Purpose
The purpose of this experiment is to prepare soap through the saponification process and use it to test water hardness.
Procedure
The saponification process began by placing approximately 5 grams of lard in a beaker. 15 mL of sodium Hydroxide (6 M) was slowly and carefully added followed by an addition of 25 mL of ethanol. After adding ethanol, the beaker was heated while stirring until the base fully reacted with the lard. The result was a clear and homogenous solution. After cooling the solution, 20 mL of water was added. The next step involved the preparation of saturated NaCl by dissolving 12 grams of NaCl in 50 mL of water. The cooled fat base solution was then poured into the saturated NaCl and allowed to cool. A solid cake precipitated out of the solution which is Soap. Buchner funnels and cheese cloth was used to collect the soap by suction filtration. The purity of the soap was enhanced by washing it in distilled water two times.
The procedure to test the hardness of water was performed as follows; a small amount of soap was ground in 10 mL of distilled water using a glass rod. The soap solution was then transferred into four clean labelled test tubes. While test tube 1 was taken as the control of the experiment, 20 drops of 1% Calcium Chloride, 20 drops of 1% Iron (III) chloride and 20 drops of 1% Magnesium (II) chloride was added to test tube 2, 3 and 4 respectively. Each test tube was shaken while adding the salts while comparing it with the control.
Data Analysis
On mixing the salts with the soap solution as explained in the procedure, test tube one had the highest amount of suds, and had no precipitation process taking place. However, a significant reduction of suds as compared to test tube 1 was evidenced in all the other test tube with salts. The reactions in test tubes 2,3and 4 resulted in the formation of a precipitate.
Discussion
Soaps are formed by reacting fats with sodium hydroxide as in the following reaction:
Fat + Sodium Hydroxide --> sodium salt of fatty acid + glycerol
Soaps are salt of amines, Sodium or Potassium thus less soluble in fatty acids than water. However, chain length of fatty acids increases, soap solubility in water declines. Water is regarded as hard water when 7-10.5 grains/gallon (gpg) or 120- 180 milligram/litre (mg/l) of minerals such as magnesium and calcium are contained in it. Ethanol is used in the saponification process as a solvent. It acts as a catalyst in the reaction between melted fatty oils and Sodium hydroxide solution. Ethanol is a precious additive in ensuring a high clarity of transparent glycerin soap.
When salts are added to the soapy solutions in the test tubes the soap solution is precipitated as bath-tub ring by Iron, magnesium or calcium ions. Hard water such as tap water contains dissolved salts such as magnesium, Iron and Calcium which react with soap solution forming scum which is insoluble and is clearly seen as a precipitate. This leads to the use of much quantity of soap. In order to reduce the hardness of water, that is to reduce the scum level or completely eliminate them; builders are added to soap forming detergents. Detergents have special agents, the builder which removes the calcium and magnesium ions in water making it easier to bubble and form foam. As in the case of ocean water, soap will lather easily. The reason behind it is that when soap is dissolved in sea water, the ionic-salt end of the molecule is heavily attracted to ocean water molecules, dissolving in it giving lather or foam.
Conclusion
Soaps are chemical salts formed with long chains of fatty acids. When soaps are dissolved in water they produce lather or foam. However, when dissolved in hard water; containing magnesium or calcium ions, scum which is a white precipitate is formed.
