LAB 4: LIPIDS
Part 1: Preparation and Properties of Soap
Purpose and Concepts:

Saponification (Basic Hydrolysis) of Fats and Oils:
o

Prepare soap by reacting fats and oils with lye (sodium hydroxide).
Properties of Soaps and Detergents:
o
o
o
Solubility: Compare the solubility of soaps and detergents in salt water.
In hard water: Compare the reactivity of soaps and detergents with hard water ions.
In acid: Compare the reactivity of soaps and detergents with hydrochloric acid.
Reading:
Fats & Oils: “On Food & Cooking” p. 797-802
Emulsions: “On Food & Cooking” p. 625-628
Saponification (Basic Hydrolysis) of Fats and Oils:
Reactions of Soaps and Detergents with “hard water” ions:
Safety:
The lye (sodium hydroxide) used to hydrolyze the esters in fats will also hydrolyze the amides in your skin
and eyes. It is critical that you avoid getting sodium hydroxide in your eyes. Wear safety goggles at all
times when working with sodium hydroxide.
Supplies needed: (*Included in your chemistry kit.)
Beakers (2 at 50 mLs)
Beakers (150 mL)
Beaker (250 mL)
Beaker (400 mL)
Stirring rod (glass or wood)
Porcelain Evaporating dish
Weighing boat or soap mold
Test tubes with stoppers
Hotplate or Burner
10 mL Graduated Cylinder
pH paper
Filter paper
Safety Goggles
Thermometer
Sodium Hydroxide (Lye)
Lard
Coconut Oil
Olive Oil
Water
Essential Oil fragrance (optional)
Vegetable oil
Ethanol
Detergent (dilute solution)
Sodium Chloride (Table Salt)
1M Calcium Chloride (CaCl2)
6M Hydrochloric acid (HCl)
Discussion:
In this lab we will be performing the hydrolysis (the breaking of a bond with water) of the ester functional groups
in fats and oils under basic conditions. The general process of hydrolyzing esters with caustic alkali’s (strong bases
such as sodium hydroxide, NaOH or potassium hydroxides, KOH) is called saponification. The products of basic
hydrolysis of fats or oils are glycerol and the salts of fatty acids which are called soaps.
We will make a bar of soap that you can take home after a couple weeks.
We will test a previously made soap sample and a commercial detergent and compare their properties in the
presence of salt, hard water ions such as calcium, and in the presence of acid.
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
1
Background Information:
Soap:
The chemical equation for the basic hydrolysis of esters (saponification) with Sodium Hydroxide (Lye) to form
soap is shown here.
EMULSIONS:
An Emulsion is a single layer that occurs when two layers that would normally not mix with each other are brought
together into one. In order to get a nonpolar oil and a polar water solution to mix an emulsifying agent is
necessary such as soap, detergent, or a lecithin. An emulsifying agent has both a polar part that attracts water and a
nonpolar part that attracts oil.
Soap owes its cleaning ability to the formation of micelles which can encapsulate grease or oil and make it water
soluble.
Micelles are destroyed by “hard” water ions such as Ca2+ and Mg2+. These ions precipitate the fatty acid anions
causing a “scum” to form.
O
Na O
O
C
(aq) + CaCl2
Sodium Stearate (A Soap)
2+
1-
Ca O
C
2 (s)
+ 2NaCl
Calcium Stearate (A Soap Scum)
Synthetic detergents (called “syndets”) have been developed which are less affected by hard water ions since the
magnesium and calcium salts are quite a bit more soluble.
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
2
NOTES:
PROCEDURES:
1
Choose one of the following recipes: (recipes w/ 2%
superfatting) These recipes are ¼ scale of a regular soap recipe. A
ACTIONS:
I. Soap: Preparation
1. Choose a soap recipe from the options given.
1
variety of vegetable oils and solid animal fat would work as
they are all triacylglycerols.
Option 1:
Ingredient
50 % Lard
25 % Coconut Oil
25 % Olive Oil
Lye (NaOH)
2. Into a weighing paper weigh the mass of
sodium hydroxide needed for your chosen
recipe. 2
3. Into a 250 mL beaker, add 8.25 mL water.
Option 2:
Ingredient
25 % Lard
50 % Coconut Oil
25 % Olive Oil
Lye (NaOH)
3
4. Slowly and carefully add half of the weighed
sodium hydroxide (NaOH) to the water in the
beaker stirring constantly with a glass stirring
rod. 3 Once the solid has dissolved carefully
stir in the remaining sodium hydroxide.
Dissolve and set this solution aside to cool to
below 50oC.
g/s or mLs needed
12.5 g
6.25 g
6.25 g
3.6 g NaOH + 8.25 mL water
g/s or mLs needed
6.5 g
12.5 g
6.25 g
3.8 g + 8.25 mL water
2
The amount of NaOH can be determined easily using the
“Lye
Calculator”
found
at
http://www.brambleberry.com/Pages/Lye-Calculator.aspx
3
4
5. Weigh the fats and oils from your chosen soap
recipe into a separate 400 mL beaker.5
6. Warm the solid fats and oil mixture gently with
stirring on a hot plate or burner. When
everything has melted turn the heat off. Cool to
below 50oC.
CAUTION: Sodium Hydroxide gets very hot when mixed
with water. A concentrated NaOH solution is extremely
dangerous. Make certain you are wearing eye protection. Do
your best to avoid splashes. If skin contact is made wash
immediately with soap and lots of water.
Placing your beaker in an ice-water bath can help to control
the heat produced by the NaOH in water.
4
Zero/Tare the balance between additions and add slowly so
you don’t add an excess.
5
7. Once the oils and lye (NaOH) water have
cooled to below 50oC (and ideally are within about
5Co of each other) carefully pour the lye solution
into the melted fat solution.
8. Continue stirring with a rubber spatula, glass
stirring rod, or magnetic stir plate5 until “trace”
6
is reached. Continue with other parts of the
lab while stirring.
If using magnetic stirring check periodically to insure even
stirring. If making soap at home an immersion blender is
ideal for stirring.
6
To test for “trace”, raise the spatula and drizzle soap onto the
surface of the mixture. The soap has “traced” when a faint
pattern is observed on the surface before sinking.
7
Do not pour clumped or watery soap into molds. As the
soap sets in the molds, heat will be generated. This heat, if
contained, can aid in hardening the soap. For this reason the
soap is enclosed in containers.
8
9. Add a drop or two of fragrance or essential oil.
Continue stirring until trace is again reached.
10. Pour the scented soap into molds7 or weighing
boats and incubate in a cardboard box or
insulated chest for a few days then open to the
air for at least a week. 8
11. Before cleaning out the beaker in which you
made your soap add a couple mLs of water to
the beaker and test the pH of the soap residue
left behind. 9
The crude basic soap is too harsh to use on your skin so it
must be either purified or allowed to stand. Four to six weeks
cure time is recommended. This allows any unreacted
sodium hydroxide to react with carbon dioxide in the air to
become sodium carbonate (washing soda) thus eliminating
the need for further purification from the harsh sodium
hydroxide. The pH will become less basic over more time
and result in a milder soap.
2NaOH + CO2 → Na2CO3 + H2O
Also excess moisture is allowed to evaporate leaving a harder
and longer-lasting bar.
9
This soap solution contains some leftover sodium hydroxide
that hasn’t yet reacted so it could show a very basic pH.
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
3
10
II. Soap: Properties & Reactivity
A. Preparation of Solution:
1. Place about 2-3 grams of a sample of previously aged soap into a 150 mL
beaker and add to it about 50 mLs of deionized water. Heat the mixture,
with occasional gentle stirring10, until all of the solid soap has dissolved
in the water. 11
2. Use this soap solution in each of the following procedures (Parts II B, C,
D, and E).
B. pH
& C. Salting Out:
1. Obtain two 50 mL beakers.
 Into beaker #1 pour 10 mLs of the soap solution you just made in Part
A and allow it to cool.
 Into beaker, #2, pour 10 mLs of a detergent solution.
2. Test and record the pH of the soap and detergent solutions.
3. To each 50 mL beaker add solid sodium chloride (NaCl) a little at a time
with gentle10 stirring, until no more NaCl dissolves and the bottom of the
beaker is covered with NaCl. Record your observations on the report
sheet and compare the behavior of soap to the behavior of detergent12.
D. Emulsions:
4. Obtain 3 small stoppered test tubes:
 Into tube 1 put 2 mLs water (as a control)
 Into tube #2 put 2 mLs soap solution (from part IIA).
 Into tube #3 put 2 mLs dilute detergent solution.
Use gentle stirring to avoid
lather bubbles. If too much lather
is produced it will be hard to see
the results of the tests.
11
If there are clumps that will not
dissolve, scoop them out and
discard them.
12
Soap can be forced out of
solution by dissolving NaCl in it.
Water can only dissolve a limited
amount of stuff and since NaCl is
more polar than the long
hydrocarbon chain of the soap,
the water lets go of the soap and
dissolves the NaCl. The soap that
has been let go floats to the
surface of the water.
This “salting out” method can be
used to purify freshly made soap.
The NaOH (sodium hydroxide)
left over from the preparation of
soap is polar like NaCl (sodium
chloride) so it stays dissolved in
the water. Therefore, the soap
that comes to the surface of the
water gets separated from the
NaOH so is now more pure.
It is possible to remove the mass
of pure soap floating on the
surface by scraping it off the top
with a spatula or piece of filter
paper.
13
5. Into each of the 3 tubes drop 1 drop of vegetable oil. Stopper and shake
each to mix.
You could also test the lathering
ability by using the soap to wash
your hands.
6. Stopper the tube and shake the soap to see if it lathers.13 Observe any
emulsions formed.
E. Reactivity with Hard Water Ions:
O
Na O
O
C
(aq) + CaCl2
Sodium Stearate (A Soap)
2+
1-
Ca O
C
2 (s)
+ 2NaCl
Calcium Stearate (A Soap Scum)
1. Obtain two test tubes.
 Into test tube #1 pour 5 mLs of the soap solution (prepared in Part
IIA).
 Into test tube #2 pour 5 mLs of detergent solution.
14
2. Add 1M Calcium Chloride (CaCl2), one drop at a time, to each tube and
observe if a precipitate forms. Stop if a precipitate does not form by 10
drops.
3. Record the results.15
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
14
Calcium chloride is often
purchased to use as “sidewalk
salt” to melt ice.
15
The sodium salts of fatty acids,
soaps, are soluble in water. When
other metal ions like calcium
(Ca2+), magnesium (Mg2+), or
iron (Fe3+), form salts with fatty
acids they are not as soluble in
water and tend to precipitate out.
4
LAB 4: LIPIDS
Part 2: Isolation of Essential Oils by Steam Distillation
Purpose and Concepts:

Polarity vs Solubility:
o Observe the effect of molecular structure on polarity and solubility by isolating
nonpolar oils from plant sources.

Distillation:
o Use steam distillation to isolate nonpolar oils from plant sources.
Reading:
Polar Vs Non-polar molecules in Water and Oils: “On Food & Cooking” p. 814
The Chemistry & Qualities of herbs & spices: “On Food & Cooking” p. 389-393
Supplies needed: (*Included in your chemistry kit.)
*400 mL beaker
*Gram kitchen scale
Food grater or chopper
*Calibrated dropper
*Hot pad
Sample Vial
OilExTech steam distillation apparatus
Volumetric flask (10 mL)
Microwave Oven
(~100 g each) Plant sources of Essential Oils such as:
Citrus Peelings: ie Orange, grapefruit, lemon, lime
Herbs: ie. Lavender buds, Rosemary leaves, Peppermint leaves
Discussion:
Lipids are a family of compounds that are grouped by similarities in solubility rather than structure. As a
group, lipids are nonpolar and so are more soluble in nonpolar solvents such as ether, chloroform, or
benzene. Most are not soluble in water.
Natural essential oils can be isolated from plant sources by extraction with nonpolar solvents or by steam
distillation whereby the oils are vaporized with steam and then recondensed. Many essential oils from plant
extracts are commonly used as flavors and fragrances. Many are structurally terpene compounds made
from individual 5 carbon isoprene units.
Examples of Some Common Essential Oils:
Common Terpenes
(S)-(+)-Linalool
or licareol
C10H18O
HO CH3
(R)-(-)-Linalool
or coriandrol
C10H18O
Common Source:
Lavender
Common Source:
Coriander seed
(R)-(+)-Limonene
or D-Limonene
C10H16
(-)-Menthol
C10H20O
Common Source:
Spearmint
O
(R)-(-)Citronellol
C10H20O
Common Source:
Lemon Geranium
Roses
O
H
Common Source:
Vanilla
HO
OCH3
Eugenol
C10H12O2
CH3
Common Source:
Peppermint
Common Source:
Orange & Lemon
Rind
(R)-(-)-Carvone
C10H18O
Common Phenols
Vanillin
C8H8O3
CH3 OH
OH
Common Source:
Cloves
HO
OCH3
CH3
OH
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
5
NOTES:
PROCEDURES:
19
ACTIONS:
I.
ISOLATION OF ESSENTIAL OILS (Group project)
20
1. Place about 100 g of moist19 ground or chopped plant material20
around the outside of the central beaker of the OilExTech
microwave steam distillation apparatus21.
2. Place the condensation funnel and the lid with ice cone (without the
plastic shield) on the apparatus and place in a standard kitchen
microwave oven.
3. Place a mug or beaker of water next to the apparatus in the
microwave (1100 watts) and microwave on high for about 5-6
minutes. Let it cool undisturbed an additional 5-6 minutes.
Add water to moisten the plant material as
needed.
Many plants will yield oils. Some ideas
to try are:
 Grated orange rind (about 100 g)
 Orange zest (about 50 g)
 Lavender buds (50-100 g fresh or
frozen); run 7 min
 Peppermint leaves (100g; freeze for 24
hrs; add 40 g water/100 g leaf; run 6 min
on high)
 Rosemary (100 g ; freeze 24 hours; add
water ½ mL water per gram; run 6.25
min on high)
21
4. Remove the center beaker22 from the apparatus and pour some of the
water/oil mix into a small (10 - 50 mL) volumetric flask. Allow the
oil to rise to the top within the narrow cone of the flask.
For
a
demonstration
http://oilextech.com
see
22
The center beaker now contains melted
ice water and the extracted essential oil.
5. Pipet the oil layer into a vial and save for use as a soap fragrance.
.
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
6
Lab 4: Lipids: Part 1 Soap
Name ___________________
Partner __________________
Report
I. Soap:
Observations
pH
pH of crude soap dissolved in
water:
A. Preparation: Appearance of freshly made soap:
_________
II. Soap: Properties and Reactivity
Test
B.
pH:
Soap
Detergent
pH of aged soap solution: _________
pH of detergent solution: _________
Results of “salting out” the soap:
C.
“Salting out”
D.
Emulsion
Results of oil in water:
Results of “salting out” detergent:
Results of oil in soap:
Results of oil in detergent:
(is the oil
forming a
layer?)
E. Reaction Results of adding CaCl2 to soap:
with Hard
Water Ions
Complete the reaction:
Results of adding CaCl2 to detergent:
O
Na
O
C
9
18
+ CaCl2
Sodium Oleate
Name of Products formed:
Summary/Analysis: Write a brief summary (of Parts B-E)
in which you compare and contrast the properties of soap and
detergent based on your experimental findings. Explain any anomalies.
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
7
Questions:
Vocabulary:
1. Match the following terms with the structures they represent:
A.
O
H
_____ Soap
O
O
H C
O C
H C
_____ Triacylglycerol
C
H C
H
O
O
C
B.
O
_____ Detergent
C
O Na
C.
_____ Fatty Acid
O
C
OH
______Micelle
D. None of these
2. Define the following words in terms that a non-chemist can understand. Give an example, formula, or use for
each term as applicable.
Examples, Applications,
Definition or Explanation
Structures to Illustrate
A. Hydrolysis
B. Saponification
C. Lye
D. Detergent
E. Micelle
F. Soap Scum
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
8
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
9
3. Complete the following:
O
H
O
C
H C
O
H C
O C
H C
O
H
O
NaOH
H2O
C
Glyceryl Trioleate
Name the Products:
_____1. “Salting” works to purify soap because _______.
A. Salt kills bacteria that would make soap impure.
B. Salt is more soluble in water than is Soap.
C. Salt (NaCl) chemically reacts with soap to make a less soluble product that can precipitate.
D. More than one of these.
_____2. What is the advantage of using detergent instead of soap if you have “hard” water?
A. Detergent reacts with hard water ions to form new compounds that are soluble in water.
B. Soap reacts with the ions in hard water and forms insoluble soap scum solids.
C. Detergent is cheaper than soap.
D. More than one of these.
_____3. Soaps and detergents dissolve in both nonpolar oil and in polar water because ____
A. they have a nonpolar ionic end that attracts oil and a polar hydrocarbon end that attracts water.
B. they have a nonpolar ionic end that attracts water and a polar hydrocarbon end that attracts oil.
C. they have a polar ionic end that attracts water and a nonpolar hydrocarbon end that attracts oil.
D. Soaps and detergents are neither polar nor nonpolar so the solvent doesn’t matter.
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
10
Lab 4: Lipids: Part 2 Essential Oils:
Name _____________________
Partner __________________
Report:
I. ISOLATION OF ESSENTIAL OILS:
Plant Source:
Grams
Used
mLs Oil Obtained
Odor and Observations:
Analysis/Conclusions: Critique the experiment. What worked well and what might be improved.
Questions:
1.
Define the following terms and give an example or application of each:
Term
Definition or Explanation
Examples or Applications
Essential Oil
Terpenes
Phenolic
Compounds
2.
For the following compounds:
A. Label each as a terpene or a phenol.
B. For the terpenes label the isoprene units. For the Phenols circle the phenolic functional group.
1.
Limonene from oranges:
2.
Eugenol from cloves.
3. Cineole (Eucalyptol) from
Rosemary
4.
Vanillin from Vanilla
O
O
H
HO
OCH3
HO
OCH3
3. Terpenes generally have what flavor quality (ies)? (see McGee p 392) __________________________________________
4. Phenols generally have what flavor quality (ies)? __________________________________________________________
5. List at least 3 of the flavor components found in Sage and their flavor qualities (see McGee p 392):
CH117 Lab 4 Lipids: Soap & Essential Oils (F16)
11