What is the relationship between the #"normal boiling point"# and #"atmospheric pressure"#?
The normal boiling point specifies an ambient pressure of
The boiling point is those conditions of temperature and pressure where the vapour pressure of the liquid is equal to the external pressure, and bubbles of vapour form directly in the liquid. At lower pressure, the boiling point of a given liquid may thus decrease substantially; which is why low pressure distillations are performed.
The thing to remember: normal boiling point means a vapour pressure of 1 atmosphere.