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A	B	T [K]	P [bar]	D [cm²/s]	Band lower [m²/s]	Band upper [m²/s]	Source	Note	FSG
									7.87e-5
									1.64e-5
									3.52e-5
									2.08e-5
									6.68e-5
									1.80e-5
									2.76e-5
									1.58e-5
									1.85e-5
									7.13e-5
									2.18e-5
									4.36e-6
									2.18e-6
									4.36e-7

Regenerated markdown preview

This is exactly what bun run docs:wilke would write to docs/wilke-reference-values.md if your edits were in the SSOT.

<!-- AUTO-GENERATED FROM src/lib/__tests__/wilkeReferenceTable.ts — DO NOT EDIT BY HAND.
     Run `bun run docs:wilke` to regenerate after editing the source. -->

# Wilke / FSG Reference Values

This document catalogues every literature data point used by
[`src/lib/__tests__/wilkeDiffusivity.reference.test.ts`](../src/lib/__tests__/wilkeDiffusivity.reference.test.ts)
to validate the Fuller–Schettler–Giddings (FSG) binary diffusivity
correlation and the Wilke (1950) multicomponent closure.

The source of truth is the typed table in [`src/lib/__tests__/wilkeReferenceTable.ts`](../src/lib/__tests__/wilkeReferenceTable.ts).
Edit that file and regenerate this page with `bun run docs:wilke`.

---

## Citations

Each citation is anchored so binary-pair rows below can link directly back
to the source. The **Used by** column lists the row numbers (in the binary
table) that cite the entry.

| Tag | Source | Used by |
|-----|--------|---------|
| <a id="cite-poling"></a>**Poling** | Poling, B. E.; Prausnitz, J. M.; O'Connell, J. P. *The Properties of Gases and Liquids*, 5th ed. McGraw-Hill, 2001. | [#1](#ref-1), [#2](#ref-2), [#4](#ref-4), [#5](#ref-5), [#6](#ref-6), [#8](#ref-8), [#9](#ref-9), [#10](#ref-10), [#11](#ref-11) |
| <a id="cite-cussler"></a>**Cussler** | Cussler, E. L. *Diffusion: Mass Transfer in Fluid Systems*, 3rd ed. Cambridge University Press, 2009. | [#3](#ref-3), [#7](#ref-7) |
| <a id="cite-wilke"></a>**Wilke** | Wilke, C. R. "Diffusional Properties of Multicomponent Gases." *Chem. Eng. Prog.* **46**(2), 95–104 (1950). | — |
| <a id="cite-fsg"></a>**FSG** | Fuller, E. N.; Schettler, P. D.; Giddings, J. C. "A new method for prediction of binary gas-phase diffusion coefficients." *Ind. Eng. Chem.* **58**(5), 18–27 (1966). | [#12](#ref-12), [#13](#ref-13), [#14](#ref-14) |

Quoted FSG accuracy for non-polar gas pairs at near-ambient conditions is
**±5–10%**; bands here are widened to ±15–25% for polar pairs (H₂O, H₂S)
and high-pressure reservoir conditions where FSG begins to drift.

---

## Binary-pair reference values

All diffusivities are reported in m²/s (SI). For comparison with the source
literature, multiply by 10⁴ to convert to cm²/s. The `#` cell anchors each
row (`#ref-N`) and the **Source** cell links back to the corresponding
[Citations](#citations) entry.

| # | Pair | T (K) | P (bar) | Reference D (m²/s) | Test band — lower | Test band — upper | Source |
|---|------|------:|--------:|-------------------:|------------------:|------------------:|--------|
| <a id="ref-1"></a>1 | H₂–N₂ | 298 | 1 | 7.8 × 10⁻⁵ | 6.5 × 10⁻⁵ | 9 × 10⁻⁵ | [Poling, Table 11-2](#cite-poling) |
| <a id="ref-2"></a>2 | CO₂–N₂ | 298 | 1 | 1.6 × 10⁻⁵ | 1.3 × 10⁻⁵ | 1.9 × 10⁻⁵ | [Poling, Table 11-2](#cite-poling) |
| <a id="ref-3"></a>3 | CH₄–H₂O | 350 | 1 | 3 × 10⁻⁵ | 2 × 10⁻⁵ | 4.5 × 10⁻⁵ | [Cussler, App. A (literature value at ~352 K)](#cite-cussler) |
| <a id="ref-4"></a>4 | O₂–N₂ | 298 | 1 | 2.2 × 10⁻⁵ | 1.8 × 10⁻⁵ | 2.6 × 10⁻⁵ | [Poling, Table 11-2](#cite-poling) |
| <a id="ref-5"></a>5 | H₂–CO₂ | 298 | 1 | 6.5 × 10⁻⁵ | 5.5 × 10⁻⁵ | 7.8 × 10⁻⁵ | [Poling, Table 11-2](#cite-poling) |
| <a id="ref-6"></a>6 | CH₄–CO₂ | 298 | 1 | 1.65 × 10⁻⁵ | 1.4 × 10⁻⁵ | 2 × 10⁻⁵ | [Poling, Table 11-2 (CO2-EOR / huff-n-puff)](#cite-poling) |
| <a id="ref-7"></a>7 | H₂O–N₂ | 307.5 | 1 | 2.56 × 10⁻⁵ | 2.1 × 10⁻⁵ | 3.3 × 10⁻⁵ | [Cussler, App. A](#cite-cussler) |
| <a id="ref-8"></a>8 | C₂H₆–CH₄ | 298 | 1 | 1.6 × 10⁻⁵ | 1.3 × 10⁻⁵ | 1.9 × 10⁻⁵ | [Poling, Table 11-2 (dry-gas reservoirs)](#cite-poling) |
| <a id="ref-9"></a>9 | H₂S–CH₄ | 298 | 1 | 1.9 × 10⁻⁵ | 1.5 × 10⁻⁵ | 2.3 × 10⁻⁵ | [Poling, Table 11-2 (widened: polar) (sour-gas pair)](#cite-poling) |
| <a id="ref-10"></a>10 | H₂–CH₄ | 298 | 1 | 7.26 × 10⁻⁵ | 6 × 10⁻⁵ | 8.5 × 10⁻⁵ | [Poling, Table 11-2](#cite-poling) |
| <a id="ref-11"></a>11 | CH₄–N₂ | 298 | 1 | 2.2 × 10⁻⁵ | 1.8 × 10⁻⁵ | 2.6 × 10⁻⁵ | [Poling, Table 11-2 (CH4–N2 1/P series, anchor)](#cite-poling) |
| <a id="ref-12"></a>12 | CH₄–N₂ | 298 | 5 | 4.4 × 10⁻⁶ | 3.6 × 10⁻⁶ | 5.2 × 10⁻⁶ | [FSG model (CH4–N2 1/P series, P×1-bar band ÷ P) (anchor scaled by 1/P)](#cite-fsg) |
| <a id="ref-13"></a>13 | CH₄–N₂ | 298 | 10 | 2.2 × 10⁻⁶ | 1.8 × 10⁻⁶ | 2.6 × 10⁻⁶ | [FSG model (CH4–N2 1/P series, P×1-bar band ÷ P) (anchor scaled by 1/P)](#cite-fsg) |
| <a id="ref-14"></a>14 | CH₄–N₂ | 298 | 50 | 4.4 × 10⁻⁷ | 3.6 × 10⁻⁷ | 5.2 × 10⁻⁷ | [FSG model (CH4–N2 1/P series, P×1-bar band ÷ P) (anchor scaled by 1/P)](#cite-fsg) |

---

## Invariance / scaling tests

These tests do not pin a literature number; they verify that the implementation
obeys the documented FSG functional form.

| Property | Expectation | Source |
|----------|-------------|--------|
| Temperature scaling: D ∝ T¹·⁷⁵ | D(600 K) / D(300 K) = 2¹·⁷⁵ ≈ 3.3636 | FSG (1966) Eq. 1 |
| Pressure scaling: D ∝ 1/P | D(1 bar) / D(2 bar) = 2 | FSG (1966) Eq. 1 |
| Symmetry: D_ij = D_ji | identical to ≥ 12 sig figs | FSG (1966) — symmetry of M_ij and ΣV |

---

## Wilke (1950) multicomponent checks

| Scenario | Inputs | Expectation | Source |
|----------|--------|-------------|--------|
| Trace species → binary limit | y_target = 1×10⁻⁶, carrier = 1 − 1×10⁻⁶ | D_{1,m} → D_{1,carrier} within 0.1% | Wilke (1950) Eq. 12 limit |
| Shale-gas mixture at reservoir conditions | CH₄ 0.85 / C₂H₆ 0.06 / CO₂ 0.05 / N₂ 0.04 at 360 K, 200 bar | D_{CH₄,m} between 5×10⁻⁸ and 5×10⁻⁷ m²/s | Order-of-magnitude check; FSG drift at 200 bar is acceptable |
| D_ij override (binary) | y_CH₄ = y_N₂ = 0.5, override D₁₂ = 1×10⁻⁶ m²/s | D_{1,m} = override exactly | Wilke (1950) — binary collapse |
| D_ij override symmetry | only upper-triangle [0][1] set | symmetric mirror is applied | Implementation contract |
| Empty / OOB inputs | empty components or targetIndex out of range | result = 0 | Defensive defaults |

---

## Regression snapshot

A single frozen scenario locks `effectiveBinaryDiffusivityM2PerS` for the
Bakken-like shale-gas mixture above. The snapshot is quantized via the
configurable tolerance helper (see
[`src/lib/__tests__/snapshotTolerance.ts`](../src/lib/__tests__/snapshotTolerance.ts))
under module key `"wilke"` (default `relative = 1e-5`). Loosen or tighten with:

```bash
SNAPSHOT_TOL_WILKE_REL=1e-3 bun test src/lib/__tests__/wilkeDiffusivity.reference.test.ts
```

To intentionally regenerate the snapshot after a formula change:

```bash
bun run snapshots:matrix-flow:wilke
```

---

## Adding a new reference test

1. Add an entry to `REFERENCE_TABLE` in [`src/lib/__tests__/wilkeReferenceTable.ts`](../src/lib/__tests__/wilkeReferenceTable.ts).
2. Run `bun run docs:wilke` to regenerate this page.
3. Add a matching `it(...)` block in `wilkeDiffusivity.reference.test.ts`,
   citing the source in the comment.
4. Run the test; if FSG falls outside your literature value at the chosen band,
   widen the band (and document why) rather than skewing the formula.

REFERENCE_TABLE TS snippet

Paste this in place of the existing REFERENCE_TABLE array in src/lib/__tests__/wilkeReferenceTable.ts, then run bun run docs:wilke and bun run check:wilke-citations.

export const REFERENCE_TABLE: ReferenceEntry[] = [
  { pair: ["H2", "N2"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.78, band_m2_per_s: { lower: 6.5e-5, upper: 9e-5 }, source: "Poling, Table 11-2" },
  { pair: ["CO2", "N2"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.16, band_m2_per_s: { lower: 1.3e-5, upper: 1.9e-5 }, source: "Poling, Table 11-2" },
  { pair: ["CH4", "H2O"], T_K: 350, P_bar: 1, D_cm2_per_s: 0.3, band_m2_per_s: { lower: 2e-5, upper: 4.5e-5 }, source: "Cussler, App. A", note: "literature value at ~352 K" },
  { pair: ["O2", "N2"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.22, band_m2_per_s: { lower: 1.8e-5, upper: 2.6e-5 }, source: "Poling, Table 11-2" },
  { pair: ["H2", "CO2"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.65, band_m2_per_s: { lower: 5.5e-5, upper: 7.8e-5 }, source: "Poling, Table 11-2" },
  { pair: ["CH4", "CO2"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.165, band_m2_per_s: { lower: 1.4e-5, upper: 2e-5 }, source: "Poling, Table 11-2", note: "CO2-EOR / huff-n-puff" },
  { pair: ["H2O", "N2"], T_K: 307.5, P_bar: 1, D_cm2_per_s: 0.256, band_m2_per_s: { lower: 2.1e-5, upper: 3.3e-5 }, source: "Cussler, App. A" },
  { pair: ["C2H6", "CH4"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.16, band_m2_per_s: { lower: 1.3e-5, upper: 1.9e-5 }, source: "Poling, Table 11-2", note: "dry-gas reservoirs" },
  { pair: ["H2S", "CH4"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.19, band_m2_per_s: { lower: 1.5e-5, upper: 2.3e-5 }, source: "Poling, Table 11-2 (widened: polar)", note: "sour-gas pair" },
  { pair: ["H2", "CH4"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.726, band_m2_per_s: { lower: 6e-5, upper: 8.5e-5 }, source: "Poling, Table 11-2" },
  { pair: ["CH4", "N2"], T_K: 298, P_bar: 1, D_cm2_per_s: 0.22, band_m2_per_s: { lower: 1.8e-5, upper: 2.6e-5 }, source: "Poling, Table 11-2 (CH4–N2 1/P series, anchor)" },
  { pair: ["CH4", "N2"], T_K: 298, P_bar: 5, D_cm2_per_s: 0.044, band_m2_per_s: { lower: 3.6e-6, upper: 5.2e-6 }, source: "FSG model (CH4–N2 1/P series, P×1-bar band ÷ P)", note: "anchor scaled by 1/P" },
  { pair: ["CH4", "N2"], T_K: 298, P_bar: 10, D_cm2_per_s: 0.022, band_m2_per_s: { lower: 1.8e-6, upper: 2.6e-6 }, source: "FSG model (CH4–N2 1/P series, P×1-bar band ÷ P)", note: "anchor scaled by 1/P" },
  { pair: ["CH4", "N2"], T_K: 298, P_bar: 50, D_cm2_per_s: 0.0044, band_m2_per_s: { lower: 3.6e-7, upper: 5.2e-7 }, source: "FSG model (CH4–N2 1/P series, P×1-bar band ÷ P)", note: "anchor scaled by 1/P" },
];