To start the discussion of the subject matter, it appears desirable to ascertain what is meant by dielectric fluids. Obviously there are many ways in which to classify materials which depend usually on their end use. Of interest here is the one which considers a material's resistance to the flow of electricity as a guide. For example, materials having a specific resistance of less than one microohm per centimeter are called conductors, those having less than one gigaohm per centimeter are called semiconductors, and those having higher resistivities are referred to as insulators or dielectric materials. It is this last group, that comprises in addition to fluids, solids, and gases, that is of interest here.