Organic
Stone
Name: __________________
Class___________________
Date: ___________________
Saponification Lab
The manufacture of soap is one of the earliest chemical
processes: some estimates are that people have been making soap
for over 2000 years. More debatable is what this “soap” was used
for: probably it was used for cleaning and preparing fibers to make
cloth or for medicine and not used for actually taking a bath. Soap
was derived from fats, which were also used for cooking, lighting
(lamps and candles), skin care, and a variety of other purposes that
people probably valued more than being clean!
Saponification is the term for the reaction that involves
taking a glycerol ester (either solid or liquid fat) and heating it with
a strong base. The result is soap (a salt of a fatty acid) and
glycerol. (The reverse of this reaction is called Esterification).
The first step involves dissolving the fat in Sodium
Hydroxide and Ethanol. The sodium hydroxide is a strong base
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Organic
Stone
Name: __________________
Class___________________
Date: ___________________
(another name for NaOH is lye and hence the term lye soap).
People made lye from burning wood and then dissolving the ashes.
(That’s what people were doing in limekilns-making lye). The
remains of one of these kilns can be seen at the canal lock next to
the Wood Bridge here in York County). The mixture of fat, lye,
and ethanol mixture is heated gently until all the fat is dissolved.
Once dissolved, the fat is reacted with a saturated salt solution
(“salted out”) to produce soap.
There are as many variations on the above procedure as there
are chemistry teachers-so this is just one way to make soap!
The lab procedure is fairly self- explanatory; however, there
are a few cautions:
1. Extreme care must be taken in this lab with the Ethanol and
the Sodium Hydroxide. The ethanol is flammable so you
must follow the directions on heating carefully. The sodium
hydroxide is a strong base that WILL CAUSE BURNS.
2. The best soap will result from a clean starting beaker, careful
measuring and patience in dissolving the fat. Heat gently
and stir constantly.
3. Goggles must be worn continually in this lab, if you need a
break sit in the classroom portion of the lab.
4. For small volumes of 1 or 2 ml you can use a medicine
dropper (20 drops=1ml).
5. READ THE ENTIRE LAB BEFORE YOU BEGIN.
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Organic
Stone
Name: __________________
Class___________________
Date: ___________________
Materials:
Bunsen burner
Ring stand
Ring Clamp
Wire Gauze
Test Tubes
Balance
Hot Plate
Dropper
Beaker
Filter paper
Funnel
Scoop
Stirring Rods (plastic and
glass)
Test tube rack
Clay triangle
Watch Glass
Stoppers
Goggles
Litmus and Hydrion papers
Chemicals:
Saturated Soln.of NaCl
30% Soln of NaOH
Ethanol
Distilled Water
Veg. oil or lard
Commercial Detergent
Hand Soap
.1M soln. of FeCl3,
MgCl2, CaCl2
Mineral Oil
Procedure: Day 1-Lab Preparation
1. Clean your glassware: 250 ml beakers, a small beaker (50 or
100 or 150 ml) and a 250 ml Erlenmeyer flask. Use Alconox
lab detergent and scrub with one of the scrub brushes. Rinse
with water 6 times. Label with sharpie and place in the
designated bin for your class.
2. Each lab group should also wash 4 test tubes and label them
for the testing on day3.
3. Label the bottom of a Petri dish with masking tape. Place
your name on the masking tape with a sharpie marker.
4. Prepare data tables for the soap testing sections of the lab.
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Organic
Stone
Name: __________________
Class___________________
Date: ___________________
Procedure for Day 2-Soap Making: Perform as lab partners.
1. Measure 5 ml of oil (if using lard or a solid fat use about 1
level teaspoon) and pour into a clean 250 ml beaker.
2. Add 5.0 ml of Ethanol to the oil (Caution-Ethanol is
flammable). Stir vigorously with GLASS stir rod
3. Carefully add 2.0 ml of a 30% solution of NaOH (Cautionstrong base that will cause burns). Stir the solution gently with
GLASS stir rod to mix everything in the beaker.
4. Heat this gently over a low flame (you may need to move the
burner back and forth under the beaker to avoid overheating.
Have a watch class handy to place on the beaker in case the
ethanol should catch on fire.
5. Heat for about 10 minutes until the fat odor is gone and the
fat is dissolved (you no longer see the fat separating from the
aqueous solution and it starts to foam). If the beaker catches
fire, carefully place the watch glass on top to extinguish the
flames. Allow the beaker to cool.
6. While the beaker is cooling, heat 10.0 ml of distilled water
(in a 100 or 150 ml beaker) until it is just about to boil. Add
this water to the 250 ml beaker that contains your heated
solution.
7. Add 15 ml of saturated NaCl solution to the beaker and stir.
At this point you should see the soap forming as a crust or
“scum”.
8. Filter the contents of your beaker. Use the plastic stir rod to
scrape the beaker sides and transfer to the filter paper. Rinse the
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Organic
Stone
Name: __________________
Class___________________
Date: ___________________
liquid down the drain with lots of running water and save the
solid on the filter paper using forceps to transfer to your Petri
dish (this is the soap!).
Day 3: Soap Evaluation/Testing: Perform as a lab table
1. Label four flasks as:
Distilled water
Soap
Laundry Detergent
Hand Soap
2. Pour approximately 50 ml of distilled water into each of four
250 ml beakers. To each beaker add:
Distilled- add nothing
Soap-add a 1 small scoop of your soap
Laundry Detergent-1 small scoop of the laundry detergent
Hand soap- 1 small scoop of liquid hand soap
Stir each beaker until all of the soaps are dissolved. You will
use these solutions in the rest of the lab.
3. Label a set of 4 clean test tubes:
Distilled
Soap
Detergent
Hand soap
Place in a test tube rack and use these test tubes for the rest of
the lab.
Test of Detergent properties:
Place 4 drops of mineral oil in each test tube. Then add
about 5 ml of each of your solutions. Stopper and shake each
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Organic
Stone
Name: __________________
Class___________________
Date: ___________________
test tube. Record your observations. Thoroughly rinse the test
tubes and return to the rack.
pH test:
Use your glass stirring rod to test the solutions with red and
blue litmus paper and with Hydrion paper. Record your
observations
Hard water test:
a. Re-label three test tubes as:
CaCl2
FeCl3
MgCl2
b. Add about 5 ml of distilled water to each of the test tubes.
Then add the following to each:
Distilled-add 1 ml of distilled water
CaCl2- add 1 ml of 0.1M CaCl2 solution
FeCl3- add 1 ml of 0.1M FeCl3 solution
MgCl3- add 1 ml of 0.1M MgCl3 solution
Stopper each test tube and shake. Record your observations.
Empty test tubes (can go down the drain) rinse thoroughly.
c. Repeat the above tests with each of the soap solutions.
Conclusions:
1. What do the processes of saponification and esterification
have in common? How do they differ?
2. To what class of compound do soaps belong? To what class
do fats belong?
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Organic
Stone
Name: __________________
Class___________________
Date: ___________________
3. Describe how your soap compared to the other soap samples
in steps in your tests on day 3. Compare and contrast these
soaps based on your observations.
4. How do you think soaps are treated commercially before
they are sold to the public?
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