<p num="60">FIELD: measurement.</p> <p num="61">SUBSTANCE: invention relates to measurements for the purpose of identifying complex liquid substances as to molecular composition and can be used for identification of fractions of oil subjected to thermal distillation. This will make it possible to create on its basis measuring equipment intended for use in petrochemical and oil refining industries, for rapid analysis of fractions in factory laboratories. In addition, it can be useful in conducting research and development of new products in petrochemical and oil refining industries.</p> <p num="62">EFFECT: disclosed invention has high accuracy of measurements and reliability of identifying complex liquid substances with respect to molecular composition without separation thereof and measuring concentrations of constituent components.</p> <p num="63">1 cl, 2 dwg, 1 tbl</p>