Pressure dependence of dielectric constant and density of liquids

Densities and dielectric constants at 30° and at pressures up to 5000 kg/cm² have been measured for toluene, o-xylene, p-xylene, cumene, diethyl ether, di-n-propyl ether, anisole, n-butyl chloride, chlorobenzene, 1,1-dichloroethane, 1,2-dichloroethane, and 1,2-dibromoethane. Two new high-pressure piezometers are described; one measures density through change in electrical capacity, the other through change in resistance between a constantan wire and a mercury piston. Densities are reproduced by the Tait equation within about 0.2%. An equation with the same pressure-dependent term for the electrical susceptibility (ε - 1) represents the dielectric data to about the same precision. The coefficient multiplying the Tait function for dielectric dependence on pressure is greater than for the density dependence because, in addition to the density effect, it also includes the effects of increased short-range interaction between dipoles.