Liquid-Liquid Extraction and Spectrophotometric Determination of Cromium (VI) with o-Hydroxythiophenols In The Presence of Hydrophobic Amines
Abstract
The mixed-ligand complexes of chromium (VI) with o-hydroxythiophenols (HTPD) and its
derivatives [2-hydroxy-5-chlorothiophenol (HCTP), 2-hydroxy-5-bromothiophenol (HBTP), and 2-
hydroxy-5-iodothiophenol (HITP)] in the presence of hydrophobic amines have been investigated by
spectrophotometric method. The condition of complexing and extraction, physical-chemical and
analytical characteristics of this complex have been found. As hydrophobic amins aniline (An), Nmetilaniline
(mAn) and N, N-dimetilaniline (dAn) were used. It has been found that mixed-ligand
complex were formed in weakly acidic medium (pH 3.0 – 5.0). The optimal concentration of ohydroxythiophenols
(HTPD) and Am for formation of the complex was found to be 1.0∙10-3 M and
1.12∙10-3M, respectively. Maksimum of light absorption observed at 475-488 nm. The calculated
molar absorptivities (emax) belong to the interval (2.7 – 3.02)× 104
dm3
·mol–1
· cm–1 . The
stoichiometric coefficients of the reaction were determined by the Asmus method, by the relative
yield method and by the equilibrium shift method. The results show a complex composition of 1:3:3
(Cr(III):HTPD:Am).
A linear calibration graph drawn between absorbance and the metal ion concentration
indicates that Cr(III) may be determined in the range 0.5-16 μg ml-1
. The extraction-photometric
methods of chromium determination have been worked out. The proposed method was applied
successfully to determine amount of chromium in alloys and in soil.
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