Soap in a Tube Saponification Reaction

Test Tube Soap Bubbles (Jason Hickey)

Test Tube Soap Bubbles (Jason Hickey)

Soap in a tube? Why not! Typically when people make soap, they make a lot of it. However, you can make a small amount of soap in a test tube as a chemistry demonstration. This is a terrific example of the saponification reaction, plus it results in a product you can use.

Soap Materials

  • sodium carbonate (a home canning chemical)
  • calcium oxide (used to control humidity, sold in home stores)
  • sodium chloride (table salt)
  • butter or lard
  • water
  • 2 test tubes (or small heat-safe cups, if you don’t have test tubes)
  • candle or alcohol lamp
  • teaspoon or other measure

Make Soap in a Tube

  1. Add two scoops of sodium carbonate and 3 scoops of calcium oxide into a test tube.

    Once you master soap in a tube, upscale and try making homemade bars of soap. (kahvikis)

    Once you master soap in a tube, upscale and try making homemade bars of soap. (kahvikis)

  2. Fill the test tube about 3/4 full with water.
  3. Heat the test tube in the flame, but don’t bring the solution to the boiling point. As a safety measure, point the open end of the test tube away from your face. This is a good lab practice when heating any chemicals.
  4. Remove the test tube from heat and allow it to cool.
  5. When the liquid has cleared, add a pea-sized amount of butter or lard.
  6. Return the test tube to the flame. First, the butter or lard will melt. When it starts to mix with the water, add 6 scoops of sodium chloride.
  7. Carefully shake the test tube to mix the ingredients. The soap will rise to the top of the test tube.
  8. Allow the tube to cool and then remove the soap. If you rub it between your fingers, you’ll feel the characteristic slippery texture of your creation.

Soap in a Tube Saponification Reaction
Last modified: June 11th, 2015 by Anne Helmenstine