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Tyndall Effect


Slide Projector

Stirring Rod

Small Aquarium or Fish Bowl (as long as it has 2 flat sides)

Mirror (about the size of the small side of the aquarium)

Water to fill the Qquarium

Gloves and Goggles

For each gallon of water:

20 mL saturated sodium thiosulfate

5 mL 6 M HCl



Shine light through the aquarium filled with water. It will be virtually invisible where it passes through the aquarium and bright white where it emerges and shines toward the viewers.

Add the thiosulfate and HCl and stir. Mixture will become turbid in 1 - 2 minutes, and the turbidity will increase for ~10 min. As turbidity increases, the beam will become visible where it passes through the mixture. The beam passing through the solution appears blue, while the emerging beam appears orange. The blue beam will gradually widen.


Waste Management

The solution can be flushed down drain with water.



Combine 50 mL distilled water with 90 g Na2S2O2 * 5H2O. Warm the mixture until it is liquid and allow to cool; decant the liquid, which is the saturated solution.


from Shakhashiri, B. Z., Volume 3, p 353