Ehrlich's aldehyde reagent is used to detect urobilinogen in urine. Urobilinogen is one of the bile pigments found in urine in case of liver defects, (epidemic icterus, cirrhosis) or as a result of excessive formation of bilirubin (haemolytic jaundice). The colourless urobilinogen reacts with Ehrlichs aldehyde reagent in an acidic medium to form pink-red condensing products.