title: Liquid-liquid distribution of ion-associates of acidic dyes with quaternary ammonium counter-ions.
abstract: Diprotic acid dyes [H(2)A: Bromophenol Blue (BPB), Bromochlorophenol Blue (BCPB), Bromocresol Purple (BCP), Bromocresol Green (BCG), Bromothymol Blue (BTB)] can be extracted as 1:1 ion-associates Q(+)HA(-) and 1:2 ion-associates (Q(+))(2)A(2-) with quaternary ammonium cations (Q(+)) into chloroform. The extraction constants (log K(ex)) of the 1:1 and 1:2 ion-associates have been determined. Linear relationships between log K(ex) and the number of methylene groups in the quaternary ammonium ions were observed; from the slope of the line, the contribution of a methylene group to log K(ex) was found to be 0.43-0.65. The extractability with alkyltrimethylammonium cations was larger than that with symmetrical tetra-alkylammonium cations, for both the 1:1 and 1:2 ion-associates. From the extraction constants obtained, the extractability of acidic dyes was in the order BTB > BCG > BPB > BCPB > BCP.
authors.affiliation: Department of Industrial Chemistry, Yonago National College of Technology 4448, Hikona-cho, Yonago-shi, Tottori 683, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Yamamoto
authors.forename: S
authors.initials: S
authors.lastname: Motomizu