Simple Distillation of Close-Boiling Substances
Analysis by Gas Chromatography
Carefully read the chapters in Zubrick concerning Simple Distillation (“class 1” in chapter 20)
and also on the Theory of Distillation (chapter 35). You will find that the guideline that simple
distillation is used to separate liquids from each other with boiling points of 25°C or more apart.
This begs the question- “What happens if you perform a distillation on liquids whose boiling
points are LESS than 25°C apart?” That is exactly what you will do in this experiment using gas
chromatography to analyze the composition of the distillate at different points during the
distillation. You will record the distillate temperature frequently throughout the distillation.
Before you come to lab
Read the chapters on Distillation and Theory of Distillation in Zubrick. Also, briefly skim
through the chapter on Gas Chromatography to familiarize yourself with the basics, but realize
that we will use a computer
controlled instrument with
parameters already adjusted
for you. You will likely find
it helpful to view the
clamp attached to
distillation videos posted on round bottomed flask
the class website under the
laboratory techniques use thermometer water out
adapter here water in
section. Prepare your prelab
in the notebook as usual. note bulb of
Procedure flask touches bottom
You will work with one of heating mantle
laboratory partner to perform heating mantle in graduated
stirring bar cylinder
the distillation and collect
data. You will write your stirring plate
independently. Set up a
simple distillation as shown block of wood
in the diagram. Start by
setting up a 50 mL round bottomed flask on the clamp and to this flask add 5 mL of acetone and
5 mL of methyl ethyl ketone (MEK). Add the remaining glassware to complete the setup. Do
not plug anything in or start the water until the instructor or TA has checked your setup.
Once your setup has been checked, start a gentle flow of water through the condenser. Turn on
the stirring portion of the stirring plate (but NOT the heat). Turn the controller of the heating
mantle to about ½ of the power (a setting of about 40 or 45 on most controllers). Once the liquid
starts boiling and the vapors rise high enough, the thermometer will be able to read the
temperature of the vapor. The distillate should collect slowly, one drop every 2 or 3 seconds.
Record the temperature versus volume collected frequently (every 0.25 to 0.5 mL). Most of the
distillate will be collected in the graduated cylinder. You will also be provided with 2 screwtop
vials. When the distillate volume reaches the 2 mL mark, catch the next 5 or 6 drops of distillate
in one of the vials. Then continue to collect in the graduated cylinder. At 6 mL, collect 5 or 6
drops in the other vial. Place caps on these vials immediately so the distillate does not evaporate
away. The samples in the vials will be analyzed by GC (gas chromatography).
Raise the distillation apparatus out of the hot heating mantle when the remaining liquid is a fairly
low volume. Don’t let it go dry (fire/explosion hazard it you let it go dry). Thus when you have
collected about 8 mL, there is likely only 1 mL left behind. Remove the wooden block to
separate the glassware from the heat. Then raise the clamp to lift the apparatus up far enough
away to cool effectively.
Analysis of the distillate by GC
Once you have finished your distillation and started the cooling process, you will take your vials
to room E3003. There are 2 gas chromatographs that will be in use for the class. They have the
identical performance, despite the fact that one is controlled by an internal computer and the
other is controlled by an external Windows PC.
Using the Hewlett-Packard 5880A GC (near back of room by windows)
The temperature will be set for 160°C for you and the instructor or TA will assist with running
1. Inject 0.2 microliters into injection port A
2. Immediately press the green Start button on the console. The results will be plotted as
the data is collected.
3. When the last peak finishes (about 3 ½ minutes), press the Stop button. The peak
integrals will automatically print.
4. You can now inject the sample from your second vial or next person can now inject their
sample. When the paper runs up enough, use scissors to cut off your plot.
Using the Shimadzu GC-14B (near center of room)
The temperature will be set for 200°C for you and the instructor or TA will assist with running
1. From the left menu, click “Single Run”.
2. Now click “Sample Login”. The 3rd line down will have the file name that should
automatically increment, thus allowing you to merely press OK.
3. Now click the green “Start” icon from the left menu. The instrument should now display
READY in blue lettering at the top.
4. Inject 0.2 microliters into left side injection port.
5. Immediately press the green Start button on the console panel of the instrument (not on
the computer). The results will be displayed on the screen as the data is collected.
6. The data acquisition will automatically stop after 3 ½ minutes and the data will be sent to
the laser printer.
7. You can now start the “Sample Login” process for the sample from your second vial or
the next person can start with their sample.
Most of your report will be wordprocessed with a hand-drawn graph of your distillation
-Start with a title and then a purpose statement that describes the type of scientific conclusions
that the collected data lead to.
-Under results, please construct a table showing the distillate volume and the temperature.
-Also under results, construct a hand-drawn graph (not a computer graph) of the distillation data
points and connect them to form a smooth curve.
-Finally, under results, you should include the data from your two GC runs. You can attach
copies of the printouts if desired, or somehow insert them into the document. Make sure the area
percentages of each peak are included as part of the data.
-Your discussion section should first give a brief overview (in several sentences) of what simple
distillation is used for, what materials are appropriate, the basic theory of how separation is
achieved, and the major precautions necessary to achieve good separation (with a brief rationale
Next the temperature results should be discussed, focusing on the boiling points of each
compound compared to the actual observed temperatures at the beginning, middle, and end of the
distillation. Suggest reasons why the particular temperatures were observed and the materials
present in the distillate at each of these points. Suggest which, if any, of the drops of distillate
consisted of a single substance (and justify your answer).
The GC results should now be addressed. Briefly explain what each of the chromatograms (and
calculated area percentages) tell you about the distillate. Furthermore, reconcile the GC results
with the temperature results to give a full picture of what was happening during the distillation.
-In a separate section, provide answers to each of the following questions. Explain the rationale
for your predictions as part of your answers.
1. If your distillation provided complete and perfect separation of the two substances, what
would the GC results look like for the 2nd mL sample vial and the 6th mL sample vial?
2. Your two liquids differed by 24°C in boiling point. How would your GC results for the 2nd
mL sample vial have been different is the liquids differed by 100°C?
3. Your two liquids differed by 24°C in boiling point. How would your GC results for the 2nd
mL sample vial have been different is the liquids differed by only 1°C?