Jack Barrett, PhD, CChem, MRSC, Department of Chemistry, Imperial College of Science & Technology, London; Gold Biohydrometallurgy Chemistry Consultancy, Kingston- on-Thames, UK; formerly Physical & Inorganic Chemistry Research Supervisor and Lecturer in the Universities of Kings College London and Hertlordshire. Dr. Barrett is greatly respected for his chemical knowledge and contribution to teaching and research, which is as well known within the metal industry as in academia, He has been responsible for two books in recent years from the publishers Ellis Horwood Limited, namely Understanding Inorganic Chemistry, and also Metal Extraction by Bacterial Oxidation which reflects his standing and authority as a consultant in gold hydrometallurgy and mining.