title: Spectrophotometric study of the reaction of iron(iii) with methylthymol blue.
abstract: The reaction between iron(III) and Methylthymol Blue (MTB or H(6)A) has been investigated by spectrophotometry. It has been established that iron(III) and MTB form two complexes with compositions iron(III): MTB = 1:1 and 1:2. The 1:1 complex is stable in acidic medium containing excess of iron, and the 1:2 complex is stable in slightly acidic or alkaline media containing excess of MTB. The absorption maxima are at 610 mmu (1:1) and 515 mmu (1:2), the molar absorptivities being 1.73 +/- 0.01 x 10(4) and 3.21 +/- 0.05 x 10(3) respectively. The nature of the two complexes at pH 6 and the stability constants have been determined: log beta(11) = 20.56 +/- 0.07, log beta(112) = 43.29 +/- 0.09, log beta(12) = 6.66 +/- 0.05.
authors.affiliation: Department of Analytical Chemistry, Higher Institute of Chemical Technology and Metallurgy, Darvenitza, Sofia, Bulgaria.
authors.forename: B
authors.initials: B
authors.lastname: Karadakov
authors.forename: D
authors.initials: D
authors.lastname: Kantcheva
authors.forename: P
authors.initials: P
authors.lastname: Nenova