Given a mixture of oil gas with
a total mass of oil component
m_O = m_{Oo} + m_{Og}
total mass of gas component
m_G = m_{Gg} + m_{Go}
then
the mass share of oil component in oil phase m_{Oo}(p,T) and the mass share of gas component in gas phase m_{Og}(p,T)
the mass share of gas component in oil phase m_{Go}(p,T) and mass share of gas component in gas phase m_{Gg}(p,T)
are all functions of temperature and pressure (p, T).