Separating Water and Petrol: Gravity, Funnel, Absorbents, Distillation

Water (ρ≈1.0 g/mL) and petrol/gasoline (ρ≈0.7–0.75 g/mL) are immiscible with a large density difference. Separation methods:

1. Gravity Settling (Decantation): Let stand in clear container → water bottom, petrol top. Slowly pour off upper layer. Simple, no equipment.
2. Separatory Funnel: Standard lab technique. Drain lower aqueous layer via stopcock; collect petrol separately. Efficient, scalable.
3. Water-Absorbing Agents: Anhydrous Na₂SO₄, CaCl₂, MgSO₄, silica gel. Add, swirl, filter. Removes trace water from petrol. Not for bulk water.
4. Distillation: Exploits boiling point difference (water 100°C, petrol 40–200°C). Heat mixture → petrol vaporizes first → condense → collect. Water remains. Energy-intensive; fire hazard (petrol vapors). Use vented apparatus, no open flame.

Safety: Petrol is highly flammable (flash point -43°C). Work in fume hood/outdoors. Ground containers. No ignition sources. Dispose of waste per hazardous waste regulations.