In the Thionin—The Two-Faced Solution: Chemical Demonstration—ChemTopic™ Lab Activity, place a large beaker with a bright purple solution on a lit overhead projector half-covered with aluminum foil. In seconds, the solution exposed to light turns colorless while the unexposed side remains purple, appearing to be divided by an invisible line through the beaker. Available as part of the Exploring Equilibrium—ChemTopic™ Labs digital collection. Click the Price link for digital collection pricing.