vX properties of CH (sub 4) -CO (sub 2) and CO (sub 2) -N (sub 2) fluid inclusions; modelling for T<31 degrees C and P<400 bars

vX properties of the binary systems CO (sub 2) -CH (sub 4) and CO (sub 2) -N (sub 2) are described with improved accuracy and for the full ranges of composition and molar volume. PTX conditions of phase transitions including liquid, gas and solid are modelled by the Soave-Redlich-Kwong equation of state, and molar volumes by the Lee-Kesler correlation. The Soave-Redlich-Kwong equation of state has been improved for critical fluids. vX diagrams are presented, which describe phase transitions involving liquid, gas and CO (sub 2) solid phases for CO (sub 2) -CH (sub 4) and CO (sub 2) -N (sub 2) fluid inclusions. Also discussed are the conditions of the metastable liquid-liquid-gas phase assemblage.