At first glance, this looks like a terrible idea. Potassium Ferricyanide can be turned into the deadly toxin Potassium Cyanide.
But this pair is for something far more innocuous - the reaction with Ferric Ammonium Citrate makes Cyanotype, also known as Blueprint, which is part of a photographic process that predates silver-based photography. It can be used to photocopy with a strong light source, or for Sun Printing.













