# Lever rule doubt

by jmex
Tags: doubt, lever, rule
 Sci Advisor HW Helper Thanks PF Gold P: 5,060 This is usually done algebraically. Let L be the fraction liquid, and S be the fraction solid, so that L+S=1. Let $\bar{x}_B$ be the overall concentration of species B, corresponding to the vertical line through point M, let $x_{Bliq}$ correspond to the concentration of B in the liquid at point O (along the liquid equilibrium line), and let $x_{Bsol}$ correspond to the concentration of B in the solid at point P (along the solid equilibrium line). Then, $$Lx_{Bliq}+Sx_{Bsol}=\bar{x}_B$$ This can be combined with the equation L+S=1 to solve for L and S. From this, you will see that that the lever rule follows. Chet