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
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:
These are essentially used to build up soaps. Examples of alkali builders are sodium carbonate, sodium silicate and sodium sulfate.
Fillers increase the bulk of soap by adding weight, thus reducing the production cost. Clay, kaolin, talc, starch, common salt, chalk and magnesium carbonate are the most commonly used fillers in soap making. * Common salt (Brine)
It is used to separate out glycerin and excess caustic from the genuine soap.
Color is added to make the soap more enticing and also to mask its original color. e.g. methyl violet, bismark brown, rhodamine, zinc oxide, chrome green, cadmium yellow, ultramarine, eosin and vermilon
Since oils and fats contribute to the unpleasant odor of the soap, perfume is added to add fragrance. e.g. clove oil, vanillin, lemon grass oil, citronella oil
3. Describe the saponification process and include the chemical reaction Saponification is the process wherein esters undergo base-promoted hydrolysis. It is the alkaline hydrolysis of triacylglycerols, leading to glycerol and a mixture of long-chain carboxylic acids:
Nucleophilic addition-eliminatiion at the acyl carbon is the mechanism for base-promoted hydrolysis of ester. Reacting an ester with aqueous sodium hydroxide yields alcohol and the sodium salt of the acid. This reaction is done through boiling of fats and oils in aqueous sodium hydroxide until hydrolysis is complete. In the process of saponification, hydrogen atoms are released from the bonds and this is where the fats are hydrolyzed. The salts of long-chain carboxylic acids are the soaps which is the end-product of the reaction. Soap will precipitate when sodium chloride is added to the mixture. And through several reprecipitations, crude soaps are usually purified.
4. Flowchart on soap-making, outline the process