v. Formation of negative ions by processes other than attachment in the gaseous phase at low X/po 17. Introduction. As early as 1912, J. J. THOMSON [32J in his first mass spectro­ graph observed negative ions of 0-, Cl-, H- and what he believed to be N-. He at first ascribed these to possible dissociation of polar gaseous compounds by electron impact but control studies using ionization at low energies in glow discharges indicated that this was not the origin. O. W. RICHARDSON [33J in his book on emission of electricity from hot bodies reported negative ions to come from hot salts. From there on many experimental studies over the years indicated that negative ions could be formed by various processes. By the middle nineteen hundred and thirties the data fairly clearly identified several processes as being active and MASSEY and SMITH [34J developed the theory underlying some of them. More data are summarized in MASSEY'S excellent little monograph on Negative Ions and in )LSSEY and BURHOP'S recent book [35]. Since that period, stimulated by various investigations and certain industrial problems, very careful studies of the appearance of such ions by mass spectrograph have been carried out in the laboratory of K. G. EMELEUS in Belfast by SLOANE and his co-workers [3J that haw clarified the questions and indicated what ions have been observed and something of the processes at work.