Write down the purity test of ethanol.

Testing the purity of ethanol is essential in pharmaceutical, industrial, and laboratory settings to ensure it meets required standards. Here are the most common and reliable methods used:

🧪 Common Purity Tests for Ethanol
1. Specific Gravity Test
Purpose: Measures the density of ethanol compared to water.
Method: Use a hydrometer and temperature correction tables.
Pure ethanol typically has a specific gravity of 0.789 at 20°C.
2. Flash Point Test
Purpose: Determines the lowest temperature at which ethanol vapors ignite.
Method: Use a flash point tester.
Pure ethanol has a flash point around 13°C.
3. Water Content Test (Karl Fischer Titration)
Purpose: Measures trace amounts of water in ethanol.
Method: Uses iodine and sulfur dioxide in a titration reaction.
Ideal for: Absolute ethanol (99.5% purity or higher).
4. Acidity Test
Purpose: Detects acidic impurities.
Method: Use a calibrated pH meter.
Pure ethanol should have a neutral pH close to 7.
5. Gas Chromatography (GC)
Purpose: Identifies and quantifies volatile impurities like methanol, acetaldehyde, benzene.
Method: Inject ethanol sample into a GC system.
Highly accurate and used in pharmacopoeial standards.
6. Infrared Spectroscopy (FTIR)
Purpose: Confirms ethanol identity and detects impurities.
Method: Compare sample spectra with reference spectra.
Used by: Japanese, U.S., and European pharmacopoeias.
7. UV Absorbance Test
Purpose: Detects organic impurities.
Method: Measure absorbance at specific wavelengths (240–340 nm).
Limits: Absorbance must be below defined thresholds (e.g., <0.40 at 240 nm).
8. Triiodomethane (Iodoform) Test
Purpose: Confirms presence of ethanol.
Method: Add iodine and sodium hydroxide; a pale yellow precipitate indicates ethanol.
🧾 Summary Table

1. Specific Gravity- Density, Hydrometer, Quick and basic test
2. Flash Point- Volatility, Flash point tester, Safety-related
3. Karl Fischer Titration- Water content, Titrator, Precise for trace moisture
4. pH Test Acidity- pH meter, Should be near neutral
5. Gas Chromatography- Volatile impurities, GC system, Highly sensitive
6. FTIR Spectroscopy- Identity & impurities, FTIR spectrometer Used in pharmacopoeias
7. UV Absorbance- Organic impurities, UV-Vis spectrophotometer, Must meet absorbance limits
8. Iodoform Test- Ethanol presence, Basic lab reagents, Pale yellow ppt confirms ethanol