This volume contains all of the papers presented at the American Chemical Society Symposium on Reflectance Spectroscopy. The Symposium was presented under the sponsorship of the Division of Analytical Chemistry, and was held on September 11 and 12,1967, at the 154th National Meeting of the American Chemical Society, Chicago, Illinois. The papers presented herein represent a renaissance of interest in reflectance spectroscopy. The techni~ue of reflec tance spectroscopy is not, of course, a new techni~ue, however, it has only been applied to problems of a chemical interest in the last decade or so. The instrumentation for this techni~ue in the ultraviolet, visible, and near infrared regions of the spectrum has been available for many years. New and exciting research is being carried out at the present time to extend these techni~ues to the infrared and far infrared regions as well. It is a pleasure for the Editor to express his gratitude to Drs. John K. Taylor and E. C. Dunlop of the Division of Analytical Chemistry, ACS, for their cooperation in making the Symposium a reality. The assistance of Miss Julie Norris of the University of Houston for her typing and manuscript organi zation skill is greatly appreciated. And lastly, but certainly not the least, the Editor would like to acknowledge the coopera tion of all of the contributors to this volume. Certainly without their cooperation, this Symposium would not have been a success.

Optical Properties of Inhomogeneous Materials: Applications to Geology, Astronomy, Chemistry, and Engineering reviews the results of studies of the optical properties of inhomogeneous materials and provides a guide for solving a number of related scientific and engineering problems based on these studies. Some of these studies focus on the surface and atmosphere of Mars, the earth's atmosphere, and the interstellar medium. The tools necessary for modeling the radiation scattered from diffuse surfaces are also described. Comprised of 12 chapters, this book begins with a brief introduction to the formalism for optical properties of inhomogeneous materials, followed by a description of surface scattering models in order of increasing complexity and a discussion of atmospheric scattering by particulates. The experimental approaches for the determination of the refractive and absorptive components of the optical complex indices of refraction are then considered. Subsequent chapters present actual diffuse surface modeling examples and discuss applications such as remote sensing of planetary surfaces; study of the interstellar medium; research on thermal energy collectors; analysis of coatings and paints; and remote mineral exploration. This monograph will be of interest to scientists, students, and researchers in different disciplines such as geology, optical mineralogy, astronomy, chemistry, soil mechanics, mechanical engineering, and optics.