Soaps and Detergents, Paints - Chemistry, General Science UPSC Notes | EduRev

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UPSC : Soaps and Detergents, Paints - Chemistry, General Science UPSC Notes | EduRev

The document Soaps and Detergents, Paints - Chemistry, General Science UPSC Notes | EduRev is a part of the UPSC Course Science & Technology for UPSC CSE.
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A soap is actually, a specific type of salt, the hydrogen alone of the fatty acid being replaced by a metal, which in common soaps is usually sodium. A typical commercial cleaning soap is prepared by reacting sodium hydroxide with a fatty acid. The lower the hydrogen content of the acid, the thinner the soap. The by-product of reaction is glycerol. Many different carboxyl-containing substances are used, including, vegetable and animal oils, and fats, (stearic, palmitic, and oleic acids). Transparent soaps are made from decolorized fats.

Heavy Metal Soaps (Metallic Soaps)

These are soaps (formed by metals heavier than sodium (aluminium, calcium, cobalt, lead, zinc). These soaps are not water soluble, specific types are used in lubricating greases, get thickeners, and in paints as driers and flattening agents.


Any substance that reduces the surface tension of water, specifically, a surface active agent which concentrates at oil-water interfaces, exerts emulsifying action and thus aids in removing oils, is termed as detergent. Chemically, detergents are quite different from soaps, the salt of higher fatty acids.
Detergents

Synthetic detergents are preferred to soaps on account of economy and efficiency. Unlike soaps, the synthetic detergents remain unaffected by the presence of naturally occurring lime and magnesium salts, and maintain their cleansing potentialities with practically no wastage. Certain synthetic detergents remain active even in acidic solutions.
In households, synthetic, detergents are used in powdered form mostly for washing clothes, linen and other textiles. Liquid detergents are employed for dish washing and for cleaning floors and walls. The principal types of synthetic detergents are: Anionic, non-ionic and the ampholyties.The popular anionic type is the sodium dodecyl benzene sulphonate while the non-ionic type is nonylphenol polyethylene oxide obtained from ethylene oxide. To the class of ampholyties, belong the N-alkyl * amino propionates which behave like cations in acidic solutions and like anions in alkaline solutions. But the most widely used group comprises linear alkyl benzene (LAB). 

Paints 

Paints is a mechanical mixture consisting of pigments and extenders suspended in a vehicle. The make dilute or thin, other volatile liquids like turpentine or acetone is added. Extenders are low gravity materials used in paint to increase pigment volume concentration, and thus decrease the gloss. Vehicle: A term used to indicate liquid portion of a paint, comprising of drying oil or resin, solvent and thinner in which the solid components are dissolved or dispersed.

Types of Paints

(A) Latex Paint: It is composed of dry powders. The principal latex paints and styrene butadiene, polyvinyl acetate and acrylic resins.

(B) Inorganic paint: It is a potassium silicate based corrosion resistant for use on bridges and other metal work subject to marine environment.

(C) Metallic paint: A paint in which the primary pigment is a finely divided metal dispersed in vehicle. Most common metallic paint is aluminium paint.

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