Binary equilibrium phase fractions
For two equilibrium phases α and β with compositions x_α<x_β and bulk composition x₀ between them, conservation gives f_α=(x_β−x₀)/(x_β−x_α) and f_β=1−f_α.
Key knowledge
For two equilibrium phases α and β with compositions x_α<x_β and bulk composition x₀ between them, conservation gives f_α=(x_β−x₀)/(x_β−x_α) and f_β=1−f_α. The phase compositions come from the endpoints of the equilibrium tie line at the same temperature and pressure; the bulk composition is not generally the composition of either phase.
Values and equations
x₀=f_αx_α+f_βx_β; f_α=(x_β−x₀)/(x_β−x_α); f_β=1−f_α
- x₀,x_α,x_β
- consistent bulk and equilibrium phase component fractions 1
- f_α,f_β
- phase fractions on the matching basis 1
Conditions and scope
- Use one consistent composition/fraction basis: mass fractions with mass fractions, or component mole fractions with compatible phase mole fractions. The endpoints must be distinct and phases in equilibrium.
- A single phase, kinetic zoning, isolated fractionated crystals or an open system needs different accounting. A diagram projected across unspecified pressure, volatiles or extra components is not automatically this binary model.
Sources · 1
References
Sources retain their recorded scope. A source link alone does not establish verification of every statement.
Evidence and review
Read the actual A–B two-phase mass balance and lever-distance expressions. Re-expressed the displayed percentages as fractions and checked the endpoint signs and normalization; no numerical diagram temperatures adopted.
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Entry details
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