A description of the method for the milligram determination of toluidine red, chlorinated p-nitro aniline red, para red and potassium ferrocyanide in Prussian blue pigments. Milligram amounts of the samples were allowed to react with a known excess of N-bromosuccinimide in the presence of acetic acid at room temperature (27°C). After the reaction was completed, the consumed reagent was estimated iodometricaliy. The results obtained were within the accuracy of ± 0.8 -- AATA