Project light through tank of
sodium thiosulfate
solution onto screen in darkened room. Add a couple of drops of
concentrated sulfuric acid to tank. This produces a suspension
with particles
the right size to scatter blue light and transmit orange. As the
reaction proceeds, the particles increase in size, and transmitted
light becomes increasingly red.
Use polarizing filter to show that
scattered light is polarized and transmitted light is not.
NOTES
The rate of reaction is
temperature-dependent and takes about 4 minutes at room
temperature. Leave tank of water out over night so that water
reaches room temperature by the time it is needed.
Warm water can be added to speed
up the process during the demo if needed.
Clean up immediately – product is
sulfur and smells bad.
Pine-sol can be used in place of the hypo and acid.
