Phase behavior of Dieterici fluids

This study presents an analysis of the Dieterici equation of state using the global phase diagram methodology. The main difference between the EOS of Dieterici and equations of state of the van der Waals type is that Dieterici isotherms do not give negative pressures. It is shown that this feature results in the inability of the Dieterici EOS to describe liquid properties at very low pressures and temperatures and it limits the possibility to generate transitional mechanisms with negative pressure critical lines. Common behavior, such as liquid-liquid immiscibility in real fluids at very low temperatures, cannot be described with this EOS. Thus, without major modifications, the Dieterici EOS cannot be expected to replace EOS of van der Waals type for the correlation and prediction of data of mixtures. The most important conclusion of the present study is that in order to be useful in practice, an EOS should be able to generate isotherms that present negative pressures.