Small-parameter and caloric equations of the state of a real gas

By means of the stepwise spherically symmetrical potential of interaction, we obtain the equations for the high-precision description of the second virial coefficient and the equations in “elementary functions” for the compressibility factor of a real gas with nonpolar and polar molecules, describing the thermal properties of substances in a wide range of parameters of state with an error close to experimental. It is shown that these equations make it possible to extrapolate with sufficiently high accuracy beyond the limits of the described area. It is established that using these equations, we can calculate the caloric properties of substances with an error, close that of calorimetric experiment.