In the past ten years the study of the mechanisms of chemical transformations on metal surfaces has advanced appreciably. Today complex reaction networks can be unraveled by combining several spectroscopies, derived principally from the practice of ultrahigh-vacuum surface physics. Of paramount importance in this field is the combination of mass spectrometric methods for the identification of reaction products with spectroscopies which help identify surface-bound reactive intermediates. This quasi-monograph highlights the progress in this field with studies which clearly exemplify such research and at the same time provide more general understanding of chemical reactivity at surfaces. This book was constructed to be a resource to all scientists interested in the chemical reactivity of metals, including those whose primary interest may lie in fields outside surface reactivity. The book is'intended to be an advanced case­ study text, not a "review" in the standard sense. Each chapter develops principles and illustrates the use of experimental methods. Consequently, more attention is given to experimentation than normally found in journal articles or review articles. My intent in organizing these chapters was to make this field accessible to professionals and graduate students in the fields of chemistry, material science, and physics. Even so, we hope that experts in the field of surface reactivity will also find these chapters informative. After the introduction (Chap. 1) the book consists of chapters on the mechanism of selective oxidation by silver (Chap. 2 by R.1. Madix and J.T.