ALYSTTHE ANALYTICAL JOURNAL OF THE CHEMICAL SOCIETYEDITORIAL ADVISORY BOARD"Chairman: J. M. Ottaway (Glasgow)R. Belcher (Birmingham)L. J. Bellamy, C.B.E. (Walthsm Abbey)L. S. Birks (U.S.A.)E. Bishop (Exeter)L. R. P. Butler (South Africa)E. A. M. F. Dahmen (The Netherlands)A. C. Docherty (Billingham)D. Dyrssen (Sweden)J. Hoste (Belgium)H. M. N. H. Irving (South Acrica)M. T. Kelley (U.S.A.)W. Kemula (Poland)*J. H. Knox (Edinburgh)G. W. C. Milner (Harwell)G. H. Morrison (U.S.A.)*H. J. Cluley (Wembley)*P. Gray ( f e e d s )H. W. Nurnberg (West Germany)"G. E. Penketh (Wilton)E. Pungor (Hungary)D. I. Rees (London)"R. Sawyer (London)P. H. Scholes (Middlesbrough)"W. H. C. Shaw (Greenford)S. Siggia (USA.)"D. Simpson (Thorpe-/e-Soken)A. A.Smales, O.B.E. (Thornaby)*A. Townshend (Birmingham)A. Walsh (Australia)T. S. West (Aberdeen)"J. Whitehead (Stockton-on- Tees)A. L. Wilson (Medmenham)P. Zuman (U.S.A.)"Members of the Board serving on The Analyst Publications CommitteeREG I0 NAL ADVl SO RY EDITORSDr. J . Aggett, Department of Chemistry, University of Auckland, Private Bag, Auckland, NEW ZEALAN D.Professor G. Ghersini, Laboratori CISE, Casella Postale 3986, 201 00 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 29, 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 of Czechoslovakia, Kostelni 26, Praha 7, CZECHOSLOVAKIA.Professor J . RGziEka, 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 335, Pretoria, SOUTH AFRICA.Bruxelles, BELGIUM.Mich. 481 06, U.S.A.DENMARK.Published by The Chemical SocietyEditorial: The Director of Publications, The Chemical Society, Burlington House,London, WIV OBN. Telephone 01 -734 9864. Telex No. 268001Advertisements: Advertisement Department, The Chemical Society, Burlington House, Piccadilly,London, h'l V OBN. Telephone 01 -734 9864Subscriptions (non-members): The Chemical Society, Distribution Centre, Blackhorse Road,Letchworth, Herts., SG6 1 HNVolume I04 No 1237 April 1979@ The Chemical Society 197