Pressure–Temperature Nomograph

Solve any two of compound + pressure, compound + observed boiling point, atmospheric bp + pressure, or atmospheric bp + observed bp. When the compound has Antoine constants in our database, the answer is computed exactly from log₁₀(P) = A − B/(T+C); otherwise we fall back to the compound-agnostic Clausius-Clapeyron approximation (the same one Sigma-Aldrich's tool uses).

Antoine: NIST WebBook constants in the antoine_parameters table. Sigma fallback: Clausius-Clapeyron at constant ΔH_vap, valid to ~±5 °C for non-polar compounds and less reliable for polar/H-bonding species — the very reason replacing Sigma's compound-agnostic nomograph with our compound-specific one is meaningful.