The Science of Saponification: Test of Oils to Create Soap

The purpose of this lab is to create soap through saponification of a triglyceride and compare it to commercial detergent and hand soap. Soap is one of society’s major defenses against diseases. Soap’s origins, however, are not clear. There are ruins from ancient Egyptian times where substances believed to be soap have been discovered. There are also documents that suggest it was used by ancient Phoenicians over 5,000 years ago. The most acknowledged story of the creation of soap is attributed to the ancient Romans. They learned to make soap when animals were used as burnt offerings on Mount Sapo. The fats from the animals mixed with ashes on the ground, a natural source of sodium hydroxide. When it rained, there was a substance left behind in the puddles of water. It was discovered that this substance was able to clean surfaces.(3) The powerful cleansing properties of soap helps rinse away many disease-causing organisms. The main components of the fats and oils are triglycerides, esters of glycerol, and various fatty acids. The ester bonds of triglycerides are hydrolyzed, with solutions of sodium hydroxide. This process is called saponification. The final products of this hydrolysis reaction are soap and glycerol.

Safety Considerations

There are a few safety precautions that should be taken while performing this lab. One should wear goggles and gloves to prevent contact with any harmful chemicals. Sodium hydroxide (lye) is a very powerful base and can cause burns if it comes in contact with skin. While dissolving the sodium hydroxide in the ethanol/water solution, the mixture will heat up significantly, due to the exothermic reaction.

Purpose

To prepare and isolate a soap by saponification of two different triglycerides and compare the differences.

Materials

The materials needed are safety goggles, apron, dropped pipet, 2 250-ml beakers, 3 cork stoppers, 2 50-ml beakers, plastic wash bottle, 10-ml graduated cylinder, scoopula, gas burner, vegetable oil and Coconut oil, ring stand, 50% (v/v) ethanol-water mixture, ring support, sodium hydroxide, NaOH, wire gauze, saturated sodium chloride solution, NaCl, glass stirring rod, paper towels, 50-ml graduated cylinder, laundry detergent, spatula, hand soap, 3 medium test tubes, wide-range test paper, centigram balance, 0.1M calcium chloride, CaCl2, glass-marking pencil, 0.1M iron(III) chloride, FeCl3, test-tube rack, and 0.1M magnesium chloride, MgCl2.

Procedure

Part A. Preparation of Soap 5 mL of vegetable oil was placed in a 250-mL beaker. 15 mL of 50% ethanol-water mixture was placed into 50 mL beaker. 2.5 g of NaOH pellets was slowly dissolved in ethanol-water mixture. 2-3 mL of NaOH solution was added to beaker containing oil. CAUTION: Keep face away from beaker. Mixture heated over low flame while stirring. Portion of ethanol-water mixture added every few minutes for 20 minutes while continuously stirring. For approximately 10 minutes, mixture was heated and stirred. Oil was dissolved until a homogeneous mixture was acquired. 25 mL of cold water was added to hot solution. The solution was poured into 250-mL beaker of 150 mL of saturated NaCL. The mixture was carefully stirred for several minutes.

Mixture was left to cool. Top layer of soap skimmed off using spatula. Finally, the soap was placed in 50 mL beaker. ethanol/water/NaOH solution being poured into vegetable oil Part B. Properties of Soaps and Detergents Pea-sized lump of soap placed into test tube. Scoopula used to place similar amount of laundry detergent in second test tube, while hand soap was placed in third test tube. 10 mL of water was added to each tube, stopper added to top, and then mixture was shaken. Test tube rack was used as needed. The pH of solution was estimated using wide-range test paper or if preferred wide-range indicator. Results recorded. Contents were poured down the drain. Three test tubes marked with labels “CaCl2, FeCl3, and MgCl2”. 0.1g of detergent was added into 10 mL of water in order to prepare the solution. Solution was evenly divided among 3 Test tubes.

Solutions added to test tubes as stated. (CaCl2 test tube: 1.0 mL and or 20 drops of 0.1M CaCl2, FeCl2 test tube: 1.0 mL of 0.1M FeCl2, MgCl2 test tube: 1.0 mL of 0.1M MgCl2). Each test tube was stoppered and shook in order to mix. Observations were written down and recorded. Contents poured down the drain. Test tubes and stoppers were rinsed off with water. Step 9 was repeated, but detergent solution was replaced with hand soap solution of same strength. Observations were written down and recorded. Step 9 was repeated, but detergent solution was replaced with vegetable oil soap and coconut oil soap solution of same strength. Observations were written down and recorded. Teachers instructions were followed for proper disposal.

Data and Observation

Soap made with vegetable oil: This oil yielded less product than the coconut oil soap. It was slightly yellow in color. Both soaps were solid and formed clumps that were slightly grainy. This soap produced more suds than the other. When heating over low flame while adding the ethanol/water/ NaOH solution, the soap was thicker than the coconut oil soap and gradually solidified, while bubbling. This soap felt slightly waxy compared to the coconut oil soap.

Soap made with coconut oil: This oil produced much more soap than the vegetable oil soap. When the ethanol/water/ NaOH solution was added over the low flame, a clear film formed at the top of the solution and the glass stirring rod started sticking to the bottoms of the beaker. It stayed white like the color of the oil when solidified. It remained solid and formed similar grainy clumps to the first soap. It was slightly more solid and crumbly but was still malleable like the vegetable oil soap. This soap did not produce very much suds when mixed with water. pH was tested using wide range test paper (from left to right- vegetable oil soap, coconut oil soap, commercial hand soap, laundry detergent).

Discussion

The purpose of this lab was to create soap through saponification using two different types of oils and compare the differences in the two soaps using various methods. All parts of our lab were successful. The fatty acids used (vegetable oil and coconut oil) reacted with a strong base (sodium hydroxide) which produced glycerol and soap. The soaps had different properties due to the unique chemical makeups of the oils. Every acid has a differing combination of triglycerides, which are compounds made of three fatty acids attached to a single glycerol molecule. As the acid and base are combined, the triglycerides give up the glycerol molecule, which become glycerin. This allows the hydroxide ions in the base to combine with the fatty acids in the oil or animal fat, forming the soap. Within this reaction, two reactions actually occur simultaneously.

The first being the glycerol turning into the skin-nourishing glycerin, and second being the combination of the acid and base to form a salt, essentially the soap. Because the two oils have different triglyceride combinations, the final products will differ from each other, in quality, quantity, and lathering/ cleansing abilities.(1) This is the reason why the vegetable oil produced far less soap than the coconut oil in the experiment and created more suds. This also caused the coconut oil soap to be more solid than the vegetable oil soap, due to the fact that it is a saturated fat (solid at room temperature).(4) Coconut oil fatty acid chain Vegetable oil fatty acid chain The reason why soap is able to clean is due to the makeup of the fatty acids. The fats are hydrolyzed into fatty acids when it reacts with a strong base, for example sodium hydroxide.

Fatty acid chains have one end that is hydrophilic, or water loving, and another end that is hydrophobic, or water repelling. The hydrophilic end is considered the “acid” part and the hydrophobic end is the “fatty” part. The nature of this allows soap to breakdown oils, grease, and grim in water. Without this component, the soap wouldn’t be able to breakdown these parts in water. (3) The soap produced in both experiments was solid. This is due to the base used in both experiments being sodium hydroxide, more commonly called lye in soap making. In order for the saponification to be successful, the base must have one hydroxide ion. The sodium actually serves no purpose in the actual reaction. Another common base used is potassium hydroxide, called potash or lye as well. This base is used to achieve a liquid soap. The potassium hydroxide is a hygroscopic substance, meaning it attracts and absorbs moisture and liquifies very easily.

Also, it won’t crystallize like the sodium hydroxide so the final product remains clear and a liquid. (2) The salts in our experiment are used to purify soap. Some salts are better than others when it comes to purification. The most common salt used to purify soap is sodium chloride. The sodium ions in the salts bond with the fatty acid chains which produces a soap that is less soluble in water. This was observed when the soap separated from the water in the test tubes when the salt solution was added. This process is called precipitation. However, this only occurred when using calcium chloride and magnesium chloride solutions. Also, the salts primarily affected the soap made in the experiment since the commercial soaps had already been purified. This is an effective way to purify the soap because it separates the substance wanted (soap) from any unwanted or harmful chemicals used in the saponification process (like sodium hydroxide).(3)

Although the lab was successful, there are multiple factors that could have led to error. First, different amounts of oils are traditionally used depending on the specific oil in soap making. This is a possible cause of the dramatic differences in amount obtained from the two soaps. In both experiments, the same amount of oil, 5ml, was used. The collection process of the soap could have led to error as well, since the soap was manually scooped out of the beaker containing the soap suspended in the liquid, rather than filtered. Also, the creation of the 0.1M solutions of the salts could have been altered slightly. The calculations to find the molar mass were done by hand, as well as the measurements with the centigram balance, as shown in the data and observations. The hypothesis of the coconut oil mixture was as stated. Solid chunk of coconut oil was placed into beaker. Coconut oil would heat and melt. Easy to stir and smooth mixture would take place. Uniform state throughout, clear liquid. The proven occurrence of the coconut oil mixture was as stated. Stirred instead of smoothly going through mixture, slightly stuck to bottom when stirred. Mixture began to separate.

Mixture had scatter particles of coconut oil on top. Flem left on top. The hypothesis of vegetable oil mixture was as stated. State would stay the same. Light yellow color would remain throughout heating process. Easy to stir light liquid consistency. Bubbly effect due to lack of moisture in oils components. Same amount of oil on top as coconut oil. The proven occurence of vegetable oil was as stated. Color changed from light yellow to deeper yellow as experiment went on. Bubbly effect took place due to lack of moisture in oil. Mixture changed consistency. Began to thicken as experiment went on. At one point mixture separated into gel like substances. After gel phase, mixture went back and was more uniform but thicker than original. Mixture solidified. Not as much soap was produced as was thought. Example: coconut Oil- coconut oil produced more soap than vegetable oil. Expected the same amount of soap to be produced, considering same proportions were used. Vegetable Oil- vegetable oil produced less soap than coconut oil. Expected same amount of soap to be produced, considering same proportions were used.

Conclusion

In conclusion, the experiment was successful. Coconut oil was successfully substituted for vegetable oil in order to create soap and the differences in the two soaps was analyzed using various methods.