Synthetic Inorganic Chemistry

ANHYDROUS ALUMINUM BROMIDE 213

safety tube (Fig. 23, on page 191). The gas will then pass into the

flask containing the aluminum chloride solution. The end of the

delivery tube dipping into the solution must be at least 1.5 cm. in

diameter, else it will become stopped with the precipitated prod-

uct. To the latter flask fit an exit tube which will lead any

waste gas to within \ inch of the surface of water in a bottle.

Surround the flask of aluminum chloride with cracked ice and

water, and pass the gas into the solution until it is saturated.

Observe the usual caution about disposing of the hot contents of

the generator. Collect the crystalline precipitate in a 5-inch

funnel containing a marble and dry it as completely as possible

with suction while pressing the crystal mass with the round end of

a test tube. Place the product in a 4-inch porcelain dish in the

desiccator over solid sodium hydroxide. It will take several days

for the excess of hydrochloric acid to evaporate from the crystals.

When it is dry put the product in an 8-ounce cork-stoppered bottle.

QUESTIONS

1. Treat some of the aluminum chloride with water. Does it
   dissolve to give a clear solution? Is there any noticeable heating?
   Test the solution with litmus. Is the salt hydrolyzed? Is it
   hydrolyzed extensively? Explain how you reach your conclusion
   from this experiment.


2. Warm about 1 gram of the preparation in a porcelain dish
   over a flame until fumes cease to come off. What are the vapors
   given off, and by what tests do you make your conclusion? Is the
   residue soluble in water? Of what does it consist?


3. Explain the difference in the extent to which the hydrolysis
   takes place when the salt is dissolved in a large amount of water
   and when it is heated with merely its water of crystallization.

PREPARATION 26
ANHYDROUS ALUMINUM BROMIDE, AlBr 3
Like aluminum chloride this salt is completely hydrolyzed if its
solution is evaporated to dryness. Only the hydrated salt can be
prepared by the action of hydrobromic acid solution (see preceding
preparation); the anhydrous substance is prepared by the direct
action of the elements on each other. The action is one of such