Dew Point:  The dew point of a system at pressure P whose vapor composition is given by mole fraction yi is that temperature at which there is onset of condensation.  Mathematically, it is then temperature at which

And for a binary mixture

Bubble Point:  The bubble point of a system at pressure P and whose liquid composition is given by mole fraction xi is that temperature at which there is onset of vaporization.  Mathematically it is the temperature such that

For a binary mixture, this equation can be rearranged to yield

The procedure for determining the bubble/dew point is as follows: 

(1)    Guess a temperature,

(2)    Calculate the Ki, and

(3)    Check if the bubble/dew point equation is satisfied. 

(4)    If not, repeat the procedure with a different guess.

Module for dew and bubble points calculations:

A1 (vapor pressure data constant A for more volatile component)
B1 (vapor pressure data constant B for more volatile component)
C1 (vapor pressure data constant C for more volatile component)
A2 (vapor pressure data constant A for less volatile component)
B2 (vapor pressure data constant B for less volatile component)
C2 (vapor pressure data constant C for less volatile component)
Pt (Total pressure, mmHg)
x (liquid mole fraction of more volatile component)
y (vapor mole fraction of more volatile component)