Miscellaneous Topics

Abstract

The lever rule is a graphical method used in determining the amount of phases present in a system. The horizontal segment of an isotherm connecting two phases which are in equilibrium in a two-phase region is known as a ‘tie-line’ (figure 10.1). This tie-line, according to the rule, may be considered to be a lever whose fulcrum is placed at the total composition and whose arms carry weights (i.e. relative amounts of phases) inversely proportional to their lengths.