Physics: L. B. Loeb the Mobility of Gas Ions in Hci Mixtures and the Nature of the Ion

The nature of the ordinary gaseous ion appears today to be as far from a definite solution as it was in 1909 when Wellischl and Sutherland2 independently put forward the small ion theory as a possible alternative to the then generally accepted cluster ion theory. While at different times it has been thought that various critical experiments -decided the question in one way or another the writer3'4 has shown that none of the evidence thus far has been conclusive. In a more recent paper on the theory of ionic mobilities the writer4 concluded.with J. J. Thomson5 that if one assumed the mobilities to be controlled by the charge on the ion acting according to an inverse fifth power law, the actual nature of the ion had very little to do with the values of the mobilities as they were found in measurements in pure gases. The theory there advanced, while it agreed with most phenomena observed in such gases for ions better than previous theories, appeared to be seriously impaired by recent results of Tyndall and Grindley.6 It also encountered some difficulty in explaining the recent results of Erikson.7,8 9,10,11 In 1923 Miss Ashley and the writer'2 pointed out that an ultimate answer to the question of the nature of the ion might be found through a study of the mobilities of the ions in mixtures of gases of widely different constitution. The answer to be derived from such a source would not, however, in any way contravert the theory already proposed, but would enable one to extend the knowledge of facts beyond the scope of the conclusions to be derived from that theory. To this end they investigated the mobilities of ions in mixtures of NHs and air. They found that for this case the mobility could be computed by an equation which then appeared to be in good agreement with the theory of the writer. This equation, as was stated above, seemed to be a consequence of assumptions which could not distinguish the presence of clustering did it occur. Hence while the agreement observed tended to confirm the theory it was not supposed to throw any light on the controversy. This equation found stated that the mobility KC of an ion in a mixture of two gases A and B of masses MA and MB and of dielectric constants DA and DB could be computed from