A nonvolatile liquid is defined as a substance that does not actively evaporate into a gas. An example of a nonvolatile substance is glycerol, or glycerine.
A volatile substance is defined by the readiness at which it evaporates. In general, any substance with a boiling point below 100 degrees Celsius is considered volatile, while all other liquids are called nonvolatile. Sugar and sodium chloride are nonvolatile substances.
Nonvolatile solutes produce vapors that are pure solvent. A solute is the substance that dissolves, while a solvent is the liquid in which it dissolves. Unlike a volatile solute, a nonvolatile solute does not appear as a component of vapor.