Boiling point of vodka
Vodka is a solution of water and ethanol.


Water boils at 100 °C
Ethanol boils at 78.37 °C


A mixture of both liquids will start boiling close to the boiling point of ethanol (otherwise distillation wouldn't work). 

The lowest boiling temperature is a mixture of:


95.63 mass-% ethanol
4.37 mass-% water


which boils at 78.2 °C.

Read more about this effect at: Azeotrope There is also a picture of a phase diagram there.