title: Complexation equilibria between niobium(V) and 4-(4'H-1',2',4'-triazolyl-3'-azo)-2-methylresorcinol Extraction-spectrophotometric determination of niobium in pyrochlore-bearing rocks.
abstract: The complexation equilibria between niobium(V) and 4-(1'H-1',2',4'-triazolyl-3'-azo)-2-methylresorcinol has been studied by spectrophotometric methods and graphical and numerical calculation methods. The 1:2 Nb:R complex species formed at pH 6.2 ( = 2.16 x 10(4) l.mole(-1).cm(-1) at 490 nm) allows the determination of 0.15-2.50 ppm Nb. A 1:1 Nb:R complex species can be extracted into n-butanol from 0.1-1.5M hydrochloric acid ( = 1.28 x 10(4) l.mole(-1) .cm(-1) at 510 nm) and Beer's law is obeyed over the range 0.77-4.64 ppm Nb. Interferences and their elimination have been studied and the methods applied to the determination of niobium in pyrochlore-bearing ores.
authors.affiliation: Department of Analytical Chemistry, University of La Laguna, 38204-La Laguna, Tenerife, Spain.
authors.forename: M J
authors.initials: MJ
authors.lastname: Sánchez
authors.forename: A
authors.initials: A
authors.lastname: Francisco
authors.forename: F
authors.initials: F
authors.lastname: Jiménez
authors.forename: F G
authors.initials: FG
authors.lastname: Montelongo