THE ANALYSTTHE ANALYTICAL JOURNAL OF THE CHEMICAL SOCIETYEDITORIAL ADVISORY BOARD"Chairman: J. M. Ottaway (Glasgow, U.K.)R. Belcher (Birmingham, lU.K.)L. J. Bellamy, C.B.E. (Waltham Abbey, U.K.)L. S. Birks (U.S.A.)E. Bishop (Exeter, U.K.)L. R. P. Butler (South Africa)"H. J. Cluley (Wembley, U.K.)E. A. M. F. Dahmen (The Netherlands)A. C. Docherty (Bi//ingham, U.K.)D. Dyrssen (Sweden)"P. Gray (Leeds, U.K.)J. Hoste (Belgium)H. M. N. H. Irving (South Africa)M. T. Kelley (U.S.A.)W. Kemula (Poland)G. W. C. Milner (Harwell, U.K.)G. H. Morrison (U.S.A.)"J. H. Knox (Edinburgh, L!K)H. W. Nurnberg (West Germany)"G. E. Penketh (Wilton, U.K.)E. Pungor (Hungary)D. I. Rees (London, U.K.)"R. Sawyer (London, U.K.)P. H. Scholes (Middiesbrough, U.K.)"W.H. C. Shaw (Greenford, U.K.)S. Siggia (U.S.A.)"D. Simpson (Thorpe-Ie-Soken, U.K.)A. A. Smales, O.B.E. (Thornaby, U.K.)"A. Townshend (Birmingham, U.K.)A. Walsh (Australia)T. S. West (Aberdeen, U.K.)"J. Whitehead (Stockton-on- Tees,A. L. Wilson (Medmenham, U.K.)P. Zuman (U.S.A.)U.K.)"Members of the Board serving on The Analyst Publications CommitteeREGIONAL ADVISORY EDITORSDr. J . Aggett, Department of Chemistry, University of Auckland, Private Bag, Auckland, NEW ZEALAND.Professor G. Ghersini, Laboratori USE, Casella Postale 3986,20100 Milano, ITALY.Professor L. Gierst. Universit6 Libre de Bruxelles, Facult6 des Sciences, Avenue F.-D. Roosevelt 50,Professor R . Herrmann, Abteilung fur Med. Physik., 63 Giessen, Schlangenzahl 14, W.GERMANY.Professor W. A. E. McBryde, Faculty of Science, University of Waterloo, Waterloo, Ontario, CANADA.Dr. W . Wayne Meinke, KMS Fusion Inc., 3941 Research Park Drive, P.O. Box 1567, Ann Arbor,Dr. I . Rubeska, Geological Survey crf Czechoslovakia, Kostelni 26, Praha 7, CZECHOSLOVAKIA.Professor J . Rhiicka, Chemistry Department A, Technical University of Denmark, 2800 Lyngby,Professor K. Saito, Department of Chemistry, Tohoku University, Sendai, JAPAN.Dr. A. Strasheim, National Physical Research Laboratory, P.O. Box 395, Pretoria, SOUTH AFRICA.Bruxel les, BELGIUM.Mich. 481 06, U.S.A.DENMARK.Published by The Chemical SocietyEditorial: The Director of Publications, The Chemical Society, Burlington House,London, W1 V OBN. Telephone 01 -734 9864. Telex No. 268001Advertisements: Advertisement Department, The Chemical Society, Burlington House, Piccadilly,London, W1 V OBN. Telephone 01 -734 9864Subscriptions (non-members) : The Chemical Society, Distribution Centre, Blackhorse Road,Letchworth, Herts., SG6 1 HNVolume 104 No 1239 June 1979((3 The Chemical Society 197