Binary separation between two regions in a closed vessel

1 Binary separation between two regions in a closed vessel 

1 will have now species 2 as an impurity, whereas region 

Another estimate of the separative efficiency of the process is provided by how far removed the compositions of the separated regions are from the original mixture in vessel A. Before we develop and use an index of separation, which serves as a criterion of merit to indicate the separative efficiency, we need to examine the quantities that describe the composition of a binary mixture. However, knowing the composition only can sometimes be misleading. For example, see the condition represented by III in 

We have used the notion of a region in a separation system without much explanation it is worthwhile to 

In each of these four examples, the top phase, which is the lighter phase, is usually referred to as the light fraction, while the bottom phase is called the heavy fraction. Remember that for separation systems containing immiscihle phases, phase or fraction is more commonly used than region. 

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