soap and other elements

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MONIKA

XII


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SOAP

Introduction

Saponification

Soap molecule(Micelles)

Cleansing action ofsoaps

Advantages anddisadvantages

DETERGENT

Introduction

Cleansing action ofdetergents

DIFFERENCESBETWEEN SOAPSAND DETERGENTS


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SOAPS


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Soaps are the sodium and potassium salts ofthe long chain carboxylic acid.A soapmolecule consists of a long hydrocarbon chain

(composed of carbons and hydrogens) with acarboxylic acid on one end which is ionicbonded to metal ion usually a sodium orpotassium.

A soap has a large non-ionic hydrocarbongroup and an ionic group COO-Na+.


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Sodium stearate (Chemical formula:C17H35COO-Na+)

Sodium palmitate (Chemical formula:

C15H31COO-Na+) Sodium oleate (Chemical formula:

C17H33COO-Na+)


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The process of making soap by the hydrolysisof fats and oils with alkalies is calledsaponification.

Soap is made by heating animal fats orvegetable oil with concentrated sodiumhydroxide (NAOH).

Fat or Oil + NaOH Soap + Glycerol


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Glyceryl tripalmitate(tripalmitin)

Glycerol 3 sodium palmitate(soap)


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A soap molecule has two ends withdifferent properties-

1. A long hydrocarbon part which ishydrophobic (i.e. it dissolves inhydrocarbon).

2. A short ionic part containing COO-Na+ which is hydrophilic (i.e. itdissolves in water).

micelle


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ADVANTAGES

Soaps are eco-friendlyand bio degradable

DISADVANTAGES

Soaps are not suitablein the hard water.

They have weakcleansing propertiesthan detergents.


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DETERGENTS


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Detergents are the sodium salts of long chainbenzene sulphuric acids.

Detergents are primarily surfactants, which

could be produced easily frompetrochemicals. Surfactants lower the surfacetension of water, essentially making it 'wetter'so that it is less likely to stick to itself and

more likely to interact with oil and grease. The ionic group is in a detergent is


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Synthetic detergents have the same type of molecular structure assoaps i.e. a tadpole like molecule having two parts at each end i.e.,one large non-polar hydrocarbon group that is water repelling(hydrophobic) and one short ionic group usually containingthe or group that is water attracting (hydrophilic). Thus thecleansing action is exactly similar to that of soaps whereby the

formation of micelles followed by emulsification occurs. However,synthetic detergents can lather well even in hard water. This isbecause they are soluble sodium or potassium salts of sulphonic acidor alkyl hydrogen sulphate and similarly form soluble calcium ormagnesium salts on reacting with the calcium ions or magnesiumions present in water. This is a major advantage of the cleansingproperty of detergents over soap.


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Since detergents are the salts of strong acids they donot decompose in acidic medium. Thus detergentscan effectively clean fabric even if the water is acidic.

Synthetic detergents are more soluble in water thansoaps.

They have a stronger cleansing action than soaps.

As detergents are derived from petroleum they save

on natural vegetable oils, which are important asessential cooking medium


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Many detergents are resistant to the action ofbiological agents and thus are not biodegradable.Their elimination from municipal wastewaters by theusual treatments is a problem.

They have a tendency to produce stable foams inrivers that extend over several hundred meters of theriver water. This is due to the effects of surfactantsused in their preparation. Thus they pose a danger toaquatic life.

They tend to inhibit oxidation of organic substancespresent in wastewaters because they form a sort ofenvelope around them.


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SOAPS

They are metal salts oflong chain higher fattyacids.

These are prepared fromvegetable oils and animalfats.

They cannot be usedeffectively in hard water as

they produce scum i.e.,insoluble precipitates ofCa2+, Mg2+, Fe2+ etc.

DETERGENTS

These are sodium salts oflong chain hydrocarbonslike alkyl sulphates or

alkyl benzene sulphonates. They are prepared from

hydrocarbons of petroleumor coal.

These do not produce

insoluble precipitates inhard water. They areeffective in soft, hard orsalt water.

soap and other elements

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