Practical Tests

Question 1

What is the test for lipids?

Answer 1

Emulsion test

Question 2

What is the method for the emulsion test?

Answer 2

A substance is shaken with ethanol and poured into distilled water. A positive result is a milky emulsion on top.

Question 3

Explain why the emulsion test works for lipids.

Answer 3

• Lipids are non-polar, so are dissolvable in organic solvents such as ethanol
• Ethanol is miscible in water due to hydroxyl group and shortness of chain (hydroxyl group participants in hydrogen bonding w water)
• Ethanol extracts the lipid from crushed solid sample
• Water is added and is dispelled as micelles (this is due to hydrophobic/phillic interactions within the lipid)