Saponification-The process of Making Soap

Materials required: 

  • Vegetable oil (castor oil, olive oil, coconut oil or palm oil)
  • 20% sodium hydroxide solution
  • Common salt
  • Measuring cylinders
  • Glass beaker (250 ml)
  • Blue and red litmus papers
  • Glass rod
  • Bunsen burner
  • Wire gauze
  • Tripod stand
  • Filter funnel
  • Filter paper
  • Spatula
  • Knife

Real Lab Procedure:

  • Take 25 ml of coconut oil in a measuring cylinder and pour it into a 250 ml glass beaker.
  • Measure 30 ml of 20% NaOH solution in another measuring cylinder and add it into the beaker containing vegetable oil.
  • Vigorously stir the mixture using a glass rod.
  • Touch the beaker from outside.  It is observed that the beaker is warm.
  • Place the beaker on a wire gauze placed over a tripod stand.
  • Heat the beaker using a Bunsen burner till the mixture become a whitish paste.
  • Remove the beaker from the flame and allow it to cool.
  • Dip a red litmus paper in the suspension formed.
  • When dipped in the suspension, the red litmus paper changes its colour to blue.
  • Dip a blue litmus paper in the suspension.
  • The colour of blue litmus paper remains the same.
  • To the above suspension, add 15g of common salt and stir it well with a glass rod.
  • After adding common salt, soap in the suspension gets precipitated out as solid.
  • Take a filter funnel and place a filter paper in it and fix it in a stand.
  • Place a beaker below the funnel.
  • Pour the contents of the beaker into the funnel over a glass rod and filter the contents of the beaker.
  • After filtration, soap is left behind in the filter paper.
  • Transfer the soap into another filter paper using a spatula and dry it by pressing with another filter paper.
  • Then, cut it into desired shape with a knife.

Simulator Procedure:

  • To start the simulator, click on the measuring cylinder containing 25 ml coconut oil to pour it into the beaker.
  • Click on the measuring cylinder containing 30 ml 20% NaOH solution to pour it into the beaker containing coconut oil.
  • Click on the glass rod to stir the mixture.
  • Click on the information icon to see the inference.
  • Click on the 'NEXT STEP' button to go to the next process.
  • Turn on the burner by clicking on the 'knob' of the burner.
  • Click on the beaker to place it over the Bunsen burner and heat it.
  • Click on the information icon to see the inference.
  • Click on the beaker to place it back from the burner for allowing it to cool.
  • Turn off the burner by clicking on the 'knob' of the burner.
  • Click on the 'NEXT STEP' button to go to the next process.
  • Click on the red litmus paper to dip it into the soap suspension.
  • Click on the information icon to see the inference.
  • Click on the blue litmus paper to dip it into the soap suspension.
  • Click on the information icon to see the inference.
  • Click on the watch glass containing common salt to add it into the soap suspension.
  • Click on the glass rod to stir the mixture.
  • Click on the information icon to see the inference.
  • Click on the 'NEXT STEP' button to go to the next process.
  • Click on the beaker to filter the contents.
  • Click on the spatula to take soap from the funnel.
  • Click on the filter paper to dry the soap.
  • Click on the information icon to see the inference.
  • You can redo the experiment anytime by clicking on the 'Reset' button.

Observations:

  • When 20% NaOH solution was added to the beaker containing vegetable oil, it was observed that the beaker was warm when touched from the outside.
  • A whitish suspension was formed by heating the mixture of vegetable oil and 20% NaOH solution.
  • Red litmus paper changed colour to blue when dipped in suspension.  Blue litmus paper was not affected by the suspension.
  • After adding common salt, the soap in suspension form precipitated out as solid.

Conclusions:

  • The reaction between vegetable oil and sodium hydroxide solution is exothermic in nature because heat is liberated during the reaction.
  • The white suspension formed is made up of soap and glycerol. The process of formation of soap is called saponification.
  • Test using red and blue litmus papers shows that soap suspension is basic in nature and not acidic in nature.
  • The process of precipitation of soap from the suspension is called salting out.

Precautions:

  • Do not touch the NaOH solution with bare hands as it may burn the skin.
  • Do not breathe the fumes of NaOH or let the fumes get in your eyes. Keep the windows of the laboratory open.
  • The mixture of oil and alkali should be stirred thoroughly.
  • It is necessary to stir the soap solution after adding common salt to it, in order to precipitate out the soap in solid form.

Cite this Simulator: