The McCabe-Thiele method was presented by two graduate students at Massachusetts Institute of Technology

Massachusetts Institute of Technology

The Massachusetts Institute of Technology is a private research university located in Cambridge, Massachusetts. MIT has five schools and one college, containing a total of 32 academic departments, with a strong emphasis on scientific and technological education and research.Founded in 1861 in...

 (MIT), Warren L. McCabe and Ernest W. Thiele in 1925. The technique is considered to be the simplest and perhaps most instructive method for analysis of binary distillation

Distillation

Distillation is a method of separating mixtures based on differences in volatilities of components in a boiling liquid mixture. Distillation is a unit operation, or a physical separation process, and not a chemical reaction....

. This method uses the fact that the composition at each theoretical tray

Theoretical plate

A theoretical plate in many separation processes is a hypothetical zone or stage in which two phases, such as the liquid and vapor phases of a substance, establish an equilibrium with each other. Such equilibrium stages may also be referred to as an equilibrium stage, ideal stage or a theoretical...

 (or equilibrium stage) is completely determined by the mole fraction of one of the two components.

The McCabe-Thiele method is based on the assumption of constant molar overflow which requires that:

• the molar heats of vaporization
  Standard enthalpy change of vaporization
  The enthalpy of vaporization, , also known as the heat of vaporization or heat of evaporation, is the energy required to transform a given quantity of a substance into a gas at a given pressure .It is often measured at the normal boiling point of a substance; although tabulated values are usually...
  
   of the feed components are equal
• for every mole
  Mole (unit)
  The mole is a unit of measurement used in chemistry to express amounts of a chemical substance, defined as an amount of a substance that contains as many elementary entities as there are atoms in 12 grams of pure carbon-12 , the isotope of carbon with atomic weight 12. This corresponds to a value...
  
   of liquid vaporized, a mole of vapour is condensed
• heat effects such as heats of solution
  Enthalpy change of solution
  The enthalpy of solution, enthalpy of dissolution, or heat of solution is the enthalpy change associated with the dissolution of a substance in a solvent at constant pressure resulting in infinite dilution....
  
   and heat transfer
  Heat transfer
  Heat transfer is a discipline of thermal engineering that concerns the exchange of thermal energy from one physical system to another. Heat transfer is classified into various mechanisms, such as heat conduction, convection, thermal radiation, and phase-change transfer...
  
   to and from the distillation column
  Fractionating column
  A fractionating column or fractionation column is an essential item used in the distillation of liquid mixtures so as to separate the mixture into its component parts, or fractions, based on the differences in their volatilities...
  
   are negligible.

Before starting the construction and use of a McCabe–Thiele diagram for the distillation of a binary feed, the vapor-liquid equilibrium (VLE)

Vapor-liquid equilibrium

Vapor–liquid equilibrium is a condition where a liquid and its vapor are in equilibrium with each other, a condition or state where the rate of evaporation equals the rate of condensation on a molecular level such that there is no net vapor-liquid interconversion...

 data must be obtained for the lower-boiling component of the feed.

The first step is to draw equal sized vertical and horizontal axes of a graph.