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❄️ Separation & Purification · Method

Recrystallization

Dissolve hot, crystallize cold—get it purer
🎯 Difficulty ★★☆ Medium Duration About 2–3 h 🎯 Use Purify a solid by exploiting solubility changes with temperature.
📖 Principle
Dissolve everything hot; on cooling, product crystallizes while impurities stay in solution.
Below are 5 steps. Open each to see how to do it and add products to your shared list.

📋 Workflow

Full workflow, products add-to-cart directly
1

Choose the solvent

15 min
Pick a single or mixed solvent where product dissolves hot/crystallizes cold and impurities stay soluble.
💡 Tip Use the minimum boiling solvent to reach saturation
⚠️ Caution Too-good solubility may give no crystals
🧪 Materials for this step (click to shop by spec/brand)
2

Dissolve by heating

20 min
Heat the solvent under reflux, add solid in portions until just dissolved.
💡 Tip Add activated charcoal to adsorb colored impurities
⚠️ Caution Avoid excess solvent or yield drops
🧪 Materials for this step (click to shop by spec/brand)
3

Hot filtration

15 min
Filter hot, hot-funnel/folded paper, to remove insoluble impurities.
💡 Tip Pre-warm the funnel to avoid crystallization on the filter
⚠️ Caution Cooling crystallizes and clogs the filter
🧪 Materials for this step (click to shop by spec/brand)
4

Cool and crystallize

1 h
Cool the filtrate slowly to room temperature, then ice; scratch the wall to seed if needed.
💡 Tip Slow cooling gives large, pure crystals
⚠️ Caution Rapid cooling traps mother-liquor impurities
🧪 Materials for this step (click to shop by spec/brand)
5

Filter, wash, and dry

30 min
Vacuum-filter on a Buchner funnel, wash with cold solvent, dry in oven or under vacuum.
💡 Tip Washing with cold mother liquor improves recovery/purity
⚠️ Caution Over-washing washes product away
🧪 Materials for this step (click to shop by spec/brand)

⚠️ 5 Common Beginner Mistakes

  • Excess solvent, product never crystallizes
  • Rapid cooling traps impurities
  • Heat loss precipitates product on the filter
  • Over-washing loses product
  • Wrong solvent fails to dissolve or crystallize

❓ FAQ

+No crystals form?
Seed or scratch; concentrate or swap solvent pair if needed.
+How to verify purity?
Melting point, single TLC spot, or HPLC purity.
+Which impurities are removable?
Insoluble, freely soluble, and crystallization-different impurities.

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Data authenticity: Product categories from JW Supply Chain standard taxonomy; method→step→product connected. Last updated: 2026-08-23 · v3.0