LAB 23: LIPIDS; FATS, OILS, & SOAP:
PROPERTIES & PREPARATION
PURPOSE: To observe physical and chemical properties of fatty acids and triacylglycerols.
To synthesize soap by saponification of vegetable oil.
To compare the physical and chemical properties of soap and detergent.
To isolate essential oils from natural products.
SAFETY CONCERNS:
Always wear safety goggles.
Lye (Sodium Hydroxide) is caustic to skin and will dissolve eyes especially the hot concentrated solution
used in this experiment. Wash with soap and copious amounts of water if contacted.
Bromine is toxic and irritating to eyes and mucus membranes.
LIPIDS:
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:
Structure
(S)-(+)-Linalool
or licareol
C10H18O
HO CH3
(R)-(-)-Linalool
Structure
or coriandrol
C10H18O
Common Source:
Common Source:
Lavender
Coriander seed
Structure
Vanillin
C8H8O3
CH3 OH
O
H
Common
Source:
HO
OCH3
Vanilla
(R)-(+)-Limonene
(-)-Menthol
C10H20O
or D-Limonene
C10H16
Eugenol
C10H12O2
CH3
HO
Common Source:
Common Source:
Orange
Rind
Peppermint
&
Lemon
OH
Common
Source:
OCH3
Cloves
(R)-(-)-Carvone
C10H18O
(R)-(-)-Citronellol
O
CH3
C10H20O
Common Source:
Common Source:
Spearmint
Lemon Geranium
Roses
OH
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
29
FATS, AND OILS FROM FATTY ACIDS:
Fats and fatty oils are mixtures of complex esters. Fat esters are made from long chain carboxylic acids
(called fatty acids) and an alcohol containing three OH groups (called glycerol).
A common fat is called a triacylglycerol or triglyceride. The hydrocarbon chain of the fatty acids
determines the physical and chemical properties of the compound. Triacylglycerols made from longchain (C-16 to C-18) saturated fatty acids (like palmitic and stearic acids) are solid or semisolid at room
temperature. Solid animal fats contain an abundance of long saturated fatty acids.
Common Fatty Acids
Saturated
Unsaturated
O
C
12
O
C
14
O
9
OH
Lauric Acid
O
OH
Myristic Acid
O
C
16
O
C
18
C
16
9
C
18
OH
Palmitoleic Acid
OH
Oleic Acid
OH
Linoleic Acid
O
OH
Palmitic Acid
OH
Stearic Acid
12
9
C
18
Triacylglycerols made from long-chain unsaturated fatty acids (like oleic or linoleic acids) are liquid oils
at room temperature. Liquid vegetable oils contain an abundance of long unsaturated fatty acids.
A few oils owe their characteristic liquid nature to the presence of shorter chain fatty acids (C-6 to C-14).
Coconut oil contains large amounts of lauric (C-12) and myristic (C-14) acids, as well as smaller amounts
of C-6, C-8, and C-10 acids.
Synthesis of a Typical Triacylglycerol:
O
H
H C OH
HO
O
C
H
H+
O
H C OH + HO C
O
H C OH
C
H
HO
Glycerol
1,2,3-propantriol
O
C
H C
O
H C
O C
H C
O
H
Stearic Acids
O
+ 3H2O
C
Glyceryl Tristearate (Tristearin): a typical triacylglycerol
TESTS FOR UNSATURATION:
Bromine Test:
Just as in our previous study of alkenes,
the presence of unsaturation in a fatty acid or a triacylglycerol
can be detected by reaction with bromine. If the orange color
of a bromine solution added to a lipid fades quickly, an
addition reaction has occurred with existing double bonds and
the oil or fat is unsaturated.
Acrolein Test:
When triacylglycerols are heated with
potassium hydrogensulfate, KHSO4, (also known as potassium
bisulfate or potassium acid sulfate) the glycerol is dehydrated
and oxidized to acrolein. As KHSO4 is a weak acid it can
catalyze both the hydrolysis of the triglyceride esters as well
as the dehydration/elimination reaction of the glycerol
carbohydrate. Acrolein may be detected by its distinctive
sharp irritating odor. It can often be present in charcoal
broiling of fatty food. It is volatile and will evaporate and
be lost with continued heating.
30
Br Br
H
H
C C
H
H
(colorless)
+
H H
O
H C OH
H C OH
H
Glycerol
1,2,3-propantriol
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
(colorless)
(red-brown)
H
H C OH
H C C H
Br2
C H
KHSO4
C H
C H
H
Acrolein
+
H2O
OXIDATIVE RANCIDITY:
Oils are more easily digested than fats. They also become rancid more easily than fats because of the ease in which
their double bonds can be hydrolyzed or oxidized into small smelly and foul tasting aldehydes, ketones, and
carboxylic acids. Radicals form with oxygen (O2) which causes double bonds to cleave into aldehydes which can
further oxidize to carboxylic acids.
O
H
C
O
H
C
O
H
C
O
C
H
C
O
O
H
C
Oxidation
(rancidity)
[O]
O2
O
H
O
H
C
O
H
C
O
C
H
C
O
O
O
O
O
H
H
O
C
OH
HO
H
H
O
O
O
O
HO
C
Kreis Test: The most commonly used test to determine
oxidative rancidity is the Kreis test. A small quantity of
concentrated hydrochloric acid is added to the lipid to be
tested, followed by the addition of a 0.1% solution of
phloroglucinol (1,3,5-trihydroxybenzene) in ether. The red
or pink color indicating rancidity is believed to result from
a reaction of epihydrin (an isomer of malonaldehyde) or
other oxidation products with the phloroglucinol.
HO
O
OH
O
Red colored
complex
+
H
H
Malonaldehyde
OH
Phloroglucinol
SOAP:
Hydrolysis of an ester is the reverse of the synthesis of an ester. Hydrolysis of a triacylglycerol into glycerol and
fatty acids can be catalyzed by either strong acid or strong base.
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 called soaps.
O
O
H
O
H C
O
H C
O C
H C
O
H
O
H
C
Na O
H C OH
NaOH, H2O
C
Glyceryl Tristearate (A Fat)
H C OH
C
O
+
H C OH
Na O
H
Glycerol
1,2,3-propantriol
Na O
C
O
C
Sodium Stearate (A Soap)
Polar hydrophilic end
attracts water
Nonpolar lipophilic end
attracts grease
MICELLES:
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. 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.
O
Na O
A Micelle
O C
O
C
O
O
O
C O
O
C
O
O
C O
A Detergent
S
O C
O
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
O
O
C
O
31
HISTORY OF SOAP:
According to Roman legend, soap was discovered after a heavy rain fell on the slopes of Mount Sapo (the name
means "Mount Soap" in Latin). The hill was the site of an important sacrificial altar, and the rainwater mixed with
the mingled ashes and animal fat around the altar's base. As a result of this fortuitous coincidence, the three key
components of soap were brought together: water, fat, and lye (potash leached from the ashes). As the mixture
trickled down to the banks of the Tiber River, washerwomen at work there noticed that the mysterious substance
made their job easier and the wash cleaner. They were so impressed with the cleansing power of this mysterious
substance that trickled down from the mountain, they named the mountain in its honor. They knew to name it after
“soap” as there was another substance that they were familiar with that also had exceptional cleansing powers.
Clothes have been cleaned for ages by beating them on rocks near a stream. Near these streams grew certain plants,
such as soapworts, whose leaves produced saponins, chemical compounds that give a soapy lather. By mixing these
saponins with their wash water, they were getting much cleaner clothes than they got from the water alone. So it was
the soapwort plant that gave its name to Mount Sapo. This plant is also known as bouncing bet, a pink-blossomed
perennial that grows wild throughout most to the United States.
Over the centuries the basics of soapmaking have remained essentially unchanged from the Roman prescription.
Although we don't sacrifice animals at the altar to obtain our fat and then wait for the next heavy rain, we use the
same ingredients. To this day in parts of rural America soap is being made much as it was in ancient Rome: out of
potash, rainwater, and animal tallow. The potash is found in wood ashes and, when this ash is extracted with water
and the resulting solution evaporated in iron pots, a solid is produced. This solid is called potash. It is known
chemically as potassium carbonate and when dissolved in water, it gives us a very basic (caustic) solution. Most
people who make soap at home do not go to all the trouble of extracting the potash from wood ashes. They use
instead the more caustic substance, sodium hydroxide, which is also known commercially as lye. Animal fat is often
substituted by a variety of vegetable oils. Avocado oil, olive oil, coconut oil, palm oil and cinnamon oil are just a
few of the many oils that are used in today’s soap formulations. No matter which fat or caustic solution is used, the
same basic chemical reaction takes place. The net result of the reaction, called saponification, is the formation of
salts from the fatty acids that once were part of the larger fat molecules.
SOAP MAKING:
Soap manufacturers use at least two different fats and oils because each one contributes different properties to the
finished soap. These properties are defined by the fatty acids that make up the fats and oils and their respective
percentage. In this experiment, you will prepare a quality bar of useable soap from three or more fats and oils, like
in industry.
The by-product glycerin is both a humectant (attracts moisture from the air) and an emollient (soothes or softens the
skin). Due to glycerin’s properties, some manufacturers add more to the prepared soap while others remove it for
use in their cosmetic products.
In this experiment, the soap will be made via the cold process. In this method, pre-melted and warmed fats and oils
are combined with base. The resultant mixture is stirred until it thickens and subsequently poured into molds;
saponification reaches completion within one week.
32
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
Soap Formulation:
Each fat or oil is composed of varying percentages of different fatty acids (Table 1).
Almond
Apricot
Avocado
*Canola
*Castor
Cocoa Butter
*Coconut
*Corn
*Lard
Mango Butter
*Olive
Palm
*Safflower
Shea Butter
*Sunflower
15
48
17.3
27
15
20
3.5
2.1
2.5
34.3
6
2.7
4.6
10.3
76
4.3
66.2
1.2
1
12
4
17.5
1.4
1.3
0.3
1.4
77.0
64
70
60
8.6
38.1
6
49.6
48
44.8
84.4
42.7
17
49.0
25.1
4.5
5
10
4
1
%
Other
1
85.9
24.4
8.8
10.2
28.3
7.4
6.9
40.1
4.5
5.7
5.6
%
Stearic
%
Ricinoleic
%
Palmitolei
c
%
Palmitic
%
Oleic
%
Linolenic
%
Linoleic
%
Lauric
%
C6,8,10 FA
Fat or Oil
% Myristic
Table 1: Fatty Acid Composition of Common Fats and Oils
1.5
2.7
2
2
35.4
2
3
11.9
41.8
2.3
5.5
2.5
41
2.2
.79
2.6
3.0
0.37
0.03
0.9
*Available for use in our class preparation of soaps.
The predominant fatty acids provide soap its characteristics (Table 2). For instance, coconut oil contains 48.0% lauric acid,
which produces a hard and effective cleanser with fluffy lather.
Table 2: Soap Characteristics Promoted by Common Fatty Acids
Fatty Acid
Lauric
Linoleic
Myristic
Oleic
Palmitic
Ricinoleic
Stearic
Hard Bar
Yes
No
Yes
No
Yes
No
Yes
Cleansing
Yes
No
Yes
No
No
No
No
Fluffy Lather
Yes
No
Yes
No
No
Yes
No
Conditioning
No
Yes
No
Yes
No
Yes
No
Stable Lather
No
No
No
No
Yes
Yes
Yes
Table 3 gives the percent maximum recommended usage for each fat or oil in saponification, based on price, therapeutic benefits,
and soap qualities. A more detailed list can be found at https://www.fromnaturewithlove.com/resources/sapon.asp
Table 3: Percent Maximum Recommended Usage and Saponification Values of Select Fats and Oils
Column A
Fat or Oil
Column B
% Max Usage
SAP Value
Fat or Oil
% Max Usage
(mg KOH/1g fat or oil)
*Coconut Oil
*Lard
*Olive Oil
10-50
10-60
10-50
257
198.5
192
SAP Value
(mg KOH/1g fat or oil)
*Canola Oil
*Castor Oil
*Safflower Oil
*Sunflower Oil
*Corn Oil
10-15
10
10-15
10-15
10-15
174.7
180.3
192
188.7
190
Most oils in excess of the given percentages will yield an especially soft soap. Beeswax can be used to harden soap. Excesses of
coconut or palm oils will give a crumbly bar. Manufacturers use high percentages of coconut and palm oils as they are
inexpensive and produce a hard and effective cleanser with fluffy lather. Due to the presence of coconut milk consumers find
soap dries the skin. Therefore manufacturers use a 1-7% excess of fats and oils that serve as an emollient. These “superfatted”
soaps provide a dense and creamy lather that leaves the skin feeling soft and smooth. All formulations in this experiment use a
5% excess of fats and oils.
The components of the soaps you will make are fats and oils, sodium hydroxide, deionized water, and an essential oil as scent.
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
33
Sample Soap Recipes:
Following are general instructions and several recipes for preparing usable soap at home:
Safety observations:
Lye (sodium hydroxide) is very corrosive to animal tissue, especially the hot concentrated solution used in making
soap. Protective safety goggles and rubber gloves should be worn.
General Procedure:
The basics are the same no matter what kind of soap you wish to make. The three ingredients needed to make soap-fat, water, and
lye-are all readily available.
 Lye in the form of sodium hydroxide is sold as dry crystals in many supermarkets and hardware stores, while lye in the
form of potash can be make at home from wood ash. Because all types of lye are highly caustic substances that react
with plastic, aluminum, and tin, soap making utensils should be made of wood, glass, enamel, stainless steel, or
ceramic.
 Fat for soap making can be almost any pure animal or vegetable oil from reclaimed grease to castor oil. The water
should be soft. If you are in a hard water area, treat the water with a commercial softener or add a few tablespoons of
borax to it. You can also collect rainwater and use it to make soap.
 The following equipment is needed for soapmaking:
1. A container to hold and pour the lye solution such as a 2-quart juice bottle or glass mason jar.
2. A 10- to 12-quart pot to hold the fat and lye.
3. A wooden spoon to stir the lye solution and fat.
4. A candy or dairy thermometer that is accurate to within 1 oF in the 80oF to 120oF range. For convenience you may
want to have two such thermometers.
5. Rubber gloves. Wear as a precautionary measure, since lye will burn if it touches the skin.
6. Safety goggles. Lye is very caustic and if splashed into the eyes it could cause severe damage.
7. Molds for the soap. Prepare the molds by lining them with plastic or greasing them with Vaseline. Heavy duty
waxed paper also works well.
8. Insulation to keep the soap warm after it is poured into the molds. Cardboard, Styrofoam, or an ordinary blanket
can be used.
9. Enough newspapers to cover work surfaces and floor areas where you will be working.
Prepare the lye solution before beginning the soap-making process so that it will have a chance to cool. Caution concentrated
lye is very caustic. Protect your eyes and skin. You and any helpers must wear goggles and rubber gloves while
performing this experiment. To make the lye solution, pour cold water into an enamelware pot, then add the lye slowly while
stirring the solution steadily with a wooden spoon. The reaction between the lye crystals and water is exothermic and will
generate temperatures over 200oF. The container can be placed in a basin of ice cold water to hasten cooling. Once the solution
has cooled, pour it carefully into the 2-quart glass container. The type of fat you should use and the relative amounts of fat, lye,
and water that should be combined depend on the particular type of soap being made. The standard recipe calls for 6 pounds (2.7
kg) of beef fat, 2 ½ pints (1182 ml) of water, and 13 ounces (369 g) of lye crystals. In order for saponification to take place, the
temperature of the lye solution and fat has to be carefully controlled. The simplest method is to bring both the lye and the fat to a
temperature of 95oF to 98oF before mixing them together. Some experts recommend that the fat be at a higher temperature than
the lye: about 125oF for the fat and 93oF for the lye when beef tallow is used, 83oF and 73oF when lard is used.
Occasionally, saponification does not take place and the soap mixture separates into a top layer of fat and a bottom layer of lye
solution. Generally, the mixture can be reclaimed by heating it to about 140 oF while gently stirring with the wooden spoon. Then
remove from the heat and keep stirring until the mixture thickens into soap. To test your soap solution, spoon up a bit and let a
few drops fall on the surface of the soap; if the surface supports the drops for a moment or two, the soap is ready for the molds.
Option #1: Fast and Cheap
This procedure is much less expensive than others but the soap obtained is not as soft and mild as finer soaps. It is much more
like the lye soap our ancestors once made. For a simple trial reduce the quantities to 1/3 of the amounts suggested in the
procedural discussion above to make the experiment go faster as well as cost less. DO NOT USE ALUMINUM!!
1.
To 400 ml (13 - 14oz) of water slowly add 123 grams (4.3 oz) of sodium hydroxide. A 1-quart Mason jar or plastic drink
bottle should work well as a container. Place the container in an ice bath to speed the solution process and to help cool the
resulting mixture. If the temperature of the solution drops below 73oF (23oC) remove from the ice bath.
2.
Warm 2 lbs (908 g) of lard in a 6 quart pot while stirring with a wooden spoon. Once it reaches 83 oF (28.3oC), try to
maintain this temperature.
3.
Pour the 23oC lye solution into the 28.3oC fat in a steady stream while continuing to stir with and even, circular motion.
The mixture should turn opaque and brownish, and then lighten. The soap will be ready when its surface can support a
drop of mixture for a moment; consistency should be like sour cream.
Add colorants, scents, and other special ingredients at this time. Adding them earlier would hinder the saponification
reaction.
4.
34
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
5.
The molds should have been prepared in advance. Rectangular cake pans, cardboard boxes, etc. work well. Line the mold
with plastic, wax paper, or Vaseline to allow for easy removal.
6.
Pour the liquid into your mold and place in a warm location. Cover with cardboard, Styrofoam, or blanket. Soap should
be removed from the molds after 24 hours, and then left uncovered in freely circulating air for two to four weeks.
Option #2: Expensive but high quality
This is a recipe for Lavender soap; A softer and milder soap. Instead of using only lard or Crisco, it calls for a mixture of oils.
Using these oils also necessitates more careful temperature control. Reduce the quantities to 1/3 of the amounts normally
suggested in the commercial recipe for a sample batch. This should make the experiment go faster as well as cost less.
REMEMBER, DO NOT USE ALUMINUM!!
1.
To 315 ml (10 - 11 oz) of cold water slowly add 113.5 grams (4 oz) of NaOH. A 1-quart glass bottle should work well as
a container but you can also use a glass bowl if necessary. Initially mixing the water and lye in an enamelware pot and
then pouring it into the glass container is a good idea. The reaction will heat the lye solution to over 200 oF so set the
container aside in a safe place to cool down to 80oF. If you plan to cool the lye overnight, cover the container tightly to
avoid evaporation caused weakening of the solution. If you are anxious to do this quickly, place the container in an ice
water bath to speed the solution process and to help cool the resulting mixture. If the temperature of the solution drops
below 80oF (27oC) remove from the ice bath.
2.
While the lye is cooling, you can begin mixing the oils. Place 360g (13 oz) of Crisco and 227 grams (8 oz) of coconut oil
in a 3 quart pot and heat on a low setting until most of the solid pieces have melted. The few remaining chunks will melt
from the heat in the pan. Pour the melted oils into a 6 quart pan that has 227 grams of olive oil in it. (If you want to add a
natural preservative, add about 10 grams of grapefruit seed extract.) Let the mixture cool to 80 oF (27oC).
3.
You are ready to make soap when the oils and the lye solutions have both cooled to 80 oF (27oC). Wearing goggles and
gloves slowly drizzle the lye into the oils, stirring briskly as you pour. Continue to stir, circling the edges of the pan and
cutting through the middle of the pan to keep as much of the solution as possible in constant motion. Do not beat or whip
the mixture, but stir briskly throughout the entire soap making process. Do not scrape any residue off the sides of the pan.
Once a small amount of soap drizzled across the solution’s surface leaves a faint pattern before sinking back into the
mass, the soap is ready for the Lavender. (Consistency should be like sour cream).
4.
Add the Lavender oil (this and other scents can be purchased from Liberty Natural Products in Portland -most craft stores
should also carry essences), stirring swiftly and thoroughly with a spatula without beating. (Adding them earlier would
hinder the saponification reaction.) Stir for twenty to thirty seconds, or as little time as needed to fully incorporate the
essential oils. Too much stirring causes streaking and seizing (a quick setup which makes it hard if not impossible to pour
the soap into the frames).
The molds should have been prepared in advance. Rectangular cake pans, cardboard boxes, etc. work well. Line the mold
with plastic, wax paper, or Vaseline to allow for easy removal.
5.
6.
Quickly pour the soap into the mold without scraping the residue off the sides of the pan. The mixture should be smooth,
with no lumps, and the texture and color should be uniform. Watery or oily puddles signal a poorly mixed solution that
will result in pockets of solid lye in the final bars. Try to pour evenly from one end of the mold to the other for uniform
bars. If you see a change in texture, stop pouring. If the last bit of soap mixture at the bottom of the pan is watery and
uneven, the stirring process was not quite complete. Do not pollute the rest of your batch by adding this unsaponified
portion.
If you don’t pour the mixture into the mold quickly enough, it may begin to set unevenly. Use a spatula to spread it out to
the corners.
7.
Cover the filled frame with another frame, a piece of plywood, or a piece of heavy cardboard; cover with a blanket and
place in a warm location. IT MUST BE WELL INSULATED. Soap should be kept in the molds for at least 24-hours then
left uncovered in freely circulating air for two to four weeks.
[Soap maker’s note: “I have found that covering the top of the soap with plastic wrap to where it actually touches the surface helps a lot. I have
also found that leaving the soap for 5 to 7 days before removing it from the mold produces a better product. If you should decide to do this on a
regular basis, experiment with times and other variables and see what gives you the best results.”]
Option #3:
For a recipe that gives excellent results and is preferred by many home soap makers. You’ll get about 40 (4-ounce) bars from this
recipe. It is a little spendy, but buying this quality of soap retail would be much more. Use the above procedures with the following
ingredients:
3 pounds (3 pints) cold distilled water (does not need to be refrigerated)
473 grams (1.04 pounds) of sodium hydroxide
4 pounds (1.81 kg) of olive oil
2 pounds 8 ounces (1.13 kg) coconut oil
1 pound 8 ounces (680 g) palm oil
30 grams grapefruit seed extract (natural preservative), optional
45-50 grams (15-18 tsp) pure essential oil, optional
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
35
NOTES:
PROCEDURES:
1
ACTIONS:
I. SOAP: METHOD 1
1. From Table 3 choose
 2 fats or oils from column A and
 2 fats or oils from column B.
Plan to make a 25 g bar of soap with the composition of your
soap being 40% each of the column A fats and 10% each of the
column B fats.
2. On the report sheet show the amounts of chosen fats/oils and
sodium hydroxide needed to make a 95% hydrolyzed bar of
soap. 1
3. Into a weighing paper weigh the calculated1 mass of sodium
hydroxide needed.
4. Into a 250 mL beaker, measure about 7 mLs deionized water.
5. Slowly and carefully2 add half of the weighed sodium
hydroxide to the water in the beaker stirring constantly with a
glass stirring rod.
6. Once the solid has dissolved, carefully stir in the remaining
sodium hydroxide. Dissolve and set aside.
7. Weigh3 the fats and oils into a separate 400 mL beaker.4
Calculations should be done on the
report sheet part I similar to those
done in the prelab but on your choice
of fat and oils. They must be approved
by your instructor before starting lab.
2
Sodium Hydroxide gets very hot with
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.
3
Zero/Tare the balance between
additions and add slowly so you don’t
add an excess.
4
If you were using any butters (cocoa,
mango, shea butters) or beeswax in
your formulation you would need to
weigh these together in a separate
100mL beaker and melt them carefully
(avoid smoking) over a hot plate and
then add them to your melted fat/oil
mixture.
5
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.
6
8. Warm the fats and oils mixture gently with stirring on a hot
plate. 4 When everything has melted turn the hot plate off.
9. With stirring, add the NaOH solution from step 4. Continue
stirring with a rubber spatula until “trace” 5 is reached.
10. Remove a pea sized glob of your soap and place in a large
stoppered test tube. Add water and shake to dissolve.
This soap solution contains some
leftover sodium hydroxide that didn’t
react so it will show a very basic pH.
The crude basic soap is too harsh to
use on your skin so it must be purified
or allowed to sit so that the residual
NaOH can either react with remaining
triglycerides or react with carbon
dioxide in the air.
7
11. Test the pH of the dissolved soap solution and record the
result.6
12. To the remaining soap add fragrance or essential oil. Continue
stirring until trace is again reached.
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
13. Pour the scented soap into molds or weighing boats and
incubate in a cardboard box or insulated chest for several
weeks. 8
Any unreacted sodium hydroxide will
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.
14. After several weeks repeat steps 10-11. If pH is < 9 your soap
is good to go.
2NaOH + CO2  Na2CO3 + H2O
7
36
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
9
Vegetable oils, or solid animal
fat would work as they are all
triacylglycerols.
II. SOAP: METHOD 2
A. Preparation:
1. Into a porcelain evaporating dish pour
2 mLs vegetable oil9
3 mLs ethanol10
20 drops 50% Sodium hydroxide (NaOH) 11
Stir with a stirring rod to mix well.
2. Heat the mixture gently over medium heat on a hot plate or the
moderate flame of a laboratory burner. Stir constantly until it
becomes a thick paste.12
3. Allow the dish to cool and record your observations on the report
sheet.
4. Place the soap you just prepared into a 150 mL beaker with about 50
mLs of deionized water. Heat the mixture, with stirring, until all of
the solid soap has dissolved in the water. 13
5. Test the pH of this soap solution and record the result.14 Use this soap
solution in each of the following procedures (Parts B, C, and D).
B. Purification:
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. To each beaker add solid sodium chloride (NaCl) a little at a time
with stirring, until no more NaCl dissolves and the bottom of the
beaker is covered with NaCl. Record your observations on the report
sheet15.
3. Remove the mass of pure soap floating on the surface of beaker #1.
This could be done by scraping it off the top with a spatula or piece of
filter paper.
4. Put a small piece of the purified soap into a test tube and dissolve it in
deionized water. Stopper the tube and shake the soap to see if it
lathers.16
5. Test the pH of the purified soap solution in the test tube and also test
the pH of the detergent solution in the second beaker. Record the
results.
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
10
Ethanol is a good solvent to
dissolve both the nonpolar oil
and the polar NaOH in order to
better mix them together.
11
Sodium Hydroxide (50%
NaOH) 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.
12
Do not overheat and burn your
soap.
13
If there are clumps that will
not dissolve, scoop them out
and discard them.
14
This soap solution contains
some leftover sodium hydroxide
that didn’t react so it will show
a very basic pH. The crude
basic soap is too harsh to use on
your skin so it must be purified.
15
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. The NaOH leftover from
the preparation of soap reaction
is very polar like sodium
chloride so stays dissolved in
the water. Therefore, the soap
that comes to the surface of the
water is now more pure.
16
You could also test the
lathering ability by using the
purified soap to wash your
hands.
37
C. Reactivity with Hard Water Ions:
O
Na O
O
C
(aq) + CaCl2
2+
1-
Ca O
C
2 (s)
Sodium Stearate (A Soap)
1.
+ 2NaCl
Calcium Stearate (A Soap Scum)
Obtain two test tubes.
17
The sodium salts of fatty acids,
soaps, are soluble in water. When
other metal ions like calcium,
magnesium, or iron, form salts
with fatty acids they are not as
soluble in water and tend to
precipitate out.
 Into test tube #1 pour 5 mLs of the unpurified soap solution (prepared
in Part A).
 Into test tube #2 pour 5 mLs of detergent solution.
2.
Add up to 10 drops of 1M Calcium Chloride (CaCl2), one drop at a time,
to each tube and observe if a precipitate forms.
3.
Record the results.17
D. Reactivity with Acid:
O
Na O
O
C
(aq)
+ HCl
HO
C
(s)
+ NaCl
Stearic Acid (A Fatty Acid)
Sodium Stearate (A Soap)
4. Obtain two test tubes.
 Into test tube #1 pour 5 mLs of the unpurified soap
solution (prepared in Part A).
 Into test tube #2 pour 5 mLs of detergent solution.
5. Add up to 4 drops of 6M HCl (hydrochloric acid), one drop at a
time to each test tube and observe if a precipitate forms.
18
A soap is a weak base so it reacts
with HCl by taking an H+ which turns
it into a carboxylic acid. The newly
made carboxylic acid is a fatty acid
with a long hydrocarbon chain and
now that it has no charge it is no
longer soluble in water.
6. Record the results.18
III. ISOLATION OF ESSENTIAL OILS (Group project)
6. 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.
19
Add water to moisten the plant
material as needed.
20
7. 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.
8. Place a mug or beaker of water next to the apparatus in the
microwave and microwave on high for about 4-5 minutes. Let
sit undisturbed an additional 10-15 minutes.
Many plants will yield oils. Some
ideas to try are:
 Lavender buds
 Grated orange rind
 Peppermint leaves
21
For
a
demonstration
http://oilextech.com
22
9. 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.
10. Pipet the oil layer into a vial and save for use as a soap
fragrance.
38
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
see
The center beaker now contains
melted ice water and the extracted
essential oil.
IV. KREIS TEST FOR OXIDATIVE RANCIDITY:
1.
Obtain 2 large test tubes or small Erlenmeyer flasks and label
them #1(old) and #2( new). Record brands names and date of opening of
23
You do not need to measure 1 g
exactly. A gram of a fat is a hunk
about the size of the tip of your little
finger.
each sample if available.
24
2. Into tube #1 place about 1 g of “old” solid
drops) of “old” liquid vegetable oil. 24
23
fat or 1 mL (20
3. Into tube #2 place about either 1 g of “new” solid shortening or 1
mL (20 drops) of “new” commercial vegetable oil.
4. To each fat or oil sample add 8 drops of concentrated
hydrochloric acid (12M HCl).25 Stopper and shake to mix.
The fats tested can be shortening,
oils. lard, or other triglyceride
containing products.
25
12M
HCl
is
concentrated
hydrochloric acid (con HCl). Use
with caution.
18
Phloroglucinol is another name for
1,3,5-trihydroxybenzene.
26
5. Now to each sample add 1 mL (20 drops) of 0.1%
phloroglucinol26 in ether solution. Stopper and gently shake to
mix. Let stand for about 10 minutes.19
6. Compare the color27. Record your results and make conclusions.
Ether evaporates rapidly; slight
pressure may build up in the stoppered
test tube.
If too much ether is
evaporating add another 1 mL of
ether, stopper and gently shake then
let stand.
27
A red or pink color indicates
rancidity.
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
39
40
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
LAB 23: LIPIDS: FATS, OILS, AND SOAP:
NAME_____________
PRE LAB EXERCISES:
DATE______________
1.___
An unsaturated lipid ____________________than a saturated lipid.
A. is more difficult to digest
B. has a lower melting point
D. spoils less easily
E. more than one of these.
C. is more soluble in polar solvents
2.___
If a commercial lipid produced a positive Kreis test, you should
A. return it to the store and demand a refund.
B. use it regularly for cooking.
C. use it as a salad dressing.
D. classify it as a nonsaponifiable lipid.
E. more than one of these.
3.___
Which of the following makes water considered to be “hard” water?
A. Ca2+
B. Na1+
C. NH41+
D. More than one of these.
Match each of the following terms with the best structure it represents:
4.___
Fatty Acid
5.___
Triacylglycerol
H H O
H C
Detergent
7.___
Soap
8.___
Micelle
9.___
Ester
H H
C C O C C H
H H
6.___
O
E.
A.
H
H
C
H
C
H
C
O
O
O
H
H H
C
O
C
O
C
O
B.
C
OH
C
O
O
C O
O
C
O
O
C.
O C
O
C
O
F.
O
O
C O
Na
O C
O
D.
S
O
O
C
O
O Na
O
10.
Lab student, Kim Estry, is planning to make a 25 g bar of soap from the listed fats and oils.
A. Using the property tables given in the discussion calculate the grams of each fat and grams of KOH needed
to saponify this mixture.
Fat or Oil
% Composition
Coconut
40 %
Lard
50 %
Castor
10 %
100 %
B.
Grams Fat needed to
total 50 g’s
10 g Coconut Oil
1
12.5 g Coconut Oil
1
2.5 g Coconut Oil
1
25 g
total Fats & Oils
Needed
SAP Value
X
X
257 mg KOH
1 g Coconut Oil
1 g KOH
=
g KOH needed
=
2.57 g KOH
1000mg KOH
(mg KOH/1g fat
X
1 g KOH
1000 mg KOH
=
=
Total g KOH needed
You calculated the amount of KOH needed to saponify 100% of the fats/oils in Kim’s proposed soap
however she only has NaOH available to use. From the mass of KOH required use the molar mass of KOH
and NaOH to determine the quantity of NaOH required for 100% saponification. (Show your calculations.)
g NaOH
C.
To keep the soap from being too dry Kim only wants to convert 95% of the fats and oils to soap so wants to
use just 95% of the NaOH calculated. How much NaOH is needed to saponify only 95% of the fats/oils?
(Show your calculations.)
g NaOH needed
D.
What are the expected properties (from Table 2) from your selected combination of fats and oils?
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
41
42
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
LAB 23: FATS, OILS, AND SOAP:
NAME___________________
REPORT A:
I. SOAP:METHOD 1
PARTNER_________DATE___
%
Composition
Fat or Oil
Grams Fat needed to
total 25 g’s
A.
40 %
10 g
1
40 %
10 g
1
10 %
2.5 g
1
10 %
2.5 g
1
100 %
25 g
total Fats & Oils
Needed
A.
B.
B.
SAP Value
X
(mg KOH/1g fat
1000mg KOH
1 g KOH
X ……… mg KOH
1g
X
1 g KOH
=
g KOH needed
=
g KOH
=
g KOH
=
g KOH
1000 mg KOH
g KOH
= Total g KOH needed
You calculated the amount of KOH needed to saponify 100% of the fats/oils in your proposed soap however
you only have NaOH available to use. From the mass of KOH required use the molar mass of KOH and NaOH
to determine the quantity of NaOH required for 100% saponification. (Show your calculations.)
A.
g NaOH
To keep the soap from being too dry you only want to convert 95% of the fats and oils to soap so you want to
use just 95% of the NaOH calculated. How much NaOH is needed to saponify only 95% of the fats/oils? (Show
B.
your calculations.)
g NaOH needed
Instructor approval _______
What are the expected properties (from Table 2) from your selected combination of fats and oils?
OBSERVATIONS
pH
pH of crude soap dissolved in water:
Soap: Method 1
_________
1. Complete the following: Show Structures
O
H
O
C
H C
O
H C
O C
H C
O
H
O
NaOH
H2O
C
Glyceryl Trioleate
2. Name All of the Products:
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
43
II. Soap: Method 2
Observations
pH
pH of crude soap
dissolved in water:
A. Preparation: Appearance of freshly made soap:
_________
pH of purified soap
dissolved in water:
B. Purification:
1) Results of “salting out” the soap:
_________
2) Describe the “lather” after shaking the purified soap:
Results of “salting out” detergent:
pH of detergent
solution:
_________
Results of adding CaCl2 to soap:
C. Reaction
with Hard
Water Ions
Complete the reaction:
Results of adding CaCl2 to detergent:
O
Na
O
9
C
18
+ CaCl2
Sodium Oleate
Name of Products formed:
Analysis/Conclusions: Compare the behavior of soap and detergent in hard water and make conclusions regarding when
and where you might use each.
D. Reaction
with Acid
Results of adding to HCl soap:
Results of adding HCl to detergent:
Complete the reaction:
O
Na
O
C
9
18
+ HCl
Sodium Oleate
Name of Products formed:
Analysis/Conclusions: Compare the behavior of soap and detergent in acid.
44
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
III. ISOLATION OF ESSENTIAL OILS:
Plant Source:
Grams Used
mLs Oil Obtained
Odor and Observations:
Analysis/Conclusions:
IV. KREIS TEST FOR RANCIDITY:
Brand
Age
Observations
(date)
Conclusions
Rancid or Not?
Old Solid/Liquid
(circle which)
New Solid/Liquid
(circle which)
Explanation/Analysis: Why were the results this way?
Explain any anomalies.
3. Complete the following showing the products of complete oxidation (rancidity) of the double bonds:
O
H
O
C
H C
O
H C
O C
H C
H
O
[O]
with O2 or O3
O
C
Glyceryl Trioleate
RELATED EXERCISES:
___1.
Why are some solvents more effective at dissolving grease than others?
A. greases are nonpolar so will dissolve best in nonpolar solvents.
B. greases are nonpolar so will dissolve best in polar solvents.
C. greases are polar so will dissolve best in nonpolar solvents.
D. greases are polar so will dissolve best in polar solvents.
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)
45
___2.
The odor of acrolein is frequently strong in restaurants that feature charcoal-broiled food. Which of the
following best explains the presence of this odor?
A. the proteins in cooked meat decompose to form acrolein.
B. the tracylglycerols in meat decompose in high heat and the resulting fatty acids then dehydrate to form
acrolein.
C. the tracylglycerols in meat decompose in high heat and the resulting glycerol dehydrates to form
acrolein.
D. the charcoal used to cook food decomposes to form acrolein when the heat is high enough.
___3.
List each of the following that would be expected to produce Acrolein upon heating with KHSO 4?
A. olive oil
B. stearic acid
C. glycerol
D. palmitic acid
E. oleic acid
F. coconut oil
___4.
“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.
___5.
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.
___6.
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.
7.
Label the isoprene units in the essential oil limonene from oranges:
REFERENCE SEARCH:
8.
During World War II homemakers were asked to contribute their bacon grease to the war effort for the
production of nitroglycerin. Use a source of your choice to find the structure of nitroglycerin and how it is
made. Propose a sequence of reactions (using structures) to show the production of nitroglycerin from a fat (ie
bacon grease.)
Reference Source =
46
CH106 Lab 23 Lipids: Fats, Oils, & Soap (W16)