Synthetic Inorganic Chemistry

ANHYDROUS STANNIC BROMIDE 277

been expelled and the liquid begins to distil slowly into the tube.
The first part of the distillate is usually dark colored and boils
around 150°. It should be rejected. Watch the color and boiling
point of the distillate; when it becomes colorless and the tem-
perature reaches 200°, change the receiver to a weighed, dry,
6-inch Pyrex test tube. This should be done without interrupting
the distillation. If the distillation is not too rapid, all the vapor
will condense in the side arm of the flask and the test tube. When
the distillation is complete, immediately stopper the test tube
and allow it to stand in an upright position until the stannic
bromide has crystallized.
The product should be colorless. If a satisfactory result is not
obtained, the stannic bromide may be redistilled from a clean,
dry flask, to which one or two small pieces of tin have been added.

QUESTIONS
In each of the following experiments record your observation
and write an equation.
Make a solution of stannic bromide by mixing in a graduated
cylinder 1 cc. of your preparation of anhydrous stannic bromide,
4 cc. of 6N HC1, and 15 cc. of water. Shake the mixture until
solution is complete. Use this solution for the following tests.

1. (a) To 3 cc. of the solution add a few drops of 6N NaOH.
   Then add an excess of NaOH.
   (6) To 3 cc. of the solution add a few drops of 6N NaOH.
   Then add an excess of 6 N HC1.
   (c) Repeat (a) using stannous chloride solution.
   (d) Repeat (6) using stannous chloride solution.


2. (a) To 3 cc. of mercuric chloride solution add an equal
   volume of the stannic bromide solution.
   (6) To 3 cc. of mercuric chloride solution add an equal volume
   of stannous chloride, and then 3 cc. more stannous chloride.
   Compare the reducing properties of stannous and stannic ions.


3. (a) To 3 cc. of stannic bromide solution add a few drops of
   sodium sulphide, and then an excess of sodium sulphide.
   (6) To 3 cs. of stannous chloride add a few drops of sodium
   sulphide, and then an excess. To the mixture add sodium poly-
   sulphide, Na 2 S:e.
   Name the different compounds of tin formed in these reactions.