DISTILLATION OF WATER FROM AN AQUEOUS SOLUTION USING A DISPOSABLE APPARATUS
Using readily available materials, students
separate a colorless liquid from a common colored solution by distillation.
This experiment is particularly
appropriate for middle school science classes or for a general or first-year
course where scientific glassware is unavailable. A simple distillation is
performed using a soda can and aluminum foil in place of traditional glassware.
The experiment works sufficiently well to enable students to obtain a colorless
liquid from a colored solution. Not only is the equipment inexpensive and
readily available, but the entire apparatus is disposable.
One lab period.
*See Modifications / Substitutions
If alcohol burners are used, they should be
filled when cold, only by the teacher. Adding common salt to the burner fuel
makes it easier for students to see the flame and thus avoid possible burns. The
aluminum foil condenser becomes quite hot during the distillation. Care should
be taken to avoid touching it during collection of the distillate. Goggles must
be worn throughout the experiment.
- crushed ice solution to be
distilled--cranberry or apple juice, coke, orange soda, or colored aqueous
- empty soda can--Pepsi, 7-Up, etc.
- 4 to 8-oz clear glass jar
with narrow opening at top larger jar or other container to hold jar above 4-In
x 12-in piece of aluminum foil
- Bunsen or alcohol burner
- ring stand
- iron rings
- A wide variety of
common household solutions can be distilled in this experiment, including fruit
juices and strongly colored sodas.
- Highly colored inorganic chemical
solutions (KMnO4, K2Cr2O7, CuSO4, etc.) should be avoided because they will react with the aluminum in the cans.
After pouring the mother liquor down the
drain, the entire distillation apparatus may be disposed of with the solid
waste. If desired, the jars may be saved for re-use. The aluminum cans could be
Review the processes of evaporation and
condensation with students. Emphasize the principles which allow distillation to
be used as an effective purification tool (i.e., contaminants must be
non-volatile). Be sure to compare the color of the starting material with that
of the distillate.
For better sealing of the condenser tube, use
one of the following procedures. The aluminum foil at the mouth of the can may
be sealed with masking tape. Alternately, the condenser tube can be fitted
carefully Into corks or stoppers at the mouths of the can and the collection
bottle; however, the system should not be completely sealed.
Holtzclaw, H.F., Jr., Robinson, W.R.,
and Nebergall, W.R., College Chemistry with Qualitative Analysis,
D.C. Heath and Company, Lexington, MA, 1984, p. 285.
- Rinse the soda can clean.
- Add the solution to be distilled until the can is l/3 to l/2 full. Boiling
chips may be added if available, but are by no means necessary.
- Mount the soda can above the burner on a wire screen supported by an iron
ring (attached to the ring stand). Mount the second iron ring around and near
the top of the can to prevent it from tipping over.
- Insert the smaller glass jar into the larger one and surround liberally
with an Ice-rich slush bath.
- Prepare an air-cooled condenser made of aluminum foil. This is best done by
wrapping the foil lengthwise around a dowel rod or broom handle, taking care to
seal the seam that runs the length of the foil tube by making several folds of
foil neatly pressed back on itself. (Failure to do this will result in. poor
efficiency during distillation.)
- Fit one end of the condenser into the opening at the top of the soda can.
Gently bend the other end down and Insert it into the smaller glass jar which
serves as a receiver flask for the distillation.
- Heat the soda can and its contents with a steady flame. As the solution
boils, some vapor can be seen escaping from around the mouth of the can. Still,
enough vapor makes its way through the air-cooled condenser so that condensation
soon occurs In the chilled receiver flask.
This work describes the
theory of distillation. A similar discussion could be found in any college-level
Submitted by Stephen Cotton, Jean Crowley, Joan D'Agostino, Dan Holmquist, and John Hnatow
Woodrow Wilson Leadership Program in Chemistry
The Woodrow Wilson National Fellowship Foundation
CN 5281, Princeton NJ 08543-5281