What are detergents and soaps?

What are detergents?

Detergents are cleansing agents that have all the properties of soaps, but which actually do not contain any soap. Detergents can be used in both hard and soft water as they give foam even in hard water.

What are ionogenic and non-ionogenic detergents?

Ionogenic Detergents: The detergents that have anionic or cationic are termed ionogenic detergents that include sodium lauryl sulfate [CH₃(CH₂)₁₀CH₂OSO₃^–Na⁺] as Anionic detergents and letyl tri methyl ammonium bromide [CH₃(CH₂)₁₅ -N(CH₃)₃]⁺ Br^-1 as cationic detergents.

Non-ionogenic detergents: Non-ionic detergents do not contain any ion in their constitution.

Give the principle of the detergent’s cleaning action.

Principle of the cleaning action of detergents: The mechanism of the cleansing action of detergents is the same as that of soaps. They also remove grease and oil by micelle formation. In anionic detergents; the anionic part of the molecules is involved in the cleansing action in the cationic part possesses a long hydrocarbon chain and a positive charge on the nitrogen atom is involved in the cleansing action.

What is soap? How it is manufactured ?

Soap: Soap is an alkali salt of a higher fatty acid derived from an oil or fat and is obtained by hydrolyzing the oils or fats with caustic alkalies. If the alkali is used in NaOH we get hard soaps and if it is a caustic potash we get soft soaps. The process is called ‘saponification’ and the lines of the two methods commonly employed in its manufacture.

How soaps are manufactured

1. The cold process: It is used on a small scale and the foreign matter present in the oil as well as the glycerol formed as a result of saponification is allowed to remain in the soap. A certain amount of the oil or fat is taken in an open pan and warmed to a suitable temperature (50-60°C) depending upon the weather. The pan is provided with a stirring arrangement. The calculated quantity of caustic soda solution of the required specific gravity (called lye) is now slowly added with regular stirring. The thick paste produced as a result of saponification is transferred to a soap frame where it is allowed to remain for a few days and then taken out and cut into bars.
2. The Hot process: Two special features of this process are :
   (a) Any the of oil or fat can be utilized and its saponification is complete.
   (b) Glycerol is recovered as an important by-product.

The process is carried out in cylindrical copper kettles provided with steam pipes. The requisite amount of the lye is added in installments while the whole mass is being agitated with the open stem. After it has become homologous and clear, a common slat is thrown in when soap separates out. This process is called salting out of soap and is based on the principle of Solubility product.

The lower aqueous layer known as spent lye is treated for the recovery of glycerol. The soap which comes to the surface has a granular shape due to the loss of water. It is first boiled with caustic soda solution to ensure complete ‘saponification and then with water (hydration). The pasty mass thus produced is transferred to soap frames and allowed to solidify.

To get toilet soap, the solid mass is shredded into very small chips which are thoroughly mixed with perfume and color and then compressed into tablets. Rasin if added to the extent of 10% of the soap, increases its solubility. Filling materials like sodium silicate, finely powdered soap-stone, etc are added to cheap toilets as washing soaps to increase their bulk. In the presence of a filling material,the soap absorbs a large amount of water.

To manufacture transparent soap, the common toilet soap is dissolved in alcohol and the filtrate is ex exaporated to expel alcohol, the residue on solidification gives a transparent soap.