exp _ 4 a , distillation
TRANSCRIPT
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Experiment # 4
Distillation
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Recrystallization
Extraction
Impure
compound
Isolation
Distillation Liquids only
Chromatography Solids or Liquids
Purification
Establishingpurity
Melting point Boiling point
Spectroscopy
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Distillation
Purification of liquids by vaporization and condensation
vaporization condensation
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Purification methods for liquids
Distillation
Simple
distillation
Fractional
distillation
Vacuum
distillation
Steam
distillation
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Simple DistillationSeparating liquids from
a. Non volatile impuritiesb. Another liquid boiling at least 400 C higher than the first.
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Theory of simple distillationDiagram of dependence of vapor pressure on temperature. Blue curve is forpure water, and green curve is for a solution of water and sugar
Vaporpressure(torr)
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Simple DistillationPurpose
Purification of Cyclohexane (b.p. 810C at 760 torr), volatile organic liquid,containing a nonvolatile impurity, Dye
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Simple DistillationSetting Up
1 2 3 4
7 85 6
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Simple Distillation
Dos and Don'ts
Place 10 mL of cyclohexane, 2 drops of dye, stir bar in R.B
flask
Place the heating mantle after adding the liquid to the round bottom
as g. 3
The top of the mercury bulb of the thermometer should be adjacent
to the side arm of the still head. (fig. 5)
Use Keck clips to hold the condenser, vacuum adapter, and receiver
in place ( fig.8)
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Simple Distillation
Begin heating the R.B. flask. As soon as the liquid begins to boil and
the condensing vapors have reached the thermometer bulb, regulate
the heat supply so that distillation continues steadily at a rate of 2-4drops per second
If a drop of liquid cannot be seen suspended from the end of the
thermometer, the rate of distillation is too fast.
As soon as the distillation rate is adjusted and the head temperature is
constant, note and record the temperature
Stop heating when only 2-3 ml of impure cyclohexane remains in
the distillation flask.
Record the volume of distilled cyclohexane that you obtained
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Fractional Distillation
The technique can be used to separate pure liquid components from
a mixture containing two or more volatile substances if their boiling
points are close to each other
It involves multiple simple distillations
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Theory of Fractional Distillation
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Fractional DistillationPurpose
To separate the two volatile components, Cyclohexane ( b.p. 810C),
and Toluene ( b.p. 1100C)
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Fractional DistillationSetting Up
1 32 4
5 6 7
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Fractional DistillationDos and Donts
Place 10 mL of cyclohexane, 20 mL of toluene, stir bar in R.B. flask
When packing the column, be careful not to break off the glass
indentations at the base of the column
Do not pack the column too tightly
The top of the mercury bulb of the thermometer should be adjacent
to the side arm of the still head.
Use Keck clips to hold the column, condenser, vacuum adapter, and
receiver in place
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Fractional Distillation As the mixture is heated, the head temperature will rise to 810C(760
torr), and distillation will begin
faster than one drop of distillate every 1-2 sec
If a drop of liquid cannot be seen suspended from the end of the
thermometer, the rate of distillation is too fast
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Fractional Distillation
Collecting fractions
Collect the first fraction at 810C 30C , label it A
Change to the second receiver and increase the heat, label it B
Collect the last fraction when temperature reaches 1100C, label it C
Results
The temperature range while the distillation is steady ( 1 & 3fractions )
The volume of distillate collected in each receiver
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Fractional Distillation
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Save samples, Waste disposal
Three fractions obtained from fractional distillation should be saved
for the future lab gas chromatography
The cyclohexane obtained from simple distillation should be
disposed of in non halogenated waste container
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