The main subject of this book is the characterization of plastics. To a high degree the properties of these polymers depend on the distribution of the molar mass and of other structural features, and small deviations frequently have a great effect. Therefore the characterization of polymers cannot be restricted to the determination of mean values but must yield information on these distributions. Using classical methods, the analytical fractionation of polymer homologues and structurally isomeric polymers is extremely time-consuming. Therefore, efficient chromatographic techniques are being increasingly employed in modern polymer characterization. In the first place, high-performance liquid chromatography is applied, in the form of size exclusion chromatography. It is also possible, however, to use other separation modes. More space is devoted to these other possibilities in this volume than is merited by their current range of applications, as the author believes that many separation problems will be solved by separation techniques of the non-exclusion type. Nevertheless, much emphasis is placed on size exclusion chromatography.