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WEEK 4
TOPIC: SOAP AND DETERGENT
CONTENT:
- Soap preparation and structure
- Action of soap as an emulsifying agent
- Detergents: preparation, mode of action of soap
- Differences between soap and detergent
PERIOD 1: SOAP PREPARATION (Laboratory)
Soaps are saponification products of fats and oils. They are sodium salts of fatty acids. They are usually referred to as soapy detergents.
- A mixture of about 100cm3 of vegetable oil (palm kernel oil) and 100cm3 of 10% sodium hydroxide solution is boiled and agitated by passing steam until it is homogenous.
- Saturated solution of sodium chloride (brine) is then added to the slightly cooked mixture, in order to salt out or separate the soap and from the liquid propan-1,2,3 – triol (glycerol).
- The soap cord obtained is then slightly dried and mixed thoroughly with perfumes and covalent
- Again, the soap is slightly dried, then pressed before being cut into tablets or bar.
PERIOD 3: ACTION OF SOAP AS AN EMULSIFYING AGENT
If an oil-water mixture in a container is shaken together vigorously, since oil does not dissolve water, the oil will be suspended as tiny droplets in the aqueous layer. This forms what is called an oil-water emulsion. This emulsion is very unstable, on standing; the droplets will coalesce to form the oil layer again. On addition of some soap solution to the oil-water emulsion, the soap molecules will crowd around each oil droplet as shown in the diagram below:
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