The teaching of Chemistry at the introductory stage becomes each day a more challenging task as the subject matter becomes more diverse and more complex. These challenges have evoked a series of responses?the present set of introductory chemistry monographs is one such. The teaching of chemistry recognises a number of problems, that confront those who select text books. In order to overcome these problems, this volume ?Chemicals in the Environment? ? one of about fifty in the Chemistry Monograph Series?is introduced. Each volume is independent of the others deals with one of Chemistry topics and constitutes a complete entity. Each volume is more comprehensive than can be possible in a single volume text. It is intended to provide a range, of topics to cover most undergraduate and chemistry main courses of study. These volumes can be used to enrich the more conventional courses of study.