Spectrophotometric Study of Solvent Extraction of Ternary Complex Composed of Cobalt, Nitroso-R Salt and Zephiramine

Abstract

A spectsophotometric method of determination of cobalt was studied by the solvent extracti on of the nitroso-R salt (Na2HNRS) complex of coba1t i4 the presence of zePhiramine (Z Cl-). The NRS-Z complex was extracted into chlbroform quantitatively. The e xtracted species had abs6rpti6ri makima at 420 nm and about 500 nm, respectively, and was stable within shrs. The maximum eXtraction was obtained in the optimum pH range of 6.0, y8.0. The extraction equilibrivm was attained by i shaking for 10 min. For the first extract, Beer s law held for up to 11 ptg cobalt per 5. O ml of chloroform. The molar absorption coefficient of the ternary complex was 10.55 103 cm-iemol-iedmg at 550 nm, and 11.70 103 cm-iemol-iedm3 at 505nm., Composistion of the complex was estimated to be Co: NRS: Z=1: 3: 6 by the moe ratio and bontinuous variation methods applied to the three components system. Consequen tly it may be assumed that the ternary complex was an ion-pair com pound of the composition of [Co8 (NRSSnt)3(Z)6]. With respect to sensitivity and selectivity, the present method was someWhat superior to t: he original NRS method. The large amount of iron(III)was satisfactorily"masked by citric acid; The logarithm of the equilibrium constant K for the formation of ion-pair compound was found to be 36, 310 0, 144,