An attempt to estimate the relative amounts of krypton and of xenon in atmospheric air

Extract

When Dr. Travers and I isolated krypton and xenon from air, we had very little idea of the total amount of liquid air from which, by its evaporation, these gases had been obtained. And we were then more concerned with the isolation of the gases in a pure state than in the determination of the proportion in which they exist in the atmosphere. Our knowledge of the composition of the air, however, is not Complete until the total yield of krypton, xenon, neon, and helium has been determined. An estimation of the two last is being undertaken by Dr. Travers.