This states that as the pressure of a real gas approaches zero, the Fugacity of each component in the mixture approaches its Partial Pressure.
This is often reinterpreted as meaning that as pressure approaches zero, a real gas becomes 'perfect'. Care must be taken when making this sort of reinterpretation since not all properties of real gases approach their 'perfect' values at zero pressure. The Joule-Thomson Coefficient is a notable example of this. It remains nonzero at P = 0, whereas the perfect gas value is identically zero. (See also Perfect Gas.)