Description
A clear, colorless solution turns orange when another clear colorless solution is added, and then turns clear when more of the same solution is added.

Application
Solubility K_sp Chemical change

Theory
When the solubility product of a solution is exceeded a precipitate forms.

Materials
Potassium Iodide solution
Mercury II chloride solution

Safety
POISON: YOU CANNOT DRINK THE 'ORANGE JUICE'
Wear protective gloves and safety goggles

Preparation
Solution 1) 100 g KI in 1.0 L DI water
Solution 2) 25 g HgCl₂ in 1.5 L DI water

Pour 100 mL of KI in a beaker. Stir with a magnetic stirrer.
Add the HgCl₂ until the orange appears (about 75 mL).
Add more HgCl2 until the precipitate disappears (about 75mL)

Disposal
KI solution may be poured down the drain and flushed with water.

Reference
California State University, Stanislaus