6F40.10 Scattering Sunset

PIRA 6F40.10 Scattering Sunset

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Photo of the Demonstration at the University of Texas at Austin.

Instructions / Notes:

A light beam is projected through a 4 liter beaker atop of an overhead projector.
Demo Staff: The beaker sits atop of a black piece of cardboard with a hole cut out of it.
The beaker contains a sodium thiosulfate solution. A separate 125 ml flask contains a sulfuric acid solution.
Sodium Thiosulfate Solution: 20 grams of Na₂S₂O₃ dissolved into 4 liter beaker of H₂O.
Mix the sodium thiosulfate solution on the preceding day or very early in the morning.
Sulfuric Acid: 1mL of H₂SO₄ is added to 124mL H₂O in a separate flask before the class.
During class the sulfuric acid solution in the flask is mixed with the sodium thiosulfate solution.
Briefly stir the sulfuric acid in the tank, turn on the lamp and wait four to five minutes.
A sulfate precipate begins to cloud the tank causing the first scattering effect, which appears nearly sky-blue within the tank.
The projected light seen on the opposite wall at this point changes from white to yellow.
The next phase, which occurs very briefly, two scattering colors are noticed in the tank, while the light projected on the wall becomes orange.
When the light projected on the wall appears to be red, the chemical reaction is complete.