Watch as the sun sets over a chemical reaction with the Aloha Chemical Sunset: Colloids and Light Scattering—ChemTopic™ Lab Activity. Carried out on an overhead projector, the reaction of sodium thiosulfate with hydrochloric acid produces colloidal sulfur particles that scatter the light from the projector. Available as part of the Solubility and Solutions—ChemTopic™ Labs digital collection. Click the Price link for digital collection pricing.