ANDREW LAMBERT PHOTOGRAPHY / SCIENCE PHOTO LIBRARY ANDREW LAMBERT PHOTOGRAPHY / SCIENCE PHOTO LIBRARY
Cobalt chloride (CoCl2) paper with a drop of water. Cobalt chloride paper is used to indicate the presence of water - changing from blue to pink in a hydration reaction. The blue form is cobalt chloride dihydrate, with two attached water molecules. The compound in the presence of water gains four extra water molecules to become the pink hexahydrate, with heating reversing the reaction.
Model release not required. Property release not required.