The papers in this book were submitted for the 1988 London International Chlorine Symposium. This was the fifth symposium organised by the Electro chemical Technology Group of the Society of Chemical Industry and proved as popular as ever, attracting a record number of 294 delegates from 31 countries. Twenty-seven papers were presented during the two and a half-day event covering the latest developments in chlor-alkali technology. The field of membranes and membrane cells was well represented by some 15 papers, reflecting the importance of membrane technology to the future of the industry. This is particularly relevant in view of increasing environmental pressures and rising costs. However, papers relating to the more traditional mercury and diaphragm cell technologies were also presented, together with a paper concerned with sodium chlorate manufacture. In addition, there were presentations covering the commercial and safety aspects of the chlor-alkali industry. The Electrochemical Technology Group of the Society of Chemical Industry offer thanks to the many people and organisations whose help ensured the success of this symposium. In particular, we would like to thank: 1. The contributors of the papers. 2. The session chairmen: Dr R. G. Smerko (The Chlorine Institute Inc.); Mr B. Lott (The Associated Octel Company Limited); Mr T. F. O'Brien (United Engineers and Constructors); Dr B. S. Gilliatt (ICI Chemicals and Polymers Limited); Mr D. Bell (Hays Chemicals Limited). 3. The Chlorine Institute for assistance with printing costs and for active participation.