Metal–ion complexation reactions in the presence of surfactants. Part 2.—Mechanism of pH-dependent reaction between nickel(II) and murexide in aqueous solution and application of the reaction to study of micellar phenomena
- 1 January 1979
- journal article
- research article
- Published by Royal Society of Chemistry (RSC) in Journal of the Chemical Society, Faraday Transactions 1: Physical Chemistry in Condensed Phases
- Vol. 75, 119-131
- https://doi.org/10.1039/f19797500119
Abstract
The thermodynamics and kinetics of the reaction between Ni2+(aq) and the metal ion indicator murexide (Mu–) have been studied over the pH range 4.0–7.3 in aqueous solution. Rates and equilibrium concentrations are strongly pH-dependent. Rate constants were obtained using pressure-jump and stopped-flow methods and results from both techniques are in excellent agreement. All data are consistent with the reaction scheme: Ni2++ Mu– [graphic omitted] (NiMu)+ [graphic omitted] (NiMu)dep+ H+. The reaction (involving charged reagents) is studied in the absence of added inert electrolyte and, therefore, under conditions of varying ionic strength. A general treatment for handling rate and equilibrium data in this situation is described. By the inclusion of appropriate activity co-efficients the following results (at 298.2 K) are obtained: K1=k1/k–1= 3.8(± 0.2)× 103 dm3 mol–; KH= 1.8(± 0.2)× 10–6 mol dm–3, k1= 7.8(± 0.5)× 103 dm3 mol–1 s–1; k–1= 2.1 s–1. Such indicator reactions involving murexide are very convenient for the study of various aspects of micellisation and their application to the detection of micelles formed by anionic detergents is described.Keywords
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