01 · Reduce the state
Critical-property scaling
Tᵣ = T / TᶜPᵣ = P / Pᶜ
Use absolute temperature and consistent pressure units. Critical constants and the acentric factor ω are selected automatically from Appendix A.02 · Evaluate two fluids
Simple and reference correlations
Z⁽⁰⁾ = PᵣVᵣ⁽⁰⁾ / TᵣZ⁽ʳ⁾ = PᵣVᵣ⁽ʳ⁾ / Tᵣ
The calculator solves the Lee–Kesler equation of state for both the simple fluid (ω = 0) and reference fluid (ωʳ = 0.3978), choosing the largest real volume root.03 · Correct for molecular shape
Acentric interpolation
Z = Z⁽⁰⁾ + (ω / ωʳ)(Z⁽ʳ⁾ − Z⁽⁰⁾)
The same corresponding-states interpolation underlies the generalized departure functions printed in Appendix C.04 · Recover useful properties
Fugacity and departures
ln φ = ∫₀ᴾ (Z − 1) dP / PHᴿ / RT = −T ∫₀ᴾ (∂Z/∂T)ₚ dP / PSᴿ / R = Hᴿ / RT − ln φ
Continuous numerical integration replaces visual interpolation between printed cells. The calculator reports φ, f = φP, Hᴿ and Sᴿ directly.