the temperature at which the vapor pressure of a liquid is equal to 1 atm
Vapor pressure As a general trend, vapor pressures of liquids at ambient temperatures increase with decreasing boiling points. This is illustrated in the vapor pressure chart (see right) that shows graphs of the vapor pressures versus temperatures for a variety of liquids.[6] At the normal boiling point of a liquid, the vapor pressure is equal to the standard atmospheric pressure defined as 1 atmosphere[7] (760 Torr or 101 325 kPa).
Freezing-point depression The freezing point is the temperature at which the vapor pressures of liquid solvent and solid solvent are equal. When a non-volatile solute is added to a volatile liquid solvent, the solution vapor pressure will be lower than that of the pure solvent. As a result the solid will reach equilibrium with the solution at a lower temperature than with the pure solvent.[1]