Soaps and Detergents:Chemistry of Surfactants

Soaps and Detergents are chemical compound or mixture of compounds used as a cleansing agent.

Soap

Soap is a sodium salt or potassium salt of many combinations of fatty acids having cleansing action in water. Some of the examples are: Sodium stearate, sodium oliate and sodium palmitate formed using stearic acid oleic acid and palmitic acid. The soaps contain fats and oils.

Manufacturing Process of Soap

The fats and oils required for manufacturing soaps are extracted from the plants and animals. To make the fatty acids called triglyceride molecule, three fatty acid molecules are added with the one molecule of glycerine. Fatty acids are weak acids composed of two parts. A carboxylic acid group having one hydrogen (H) atom, two oxygen (O) atoms, and one carbon (C) atom, and a hydrocarbon chain attached to the carboxylic acid group. Normally, it is made up of a long straight chain of carbon (C) atoms carrying two hydrogen (H) atoms. Earlier the alkali required for making soaps were obtained from the animals but now they are clinically composed. The common alkalis used in soap making are sodium hydroxide (NaOH), also called caustic soda; and potassium hydroxide (KOH), and also called caustic potash.

Saponification

Saponification is the most common process used for soap making. A number of fats and oils are heated and mixed with a liquid alkali to produce soap and water (neat soap) plus glycerine.

Neutralization

Fats and oils are hydrolyzed with a high-pressure steam to get crude fatty acids and glycerine. The fatty acids are purified by distillation and neutralized with an alkali to produce soap.

When sodium is used as alkali, the soaps formed are solid and hard. On the other hand the soaps having potassium as Alkali are much softer and liquid in shape. The cleaning property of soaps much depends on the hardness of the water which contains harmful minerals. Hence we make use of surfactants.

Detergents

Detergent surfactants are much better solutions for the cleaning purpose as the hardness of water does not affect them. Today detergent is a better liquid form solution used for cleaning purposes. The surfactants used in detergents are made up of petrochemical solutions. Some of them are: Petrochemicals and Oleo chemicals, sulfurtrioxide, sulphuric acid and ethylene oxide. As an alkali potassium and sodium are used.

Manufacturing of Detergents

• Anionic Surfactants: The chemical reaction of hydrocarbons extracted from petroleum or fats and oils produce new acids similar to fatty acids. Then an alkali is added to the new acid to produce anionic surfactant molecule.
• Non-ionic Surfactants:  The hydrocarbon are first converted to an alcohol and then made to react with ethylene oxide. Thus produced surfactants are then reacted further with sulphur-containing acids to form another type of anionic surfactant.

Safety measures taken in manufacturing of Soaps and Detergents

The safety of these products is the priority because they are directly used by the human beings. To measure the safety first the toxicity (any harmful effect) is measured. Secondly to find out the frequency and duration of the product the solution is exposed to the environment since it has the water contents, they evaporate and the effect of the soluble is measured. Thirdly the effects are measured on the scales of effectiveness and reactions. Finally the potential risk is measured to find out the feasibility of the product, whether it can be used or not. These safety measures are important to find out the concentration level of the solution which can have harmful effects.