This standard provides the gas processing industry with a convenient compilation of authoritative numerical values for hydrocarbons and other compounds occurring in natural gas and natural gas liquids as well as other compounds of interest to the industry. The physical properties selected are those considered most valuable for engineering and analytical computations. Most properties are based upon two NIST Standard Reference Databases: the Web Thermo Tables, WTT (NIST SRSD-3), and the Reference Fluid Thermodynamic and Transport Properties Database, REFPROP 9.1 (NIST SRD-23). The data in this publication were checked, evaluated, and recalculated when necessary by the Applied Chemicals and Materials Division of the Material Measurement Laboratory at NIST. The listed flammability limits and octane numbers were not evaluated at NIST and sources for these properties are provided in the references.