The dispersion in the measurements of the electric strength of pure hydrocarbon liquids using direct voltage is significantly reduced using a hydrogen thyratron by-passing circuit. The damage due to discharge, mainly produced on the anode, is much less, and many more measurements on a particular sample are possible. Experiments with n-hexane show that the breakdown is practically independent of both electrode material and external radiation uniform fields but that it is dependent on the cathode gradient when the field is non-uniform. The electric strengths of the paraffins, pentane to decane, at room temperature increase with chain length and with decreasing gap. The strength is higher at low temperatures but decreases rapidly near boiling point. Cyclohexane and benzene show a different temperature dependence. A possible mechanism of breakdown in these liquids, in accordance with the experimental results, is suggested. This involves the formation of an electron avalanche in the liquid and subsequent bombardment of the anode. The molecules of the liquid provide a vibrational barrier to acceleration of the electrons, this barrier being influenced by molecular orientation at very high fields.
展开▼
