The entire lower Boiling component A distills at its boiling point until it is removed from the mixture; then, the Higher boiling component B distills at its boiling point. Ideal separation are not achieved when separating mixtures of compounds with boiling points closer together than 10c .This is because the component B has an appreciable vapor pressure at the boiling point of component A. In a laboratory situation one can plot the volume of vs. temperature of the distilling vapor to determine how closely a distillation resembles an ideal separation.