Ethanol
Ethanol identity, condition-specific physical properties, concentration bases, commercial grades, and the limits of product and safety evidence.
Tags: chemicals, solvents, substances
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Identity and scope
Sigma-Aldrich 459836 is non-denatured 200 proof, with ≥99.5% assay and <0.005% water. Reagent alcohol 277649 is denatured and described as approximately 90% ethanol, 5% methanol and 5% isopropanol. Confirm the exact grade and package. Ethanol is C₂H₆O, CAS 64-17-5, 46.0684 g/mol. NIST Chemistry WebBook, SRD 69
The structure CH₃CH₂OH identifies a primary alcohol. The 190-proof 493511 catalog has separate spectrophotometric limits. Sigma-Aldrich 493511, US English catalog
Commercial forms and analytical attributes
The following products illustrate distinct meanings of an ethanol label. Catalog descriptions and limits are not measurements of a particular lot.
| Product | Published description | Selected analytical attributes |
|---|---|---|
| Sigma-Aldrich 459836 | Non-denatured, anhydrous, 200 proof | Assay ≥99.5%, water <0.005%, evaporation residue <0.0005%. Technical support identifies gas chromatography for purity and Karl Fischer for moisture. Specific methods are proprietary. |
| Sigma-Aldrich 493511 | Non-denatured, 190 proof, ACS spectrophotometric grade | Properties table gives assay 95.0%, methanol ≤0.1%, and evaporation residue ≤0.001%. UV absorbance maxima depend on wavelength. |
| Sigma-Aldrich 277649 | Anhydrous reagent alcohol with denaturants | Description gives approximately 90% ethanol, 5% methanol, and 5% isopropanol. Water ≤0.003%, with a separate ≤0.005% limit for the 100 mL package. |
Sources: 459836 properties and technical-support answer, 493511 properties, 277649 properties and notes.
The 493511 page's heading says ≥95.0%, while its properties table says 95.0%. This reference preserves that difference. Its "absolute alcohol" synonym does not override the 190-proof product description. 493511
Synthesis: "anhydrous" describes a water attribute and does not establish absence of other solvents. The 277649 page also prints "100%" in its concentration field despite its declared denaturants. That field cannot establish 100% ethanol. 277649
Concentration bases and lot evidence
The US Alcohol and Tobacco Tax and Trade Bureau defines proof as twice the ethanol volume percentage at 60 °F. Under that convention, 190 proof corresponds to 95% by volume. TTB distinguishes specially denatured alcohol and completely denatured alcohol by their respective authorized formula categories. These are US definitions, not universal purity grades. The cited tutorial was last updated December 12, 2018 and gives statutory or regulatory text precedence. TTB definitions
Synthesis: mass percent expresses component mass relative to total mass. Volume percent uses a volume basis with a stated reference temperature. A bare percentage or chromatographic assay does not establish both bases. The catalog pages do not specify a mass or volume basis for every impurity limit, nor a complete assay calculation. Their percentages therefore cannot support an exact mass balance or water-by-difference calculation.
Assay, water, residue, and individual impurities describe different attributes. A maximum water specification is not the actual water content. The manufacturer offers lot-specific certificates of analysis separately, but no current lot certificate was examined here. Catalog grades and specifications do not establish present container composition or application qualification. 459836 documentation and analytical-method answer
Physical properties and source differences
These attributed values retain their product and temperature context. Neither catalog page supplies measurement methods or pressure bases for these entries.
| Property | Published value | Source scope |
|---|---|---|
| Liquid density | 0.789 g/mL at 20 °C | Sigma-Aldrich 459836 |
| Boiling point | 78.3 °C | Sigma-Aldrich 459836, pressure unspecified |
| Melting point | −114 °C | Sigma-Aldrich 459836, pressure unspecified |
| Vapor pressure | 57.26 hPa at 19.6 °C | Sigma-Aldrich 459836 |
| Liquid density | 0.816 g/mL at 25 °C | Sigma-Aldrich 493511, 190-proof product |
Fisher's AC61510-family SDS gives density 0.785 g/cm3 at 20 °C and water miscibility. It also prints 59 kPa at 20 °C for vapor pressure. That pressure conflicts with the NIST calculation below and the Sigma value, which converts to 5.726 kPa at 19.6 °C. The discrepancy remains unresolved, with no assumed correction. Fisher US SDS, section 9, pages 4–5
Synthesis: g/mL and g/cm3 are equivalent units. Different product compositions, temperatures, rounding, and unknown methods prevent the density entries from proving a grade effect. Miscibility does not make mixture properties equal to those of pure ethanol. The melting-point entry does not establish an aqueous freezing curve.
Vapor-pressure correlations
NIST gives the Antoine form log10(P) = A − B / (T + C), with P in bar and T in kelvin. All three coefficient sets are NIST calculations from the cited authors' data.
| Valid temperature interval, K | A | B | C | Attributed data |
|---|---|---|---|---|
| 273.00–351.70 | 5.37229 | 1670.409 | −40.191 | Kretschmer and Wiebe, 1949 |
| 292.77–366.63 | 5.24677 | 1598.673 | −46.424 | Ambrose and Sprake, 1970 |
| 364.80–513.91 | 4.92531 | 1432.526 | −61.819 | Ambrose, Sprake, and Townsend, 1975 |
Source: NIST coefficients, references, and notes.
Derived example: at 293.15 K, or 20 °C, the 1970 set gives 0.05851 bar, approximately 5.851 kPa. The fit supplies no uncertainty here. These are pure-substance saturation-pressure calculations within the stated intervals, not mixture pressures, evaporation rates, or airborne concentrations.
Safety evidence and coverage limits
Fisher's US SDS, revision 10 dated December 20, 2025, classifies the AC61510-family product as flammable-liquid category 2 and eye-irritation category 2 under US OSHA HCS 2024. Section 3 reports 99–100% ethanol by weight. That disclosure is not a lot assay. Section 16 limits the information to the designated material and disclaims a quality specification or warranty. It does not establish another region's current classification. Fisher SDS, sections 1–3 and 16
The sources were reviewed on October 30, 2026 PDT. The US English catalog pages have no numbered technical revision. NIST's compilation and correlations were read, but the original experimental papers were not reviewed in full.
Coverage excludes concentration-dependent phase equilibrium, current lot certificates, material-specific compatibility tests, and process performance. No drinking, medical, disinfection, preparation, or operating procedure is supplied. The Surface-finishing processes gives broader process context, not ethanol qualification.