Effect:
A clear colourless liquid is poured into a second clear colourless liquid and swirled. This mixture is poured into a third clear colourless liquid and swirled. After a period, the solution goes to yellow-gold colour and shortly afterward to black.

What You Need:
- Soluble starch
- Sodium hydrogen sulfite
- Mercuric chloride
- Potassium iodate
- Three 500 mL beakers

What You Do Before the Show:
-Prepare the following solutions in separate beakers:
A - 0.4 g of soluble starch in 50 mL water plus 1.5 g sodium hydrogen sulfite in 50 mL water;
B - 0.3 g mercuric chloride in 100 mL water
C - 1.5 g potassium iodate in 100 mL water

What You Do During the Show:
- Pour the contents of A into B and swirl the beaker;
- Pour the A+B mixture into C and swirl the beaker.

What is Happening:
Like the iodine clock reaction, there is a series of chemical reactions. Iodate ion reacts with hydrogen sulfite ion to produce elemental iodine, which reacts first with mercuric ion to form yellow mercuric iodide. When all the mercuric ion is used up, excess iodine reacts with starch to give a dark purple (black) complex.

Hazards:
-None to speak of.

Patter:
There can be two approaches. The first would be related to Halloween colours. The second would be related to what chemists have been trying to do for centuries - produce gold. Tell of your progress in this regard. You do in fact get gold. Express surprise when it then turns black. Then say something like, well you have accidently discovered black gold (oil).