Find the boiling point of immisible liquid. PFA
Answers
Why the boiling point of an immiscible solution is less than either of the components?
Your question is related of a type of destilation, the steam distillation, a kind of distillation that uses a vapor flux to facilitate the distillation.
The refered phenomenum in the question occurs when two immiscible liquids are in a situation that both can be at equilibrium (at least a pressure equilibrium even it would n't be in thermodynamical equilibrium). Ordinarily, it can be achieved by some sort of active mixing. The vapor pressure under this conditions is the add up of the two liquids vapor pressure, taken individually.
And as to reach the boiling point is necessary that the (total) vapor pressure be equal to atmospheric pressure, the mixture may enter the distillation regime even though each individual component is under pressure below the atmospheric pressure, that is, the liquid is subjected to a temperature below the temperature of its boiling point. In other words, both liquids tend to act synergistically, and since they are immiscible, they can be separated easily after distillation.
Post Scriptum - I will post here a link to another answer of mine that could add some information about vapor pressure and will also improve and deepen the debate on this subject.
Please, also refer to any answer elsewhere to complement these information