Objective:
To calculate
saponification number
I
Introduction:
Saponification is the hydrolysis of fats or oils
under basic conditions to afford glycerol and the salt of the corresponding
fatty acid. In saponification, a water molecule is removed from a fatty acid or
an ester. Sodium stearate, sodium oleate or sodium palmitate is formed. It is
precipitated from the solution by addition of NaCl. The addition makes the
sodium salt of fatty acid partially insoluble in water and the product then
separates out of the solution the remaining solution has glycerol and sodium
chloride.
Apparatus and Materials
Corn oil
Solvent
0.5M KOH
Phenolphthalein
0.5M HCl
Procedure
Result:
Sample
|
Volume of HCl used
(litre)
|
Molarity of KOH x volume of HCl
|
Mol of reacted KOH
(Mol KOH)
|
Saponification number
= Mol KOH x 56.1 x 103
|
||
Blank
|
Test
|
Blank
|
Test
|
|||
Palm oil
|
0.0250
|
0.0245
|
0.0125
|
0.01225
|
0.0003
|
14.0 g
|
Corn oil
|
0.0260
|
0.0240
|
0.0130
|
0.0120
|
0.0010
|
56.1 g
|
Sunflower oil
|
0.0270
|
0.0220
|
0.0140
|
0.0110
|
0.0030
|
168.3 g
|
Discussion:
This week, an experiment on lipid
can be divided into two parts. The first part is a saponification of
triglycerides where the saponification number is measured. Saponification
number is equal to the measurement of the amount of KOH required to complete the
hydrolysis of one gram of fat or oil. For the second experiment, an application
on making soap is conducted.
For
the first experiment, three types of oils/triglycerides (palm oil, corn oil and
sunflower oil) have been used. These triglycerides were tested with HCl
solution with the presence of KOH and solvent via the titration process. Other
than that, a blank was used as a control for this experiment. The blank consist
of KOH and solvent, with the absence of triglyceride. Then the two solutions
were compared, which solutions required a larger amount of 0.5M HCl to
neutralize the samples from pink to colorless, either blank sample or test
sample. From the result obtained, proved that blanks samples utilized larger volume
of HCl for neutralization while test samples that contained triglycerides
required smaller amount of HCl for neutralization. For an experiment on palm
oil, 0.0250 L of HCL has been used to neutralize the blank whereas 0.0245 L of
HCl were used to neutralize the test sample. Second experiment on corn oil,
0.0260 L of HCl is able to neutralize the blank sample while only 0.0240 L of
HCl is able to neutralize the test sample. Next, an experiment on sunflower oil
shown that 0.0270 L is used to neutralize the blank while the test sample required
0.0220 L HCl for neutralization to be occurred.
As
the mol of reacted KOH is known, then the saponification number of each sample
can be calculated by using the formula provided. Noted that when the
saponification number of a sample is high, means the carbon chain of the fatty
acid in the triglycerides is short. The results shown that sunflower oil has
the highest saponification number, followed by corn oil and palm oil with the
values of 168.3 g, 56.1 g and 14.0 g. However, the results of corn oil and palm
oil was not correct and deviated from the actual values, while the
saponification number of sunflower oil was quite elevated from the actual
value. The results might be altered due to the parallax error while conducting
the experiment. The possible error which is obvious was while set up a reflux
condenser on the blank sample, right after conducting a test sample’s
experiment. The blank sample might be contaminated with the test sample’s
solution that contain triglycerides. As we know, triglycerides was difficult to
be removed unless soap or detergent is used. However, after test sample’s experiment
is done, the flask was not rinsed thoroughly and no detergent was available.
Hence, contamination between solutions did occur and alter the results totally.
The actual saponification number of corn oil is 136g while the actual
saponification number of palm oil is 141g, and the actual saponification number
for sunflower oil is 134 g.
By
comparing the actual saponification number of all triglycerides, palm oil has
the highest value, followed by corn oil and sunflower oil. Conversely,
sunflower oil has the longest chain of carbon, followed by corn oil and palm
oil with the shortest carbon chain. As stated before, sample with the lowest saponification
number has the longest carbon chain. This is because, longest chain has greater bond weight but less
fattty acid weight, thus less KOH is needed to hydrolyze the fatty acid and
this lead to the small saponification value.
Conclusion
Saponification number is determined by measuring the
amount of KOH required to complete the hydrolysis of one gram of fat or
oil. Saponification number for corn oil is 56.1g. When saponification number of a sample is
high, the carbon chain of the fatty acid in the triglycerides is
short. So, the carbon chain of fatty acid in the triglycerides for corn
oil is shorter than palm oil and longer than sun flower oil.
2. Application : Making Soap
Objective:
·
To make soap from corn oil.
Introduction:
Soap is a combination of animal fat or
plant oil and caustic soda. When dissolved in water, it breaks dirt away from
surfaces. Through the ages soap has been used to cleanse, to cure skin sores,
to dye hair and as a salve or skin ointment. Fats and oils are composed of
triglycerides, three molecules of fatty acids are attached to a single molecule
of glycerol. The alkaline solution, which is often called lye brings about a
chemical reaction known as saponification. In saponification, the fats are
first hydrolyzed into free fatty acids which then combine with the alkali to
form crude soap. Glycerol is liberated and is either left in or washed out and
recovered as a useful byproduct. Today we generally use soap as a cleanser or
perfume. Soap requires two major raw materials, fat and alkali. The alkali most
commonly used today is sodium hydroxide. Potassium hydroxide can also be used.
Potassium-based soap creates a more water-soluble product than sodium-based
soap, and so it is called "soft soap." Soft soap, alone or in
combination with sodium-based soap, is commonly used in shaving products.
In
this experiment, we have to make a soap by using corn oil. The alkali solution
that we use is sodium hydroxide.
Apparatus and materials:
·
60 ml of 6 M NaOH solution
·
17.5 g of corn oil
·
12.5 ml distilled water
·
50 ml hot sodium chloride solution
·
100 ml graduated cylinder
·
Stirring rod
·
400 ml beaker
·
250 ml beaker
·
Hot plate
·
Electronic balance
Methods:
Result:
Discussion:
Result:
The soap from the corn oil
Discussion:
In
this experiment we prepare soap from vegetable oil (corn oil, coconut oil and
palm oil.). Vegetable oils are esters of carboxylic acids; they have a high molecular
weight and contain the alcohol, glycerol. Chemically, these fats and oils are
called triglycerides. The principal acids in animal fats and vegetable oils can
be prepared from the natural triglycerides by alkaline hydrolysis
(saponification). The natural acids are rarely of a single type in any given
fat or oil. In fact, a single triglyceride molecule in a fat may contain three
different acid residues (R1COOH, R2COOH, R3COOH),
and not every triglyceride in the substance will be identical. Each fat or oil,
however, has a characteristic statistical distribution of the various types of
acids possible.
The fats and oils that are most
common in soap preparations are lard and tallow from coconut, palm, and corn
oil from vegetable sources. The length of hydrocarbon chain and the number of
double bonds in the carboxylic acid portion of the fat or oil determine the
properties of the resulting soap. For example, a salt of a saturated long-chain
acid makes a harder, more insoluble soap. Chain length also affects solubility.
Tallow is the principal fatty material used in making soap. The solid fats of
cattle are melted with steam, and the tallow layer formed at the top is
removed. Soap makers usually blend tallow with coconut oil and saponify this
mixture. The resulting soap contains mainly the salts of palmitic, stearic, and
oleic acids from the tallow, and the salts of lauric and myristic acids from the
coconut oil. The coconut oil is added to produce a softer, more soluble soap.
Pure
coconut oil yields a soap that is very soluble in water. The soap contains
essentially the salt of lauric acid with some myristic acid. It is so soft
(soluble) that it will lather even in seawater.Palm oil contains mainly two
acids, palmitic acid and oleic acid, in about equal amounts. Saponification of
this oil yields a soap that is an important constituent of toilet soaps. Corn
oil contains mainly oleic acid. It is used to prepare Castile soap, named after
the region in Spain in which it was first made.
Conclusions:
As a
conclusion for this experiment, the alkaline solution that we used, sodium
hydroxide which is often called lye brings about a chemical reaction known as
saponification. In saponification, the fats which is corn oil are first hydrolyzed
into free fatty acids which then combine with the alkali to form crude soap.
Questions:
1.
What
is the relationship between saponification and the phase of triglyceride?
For
any chemical reaction to occur, including saponification, it is necessary for
the reactants to be in the same phase (in this case, aqueous or organic).
Hydroxide will almost entirely exist in the aqueous phase, and the triglyceride
will be almost entirely in the organic phase. Increasing stirring will create
more interface for the reaction to proceed, and, as the reaction goes, we will
be producing glycerin and fatty acid salts, which can have appreciable solubility
in both phases. Thus, the reagents will increase in concentration in the phase
most favored by the other as the reaction progresses. To answer this, we need
to understand that we need to keep in mind the first sentence and remember that
the higher the concentration of the reactants, the more opportunity they have
to react and the faster the reaction will go.
2.
Why
do triglycerides with longer fatty acids have a lower saponification number
than those with shorter fatty acids?
Triglycerides
are composed of three fatty acids linked to glycerol by fatty acyl esters
(-O-CO-R). The fatty acids may be saturated (no C=C double bonds) or
unsaturated. Liquid triglycerides are oils, while solid triglycerides are fats.
Saponification; by heating a triglyceride in aqueous potassium hydroxide (KOH)
the fatty acyl esters can be cleaved off (hydrolysis) leaving behind glycerol
and the potassium salt of the fatty acid. The process is called
“saponification” (or soap formation) since the potassium salts of fatty acids
are in fact “soaps”.
The
“saponification number” is used as an indicator of fatty acid chain length in
triglycerides. The value is simply a measurement of the ml of KOH required to
complete the hydrolysis of one gram of fat or oil. Triglycerides containing
long fatty acids will have a lower saponification number than triglycerides
with shorter fatty acids -since 1 gram of lipid containing long chains will
have less chains in total than 1 gram of lipid containing short chains.
Saponification
value (or "saponification number", also referred to as
"sap" in short) represents the number of milligrams of potassium
hydroxide or sodium hydroxide required to saponify 1g of fat under the
conditions specified. It is a measure of the average molecular weight (or chain
length) of all the fatty acids present. As most of the mass of a fat/triester
is in the 3 fatty acids, it allows for comparison of the average fatty acid
chain length.
3.
Why
is the difference in the molar amount of HCl used to neutralize the control and
the amount of HCl used to neutralize the sample equivalent to the molar amount
of KOH used to saponify the test sample?
HCl+ KOH KCl + H2O
Strong Acid +Strong Base Salt +
Water
Because
one mole of HCl reacts with 1 mole of KOH. Thus the test sample will require
more acid to neutralize it because it contains more alkali than the control. Since
it is a 1:1 reaction, the moles of HCl and KOH are equivalent
4.
Why
do soaps disperse grease?
Part
of the soap is soluble with grease and part of it is soluble with water. Soap
combines with both grease and water and washes away in a shower. Combine the
two and get rid of the both. Part of the soap molecule is similar to grease and
combines, with grease, another part of the soap molecule easily combines with
water. Soap is a surfactant and combines with both grease and water.
References:
Saponification.
Retrieved May 19, 2013, from http://home.pacific.net.au/~thambilton/Saponification.html
Soap. Retrieved on May 19, 2013 from http://www.madehow.com/Volume-2/Soap.html#ixzz2TsF9z9QC
Soap. Retrieved on May 19, 2013 from http://en.wikipedia.org/wiki/Soap
