Solvent extraction is employed very widely in both fundamental research and technology because of the remarkable features of this simple but very effective technique for the separation of different materials. The International Solvent Extraction Conference 1990 was a forum for the presentation of papers on up-to-date research in this field. The collection of the papers in these volumes will be invaluable because information on solvent extraction is often scattered in various journals and proceedings which make the following of developments difficult.