The Dielectric Breakdown of some Simple Organic Liquids

The development of a method of measuring the electric strength of liquid dielectrics with direct current, alternating current and impulse voltages, is described. Experiments on normal hexane have shown that, when the electrode system is thoroughly cleaned and the liquid carefully filtered, the electric strength is independent of the form and duration of the applied voltage and the dielectric thickness. The electric strength cannot, however, be considered an intrinsic property of the liquid, since with direct current it is dependent on both the material and form of the electrodes. Investigations on a series of liquid normal paraffin hydrocarbons (pentane to nonane) have shown that the electric strength increases as the chain length of the molecule increases. The cyclic hydrocarbons, cyclohexane and benzene, have approximately the same electric strength as n-hexane. The experimental results are discussed in relation to existing theories of dielectric breakdown in liquids and solids.