Abstract :
The problem of maintaining satisfactory emission in an oxide-cathode valve over long periods of time is examined in broad rather than detailed manner. The approach is essentially experimental and starts from the basic assumption that the cathode will maintain its emission so long as it possesses a sufficiency of metallic barium in its oxide matrix. The general plan of the paper is to examine the several factors leading to loss and gain of barium metal within the cathode and then to attempt to estimate the conditions likely to result in a credit balance of barium over a long period of time. The tentative conclusion reached is that a cathode working under a current load in gas-free surroundings will continue to emit until the barium-oxide matrix is exhausted by electrolysis and evaporation.
