Example - If the relative volatility of a binary mixture alone, with no agent, is 1.28; and vapor/liquid equilibrium testing of agents produces an extractive distillation agent showing a relative volatility for the binary mixture of 1.8,  the intersection of the x and y blue dotted lines falls within a region suggesting possible economic viability for extractive distillation.

note: If you are running IE 4.01 (or above) and have Microsoft's EXCEL 2000 you can use our interactive Rule of Thumb Calculator