The dielectric strength of the vacuum: Electrostatic ionization gradient of metal electrodes

THE dielectric strength of air is 30 kv. per cm. at 0 deg. cent. and 76 cm. barometric pressure. It is proportional to the air density over a considerable range. It reaches a minumim in a moderate vacuum. Beyond this, it increases again, and in a very high vacuum reaches high values. much higher than at atmospheric pressure.