Experiment 4 Essay

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Experiment 4 Title: Preparation and properties of soap. Objective: To prepare soap by alkaline hydrolysis (saponification) of castor oil and test some of the chemical properties of soap relative to detergent. Introduction: Castor oil is used as a source of vegetable oils which, on reaction with warm concentrated alkali, form soaps. The vegetable oils in castor oil also contain hydroxyl-groups (–OH) which will react readily with concentrated sulphuric acid, forming a long chain molecule with an ionic sulfonate group on the end. Soaps are the sodium and potassium salts of long chain fatty acids that are generally made by saponification (alkaline hydrolysis) of natural fats, such as animal fats or palm oil. Soap cleans because it can emulsify and oils, convert them into a suspension of tiny droplets in water. Dirt is held to fabrics by thin film of oil or grease, and this film must be removed before the dirt can be rinsed away. Soap owes its emulsifying action to combination of polar and non-polar groups in its structure. The long chain alky group is soluble in non-polar substance (fats and oils) which is hydrophobic, and an ionic end (the salts of a carboxylic acid), hydrophilic is soluble in water. Saponification is a process that produces soap, usually from fats and NaOH. In technical terms, saponification involves base hydrolysis of triglycerides, which are esters of fatty acids, to form the sodium salt of a carboxylate. In addition to soap, such traditional saponification processes produces glycerol. Soaps are less effective in hard water, which is water that contains a significant concentration of Mg2+ and Ca2+ ions. These ions form precipitates with soap molecules, and this precipitate is often seen as a grey line on a bathtub or sink and is often called “soap scum”. Since soap forms a precipitate with these ions, it means that many of the soap
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