 It is obtained by the oxidation of ortho-phenylenediamine with ferric chloride.In a related process, oxidation of a cold mixture of "para"-aminodimethylaniline and "meta"-toluylenediamine gives toluylene blue.This indamine is formed as an intermediate product and passing into the red when boiled; and also by the oxidation of dimethylparaphenylene diatnine with metatoluylene diamine.