Experiment 27

Objective: To grow a crystal of Potash Alum

Introduction:

Potassium alum is highly soluble in water and crystallizes in an octahedral shape with flattened corners. This experiment demonstrates how a crystal of potash alum can be grown from a saturated solution.

Required Materials:

Potash alumBeakersGlass rodPiece of stringBurnerTripod stand

Procedure:

1.    Prepare a saturated solution of Potash Alum by dissolving its finely powdered form in distilled water in a beaker.

2.    Heat the mixture using a burner until all the solids dissolve completely.

3.    Allow the mixture to settle for a few minutes.

4.    Observe the crystalline formations that begin to appear at the base of the beaker, leaving clear liquid above them.

5.    Transfer the clear liquid to another beaker.

6.    Select a well-formed crystal from the deposited crystals.

7.    Suspend the selected crystal from a glass rod into the saturated solution using a piece of string.

8.    Monitor the crystal daily and remove any other crystals that form in the solution.

9.    Supplement the solution with more saturated Potash Alum from time to time to help the crystal grow larger.

Observation:

This experiment demonstrates that in the presence of an abundance of molecules, crystals can grow in size as more molecules attach themselves to the existing crystal.

Questions:

1.  Is Potash Alum soluble in water? Yes, Potash Alum is highly soluble in water.

2.  How long should the mixture be heated? The mixture should be heated until all the solids completely dissolve.