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Soap is a type of detergent used for cleaning, mainly for personal use. It usually comes in the form of a bar. Synthetic detergents have superseded soap as a laundry aid.

Soaps are mixtures of sodium or potassium salts of fatty acids which can be derived from oils or fats by reacting them with an alkali (like sodium or potassium hydroxide) at 80-100 C in the process known as saponification. Hydrolysis of the fats and oils occurs, yielding glycerol and crude soap.

CH2-OOC-R - CH-OOC-R - CH2-OOC-R (fat)

+ 3 NaOH ( or KOH)

both heated --->>

CH2-OH -CH-OH - CH2-OH (glycerol)

+ 3 R-CO2-Na (soap)


Sodium chloride is added to precipitate the soap.

Table of contents
1 Purification and ending
2 Use
3 See also
4 External links

Purification and ending

Reaction contains sodium chloride, sodium hydroxide, and glycerol. These impurities are removed by boiling the crude soap curds in water and re-precipitating the soap with salt.

Sand or pumice may be added to produce a scouring soap.


Although the soap term continues to be used informally in everyday speech and product labels, in practice nearly all kinds of "soap" in use today are actually synthetic detergents, which are less expensive, more effective, and easier to manufacture.

Soaps are useful and used primarily for cleansing because soap molecules attach readily to both nonpolar molecules (such as grease or oil) and polar molecules (such as water). Although grease will normally adhere to skin or clothing, the soap molecules can attach to it as a "handle" and make it easier to rinse away.

(water soluble end)
CH3-(CH2)n - COONa

(fatty part)

The hydrocarbon ("fatty") portion dissolves dirt and oils, while the ionic end makes it soluble in water. Thus, it allows water to remove normally-insoluble matter.

The ancient world was generally innocent of soap; the Romans built baths, but did not often use soap in them. According to Pliny the Elder, soap was invented by the ancient Gauls. They did not use it for washing, though; they used it as a pomade to keep their hair shiny.

Historically, soap was often made in the home by mixing animal fats with lye. Because of the caustic lye, this was a dangerous procedure (perhaps more dangerous than any present-day home activities) which occasionally resulted in serious chemical burns or blindness.

Before commercially produced lye was common place, lye was produced at home for soap making from the ashes of a wood fire.

One can play with soap by making soap bubbles that float in the air.

See also

External links

There was a controversial 1970s sitcom called Soap, starring future celebrity Billy Crystal.
Soap is also a colloquial term for a soap opera.
In computing, the acronym SOAP stands for Simple Object Access Protocol.