Study Guide

Topics: Soap, Saponification, Water Pages: 7 (1594 words) Published: May 19, 2013

I will treasure the knowledge imparted to me by Mrs. Anita Thomas, my grateful thanks to her for the able teaching and guidance. I thank Mr. Harsha Kumar, the Lab assistant for his cooperation. I also thank my parents and my friends for their constant support and cooperation.


Soaps and detergents remove dirt and grease from skin and clothes. But all soaps are not equally effective in their cleaning action. Soaps are the Na and K salts of higher fatty acids such as Palmitic acid, Stearic acid and Oleic acid.

The cleansing action of soaps depends on the solubility of the long alkyl chain in grease and that of the -COONa or the -COOK part in water.

Whenever soap is applied on a dirty wet cloth, the non polar alkyl group dissolves in grease while the polar -COONa part dissolves in water. In this manner, an emulsion is formed between grease and water which appears as foam.

The washing ability of soap depends on foaming capacity, as well as the water used in cleaning. The salts of Ca and Mg disrupt the formation of micelle formation. The presence of such salts makes the water hard and the water is called hard water. These salts thus make the soap inefficient in its cleaning action.

Sodium Carbonate when added to hard water reacts with Ca and Mg and precipitates them out. Therefore sodium carbonate is used in the treatment of hard water.

This project aims at finding the foaming capacity of various soaps and the action of Ca and Mg salts on their foaming capacity.


Soap is an anionic surfactant used in conjunction with water for washing and cleaning, which historically comes either in solid bars or in the form of a viscous liquid. Soap consists of sodium or potassium salts of fatty acids and is obtained by reacting common oils or fats with a strong alkaline in a process known as saponification. The fats are hydrolyzed by the base, yielding alkali salts of fatty acids (crude soap) and glycerol.

The general formula of soap is

Fatty end water soluble end

CH3-(CH2) n – COONa

Soaps are useful for cleaning because soap molecules have both a hydrophilic end, which dissolves in water, as well as a hydrophobic end, which is able to dissolve non polar grease molecules. Applied to a soiled surface, soapy water effectively holds particles in colloidal suspension so it can be rinsed off with clean water. The hydrophobic portion (made up of a long hydrocarbon chain) dissolves dirt and oils, while the ionic end dissolves in water. The resultant forms a round structure called micelle. Therefore, it allows water to remove normally-insoluble matter by emulsification.

Commercial production of soap

The most popular soap making process today is the cold process method, where fats such as olive oil react with strong alkaline solution, while some soapers use the historical hot process.

Handmade soap differs from industrial soap in that, usually, an excess of fat is sometimes used to consume the alkali (super fatting), and in that the glycerin is not removed, leaving a naturally moisturizing soap and not pure detergent. Often, emollients such as jojoba oil or Shea butter are added ‘at trace’ (the point at which the saponification process is sufficiently advanced that the soap has begun to thicken), after most of the oils have saponified, so that they remain unreacted in the finished soap.

Fat in soap

Soap is derived from either vegetable or animal fats. Sodium Tallowate, a common ingredient in much soap, is derived from rendered beef fat. Soap can also be made of vegetable oils, such as palm oil, and the product is typically softer.

An array of saponifiable oils and fats are used in the process such as olive, coconut, palm, cocoa butter to provide different qualities. For example, olive oil provides mildness in soap; coconut oil provides lots of lather; while coconut and palm oils provide hardness. Sometimes castor oil can also be used as an...
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