[mark-sev]

I heard that one can "move" the azeotrope point (say to almost pure one substance in binary mixtures)  when applying vacuum or varying pressure and so on...i would like to know is there a graph or an equation to calculate where the azeot. point would be in respect with composition of the binary mixture.

[MrTeo]

This fact is used in distillation to get more of the desired compund decreasing its concentration in the azeotropic solution. You simply have to consider that azeotropic mixtures form only when there are positive or negative deviations to Raoult's law: the azeotropic composition and temperature (in an isobaric graph) corresponds to the higher point of the distillation curve (if there are negative deviations from Raoult's law) or to the lower one when the deviations are positive. This because the azeotropic solution has the higher ebollition point in the first case and the lower in the second (and this corresponds to the lower vapor pressure and the higher one). Simply varying environmental pressure in the vapor pressure/concentration diagrams which show the deviation, you can also move the curve of distillation and the composition of azeotropic.