The purpose of this book is to help chemists, biochemists and other scientists to purify the chemical reagents which they use in their work. Despite the fact that commercially available chemicals are often of a very high quality and quite satisfactory for some applications within science and technology, it is becoming almost as important to know what impurities are present and to make allowance for them as to remove them completely. This book aims to show how. The main chapters describe processes, taken from the literature, for purifying over 4000 organic and 750 inorganic or organometallic commercially available chemicals. Further chapters describe the methods and techniques used for purification in laboratories and prescribed in the text. Methods for purifying classes of chemicals where specific compounds are not treated individually in the text are dealt with in a separate chapter. This expanded and revised fourth edition includes new material dealing with modern reagents for natural products chemistry, protein biochemistry and molecular biology. It also includes many individual compounds not previously covered, and more information is given on most entries, including melting and boiling points, molecular weights, refractive indexes, densities and CAS registry numbers, as well as likely contaminants and storage conditions in appropriate cases.