To know what is required to achieve effective cleaning, it is necessary to have a basic understanding of the chemistry of soaps and detergents.
Water, the liquid, which is primarily used for cleaning, has a characteristic known as surface tension. Under the surface of water, each water molecule is surrounded and attracted by other molecules. At the surface, however, these molecules are surrounded by only those water molecules that are on the water side. As the water molecules at the surface are pulled inside the body of water, a tension is created. This tension makes the water to bead up on surfaces (fabric, glass), as a result of which the wetting of surface and hence the cleaning process slows down.
For effective cleaning, the surface tension should be reduced in order to make water spread and wet surfaces. Chemicals that can do this effectively are known as surfactants or surface-active agents.
Surfactants also execute some other important cleaning functions, such as loosening, emulsifying (dispersing in water) and holding the soil in suspension till the time it can be rinsed away. These chemicals also provide alkalinity that has found to be effective in removing acidic soils.

Also known as surface-active agents, surfactants can also be classified on the basis of their ionic (electrical charge), anionic (negative charge), nonionic (no charge), cationic (positive charge) and amphoteric (either positive or negative charge) properties in water.
Soap is an anionic surfactant while main ingredients in todays’ detergents are other anionic as well as nonionic surfactants. Now lets have a look at the chemistry of surfactants –
Soaps
Soaps are water-soluble potassium or sodium salts of fatty acids, which are made by the chemical treatment of fats (or oils), or their fatty acids with a strong alkali. Now let us first examine the composition of fats, oils and alkalis.
Fats and Oils
Fats and oils that are used in the manufacturing of soaps come from plant or animal sources. Each fat or oil molecule is made up of a typical mixture of different triglycerides.
In a triglyceride molecule, one glycerin molecule is attached to three molecules of a fatty acid. There are several types of fatty acids, with each having a particular combination of fatty acids. Components of fats and oils, which are used in soap making, fatty acids are weak acids that are composed of two parts.
A carboxylic acid group consists of two oxygen (O) atoms, one carbon (C) and one hydrogen (H) atom with a hydrocarbon chain attached to the carboxylic acid group. Typically, a fatty acid is made up of a long straight chain of carbon (C) atoms in which each carbon atom carries two hydrogen atoms.
Alkali
An alkali is a soluble salt of an alkali metal, such as potassium or sodium. Earlier, the alkalis that were used in soap manufacturing were obtained from the ashes of plants but now they are commercially manufactured. Now days, the term alkali described a substance, which is a base (chemically) and that reacts with and neutralizes an acid.
Usually the alkalis that are used in soapmaking are potassium hydroxide (KOH), also known as potash (KOH) and sodium hydroxide (NaOH), also known as caustic soda.
Surfactants in Detergents
A detergent is a better cleaning product as it contains one or more surfactants. Due to their chemical makeup, the surfactants that are used in detergents can be engineered to function well under different conditions. Such types of surfactants are less sensitive to hardness minerals in water than soap and most of them do not form a film.
Detergent surfactants were developed during World War I in response to a shortage of animal and vegetable fats and oils. The discovery of surfactant was also driven by the need of a cleaning product resistant to hard water to make the cleaning more effective. At that time, petroleum was found to be a readily available source for the manufacture of detergent surfactants. Today, detergent surfactants can be produced with a variety oleochemicals (derived from fats and oils) and/or petrochemicals (derived from petroleum). Now let us first examine the composition of petrochemicals, oleochemicals and alkalis prior to the review of how surfactant detergents work.
Petrochemicals and Oleochemicals
Like the fatty acids that are used in soap manufacturing, both the petroleum and fats and oils contain hydrocarbon chains, which are repelled by water but attracted to grease and oils in soils. The hydrocarbon chain sources are used to form the water-repelling end of the surfactant molecule.
Other Chemicals
Other chemicals include chemicals, like sulfur trioxide, sulfuric acid and ethylene oxide, that can be used to produce the water-attracting end of the surfactant molecule.
Alkalis
As like soapmaking, an alkali is used to form detergent surfactants. Potassium and sodium hydroxide are the most commonly used alkalis.



The three types of emulsifiers that are used in fabric softeners, include –
September 6, 2024
Soaps vs Detergents,Soaps versus Detergents,Difference Between Soaps and Detergents
maximios Detergents
Both soaps and detergents are cleansing products that we frequently use in our daily lives. We use these products to clean our skin and hands wash our clothes without really paying any attention to how they work or is there any difference between them. Although both the soap and detergents perform same action, i.e. cleansing, there is a significant difference between them. We can differentiate the soaps and detergents on the basis of several factors, like – Ingredients, structure, properties, and more.
Mentioned below are some factors, on the basis of which we can differentiate soaps and detergents –
Soaps and Detergents Ingredients
Although both are surfactants (or surface active agents that means a washing compound, which mixes with grease and water), soaps and detergents are not the same thing. Soap manufacturing process is different from that of detergent making. Soaps are usually manufactured using natural materials while detergents are generally synthetic that were developed during World War II, when there was scarcity of oils that are used to make soaps.
Soaps Ingredients
Usually labeled as beauty, facial, or cleansing bar soaps, true soaps are generally produced with natural products (soap and lye) and require very less energy in the manufacturing process. It is possible to make soaps without having leftover by-products, which tend to go to the landfill, and the soap, which flows down the drain while cleaning is biodegradable. These soaps have a pH of 9.5 to 10 (alkaline) that makes them effective cleansing agents and eliminates the requirement for harmful antibacterial chemicals and preservatives.
However, some manufacturers use beef tallow (fat), in soap making, as this is an unused byproduct of meat processing, which can be obtained very cheaply. While saponified beef tallow can be used to make a satisfactory soap, there are some substances in tallow, which that do not saponify, and may cause acne and skin breakouts.
Superior quality soaps are produced with oils, like – palm, castor, coconut, or olive oils, and retain the natural glycerin, rather removing it and selling it for profit, which bulk manufacturers generally do.
Detergents Ingredients
Detergents are generally made from petroleum products with surfactants, foaming agents and alcohol being their primary constituent. To remove the disagreeable odour of these chemicals, detergents are heavily scented with cheap, synthetic and artificial fragrances. Detergents ingredients also include preservatives and antibacterial agents (to increase their shelf life) that make the detergents frequent causes of allergies and reactions. Soap Structure
StructureAll of the soaps are fatty acid salts, which can be categorized by
Any surfactant (or surface-active agent), that is not soap is a detergent.
Soap Detergent Difference- Properties in Hard Water
The most important difference between a soap and detergent is their behavior in water. A big drawback of washing with soap is that it forms a scum in hard water, which is not easy to clean and is known to turn laundry into a hue.
Soaps form a scum in hard water, which is not easy to rinse away and is known to turn laundry, a grayish hue. The insoluble film that soap leaves can leave a residue on the laundry same like as would see in a shower stall where hard water is present. On the other hand, detergents react less to minerals in water hence does not leave this residue. In case you are living in an area, where the water is soft, a soap will work satisfactorily, but even then a gradual build-up of calcium and magnesium ions (also called ‘curd’) will be left on the fabric.
Another important difference between soaps and detergents is the sensitivity of soaps to acidic conditions. On putting a soap into an acidic (pH
The protonation of oleate ion to form oleic acid forms an uncharged, insoluble molecule that is not surface-active.
The protonated soap molecule does not have a charged head, and so it becomes insoluble in water. The soap molecules precipitate out thereby producing a cloudy mixture that leads to the formation of a scum. Hence, we can say soaps are not suitable for uses in acidic conditions.
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