[dmoneyownz]

Does anyone know where I could find a good paper online which describes the Berthelot equation of state beyond just stating the equation and which relates the Berthelot equation of state with the VDW? I know they differ in the extra volume term but would like to know why. Thanks in advance.

[Hunt]

I dont know of any online paper but usually general chemistry or pchem books offer a qualitative explanation of the VDW equation of state. Some books even use statistical mechanics and a hybrid of a hard-sphere and Lennard-Jones potential model to give a clearer meaning of the constants a and b. The berthelot eq is the same as VDW except the attractive forces become temperature dependent.

P_att = a / V² ( VDW )
P_att = a / TV² ( Berthelot )

At very high temperatures, the attractive forces vanish. Therefore Berthelot included the T factor in the denominator.