Spectrophotometric determination of titanium(IV) as a mixed thiocyanate—monooctyl-α-anilinobenzylphosphonate complex |
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Authors: | B. Tamhina M.J. Herak V. Jagodić |
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Affiliation: | Laboratory of Analytical Chemistry, Faculty of Science, University of Zagreb and Institute “Rudjer Bo?kovi?”, 41000 Zagreb, Strossmayerov trg 14 Yugoslavia |
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Abstract: | Extraction of titanium(IV) thiocyanate complexes by monooctyl-α-anilinobenzylphosphonate (MOABP) dissolved in chloroform has been investigated as a function of hydrochloric and sulfuric acid concentration. Chloroform solutions follow Beer's law and are stable for at least 24 h. A sensitive and reproducible spectrophotometric determination of titanium is possible. Two complexes were identified; the first formed at acid concentrations less than 1 M, has the ratio Ti:SCN:MOABP 1:1:2 and the second, formed at higher acidity, has the ratio Ti:SCN:MOABP 1:2:2. The method is based on the extraction of titanium thiocyanate with MOABP from either 0.5 M H2SO4, and measurement of the absorbance at 336 nm (? = 11 000 l mol-1 cm-1 ), or from 6.5 M HCl, and measurement of the absorbance at 420 nm (? = 22 000 l mol-1 cm-1). The polymerization of thiocyanate has been studied; isoperthiocyanic acid has been identified as the polymerization product. Although both procedures give reproducible results, extraction from 6.5 M HCl is more sensitive, fewer elements interfere, and the precipitation of isoperthiocyanic acid is avoided. |
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