In some circumstances encountered in oil and gas separations, mercury and water will form separate phases that are essentially pure. If a hydrocarbon stream contains both mercury and water, it is possible that both a free water phase and a free elemental mercury phase will form. 

This development is intended to supplement the standard HYSYS flash calculation by providing the capability of searching for an additional liquid phase that is essentially a pure component (e.g., mercury). The standard HYSYS flash is only capable of checking for a vapor phase and two liquid phases. The dominant components in the second liquid phase and the method of identifying the second liquid phase are defined for the HYSYS flash within the Basis environment.