Properties of molten carboxylates. Part 2.—The viscosities of some molten lead and zinc carboxylates

Abstract

The viscosities (η) of molten lead and zinc n-alkanoates, with even numbered chain lengths from hexanoate to octadecanoate inclusive, have been measured as a function of temperature from the melting point to just below the decomposition point. Plots of log η against inverse temperature are linear for all the compounds studied, with slopes corresponding to activation energies varying from 18.2 kJ mol^–1 for zinc hexanoate and 30.3 kJ mol^–1 for lead hexanoate to 66.6 kJ mol^–1 for zinc octadecanoate and 89.4 kJ mol^–1 for lead octadecanoate. The data support the model of ionic dissociation previously proposed to explain the conductance data. The relatively large variation of activation energy with chain length for these compounds may indicate that the unit of flow is an aggregate of approximately 3 or 4 carboxylate molecules. Entropies of activation are the same linear function of activation enthalpy for both series of compounds.