it with continuous stirring of the beaker contents. The black precipitate obtained was digested on steam-bath at 60-70°for about half an hour. The metal complex was filtered through sintered glass crucible(G-4). washed thoroughly with distilled water, dried at 100-110°and weigh as Ru(C,H,ONSs),.It has been observed that tuthenium(III) can quantitatively be precipitated in the pH 7.0-8.5. The results of twenty-five estimations over the pH range 7.0-8.5 revealed that 3.0 mg of ruthenium in 100ml could be estimated with an average error :to.38%.The complex starts decomposing at 160'.The loss in weight at 490·C is 34.5% corresponding to a mixture of metal sulfate and oxide.The conversion factor. RujRu-Complex is 0.17i9.The chelate is soluble in chloroform, acetone, I. ChiMU Chem. Soc.. 26, 83-84 (1979)