Solid-solution equilibria of marine evaporites are important in a wide range of science and technology. However, the data had not yet been summarized in a form that is at the same time comprehensive and permits to understand how the quinary seawater system builds up from its bounding systems. Thus the goal of the present volume is at the same time scientific and educational. The understanding of solid-solution equilibria of the various systems with respect to dissolution, precipitation and transformation of solids, their application to the evolution of brines, and a fast access to data is a necessary requirement for any modelling, especially in Geoscience. Another goal is to show the avail ability of data. Unfortunately, though solubility data are numereous there are substantial gaps, especially with respect to high temperatures. But also up to about 100 0 C data are missing for some of the systems so that they cannot be described entirely. Based on the present volume further work on the solubili ties of the minerals of marine evaporites may be promoted. The data have been viewed and collected over several years by the first author. The second author entered the preparation of the volume when it was realized that besides graphics and tables a fast access to data was required. Although both authors are responsible for the whole volume, responsibility is weighted somewhat differently for the various parts."

Earth scientists, who have worked together for 6 years in the priority pro gram "Hydrogeochemical Processes in the Hydrological Cycle Within the Unsaturated and Saturated Zones," have summarized the results of their research in this volume. This is the occasion to take stock and then look ahead. The priority program was set up by the Senate of The Deutsche Forschungsgemeinschaft in October 1981. This was preceded by lengthy and careful preparation by a Program Committee, and was finally recom mended by the Senate Commission for Joint Research in Earth Sciences. The main aim was the interdisciplinary research of geochemical processes in natural systems in the total underground water cycle, whereby water pollution was not to be considered. Officially started on 1 September 1982, the program has received a grant of DM 10. 9 Mio. from the DFG, and this has enabled it to support a total of 50 projects. Although at the beginning, practice-oriented projects, which were funded elsewhere, were not to be included, many of the results are applicable. The four categories presented were investigated with vary ing intensity. An early concentration on certain representative fields of measurement and research areas proved to be the right approach - this avoided a waste of effort in other fields. During the period of the priority program, new and topical questions arose, e. g."