Cleansing Action of Soaps and Detergents

Cleaning a soiled surface appears to be a simple process, but it is quite complicated and involves several physical-chemical steps. If oil droplets and dirt particles were not suspended in the detergent solution in a stable and widely dispersed state, they were more likely to flocculate or coalesce into aggregates large enough to reappear on the cleansed surface.

Tiny oil droplets or fine, deflocculated dirt particles are more easily carried through interstices in fabrics and similar materials during washing than relatively large ones. As a result, the detergent’s action in keeping the dirt dispersed is critical in preventing the fabric from retaining detached dirt.

The cleansing action of soaps and detergents

The ability of soaps and detergents to lower the surface tension of water, emulsify oil or grease, and hold it in suspension in water results in their cleansing action. The structure of soaps and detergents contributes to this ability. A sodium soap dissolves in water, forming soap anions and sodium cations.

What are Soaps?

Soap can be defined chemically as a combination of vegetable oils (or animal fats) with sodium or potassium hydroxide in a saponification reaction. So basically, soaps are nothing but salts of potassium or sodium salts with long-chain fatty acids. The composition of soaps makes it water-soluble, and that is why it starts to dissolve when placed in water.

Characteristics of Soap

1. Hardness: Soaps are usually hard. Thus, their appearance is solid.
2. Cleansing action: Soaps are an excellent cleansing agent, which means they are good at removing dirt from surfaces. Soaps have both a hydrophobic tail and a hydrophilic head, both of which are crucial in the cleaning process.
3. Formation of lather: Soaps create a lather when used with soft water.
4. Conditioners: Emollients, which are found in soaps, are responsible for moisturising our skin after we use them.
5. Scent: Soaps usually have a distinct scent added to them. These scents help to relax us, soothe our minds, and eliminate odours from our bodies. 

What Are Detergents?

A surfactant or a mixture of surfactants with cleansing properties is used as a detergent in dilute solutions. The most common detergents are sodium salts of long-chain alkyl hydrogen sulphate or long-chain benzene sulphonic acid.

Types of Detergents

1. Cationic: Cationic detergents have a polar group called a cation, which means they are positively charged.
2. Anionic: Anionic detergents are those in which the detergent’s hydrocarbon chain is an anion or negatively charged.
3. Non-Ionic: They don’t have an ionic component, so the cleansing part isn’t charged.

Properties of Detergent

1. Detergents are called surfactants because they lower the surface tension of the water.
2. Detergents, like soaps, are water-soluble. Detergents dissolve even in hard water and do not produce scum, resolving one of the soap’s major drawbacks.
3. The critical micelle concentration is the concentration at which particle formation begins (CMC).

Structure of soaps and detergents

A soap is a salt of a long chain of fatty acids of sodium or potassium. As a result, soap is composed of two parts: an ionic component and a long carbon chain. The properties of the two halves of the soap molecule are quite different. The following are the names of these two sections:

• Hydrophobic part: This portion of the soap is naturally water repellent and dissolves in oils. It has an ionic nature.
• Hydrophilic part: This part of the soap molecule attracts water and dissolves in it. A long chain of hydrocarbons makes up the substance.

Cleansing Action of Soaps and Detergents

• Soaps and detergents clean by lowering the surface tension of water, emulsifying oil or grease, and holding it in suspension in water.
• Because of the structure of soaps and detergents, they have this ability.
• A long hydrocarbon chain with a carboxylate group on one end makes up a soap anion. 
• In oils or grease, the hydrocarbon chain, which is hydrophobic, is soluble. 
• The carboxylate group, which is hydrophilic and soluble in water, is the ionic component.
• A detergent’s anion part also has a hydrophobic and a hydrophilic component.
• Most of the time, the dirt which is there on any surface is oily in nature, because of which it is also insoluble in water. And because soap is a molecule that is made of long fatty carbon chains which can dissolve in oil helps to clean the surface.
• As we know, the carbon chain dissolves in oil, while the ionic part dissolves in water. Micelles are formed when soap molecules join together to form micelles. Micelles have two finishes: one is oriented toward the oil drop, and the other is oriented toward the outside.
• As a result, it forms an emulsion in water and aids in the dissolution of dirt after we wash our clothes.

What is micelle?

When the water-loving part of the soap, i.e, the hydrophilic part sticks its head in the water and points outwards, forming micelle.

Conclusion 

Soaps and detergents are cleaning agents that help remove dirt, bacteria, and other unwanted particles from the human body as well as other surfaces. Soaps are sodium or potassium salts of carboxylic acids with a long chain. Ammonium or sulfonate salts of long chains of carboxylic acids are used as detergents.

When soap and detergent are dissolved in water, the hydrophilic end is attracted to the water and faces outwards, whereas the hydrophobic tail is repelled by the water and faces inwards. These molecules begin to clump together around the dirt molecule, with the hydrophilic head facing outwards and the hydrophobic tail facing inwards, forming a micelle, a spherical cluster of molecules. Because the dirt is now trapped within the micelle, the soap molecule in the form of micelles can clean it.