Detergent comes from the Latin word detergere meaning to clean, it is defined as a cleansing agent. Therefore, water itself is a detergent. This essay looks at soap and soapless (or synthetic) detergents. Both substances we use everyday and have a big market commercially, they effect everyone. Soaps are made from natural products and soapless detergents are produced chemically, each having advantages and disadvantages. Soap has a much longer history than it's relatively new synthetic version. There is evidence of soap made in Mediterranean countries around 2500 years ago. The basic process has not changed much although now the chemistry is understood. Soap is made from the process called saponification, the alkaline hydrolysis of fats and oils. It is essentially the reverse of esterification. O O R-C-O-R' + NaOH ---- R-C-O-Na+ + R'OH Ester(fat) + base(caustic soda) ---- salt of fatty acid(soap) + alcohol(glycerol). Caustic potash (potassium hydroxide) can be used instead of caustic soda (sodium hydroxide)but is more expensive. The base used to come from wood ash containing potassium carbonate which formed potash as this was not plentiful it made soap a luxury. The cheapest source of the ester is animal and vegetable fats and oils.
This is an example of a soap molecule. The hydrocarbon end is non polar and hydrophilic (water hating) and the carboxylate end is polar and hydrophilic (water loving). This the property which allows it to clean, it acts as an emulsifying agent. The soap disperses in water to form miscelles where a negatively charged surface is formed and hydrocarbon chains are in the centre. These miscelles surround droplets...