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EXPERIMENT 2: PREPARATION AND PROPERTIES OF SOAPOBJECTIVES:1)To prepare a sample of soap from olive oil and to examine its properties.2)To study the saponification reaction for preparation of soap.3)To understand the cleaning mechanism of a soap.INTRODUCTION:Soaps are carboxylate salts (sodium or potassium) with very long hydrocarbon chains.Soap is produced by saponification (hydrolysis) of a triglyceride (fat or oil). In this process the triglyceride is reacted with a strong base such as sodium or potassium hydroxide to produce glycerol and fatty acids salts where the fatty acids usually contain 12 to 18 carbon atoms. The salt of the fatty acid is called as soap. Saponification also known as alkaline hydrolysis of esters. An example of a saponification reaction is shown below.Figure 1: Saponification of a Triglyceride(Taken from )Soap molecules have two parts: a polar group (-COO-Na+) and a non-polar group (R-hydrocarbon part). The polar group is called the head and the non-polar group is called thetail. Thus, a soap molecule has a polar head and a non-polar hydrocarbon tail. The polar headis hydrophilic in nature (water loving) and the non-polar tail is hydrophobic in nature (waterrepelling).1
Figure 2: General representation of Soap Molecule(Taken from: Soap can emulsify fats and oils by forming micelles around oil droplets. The soapmolecules surround an oil droplet so that their non-polar tails are embedded in the oil andtheir charged “head” groups are on the exterior of the droplets, facing the water. If the oildroplets are small enough and if there are enough soap molecules to surround them, the oildroplets become dispersed in the water and can then easily be washed away. Therefore, usinglots of soap, hot water, and agitation can help clean greasy dishes. Hot water can melt solidfats, and agitation can help break up the fats and oils into smaller droplets. Using lots of soapmakes it more likely that there will be enough soap molecules to surround and emulsify allthe fat droplets.Soap is differentiated into two types depending upon the nature of alkali used inproduction of soap: hard soap and soft soap. Hard soap is the sodium salt of long chain fattychain acid, it is difficult to dissolve in water and usually used as laundry soap, whereas softsoap is the potassium salt of long chain fatty acid and it produces more lather, used as toiletsoap and shaving soap. Since soap has free alkali ions, they are alkaline in nature. Hence, thesoap solutions are slippery to the touch.The saponification reaction is exothermic in nature, because heat is liberated duringthe process. The soap coagulates from dissolving in the water when a saturated NaCl solutionis added, and the soap salt will separates out from the mixture. It then can be collected byfiltration and washed to remove the excess base.