Tools · Calculation
Fractional Distillation Predictor
Predict which fractions you'd actually collect on your column. Antoine boiling points at the column pressure, Fenske analysis on adjacent pairs, azeotrope warnings from the database.
Boiling-point map
Each component plotted at its bp; vertical bands show predicted fraction cuts.
Predicted fractions at 760.0 mmHg
1 cut given your column setup.
Fraction 1 · 80.8–100.0 °C
~100.0%Boiling point 80.8 °C is just outside the Antoine validity range (-25–80 °C); accuracy degrades near the bounds.
Co-distilling: Acetonitrile / Water have α = 1.91 ⇒ 9.1 plates needed (1.7 available — not enough).
Pair analysis (Fenske)
Minimum plates needed for each adjacent pair to reach the target purity.
| Lower / Upper | Δbp °C | α | N_min | Verdict |
|---|---|---|---|---|
| Acetonitrile / Water | 19.2 | 1.91 | 9.1 | co-distill |
Try a different separation method
Distillation will be slow or capped here; common alternatives listed below. Future tick: a dedicated /extraction tool that ranks all methods for any input mixture.
Azeotrope: Acetonitrile ↔ Water
Distillation alone caps purity at the azeotrope point (76.5 °C). Common workarounds: (1) molecular sieves to dehydrate water azeotropes; (2) entrainer distillation with a third solvent that breaks the binary azeotrope; (3) liquid-liquid extraction if one component is much more polar/nonpolar than the other.
Azeotrope warnings
Pairs that cap purity regardless of column length.
Acetonitrile + Water: min-boiling at 76.5 °C, 84.0 wt% Acetonitrile.
Acetonitrile/water azeotrope. Common in HPLC mobile-phase recovery; PSD has limited effect, distill cautiously above 80%. PSD limited; consider entrainer or membrane.
Vapor pressure: NIST WebBook Antoine constants. Plate count from column length / packing HETP
(Perry's 8e §14). Fenske N_min = 2·log[s/(1−s)] / log(α) at total reflux gives the
lower bound on plates; reverse-mode planning factor (1.5×) follows the Gilliland correlation.
Azeotrope data from CRC Handbook + Dortmund Data Bank.
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