EXPERIMENT 5 : EXPERIMENT USING LIPID

ABSTRACT

This experiment is carried on in order to evaluate one of several triglycerides to determine the saponification number. This experiment also been carried out to make soap by the same process called the saponification, using the modern ingredient. The experiment to determine the saponification had been carried out in the fume hood. After that, it had been titrate by using 0.5M of HCL. The saponification number is used as an indicator of fatty acid chain length in triglycerides. The value is simply a measurement of the mg of KOH required to complete the hydrolysis of one gram of fat oil. For making the soap, sunflower oil had been used. The oil had been boil with 6.0M of NaOH. In the process of making soap, vegetable fat, which is triglyceride, is hydrolyzed by the action of strong base, such as sodium hydroxide, and heat. The resulting products are soap and glycerol.

INTRODUCTION

Lipids are molecules that contain hydrocarbons and make up the building blocks of the structure and function of living cells. For examples, fats, oils, waxes, certain vitamins, hormone and most of the non-protein membrane of cells. Besides that, lipids are a large and diverse group of naturally occurring organic compounds that are related by their solubility in non-polar organic solvents and general insolubility in water. The tri-esters of fatty acids with glycerol (1,2,3-trihydroxypropane) compose the class of lipids known as fats and oils. These triglycerides are found in both plants and animals, and compose one of the major food groups of our diet. Triglycerides that are solid or semisolid at room temperature are classified as fats, and occur predominantly in animals. Those triglycerides that are liquid are called oils and originate chiefly in plants, although triglycerides from fish are also largely oils. The process of saponification, by heating a triglyceride in aqueous potassium hydroxide (KOH) the fatty acyl esters can be cleaved off (hydrolysis) leaving behind glycerol and the potassium salt of the fatty acid. So, the triglycerides that contain high fatty acids number will have a lower saponification number that triglycerides with low fatty acids number.

PROCEDURE

1. Saponification of triglyceride

2. Application : making soap

RESULT

1. saponification of triglyceride

2. Application : making soap

DISCUSSION

1. Saponification of triglyceride

The saponification number (sap) measures the bonded and unbonded acids present in an oil or fat. It defines the exact amount of potassium hydrate in mg necessary to emulsify 1g of fat or oil.  The smaller the molar mass of the fat, the higher the saponification value. For saponification of triglycerides experiment to determine the saponification number of triglycerides  , we were using sunflower oil as a sample for our group. Different group used different oil which is palm oil and corn oil. Then at the end of the experiment we obtained the final results for each sample. Based on the results obtained, sunflower oil has the highest saponification number compared to corn oil and palm oil. So it shown that, sunflower oil has shorter fatty acids.

Theory said that triglycerides containing long fatty acids will have a lower saponification number than triglycerides with shorter fatty acids. Since 1 gram of lipid containing long chains will have less chains in total than 1 gram of lipid containing short chains. Actually, we should get the highher saponification number for palm oil followed by corn oil and the lowest is sunflower oil.  Low fatty acid fats like coconut oil or palm kernel fat have high saponification numbers of 250, whereas most vegetable oils have a saponification number of approximately 190 It means that, palm oil have the shorter fatty acid chain than corn oil and sunflower oil. For the palm oil and corn oil, the saponification number should higher than sunflower oil because they have shorter fatty acid chain than sunflower oil. A few error occured during the experiment that effect the results obtained that are, there is no standard colour of solution when turns colourless. the pinkish colour might still there . So, this affect the titration process. it then, affect the volume of  HCL  used.

2. Application : making soap

Soap is made by the saponification reaction. It is an exothermic chemical reaction which happens when fatty acids react with base. This process involves boiling the fats together with the base. For this experiment, we boiled sunflower oil with 6M NaOH. The hydrolysis of the oil occurs, thus producing glycerol and crude soap. Then, sodium chloride is added into it once the saponification reaction completed. Addition of sodium chloride causes the soap to precipitate. The crude soap acquired from the process consists of sodium chloride, sodium hydroxide and glycerol. The crude soap curds is then boiled in water and re-precipitated with salt in order to remove the impurities. After that, we add some color into it and the result is as the picture below.

QUESTION 

1.    What is the relationship between saponification and phase (liquid / solid) of a triglyceride?

In saponification, boiling triglycerides (oils) react with concentrated alkali (potassium hydroxide) to produce glycerol and salts of fatty acids. Triglycerides exist in the organic phase while the hydroxides exist in the aqueous phase. By increasing agitation, the reactants will happen to be in the same phase. Therefore, the oils can be hydrolyzed to form glycerol and fatty acids. The acids then react with potassium hydroxide to form potassium salts. Thus, glycerol and fatty acid salts that have appreciable solubility in both phases can be formed. The reagents will increase in concentration in the phase which is most favored by the other as the reaction progresses.

2. Why do triglycerides with longer fatty acids have a lower saponification number than those with shorter fatty acids?

It is because the longer the fatty acid chains, the fewer the number of carboxylic functional groups per unit mass of the fat. It results in a higher molecular weight. Therefore, less acid is liberated per gram of fat hydrolyzed. As less KOH is needed to hydrolyze the ester bonds, saponification number is lower.

3. Why is the difference in the molar amount of HCl used to neutralize the control and the amount of HCl used to neutralize the sample equivalent to the molar amount of KOH used to saponify the test sample?

      More HCl is used to neutralize the control as compared to the neutralization of the sample. It is because in blank test, all KOH reacts with HCl to produce a neutralized solution. On the other hand, in sample test, some KOH is used to hydrolyze the fatty acids while some is neutralized by HCl. Therefore, more HCl is utilized in the blank test than in the sample test.

4. Why do soaps disperse grease?

Soaps have hydrocarbon and ionic ends. The hydrocarbon ends are hydrophobic and non-polar. The ionic ends are hydrophilic and polar. When both oil and water present and mix with the soap. The hydrophobic part of the soap mixes with the oil, while the hydrophilic part of the soap mixes with the water. The attraction of the polar end of the soap is strong enough to pull the grease molecules into the water. Therefore, the grease molecules associated with the non-polar ends are pulled into the water along with the soap molecules. The soap and grease combine and arrange in the form of micelles. Finally the micelles will disperse in the water.   

CONCLUSION

The smaller the molar mass of the fat, the higher the saponification value,and shorter fatty acids. Sunflower oil has the highest saponification number compared to corn oil and palm oil. Soap is one of the product produced by undergo the saponification reaction. It undergo an exothermic chemical reaction which happens when fatty acids react with base. 

REFERENCES

            Chempro (2013), Chempro Edible Oil Refining ISO TUV Austria. Retrived from website,   

            on May 20th http://www.chempro.in/fattyacid.htm

            Florin Switzerland (2013), Saponification value. Retrived from website, on May 20th,

http://www.florinag.ch/index.php?sid=3ahd81hE5Q0ynses55dCxQ57BGRGh4j3lkdebwj3&c5p=495&c5l=en

Anonymous. Soap and saponification: preparation and chemical structure. Retrieved from

http://chemistry.about.com/library/weekly/blsapon.htm at 19th of May 2013.           

Anonymous. Estimation of saponification value of fats/oils. Virtual Amrita Laboratories Universalizing Education. Retrieved on May 17, 2013 from http://amrita.vlab.co.in/?sub=3&brch=63&sim=688&cnt=1

David, A. K. 2000. The science of soaps and detergents. Retrieved on May 17, 2013 from http://www.chymist.com/Soap%20and%20detergent.pdf