But first let's define "boiling point". And it's a good definition to learn off by heart. The "boiling point" is defined as the temperature at which the vapour pressure of the liquid is equal to the ambient pressure, and bubbles of vapour form directly in the liquid. The "normal boiling point" occurs when the ambient pressure (and thus the vapour pressure of the boiling liquid) is ONE ATMOSPHERE. I would get this straight in your head first, because there is a lot going on here.
So we put the kettle on, and boil for a cup of tea. The water boils at 100 ""^@C, and the vapour pressure of the steam is 1 atmosphere, and it pushes the atmosphere back..... If we have an involatile liquid, we can perform a vacuum distillation, and reduce the pressure to 10^-3-10^-4*atm, we can substantially reduce the boiling point of the liquid.
There are several so-called temperature/pressure nomographs that predict the boiling point of a liquid under reduced pressure (or under elevated pressure), that can give you an idea. Have a play with this site and report how you get on.
