title: Spectrophotometric study of the reaction of bismuth(III) with Xylenol Orange.
abstract: The reaction between bismuth(III) and Xylenol Orange (XO) has been investigated by spectrophotometry. It has been established that bismuth(III) and Xylenol Orange form complex compounds with compositions Bi(III):XO = 1:1 (up to pH 1) and Bi(III):XO = 1:2 (above pH 1) which have absorption maxima at 550 and 500 nm respectively. The formula of the 1:1 complex is [Bi(H(3)R)] whereas the 1:2 complex can take one of the following forms: [Bi(H(4)R)(2)](1-), [Bi(H(4)R)(H(3)R)](2-) and [Bi(H(3)R)(2)](3-). If the values for pK(Bi(H(3)R)) and pK(Bi(H(3)R)(2)) respectively are 9.80 +/- 0.03 and 15.53 +/- 0.03 at a constant ionic strength of 1.0.
authors.affiliation: Department of Analytical Chemistry Higher Institute of Chemical Technology and Metallurgy Sofia-56, Bulgaria.
authors.forename: D
authors.initials: D
authors.lastname: Kantcheva
authors.forename: P
authors.initials: P
authors.lastname: Nenova
authors.forename: B
authors.initials: B
authors.lastname: Karadakov