It is also of interest to investigate the changes that occur when themature of the two-phase system, such as that of Fig. ( 1)a is raisedature is increased for the system of total composition ofb. the systalong the (dashed) line The fraction of the system composed of water-gradually incrcase until, when the two-phase boundary curve is reached, the last of thebutyl alcohol-rich laver appears to dissolve in the water-rich laver. By contrast, if acomposition equal to that of the curve maximum is picked, the two layers remain inabout cqual amounts until, at the two-phase boundary, their composition becomesidentical and they form a one-phase system