[Chemistry Class Notes] on Soaps and Detergents Pdf for Exam

Soaps and detergents are known as the chemical compounds of a mixture of compounds that are used as cleansing agents. A soap is either sodium or potassium salt of different combinations of fatty acids that possess cleansing action in the water. On the other hand, detergents are far better solutions when it comes to cleaning purposes since they are not affected by the hardness of the water.

()

What is Soap?

Soaps are sodium or potassium salts of several combinations of fatty acids and have cleansing action in combination with water. They consist of several fats and oils as well. Examples of soap include sodium oleate, sodium stearate, and sodium palmitate.

Soap consists of 2 primary raw materials: (i) fat and (ii) alkali. Alkali is the most commonly used material and is also called sodium hydroxide. Potassium hydroxide is also used in manufacturing soaps. Potassium-based soap is also called soft soap because it creates a more water-soluble product than sodium-based soap. Softsoap is generally used in shaving products, alone or in combination with sodium-based soaps.

Manufacturing Process of Soap

Both fats and oils are needed to make soaps and they are extracted from animals and plants. For making the fatty acid molecules like those of triglycerides, three molecules of fatty acids get added to one molecule of glycerine. These fatty acids are weaker and consist of two different parts. One is a carboxylic group that consists of one hydrogen atom, two oxygen atoms and one carbon atom. The other is a hydrocarbon chain that is attached to the carboxylic acid group. Generally, soap is created from a long chain of carbon atoms that carry two hydrogen atoms. Previously, the alkali which was needed to make soaps was derived from animals, but today it is clinically composed. The common alkalis that are used to make soaps are sodium hydroxide, which is commonly called caustic soda, and potassium hydroxide, which is commonly called caustic potash.

The manufacturing process of soaps consists of the following different methods.

The most common method used to make soaps is known as saponification. A greater number of fats and oils get heated up and are then mixed into a liquid alkali for producing soap and water and glycerine.

Fats and oils get hydrolyzed in the presence of high pressurized steam for getting crude fatty acids along with glycerine. These fatty acids are then purified by the process of distillation and neutralized through an alkali to give a soap.

When sodium is used in the form of an alkali, the soaps that are formed are hard and solid. The soaps that contain potassium as an alkali liquid are much softer. The cleansing property of soaps entirely depends on how hard the water is since hard water consists of harmful minerals. For the same reason, detergent surfactants are preferred over soaps.

Detergents

The detergent surfactants are far better solutions when it comes to cleansing purposes since the hard water does not have any effect on them. Detergents today are much better liquid solutions for cleaning purposes. The surfactants that are used to make detergents are made through petrochemical solutions like sulphur trioxide, sulphuric acid, ethylene oxide, and oleochemicals. Sodium and potassium are used as alkalis in the detergents, just like soaps.

Detergents can be dissolved in saline water as well as hard water. They do not form layers hence they can even clean the dirt in hard water. They are used in acidic water, salty water, and for washing woollens and they are not affected by the acidic dyes in them. Detergents can be more dissolved in water than many soaps. Because detergents that have linear hydrocarbon chains do not cause pollution, they are biodegradable.

Manufacturing of Detergents

Detergents is manufactured in the following manner.

The hydrocarbons that are extracted from the fats and oils or petroleum undergo a chemical reaction and produce newer acids that are similar to the fatty acids. An alkali is then added to the newer acid produced and this gives anionic surfactant molecules.

Initially, the hydrocarbons are converted to alcohol and are then reacted with ethylene oxide. The surfactants produced are then reacted further with the acids containing sulfur and form another kind of anionic surfactant. 

Properties of Soaps and Detergents

Soaps and detergents have similar functions, but they do differ in chemistry and performance. With the help of the experiments performed in class or lab, students will be able to analyze the similarities and differences in the properties of soap and detergent, which can be done by analyzing foaming ability, testing pH, fat emulsification, examining the effect of soap and detergent on the surface tension of water, and the performance of soap and detergent in hard water. 

Difference between Soaps & Detergents

 

Advantages and Disadvantages of Detergents over Soaps

Detergents have an ample range of advantages over soaps. Hence, they are replacing soaps as washing agents. Detergents are better than soaps because of the following reasons:

• Detergents are more soluble in water than soaps.

• Soaps are not suitable for use with saline water and
  hard water, whereas detergents can be used even with saline water and hard water.

• Detergents have a more powerful cleansing action than soaps. 

The only disadvantage of detergents over soaps is that some of the detergents are not biodegradable.

Example of Soap and Detergent

The examples of soaps and detergents include:

1. Examples of Soaps – Sodium stearate and sodium palmitate

2. Examples of Detergents – Sodium lauryl sulfate or SLS, and deoxycholic acid

In the above article, the manufacturing of soaps and detergents as well as the difference between them is also discussed. It is useful for students to understand soaps and detergents.