Structure in electrolytic solutions

Abstract

Engendered by the fundamental contributions of Georg Ohm (J. Chemie and Physik, Vol. 46, p. 137, 1826) and Gustav Kirchhoff (Poggendorff's Ann., Vol. 72, 1847), and greatly fostered by electrotechnical challenges of electrical communication (telegraphy, telephony, radio, television) and electric power (lighting, generators, motors), by our time the simple, familiar electric circuit concept has become firmly established in scientific thinking. Yet insufficient note has been taken of the fact that the validity of this remarkably fruitful concept rests upon essential local homogeneity as well as upon an implicit thermodynamic assumption of an isothermal and workless environment. Ohm himself recognized the impossibility of maintaining constant and uniform temperature conditions when confronted with the necessary presence of internal heat production and the associated entropy production and temperature gradients. Kirchhoff, in turn, obtained the loop and node laws for resistive circuits by applying the circulation and divergence theorems to a plane conducting sheet, but since the discovery of mutual induction in 1831 by Michael Faraday it was known that coupling could occur between circuits which could be physically remote and topologically distinct.Active circuitry clearly commenced with the initial use in Morse telegraphy of Joseph Henry's electromagnetic relay and continued with the development of triodes and transistors. These revolutionary devices ushered in the “Second Industrial Revolution” and fostered the use of the method of controlled sources, permitting direct active intercoupling between circuits based upon instantaneous regulated manipulation and modulation of embedded sources of energy.Later, with the advent of ultrahigh frequency (microwaves, electro-optics) and ultrasmall scale (VLSI, Josephson junctions, quantized Hall effect) simple circuitry faced new difficulties and complexities. To satisfy all of the above demands, multiport bond graphs were devised to replace circuitry by adequate extensions and generalizations including wave-scatter approaches and stochastic dynamics. Nevertheless, we should acknowledge that chemistry in general, and wet-chemistry in particular, operates quite frequently under nearly homogeneous (e.g. stirred tanks) and isothermal and isobaric conditions (e.g. STP) for which complete bond graph representation may be needlessly complex. For these special cases, much simpler circuit-like “chemgraphs” and “chemnets” resurrect the powerful advantages of Ohm and Kirchhoff.