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Difference Between Soap and Detergent

Soap vs Detergent

Both soap and detergent are used as cleaning materials. They are both created using chemical compounds or mixtures of compounds, and this is why most people get confused between them and use these two words mutually. However, there are many differences between these two cleaning materials.

In this article, we are discussing the important differences between soaps and detergents, which will also help us to understand the uses and characteristics of both. This article also explains how they work and which of them we should use in different circumstances.

Let's first discuss both with the definitions:

What is Soap?

Soap is a potassium or sodium salt of several combinations of naturally occurring fatty acids having cleansing action when used in water. Air bubbles included in the melted soap usually reduce the soap's density and make the soap float on the water. Some common examples of soaps include sodium stearate, sodium oleate and sodium palmitate prepared with palmitic acid and stearic acid oleic. Typically, the oils and fats used for producing soaps are segregated from the natural plants and animals.

When it comes to manufacturing soaps, the saponification process is the widely used method. Many animal fats and vegetable oils are mixed with hot alkali to produce soap and water (clean soap) plus glycerin. Apart from this, the basic hydrolysis reaction of oils and fats can also produce soap. In this method, Animal fats and vegetable oils are hydrolyzed by high-pressure steam to obtain crude fatty acids and glycerin. These fatty acids are further purified using a distillation method and then neutralized with alkali to form soap.

Note: In case sodium is used as an alkali, the soaps produced are hard and solid. On the other hand, potassium-containing soaps in alkali form are very soft and liquid in shape (known as liquid soap). The cleaning property of soap directly depends on the water's hardness level, which contains harmful minerals.

Characteristics of Soap

The following are the main characteristics of the soap:

  • Soaps are potassium/sodium salts of a carboxylic acid that contains a huge chain of aliphatic.
  • Soaps are usually created by the saponification of specific oils and fats.
  • Soaps are surfactants, which means they tend to reduce surface tension between the liquid and other substances. This eventually helps in the process of emulsification of oils and water.
  • The two ends of the soap molecule, namely carboxylate and hydrocarbons, are hydrophilic and hydrophobic.

What is Detergent?

A detergent is usually a surfactant or a combination of multiple surfactants containing cleaning actions in a dilute solution with the water. A detergent is usually the same as a soap but having a common structure, R-SO4-, Na +, in which R is a long-chain alkyl group. Detergents are called amphiphilic like soaps, which means that the detergents also contain hydrophobic and hydrophilic areas. Most detergents are alkyl benzene sulfonates. Detergents are more soluble in hard water than soaps because the detergent's sulfonate does not readily bind calcium and other ions in hard water like carboxylate in soaps.

Detergent surfactants are considerably better and reactive remedies for cleaning purposes because water hardness doesn't affect them. Detergents produced nowadays are available in liquid form that is much beneficial for cleaning applications. Generally, petrochemical solutions are used to produce Surfactants, which are used in detergents. Some other ingredients include oleochemicals, sulfoxide, sulfuric acid and ethylene oxide. Besides, Sodium and Potassium are used as alkalis.

When it comes to manufacturing detergents, anionic surfactants and nonionic surfactants are produced using different techniques:

  • Anionic Surfactants: The chemical reaction of hydrocarbons extracted from petroleum or fats and oils produces new acids similar to fatty acids. An alkali is then added to the new acid to produce an anionic surfactant molecule.
  • Nonionic Surfactants: Hydrocarbons are first converted to alcohols and then made to react with ethylene oxide. The surfactants thus generated are then reacted with sulfur-containing acids that help produce another type of anionic surfactant, called nonionic surfactants.

Characteristics of Detergent

The following are the main characteristics of the detergent:

  • Detergents are potassium/sodium salts of a long alkyl chain that contains a sulfonate group at the end of it.
  • Detergents are generally prepared via anionic detergents (i.e., alkylbenzene sulfonates) for domestic purposes.
  • Detergents are easily soluble in hard water.
  • The sulfonates used in detergents are responsible for solubility, which means that the sulfonate group does not attach with ions present within hard water.

Key differences between Soap and Detergent

Some essential key differences between soap and detergent are listed below:

  • The use of soap is traced back to the 18th century, whereas detergents were manufactured and used in the early 19th
  • Soaps are prepared with the help of natural ingredients, such as plant oils (i.e., vegetable oil, coconut oil, palm oil, pine oil, etc.) or acids departed from an animal's fat. On the opposite side, the detergents are human-made derivatives or synthetic cleaners.
  • Soap is used for limited cleaning purposes, while detergents, on the other side, can be formulated to involve other ingredients and perform all kinds of cleaning.
  • Soaps do not properly work with the hard water and usually form scum, which may deteriorate fabrics and ruin clothing or surfaces. Besides, detergents can easily work with any water regardless of their hardness, as they do not react much to most minerals in hard water.
  • Because soaps react to many minerals in the water, they require a clear wash after use; otherwise, they usually leave a film. On the other hand, the detergents are completely free rinsing and leave no residue after application.
  • Soaps are bio-degradable, which means they eventually break down to their base components and seamlessly attach themselves to the earth, leaving no toxic behind. On the other hand, detergents are not always bio-degradable. Some detergents are non-biodegradable and may break down in a harmful manner, leaving chemicals and other harmful toxins behind in the environment.
  • Soaps have weak cleansing action, whereas detergents have strong cleansing action.

Major Differences between Soap and Detergent

The major differences between soap and detergent can be tabulated as below:

Attributes Soap Detergent
Short Definition Soaps are usually defined as the cleaning material having potassium or sodium salts of fatty acids. Detergents are defined as powerful cleansing materials having potassium or sodium salts of sulphonic acids.
Contains Soaps contain a group of '-COONa' attached to a fatty acid consisting of a long alkyl chain. Detergents contain a group of '-SO3Na', which is attached to a long alkyl chain.
Effectiveness with hard water Soaps are not effective with hard water, saline water and acidic water. Detergents are very effective and work well with hard water, saline water, and acidic water.
Biodegradable property Soaps are entirely biodegradable. Detergents consisting of branched hydrocarbon chains are non-biodegradable.
Scum issue Soaps have been seen to form scum, especially when they are used with hard water. Detergents don't have any scum issues, not even with the hard water.
Made up of Soaps are made up using natural resources like animal fats and vegetable oils. Detergents are mostly synthetic derivatives and made up of synthetic resources like petroleum fractions.
Dissolve speed Soaps have comparatively slow dissolving speed in the water. Detergents have faster dissolving speed in the water.
Precipitate formation Soaps usually produce precipitate in acidic water. Detergents do not produce any precipitate, not even when used with acidic water.
Cleansing effect Soaps have a comparatively weak cleansing effect. They can be used for limited applications. Detergents are much better in cleansing and have a strong cleansing effect. Also, they are suited for different types of cleaning applications.
Irritation Soaps may irritate human skin. Detergents do not usually irritate.
Environment friendliness As discussed above, soaps are biodegradable, and so they are considered environmentally friendly. Because detergents are non-biodegradable, they can form a thick foam that kills aquatic lives.
Impact on the Environment Soaps are usually prepared using natural resources like vegetable oils and need more water for rinsing; they somehow impact the environment. Detergents use fewer natural resources and can easily work without extra water; they impact the environment less than soaps.
Examples The most common examples of soaps are sodium stearate and sodium palmitate. The common examples of detergents include deoxycholic acid, sodium lauryl sulfate and sodium dodecyl-benzene-sulphonate.
Suited for Soaps are best suited for cleaning body parts. Detergents are suited for various applications, such as laundry, carpet care, degreasing, floor cleaning, etc.

How do Soap and Detergent work?

The cleansing action of soap or detergent can be explained in the following four steps:

  • In the first step, we are required to make the surface wet with the water. However, the water alone is not sufficient for cleaning any surface.
  • In the next step, we need to apply soap or detergent to the surface, which gets absorbed. Both soaps and detergents are surface-active agents, called surfactants. These surface-active molecules of soaps and detergents completely dissolve in water. This solution loosens the surface tension or force that holds molecules together on the surface or fabric. This helps the water to spread properly on the surface or get soaked in the fabric.
  • In the third step, when the clothes are rubbed together by hand or in the washing machine, the dust particles break down because of the surface-active molecules act. This separates the dirt from the clothes and stores them in water.
  • In the cleaning process's last step, the segregated dirt is prevented from going back on the clean cloth's surface. Dirt particles are coated with soap and detergent molecules. This keeps them hanging in the water until the dirt is rinsed off.

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