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182 CHAPTER 2

Fig 2.72. The dependence of the breakdown
potential on the log of conductivity (log S)
of NaCI (•) and of solutions. (Re-
printed from M. Szklarczyk, R. Kainthla, and J.
O’M. Bockris, J. Electrochem. Soc. 136: 2512,

be able to control, the critical field strength, the exceeding of which would break down
the dielectric and waste away the electrical energy stored within it. 45
There is not yet a consensus as to the mechanism of dielectric breakdown in
liquids. Research during the last decades of the twentieth century on the breakdown
of liquid dielectrics was funded mainly to investigate dielectric breakdown in oils
because transformers use oils as dielectrics and sometimes suffer catastrophic dielec-
tric breakdown accompanied by sparking. Insulating oil then catches on fire and
equipment costing millions of dollars is damaged beyond repair. Thus, not much
laboratory work aimed at determining the mechanism of dielectric breakdown in water
at a molecular level exists. For example, work in which all is maintained constant
except for a systematic change in the nature of the electrode surfaces seems to be
conspicuous by its absence.
The most obvious theory—one still held even today by engineers—is that a
sufficiently high electric field existing in the liquid will eventually place an electrical
force on the solvent dipoles, which will cause the force applied to break the chemical

45
In the Star Wars program of the early 1990s, giant space-borne lasers were to zap enemy missiles as they
left their silos. Their ground-based power was to he held in condensers with water or very dilute solutions
as the dielectric. Transfer of electrical energy to the orbiting satellite was to be made by beaming it in the
megacycle frequency range.