🎯 Objective
Purify a colloidal solution (Fe(OH)₃ sol) by removing ionic impurities using dialysis through a cellophane membrane.
Dialysis Setup
Distilled Water
Dialysis Bag
Cl⁻
Cl⁻
Fe³⁺
H⁺
Outer Vessel
Sol Purity:
30%
Safety Precautions
- Silver nitrate (AgNO₃) stains and is corrosive: it blackens skin and clothing on contact and is toxic if swallowed — wear gloves, avoid contact, and use only a few drops for the chloride test.
- The Fe(OH)₃ sol is made from ferric chloride: FeCl₃ solution is acidic, corrosive and staining, and the sol is prepared by adding it to boiling water — handle hot glassware with care.
- Handle the cellophane / parchment membrane gently: a torn membrane lets colloidal particles leak through and ruins the purification — do not puncture it.
- Use distilled water in the outer vessel: tap-water ions would give a misleading AgNO₃ result and could coagulate the sol.
- Dispose of silver waste separately: collect AgNO₃/AgCl residues for proper disposal rather than pouring them down the sink.
Predict Before You Test
Predict what dialysis will do before you start. The Start Dialysis button unlocks once you lock a prediction.
📚 Theory
Dialysis separates colloidal particles from crystalloids (ions) using a semipermeable membrane.
Membrane allows:
✓ Small ions (Cl⁻, H⁺, Fe³⁺) to pass through
Membrane blocks:
✗ Large colloidal particles (Fe(OH)₃)
Lab Notebook
Start dialysis to begin...