Reducers

Potassium Ferricyanide

Potassium ferricyanide is a chemical compound. The compound has widespread use in blueprint drawing and in photography. Iron and copper toning involve the use of potassium ferricyanide. It is used as an oxidizing agent to remove silver from negatives and positives, a process called dot etching. In color photography, potassium ferricyanide is used to reduce the size of color dots without reducing their number, as a kind of manual color correction. The compound is also used to harden iron and steel, in electroplating, dyeing wool, as a laboratory reagent, and as a mild oxidizing agent in organic chemistry. It is also used in photography with sodium thiosulfate to reduce the density of a negative where the mixture is known as Farmer's reducer; this can help offset problems from overexposure.