Name: Sami Atiq
Title of Experiment: Steam Distillation
Date of Completion: 09/30/2019
Date Report Submitted: 10/15/2019
Objectives of Experiment:
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1. To obtain a citral and water mixture from lemongrass oil using steam distillation
2. To extract pure citral from the distillate and calculate its percent recovery
Introduction:
When a mixture contains two liquids that are miscible with one another, the boiling point of the
mixture will be between the boiling points of the two liquids when they are by themselves.
Immiscible mixtures do not share this characteristic with miscible mixtures. The boiling point of
an immiscible mixture, for example benzene and water is found to be below the boiling points of
its pure compounds. Droplets of benzene will not be diluted by droplets of water surrounding
them and so the vapor pressure of benzene within the mixture is the same as the vapor pressure
of benzene by itself; this is the same case for water. When vapor pressure of the water and the
benzene add up to 760 torr, the temperature of the boiling point for the mixture should be found
to be below 80.1 °C.( 80.1 °C is the boiling point temperature of pure benzene at 760 torr). When
a substance within an immiscible mixture is not very volatile, a large amount of water is needed
for distill it. For this to be possible, steam is added to the boiling flask that contains the
immiscible mixture. This type of distillation is called steam distillation. Steam distillation offers
the advantage over normal distillation in that it allows substances to be purified at lower
temperatures, temperatures in which the substance remains stable and does not denature. In this
lab, citral will be isolated from lemongrass oil. Simple or fractional distillation cannot be used
for this isolation since lemongrass oil contains many substances as well as the fact that it can
decompose in these distillations since its boiling point is 229°C. Thus steam distillation is the
ideal method for the isolation of citral from lemongrass oil.
VI. Chemical Equations: N/A.
VII. Chemical Reagents:
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Name of
compound
Mol. Weight
(g/mol)
m.pt/b.pt (°C) Density
(g/mL)
Grams used
Moles used
Lemongrass
oil
777.2
B.P: 224
Water
18.01528
B.P: 100
1
10
.555
T-butyl
methyl ether
88.15
B.P: 55.2
.7
1.851
2.1x10-2
Sodium
Chloride
58.44
B.P:1,465
2.17
~4.34
~7.4x10-2
Calcium
Chloride
110.98
M.P:772
2.15
~.835
~7.5x10-3
Citral
152.24
B.P:229
.888
.04
2.6x10-4
Experimental Procedure:
Part 1: Isolation Of Citral
A 5-mL short necked flask was connected to a fractionating column and the fractionating column
was connected from its top to a distillation head. The end of the distillation end was positioned
over a vial that was contained within a 50-mL beaker filled with ice. A syringe filled with water
was connected to septum of the fractionating column of a steam distillation apparatus so that
water could be added to the mixture periodically.
A boiling chip, 0.5 mL of lemongrass oil, and 3 mL of water were added to the 5-mL short
necked flask. A sand bath was heated from beforehand so that distillation could occur
immediately. The mixture was distilled until the receiving vial contained 10-12 mL of distillate.
Part 2: Extraction Of Citral
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After the distillate was obtained it was inserted within a test tube and 2.5 mL of T-butyl methyl
ether was added to it. The test tube was shaken until two layers formed. The aqueous layer was
removed from the test tube and inserted into another test tube through the use of a pipette. 1.5
mL of T-butyl methyl was then added to the aqueous layer and the tube was shaken until two
layers developed. The aqueous solution formed here was separated again so that only ether
remained. The two solutions of ether were inserted within one test tube and about 2 mL of
saturated sodium chloride was added to the test tube. The tube was shaken again until two layers
formed and the aqueous layer was removed. Anhydrous calcium chloride pellets were then added
to the test tube until clumping ceased. The tube was shaken again for about five minutes. A
pasteur pipette was then inserted within the tube to draw out the ether and it was placed within
another test tube. A stream of air was added to this tube until ether was completely evaporated.
After this step only citral remained. The weight of the citral obtained and the percent recovery of
the citral from lemongrass oil was calculated.
Results, Summary, and Conclusion:
Part 1: Isolation Of Citral
Name of mixture
Amount of distillate (citral and water) formed
(mL)
Lemongrass oil-water mixture
~4mL
Part 2: Extraction Of Citral
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Density of Citral
0.888 g/mL
Mass of Citral + Vial
7.20 g
Mass of Vial
7.16 g
Mass of Citral
.04 g
Volume of Citral
.045 mL
Volume of Lemongrass oil
.44 mL
Percent recovery of citral from lemongrass oil
.045/.44 = .102 x 100% = 10.2%
In this lab we isolated and extracted citral from lemongrass oil. This was made possible by steam
distillation and taking advantage of the miscibility of the compounds with water and t-butyl
methyl ether.
Questions:
3.) p(t) = p(H2O) + p(Ibenz)
(1013 - 960) mbar = 53 mbar
960:53
18 g/mol:1 g/mol
1.6 g H2O/1 g I-benzene.
5.) If the steam valve is turned off before the trap is opened, the steam in the trap will condense,
creating a partial vacuum that will suck liquid from the flask into the trap and up the hose to the
steam valve. If the trap is partially opened, this process will create a siphon that will siphon all of
the liquid in the flask down the drain.
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