Preparation of Soap
Preparation of Soap
Preparation of Soap
Theory
Soaps are an integral part to maintain the good health and hygiene of individuals.
They are essential to cleanse dirt and oil off the objects including the skin surface,
and they are widely used in bathing, cleaning, washing and in other household
chores. Saponification is the hydrolysis of an ester with NaOH or KOH to give
alcohol and sodium or potassium salt of the acid. Soap is now an essential
everyday item and finds its importance in everyday life. But, how is soap made?
Saponification is simply the process of making soaps. Soaps are just potassium or
sodium salts of long-chain fatty acids. During saponification, ester reacts with an
inorganic base to produce alcohol and soap.
Saponification Reactions
Triglycerides are generally animal fats and vegetable oils. When they are reacted
with sodium hydroxide, a hard form of soap is created. This is where potassium
comes in and creates a softer version of the soap.
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The equation can be written as:
In a saponification reaction, a base (for example sodium hydroxide) reacts with any
fat to form glycerol and soap molecules. One of the saponification reactions taking
triglyceride as an ester and sodium hydroxide as the base is as follows:
Chemicals materials
Boiling chips
Procedure:
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Your instructor has a container of olive oil, preheated to 35°C, at a central
location in a crock pot. Pour 20 ml of the warm oil into a tall 250 mL
beaker. Add a magnetic stir bar to the beaker.
Add 40 of 20%sodium hydroxide solution to the beaker carefully and
slowly to the beaker. Don’t let the sodium hydroxide splash on you or the
counter.
Start the magnetic stirrer on low and don’t let the solution splash out of the
beaker. You must stir for 20-45 minutes. The mixture will slowly become
smoother and more opaque; it should thicken to a pudding-like consistency.
Pour the clear soap solution into another beaker which contain saturated
brain solution. And place in ice bath; finally, filter the soap solution through
filter paper.
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Cleansing Action of Soaps and Detergents in hard water
Objective: to investigate cleansing action of soap and detergent.
Theory
In our day to day lives, we often use detergents and soaps to clean the dirt off
our clothes. Have you ever wondered what soap molecule is made up of or how
it cleanses the dirt? In this session, we shall look upon the structure of soap and
its cleansing action but before that, we shall give a simple definition of what
soap is.
What are Soaps? Saponification reaction is the reaction between an ester and
base to give alcohol and soap as the products. The general form of saponification
reaction is shown below.
Properties of Soaps:
Hard in nature: Soaps are generally hard in nature i.e. they are in solid form.
Cleansing Action: Soaps are effective to clean away the dirt from a surface.
Soaps have a hydrophobic tail and hydrophilic head which are equally
important in the cleaning process.
Lather formation: Soaps form lather with soft water.
Conditioners: Soaps contain conditioners called emollients that are
responsible to moisturize our skin once we use the soap.
Fragrant: Soaps generally have a unique fragrance added to them. These
fragrances help calm us, soothe our minds and remove our body odours.
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Structure of Soap
Hydrophobic tail: This part of the soap is water repellent in nature and
dissolves in oils. It is made up of a long chain of hydrocarbons.
Hydrophilic head: This part of the soap molecule is water attractive or water-
loving and dissolves in water. It is ionic in nature
The dirt is generally oily in nature and insoluble in water. The soap cleanses the
dirt by the process of micelle formation. Before we study the cleansing action of
soap in detail, we need to understand what micelle is.
What is micelle?
A micelle is formed by the cluster of molecules where the molecules arrange
themselves in a spherical shape with the hydrophobic end facing inwards and the
hydrophilic end facing outwards.
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The soap molecules form micelles in water and perform cleansing action as
follows:
As we know soap has a hydrophobic and hydrophilic part, so when the soaps
are dissolved in water, the hydrophilic end is attracted by water and faces
outwards while the hydrophobic tail is repelled by water and faces inwards.
The below image shows soap molecules with the hydrophobic end facing
away from water while the hydrophilic end facing towards water.
Now, these molecules start aggregating around the dirt molecule with the
hydrophilic head outwards and the hydrophobic tail towards the dirt
molecule i.e. away from the water and form a spherical cluster of molecules
that are known as a micelle. Micelle formation by soap molecule is shown
below in the image.
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Advantages of soaps:
Soaps are readily available, cheap and convenient to use.
Soaps are very effective for cleaning in soft water
They are 100% biodegradable in nature and do not cause pollution as they
are easily degradable by the bacteria in the sewerage.
Disadvantages of soap:
Soaps are not effective for cleaning in hard water as they form scum with
hard water instead of lather formation. The reaction of soap with magnesium
ions in hard water is shown below. Soaps react with magnesium and calcium
ions from hard water to form calcium or magnesium salts of fatty acids
which do not dissolve in water and form a white precipitate that is
called scum.
2RCOO−Na+ + Mg2+ → (RCOO)2Mg + 2Na+
Scum sticks to clothes and makes washing difficult
Highly branched soaps are not easily degradable and cause pollution.
As soaps are basic in nature, they cannot be used to clean woolen garments
as they have acidic dyes.
What is Detergent?
Amphipathic molecules that contain charged hydrophilic or polar groups at the end
of long lipophilic hydrocarbon groups are called detergents. The charged
hydrophilic group is also called the head and the long lipophilic hydrocarbon group
is called the tail. Detergents are also known as surfactants as they have the ability
to decrease the surface tension of water. A detergent is a surfactant or mixture of
surfactants that has cleaning properties in dilute solution with water. A detergent is
similar to soap, but with a general structure R-SO 4-, Na+, where R is a long-
chain alkyl group. Like soaps, detergents are amphiphilic, meaning they have both
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hydrophobic and hydrophilic regions. Most detergents are akylbenzenefulfonates.
Detergents tend to be more soluble in hard water than soap because the sulfonate
of detergent doesn't bind calcium and other ions in hard water as easily as the
carboxylate in soap does.
Materials chemicals
Procedures
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Objective: To Estimate the Saponification value and iodine value of oils.
Fats and oils are the principle stored forms of energy in many organisms. They are
highly reduced compounds and are derivatives of fatty acids. Fatty acids are
carboxylic acids with hydrocarbon chains of 4 to 36 carbons; they can be saturated
or unsaturated. The simplest lipids constructed from fatty acids
are triacylglycerols or triglycerides. Triacylglycerols are composed of three fatty
acids each in ester linkage with a single glycerol. Since the polar hydroxyls of
glycerol and the polar carboxylates of the fatty acids are bound in ester linkages,
triacylglycerols are non polar, hydrophobic molecules, which are insoluble in
water.
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The saponification number is the number of milligrams of potassium
hydroxide required to neutralize the fatty acids resulting from the complete
hydrolysis of 1g of fat (oil). It gives information concerning the character
of the fatty acids of the fat- the longer the carbon chain; the less acid is
liberated per gram of fat hydrolyzed. It is also considered as a measure of the
average molecular weight (or chain length) of all the fatty acids present.
The long chain fatty acids found in fats have low saponification value
because they have a relatively fewer number of carboxylic functional groups
per unit mass of the fat and therefore high molecular weight.
Principle:
Fats (triglycerides) upon alkaline hydrolysis (either with KOH or NaOH) yield
glycerol and potassium or sodium salts of fatty acids (soap) .
Iodine value
Iodine value also called the iodine number is the amount of iodine in grams
consumed by 100 grams of a chemical compound. The relative degree of
unsaturation in oil components is measured by the iodine value, which is obtained
by halogen uptake. Because the degree of unsaturation affects the melting
point and oxidative stability,
Generally, the amount of milligrams of KOH required to neutralize the fatty acids
produced by full hydrolysis of 1 gram of an oil sample is known as the
saponification value, whereas the Iodine value is the amount of iodine that 100
grams of a particular substance can absorb.
Ws
Where: Vb is volume of sodium thiosulphate for blank
N is normality of Na2S2O3
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Refluxing condenser Iodine monochloride reagent
Umber color flask chloroform
Iodine flask potassium iodide
25ml pipette 0.1 N sodium thiosulphate
Round bottom flask 1% starch indicator solution
Iodine monochloride reagent (20 ml) should be added to the flask. The
flask’s contents should be completely combined.
The flask is then let to stand for a half-hour incubation period in the dark.
In another iodination flask, create a BLANK by adding 10 ml of chloroform
to the flask.
20 ml of Iodine Monochloride Reagent should be added to the BLANK, and
the contents of the flask should be thoroughly mixed.
The BLANK should be kept in the dark for 30 minutes.
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After 30 minutes of incubation, remove the TEST from the incubation
chamber, and then pour 10 ml of potassium iodide solution into the flask.
50 cc of distilled water should be used to rinse the stopper and the flask’s
sides.
Titrate the “TEST” until a pale straw color is seen when it is compared to a
standardized sodium thiosulphate solution.
A purple color is seen after adding around 1 ml of starch indicator to the
contents of the flask.
Till the solution in the flask loses its color and becomes colorless, keep
titrating.
The titration’s conclusion is marked by the blue color’s absence.
The process is also done for the flask marked “Blank.”
Note the BLANK’s endpoint values.
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