Ethanol Purification by Distillation

After fermenting a sugar solution with yeast, ethanol can be separated from the mixture using simple distillation. The distillate fractions collected can then be tested for ethanol content by carefully checking whether they ignite.

1. Ferment sugar with yeast until the fermentation stops or after 1 week.
2. Filter the fermentation mixture to remove solids and measure about 50 mL into a round-bottom flask.
3. Add a few boiling chips to the flask to ensure smooth boiling.
4. Assemble a simple distillation apparatus with a condenser and receiver flask; connect the condenser tubing to a steady water supply.
5. Position a thermometer so that the bulb is just below the side arm of the still head.
6. Turn on the condenser water and begin heating the flask gently with a heating mantle.
7. When vapors reach the condenser and liquid begins to drip into the receiver, collect the distillate.
8. Record the temperature at which distillation occurs and continue collecting until the temperature rises above the boiling point of ethanol.
9. Separate the distillate into small fractions.
10. In a darkened lab, place a small amount of each fraction onto a heat-proof mat.
11. With supervision, carefully attempt to ignite the fraction using a lighter or splint. Fractions containing ethanol should burn with a pale blue flame.

Simple Distillation - Professor Dave Explains:

📄 Alcohol: Production by Fermentation and Distillation - Indiana University: https://iu.pressbooks.pub/iuegenchemlabs/chapter/alcohol-production-by-fermentation-and-distillation/

• Compare fractions distilled at different temperatures to see which contain more ethanol.
• Use a hydrometer or density measurements instead of ignition tests to quantify ethanol concentration.
• Test different fermentation mixtures (e.g., sugar, honey, fruit juice) to compare ethanol yields.

• Ethanol is flammable—keep flames away from the distillation apparatus.
• Do not seal the distillation system; pressure buildup could cause explosion.
• Use heat-proof mats and ignition tests only under close supervision in a well-ventilated space.
• Wear safety goggles, gloves, and a lab coat.
• Waft vapors instead of smelling directly.
• Dispose of waste fractions down the sink with plenty of water.

• Why does ethanol distill before water? (It has a lower boiling point and higher volatility.)
• How does the distillation process purify ethanol from the fermentation mixture? (It separates based on differences in boiling points.)
• Why should boiling chips be used in distillation? (They promote smooth boiling and prevent bumping.)
• What does observing a blue flame indicate about a fraction? (That ethanol is present in a flammable concentration.)
• Why is ethanol concentration from fermentation limited to ~12%? (Yeast cannot survive at higher ethanol levels.)