Chemical reaction systems of practical interest are usually very complex: They consist of a large number of elementary reactions (hundreds or thou sands in a small system), mostly with rate coefficients differing by many orders of magnitude, which leads to serious stiffness, and they are often coupled with surface reaction steps and convective or diffusive processes. Thus, the derivation of a "true" chemical mechanism can be extremely cumbersome. In most cases this is done by setting up "reaction models" which are improved step by step using, for example, perturbation theory, numerical simulation and sensitivity analysis (and - hopefully, in the near future - parameter identification procedures), and by comparison with experimental data on sensitive properties. Because of the complexity of these processes, it was very difficult in the past to convince engineers to apply methods using detailed mecha nisms given in terms of elementary reactions, and even in basic sciences there was scepticism about this ambitious aim. A previous workshop on modelling of chemical reaction systems held in 1980 was an attempt to find a common language of mathematicians, chemists, and engineers working in this interdisciplinary area. Since then considerable progress has been made by the simultaneous development of applied mathematics, an enor mous increase of computer capacity, and the development of experimental techniques in physical chemistry that have made available well-working reaction mechanisms in some fields of reaction kinetics."

This volume consists of edited papers presented at the International Symposion Gas Phase Chemical Reaction Systems: Experiments and Models 100 Years After Max Bodenslein, held at the Internationales Wissenschaftsforum Heidelberg (IWH) in Heidelberg during July 25-28, 1995. The intention of this symposion was to bring together leading researchers from the fields of reaction dynamics, kinetics, catalysis and reactive flow model ling to discuss and review the advances in the understanding of chemical kinetics about 100 years after Max Bodenstein's pioneering work on the "hydrogen iodine reaction", which he carried out at the Chemistry Institute of the University of Heidelberg. The idea to focus in his doctoral thesis [1] on this reaction was brought up by his supervisor Victor Meyer (successor of Robert Bunsen at the Chemistry Institute of the University of Heidelberg) and originated from the non reproducible behaviour found by Bunsen and Roscoe in their early photochemical investigations of the H2/Cl2 system [2] and by van't Hoff [3], and V. Meyer and co-workers [4] in their experiments on the slow combustion of H2/02 mixtures.

This volume collects the results of a workshop held at Aachen, West-Germany, Oct. 12 - Oct. 14, 1981. The purpose in bringing together scientists actively working in the field of numerical methods in flame propagation was two-fold: 1. To confront them with recent results obtained by large ac- tivation-energy asymptotics and to check these numerically. 2. To compare different numerical codes and different trans- port models for flat flame calculations with complex che- mistry. Two test problems were formulated by the editors to meet these objectives. Test problem A was an unsteady propagating flat flame with one-step chemistry and Lewis number different from unity while test problem B was the steady, stoichiometric hy- drogen-air flame with prescribed complex chemistry. The parti- cipants were asked to solve one or both test problems and to present recent work of their own choice at the meeting. The results of the numerical calculations of test problem A are challenging just as much for scientists employing numerical me- thods as for those devoted to large activation-energy asympto- tics: Satisfactory agreement between the five different groups were obtained only for two out of six cases, those with Lewis number Le equal to one. The very strong oscillations that oc- cur at Le = 2 and a nondimensional activation energy of 20 were accurately resolved only by one group. This case is par- ticular interesting because the asymptotic theory so far pre- dicts instability but not oscillations.