Abstract
It is assumed that gas properties are defined by the motion and interaction not only of individual molecules but also of their clusters, which consist of several molecules. From the exponential cluster size distribution, the basic relationships for the parameters of cluster gas mixtures are derived, a computational scheme is suggested, and the cluster concentration and the compressibility factor for a number of gases are calculated. Using the example of the viscosity coefficient of oxygen, it is demonstrated that the cluster model fits the experimental pressure dependence of the viscosity if the variation of the cluster composition and partial contributions of cluster components to the viscosity are taken into account.