Ferric nitrate is a violet crystalline solid. Noncombustible but it will accelerate the burning of combustible materials. If large quantities are involved in the fire or the combustible material is finely divided an explosion may result. Prolonged exposure of the material to fire or heat may result in an explosion. Toxic oxides of nitrogen are produced in fires involving this material. It is used for dyeing and tanning, in chemical analysis, and in medicine. Ferric nitrate is a strong oxidizing agent. Ferric nitrate can be used in in vitro model of "iron-loaded" cells. Ferric nitrate is commonly used as a positive indicator test of the phenol group.