Absorption of gases in the discharge tube

Mey has shown that when the liquid alloy of sodium and potassium is made the cathode in a discharge tube, then, on passage of a current, if the gases nitrogen and hydrogen are present they are absorbed. The inactive gases, such as helium, are not affected, however, so he concludes that this would form a very convenient method for the preparation of helium where hydrogen and nitrogen are present as impurities. He mentions the rate of absorption compared with the quantity of electricity passing, and it is much larger than the absorption of gases by the walls of the discharge tube during the passage of a discharge. It is thought that the gases form chemical compounds with the sodium and potassium–the nitrogen giving the nitride and hydrogen the hydride. The following experiments were made to see if there were any relation between the amount of gas absorbed and the quantity of electricity passing during discharge—the measurements being made with varying pressures of the gas. In order to measure the electricity a small voltameter containing sulphuric acid was employed, and the quantity of hydrogen evolved in it was compared with the amount of gas absorbed. The current employed had to be a uni-directional high-tension one. For this, and induction coil with an Oliver Lodge value in the secondary was used. Provided the current was not too large this arrangement gave satisfactory results.