MODULE-5/5

CHEMISTRY IN EVERY DAY LIFE

CLEANSING AGENTS- SOAPS & DETERGENTS

Chemicals which concentrate on a

surface of solution form surface films, reduce surface tension, and help in removing dirt and dust are called

surface active agents or surfactants or cleansing

agents.

They contain two parts

Hydrophilic –water soluble

part

Lyophilic – oil soluble part

Soaps & Detergents

SOAPS

• Sodium and potassium salts of higher fatty acids such as lauric(C11H23COOH), Palmitic acid(C15H31COOH), stearic acid(C17H35COOH) or Linoleic acid(C17H31COOH)

• Saponification-When sodium hydroxide and glyceryl ester of fatty acid are heated together soaps are formed.

• Soap obtained in colloidal form is precipitated from solution by adding sodium chloride.

• Lye- solution left behind after removal of soap. It contains glycerol which is removed by fractional distillation.

• Soaps used for cleansing purpose are generally sodium and potassium salts which are water soluble.

Types of soaps-

• Toilet soap, floating soaps, transparent soaps, shaving soaps, medicated soaps, laundry soaps, soap chips, soap granules, soap powders and scouring soaps.

• Sequestration- Sodium tri phosphate an important builder (20%-45%) is added to detergents and liquid soaps to soften hard water by removing Mg2+, Ca2+ ions thus forming soluble complexes.

• Advantages of soaps- good cleansing agents, 100% bio- degradable, Oxides soap to CO2, does not cause pollution.

• Disadvantages of soaps- Cannot be used in hard water as they form scum. Thus, cleaning action is less, and wastage is more. Ex: washed hair looks dull; dye is unevenly absorbed on cloth. They cannot act in acidic solutions as they already contain acids.

Synthetic Detergents

• Syndets / Soapless soaps

• They are sodium salts of long chain sulphonicacids or

• Ammonium sulphonate or sulphate salts of long chain hydrocarbons containing12-18 carbon atoms.

• Detergents also called soapless soaps as they show all properties of soaps but do not contain sodium salts of higher fatty acids.

• Advantages of detergents-They can be used in hard water as they form soluble salts of Mg2+ and Ca2+, don’t form scum, show action in acidic solutions also as they are salts of sulphonic acid which is soluble in water. Some give foam even in ice cold water.

• Disadvantage of detergents- They are non- bio- degradable and cause water pollution. Foaming in rivers, ponds, streams etc. is due to effluents remaining in water inspite of sewage treatment.

• Note- Unbranched chains of hydrocarbons are comparatively more biodegradable than the branched chain counterparts and so are presently more in usage in detergents.

•

Classification of detergents

• Anionic detergents- The anionic part of molecule is involved in cleaning action. They can be

• Sodium alkyl sulphates.

• Sodium alkyl benzenesulphonates-

• Commonly used as household detergents and in toothpastes.

• Ex- sodium4-(1-dodecy) benzenesulphonate (SDS)

Classification of detergents

• Cationic detergent-

• Also referred to as Invert soaps

• Cationic detergents are quarternary ammonium salts of amines with acetates, chlorides, or bromides as anions and long hydrocarbon chain attached to nitrogen carrying positive charge.

• Cationic part of the molecule is involved in cleansing action.

• Have germicidal properties.

• Used in hair shampoos & hair conditioners. Ex-Cetyltrimethylammonium bromide

Classification of detergents

• Non-ionic detergents- The constitution of these molecules does not have any ion in them.

• They are esters of high molecular mass alcohols and are obtained by reaction between stearic acid and polyethylene glycols.

• Used as liquid dishwashing detergents.

• Remove oil and grease by Micelle formation.

Acknowledgement-

The content is referred from:

Chemistry NCERT textbook part II Class XII

New course chemistry Part-II Class XII