Chromatography, as a method for analyzing complex mixtures, is gradually replacing traditional chemical and physicochemical methods in various fields of analytical control. Chromatographic methods have already been incorporated into at least 200 technical specifications for chemical reagents. In the Soviet petrochemical and petroleum-refining industries, as much as 50% of all analyses are carried out using chromatography. More than 95% of the chromatographs used in enterprises of this sector are employed for quantitative analysis. Routine gas chromatographic analyses are used in the food, coke-chemical, natural gas, and many other industries. Numerous standards and technical regulations in these sectors are also being revised to incorporate chromatographic methods. However, the application of chromatography in research practice has advanced much more rapidly than its implementation in process control and product-quality analytical control. This situation indicates that the quantitative aspects of chromatographic analysis have not yet been sufficiently developed. According to the completeness of analysis and the attainable level of accuracy, gas chromatographic measurements may be broadly divided into two groups. In the first group, the analyst seeks to obtain the most complete possible information on the qualitative composition of a mixture and is satisfied with relatively low accuracy in determining the content of individual components. The objective of the second group is to obtain more accurate data for a limited number of components whose identities are already known. This book is concerned primarily with the second type of measurement. The field of application of these measurements is quite broad, because in process control it is often sufficient to determine the concentration of only one or two components in a mixture in order to decide whether operating conditions need to be changed. Furthermore, the compliance of many chemical products, which are themselves complex mixtures, with national standards is usually determined by the content of several key components. In technical research work as well, such as studies related to process optimization or equipment design, results are generally evaluated on the basis of a limited number of components whose concentrations must be determined with high precision.