The monograph analyzes and summarizes numerous experimental data on the thermodynamic properties of ethylene, the methods of drawing up a unified equation of state of gas and liquid and calculation of tables of thermodynamic properties on the average equation of state with assessment of tolerances of tabulated values on the basis of system of equal equations are given the equations for calculation of thermodynamic properties of ethylene in the ideal gas state and under pressure. Tables of thermodynamic properties of gaseous and liquid ethylene in the temperature and pressure range of 110-600 K and 0.1-300 MPa, including properties on saturation and solidification curves. are given. The book is intended for employees of research and design organizations , Chemical and Gas Engineers , working in the field of research and design of gas separation and processing plants , Superchargers , The book can be useful for teachers , graduate students and students of chemical-technological, Thermal Physics and Energy Faculties of Higher Education Institutions .