The Saponification Experiment

Performing a first hand investigation is crucial and certain rules and procedures as well as well known facts can be found here:
9.1 - Practical Skills

Saponification:

  1. Place 5g of NaOH pellets in a 100mL beaker.
  2. Add 30ML of water
  3. Add 5mL of coconut oil.
  4. Using a Bunsen burner, bring the solution to a boil, taking care to stir constantly so as to provide a uniform temperature.1
  5. Allow the solution to cool once the layer of oil has fully disintegrated.
  6. Add 10g of NaCl and bring the solution once more to a boil, again taking care to stir constantly.2
  7. Allow the solution to cool, lumps of soap should appear on top.
  8. Decant the solution taking take to keep the product.
  9. Flush the beaker with NaCl and decant successively.
  10. Place the soap on filter paper and allow the soap to dry in the fume cupboard.

Testing

  1. Take six test tubes, filling two with soap, two with synthetic commercial detergent, and leaving the remaining two untouched.
  2. Fill all six test tubes halfway with water, and a third as much of oil.
  3. Stopper all six test tubes, and shake each one vigorously, taking care to keep the contents within the test tubes.
  4. Record your observations for each test tube five, ten and fifteen minutes after shaking. In particular, note whether or not the liquids have formed an emulsion or separate layers, and the height of foam each time.

Expected results

  • The soap and detergent observations are likely to show varying amounts of foam depending upon the length of time the test tubes were shaken and the detergents used, as well as the purity of the soap.However, in general, the detergent products should produce the most foam.
  • The soap and detergent observations result in an emulsion of water and oil, whereas the test tube of simply water and oil is likely to seemingly form an emulsion at first, but settle into separate layers relatively quickly.

Reasons why these results are produced:

Soaps and detergents are able to form micelles which are either (depending on the dominance of water or oil, hydrophilic heads outside and hydrophobic tails inside surrounding a globule of non-polar substance or vice versa surrounding a polar substance) allows oils to be miscible in water or vice versa. They are called emulsifying agents or 'acting as an emulsifier' between water and oil.