ANHYDROUS ALUMINUM BROMIDE 215fectly dry. The glass tube may be heated, if necessary, in order
to sustain the reaction. Some uncombined bromine will pass
the aluminum and escape from the receiving flask. The alumi-
num bromide will condense and drip into the receiving flask.
If any solidifies in the tube it should be melted out.
After this phase of the process is over, clamp the receiving flask
in an upright position, using it now as a distilling flask, and close
the neck with a rubber stopper carrying a thermometer. Label
three dry test tubes and record the weight of each on the label.
Support one of these tubes with the side arm of the distilling flask
inserted about 3 inches, and start the distillation. At first bro-
mine vapor alone comes over, part of which condenses. As soon
as the red color has disappeared from the bulb of the flask, sub-
stitute a fresh tube as receiver, and catch 1 or 2 cc. of slightly
colored product; then, as soon as the aluminum bromide, comes
over entirely colorless, change the receiver again, and collect the
bulk of the product, which distils at 268°, in the third tube.
Stopper all three tubes immediately with rubber stoppers. Hand
in the third tube and contents as the preparation. Half fill the
second tube with carbon disulphide and restopper it, leaving the
aluminum bromide to dissolve. Take the stopper from the dis-
tilling flask and observe the dense fumes, caused by the reaction
of the aluminum bromide left in it with the water vapor of the air.
It is unsafe to pour water into the vessels containing any aluminum
bromide. To clean them dissolve the aluminum bromide in a little
carbon disulphide, then add water and rinse them out. Carbon
disulphide vapor is inflammable and the liquid should not be
handled near a flame. If a deposit of aluminum oxide adheres
to the inside of the distilling flask add a few cubic centimeters of
12 N HC1 and let it stand over night.
QUESTIONS- Place 3 cc. of the carbon disulphide solution of aluminum
bromide in a dry 600-cc. beaker. In another beaker place 100 cc.
of cold water, and holding it at arm's length with the face turned
away, pour it all at once into the first beaker. The effect is
startling but not dangerous if one is not too near. Heat the con-
tents of the beaker until all the carbon disulphide is evaporated.
Is the aluminum bromide now dissolved in the water? Make
tests for Al+++ and Br~ ions on separate small portions. How?