Saponification: Sodium Hydroxide and Soap

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1. Functions of Soap
Soap primarily serves as a dirt remover and a cleanser. It is used in bathing, cleaning, and also as a lubricant. Oil, grease, and other forms of dirt do not dissolve in water. Conversely, soap can suspend these in such a way that it can be discarded through its ability to act as an emulsifying agent. This emulsifying agent enables the dispersion of liquid into another immiscible liquid. In this manner, oil does not mix with water whereby able to induce dirt. 2. Raw materials and soap making

Soap making requires two major raw materials:
* Fats and oils
Fats and oils are esters of fatty acids and glycerol. These are obtained from natural substances which are classified into three: a. Nut oils
Cold process soap making is the most suitable for this type of oil which is also characterized by large proportion of fatty acids. Nut oils saponify easily with strong alkali soulution. Example: coconut oil, palm kernel oil

b. Hard fats
Slow-lathering soaps are the ones produced with these fats and are first saponified with weak alkali, then stronger alkali in the final stages. Example: palm oil, animal tallow oil, hydrogenated oil

c. Soft oils
These contain substantial amounts of unsaturated acids which cannot produce hard soap and are usually blended with nut oils. They form very good detergents and they lather freely. Example: groundnut, castor, cotton seed, fish oil, olive oil * Alkalis

In soap making, two alkalis are commonly used:
a. Caustic soda
It is very corrosive to the skin and readily absorbs moisture. b. Caustic potash
Compared to soda, potash is much stronger in chemical reaction. It is generally used for making liquid soaps, shampoos and soft soaps because it produces soap of soft consistency and higher solubility in water.

Other raw materials:
* Builders
These are essentially used to build up soaps. Examples of alkali builders are sodium carbonate, sodium silicate and sodium sulfate.

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