Determining the boiling point of a substance given the triple point and critical point

If I have the pressure and temperature of a substance in its triple point, as well as its pressure and temperature in the critical point, how can I determine the boiling point of the substance at 1 atm of pressure?




What you need is the [Clausius–Clapeyron equation](http://www.chemteam.info/GasLaw/Clasius-Clapeyron-Equation.html), which is used to relate vapor pressure and temperature (or external pressure and boiling point).


$$\ln{\left(\dfrac{P\_1}{P\_2}\right)}=\dfrac{\Delta H\_{\text{vap}}}{R}\left(\dfrac{1}{T\_2}-\dfrac{1}{T\_1}\right)$$


Step 1: Find the enthalpy of vaporizations $\Delta H\_{\text{vap}}$ by plugging in the two sets of temperatures and pressures that you have.


Step 2: Use your $\Delta H\_{\text{vap}}$ and the temperature and pressure of the triple point to determine the boiling temperature at 1 atm.


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