Soap Making by Saponification

Converting fats into soap using sodium hydroxide

Organic Synthesis Intermediate (High School) 60 min ~$10.00

Objective

Make soap by the saponification of vegetable oil with sodium hydroxide, demonstrating the hydrolysis of ester bonds in triglycerides.

Background

Saponification is the base-catalyzed hydrolysis of a fat or oil (triglyceride) to produce glycerol and soap (sodium salts of fatty acids). This ancient chemical reaction is the basis of all soap manufacturing and demonstrates ester bond cleavage.

Safety Warnings

  • Concentrated NaOH is extremely corrosive
  • Wear nitrile gloves and goggles at all times
  • Hot oil and NaOH can cause severe burns
  • Do not use the soap on skin until it has fully cured (4-6 weeks)

Required PPE

goggles gloves lab_coat

Materials

  • Vegetable oil (olive or coconut) (20 mL)
  • Sodium hydroxide (NaOH) (10 mL)
    6M solution
  • Ethanol (10 mL)
    To help mix oil and base
  • Sodium chloride (NaCl) (15 g)
    Saturated solution for salting out
  • Distilled water (100 mL)

Equipment

250 mL beaker Hot plate Glass stirring rod Cheesecloth or filter Mold (small cup)

Procedure

1

Heat 20 mL of vegetable oil in the beaker to about 40°C on the hot plate.

3 min
2

Mix 10 mL of 6M NaOH with 10 mL ethanol in a separate container.

2 min NaOH is corrosive
3

Slowly add the NaOH/ethanol mixture to the warm oil while stirring continuously.

3 min Hot caustic mixture
4

Continue heating and stirring at 60-70°C for 20 minutes until the mixture becomes thick and opaque (trace).

20 min
5

Add 50 mL of saturated NaCl solution to salt out the soap. Stir and allow to cool.

10 min
6

Filter the solid soap through cheesecloth. Press out excess liquid.

5 min
7

Mold the soap into a shape and allow to dry for 24 hours.

3 min Do not use on skin until fully cured
8

Test a small piece by dissolving in warm water — it should produce lather.

3 min

Expected Results

A solid, white to cream-colored soap that lathers when dissolved in water. The soap may feel slightly slippery, indicating successful saponification. Full curing takes 4-6 weeks to neutralize any remaining NaOH.

Cleanup

Neutralize any remaining NaOH solution with vinegar before disposal. Rinse all glassware. Wipe down work surfaces.

Details

Category
Organic Synthesis
Difficulty
Intermediate (High School)
Duration
60 min
Est. Cost
$10.00
Steps
8
Materials
5

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Frequently Asked Questions

What is the objective of Soap Making by Saponification?
Make soap by the saponification of vegetable oil with sodium hydroxide, demonstrating the hydrolysis of ester bonds in triglycerides.
How difficult is Soap Making by Saponification?
This experiment is rated as Intermediate (High School). It takes approximately 60 minutes to complete.
What safety precautions are needed for Soap Making by Saponification?
Key safety precautions include: Concentrated NaOH is extremely corrosive; Wear nitrile gloves and goggles at all times; Hot oil and NaOH can cause severe burns.
What materials are needed for Soap Making by Saponification?
The main materials required are: Vegetable oil (olive or coconut), Sodium hydroxide (NaOH), Ethanol, Sodium chloride (NaCl), Distilled water.
What results should I expect from Soap Making by Saponification?
A solid, white to cream-colored soap that lathers when dissolved in water. The soap may feel slightly slippery, indicating successful saponification. Full curing takes 4-6 weeks to neutralize any remaining NaOH.