Gmelin sample

Gmelin sample - opening of bile pigments, usually in the urine, based on the gradual oxidation of bilirubin nitrous acid.
In test tube pour the concentrated nitric acid, yellow light (contains admixture of nitrous acid), and layer analyzed urine. In the presence of bile pigments at the liquid is formed green ring, showing the presence of bilirubin, and simultaneously lower its blue or purple. Red and yellow rings, located below, there may appear in normal urine, but in this case the green ring appears only after intake of antipyrine. Cm. also Urine (research methods).