Dynamic instability at liquid-vapour interface

Dynamic instability at liquid-vapour interface 11.4.1. Introduction 

Interfacial instability is a common phenomenon since in most cases the events occurring at the interface are in the region far from equilibrium [40, 41]. A typical example is Marangoni instability [44-47]. Electric potential oscillations have been observed in biphasic systems [48, 49], Self-induced oscillations in similar systems have also been observed [10]. Theoretical efforts have also been made to understand the mechanism in some cases [23, 27], 

There is considerable interest in the above phenomena from the angle of electrophysiology. The neuronal action involving sense of smell depends on the generation of self-excited electric potential [4, 50, 51]. Hence, a deeper study from fundamental angle is likely to be of considerable use for medicinal or physiological purposes. 

Recent studies on electrical potential oscillations across a liquid membrane consisting of an oil layer, 90% oleic acid and 10% 1-propanol, containing tetraphenyl phosphonium chloride (TPPC), between aqueous solutions of 0.5 M NaCl and KCl in tow different compartments have been reported by Yoshikawa and Matsubara [52]. TPPC is a cationic lipophilic salt, which can act as a surfactant. On exposure to amine vapour, initially upward deflection occurs, indicating that the KCl solution becomes negative with respect to NaCl solution. Electric potential oscillations did not occur when the concentration of ammonia was below a critical value. 

However, their studies are limited to qualitative study of oscillations using different types of amines, only indicating that the phenomenon is general. 

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