Kinetics and Determination of Some Transition Metals with Peri-Dihydroxynaphthindenone

Abstract

A simple sensitive and selective spectrophotometric method has been developed for determination of some transition metal ions. It is based on the reaction of the metal ions with excess peri-dihydroxynaphthindenone in 80% v/v ethyl alcohol-water mixture at 30°C. The colored products obtained display maximum absorption band at 560–590 nm depending upon the type of transition metal ion used, and E_{1 cm} ^1% in the range 70–480. Under the optimum conditions results with an average recovery of 96%, (mean standard deviation ±3% are obtained for 6 different transition metal ions without any significant interference from Li⁺, Na⁺, K⁺, Cs⁺, Rb⁺, Ba²⁺, Sr²⁺, Ni²⁺, Bi³⁺, Co²⁺, Mn⁺², Cd⁺² and Al⁺³. Kinetic data reveal that the reaction proceeds via a second order route (first order with respect to either the metal cation or ligand). The activation parameters and a suggested mechanism have been presented, and the nature of bonding in the solid chelate products has been verified.