ANALYSTTHE ANALYTICAL JOURNAL OF THE CHEMICAL SOCIETYEDiTORlAL ADVISORY BOARD"Chairman: J. M. Ottaway (Glasgow, U.K.)R. Belcher (Birmingham, U.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 (WemMey, U.K.)E. A. M. F. Dahmen (The Netherlands)A. C. Docherty (Bi/lingham, 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)'J. H. Knox (Edinburgh, U.K.)"J. N. Miller ( L oughborough, U.K.)G. W. C. Milner (Harwell, U.K.)G. H. Morrison (U.S.A.)H. W. Nurnberg (West Germany)"G. E. Penketh (Wilton, U.K.)"T. B. Pierce (Harwell, U.K.)E. Pungor (Hungary)D. I. Rees (London, U.K.)P.H. Scholes (Middlesbrougy, U.K.)'W. H. C. Shaw (Greenford, U.K.)S. Siggia (U.S.A.)"D. Simpson (Thorpe-le-Soken, U.K.)A. A. Smales,O.B.E. (Thornaby, U.K.)'A. Townshend (Birmingham, U.K.)A. WaIsh (Austraiia)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 CISE, Casella Postale 3986, 201 00 Milano, ITALY.Professor L. Gierst, Universite Libre de Bruxelles, Facult4 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. RubeGka, Geological Survey of Czechoslovakia, Kostelni 26, Praha 7, CZECHOSLOVAKIA.Professor J . R&i6ka, 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.Bruxelles, BELGl U M.Mich. 481 06, U.S.A.DENMARK.Published by The Chemical SocietyEditorial: The Direcror of Publications, The Chemical Society, Burlington House,London, W1V 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 I HNVolume 104 No 1241 August 1979cQ The Chemical Society 197