The Sidney Young equation is used to correct values of this quantity based on changes in pressure. Various values of this quantity form the two axes of a Dühring plot. (-5[1])Mole fractions for the substance with a smaller value of this quantity define the axes of a McCabe–Thiele plot. By reducing pressure, a rotovap lowers the value (10[1])of this quantity for the solvent in the flask. Negative (10[1])azeotropes have a higher (10[1])value of this quantity (10[1])than either of their components, and hence cannot be separated by simple distillation. The ebullioscopic (-5[1])constant times molality times van ’t Hoff factor calculates a colligative property known as this quantity’s namesake “elevation.” For 10 points, name this quantity of a substance at which (10[1])vapor pressure equals (10[1])surrounding pressure, causing it to vaporize. ■END■ (10[3]0[1])