Properties of molten carboxylates. Part 3.—Electrical conductance, density and viscosity of some molten cadmium carboxylates
- 1 January 1976
- 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. 72, 2470-2476
- https://doi.org/10.1039/f19767202470
Abstract
The preparation of pure cadmium carboxylates of even chain length from decanoate to octadecanoate inclusive is described. Values are reported for their density, viscosity and electrical conductance as a function of temperature from just above the melting point to just below the decomposition point. Molar volumes are a linear function of chain length and of temperature. The volume occupied by the head group is small (6.34 × 10–8 m3 mol–1) and indicates a strong cadmium–carboxylate interaction. Arrhenius plots for the viscosity are linear with activation energies varying from 78 kJ mol–1 for the decanoate to 88 kJ mol–1 for the octadecanoate. The variation of activation energy with chain length is consistent with a model in which the unit of flow is a single carboxylate group, the Cd—O bond being broken in the formation of the activated complex. There is linear enthalpy–entropy compensation for the activation parameters. Arrhenius plots for the conductance show curvature, which is interpreted in terms of a simple dissociation equilibrium for which the enthalpy change is ∼170 kJ mol–1. The degree of dissociation in the high temperature region increases as the chain length increases.Keywords
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