Abstract

The definition of a perfect gas mixture varies substantially within the chemistry textbook literature. A recent International Union of Pure and Applied Chemistry (IUPAC) definition is here criticised as being insufficient to cover properties traditionally associated with such mixtures. Possible supplements to the definition to rectify the deficiency are considered. An alternative definition in molecular terms is shown to be comprehensive. The paper should serve as a summary of the properties of a perfect gas mixture and of essential components of its definition.