Gmelin's test is a

chemical test In chemistry, a chemical test is a qualitative or quantitative procedure designed to identify, quantify, or characterise a chemical compound or chemical group. Purposes Chemical testing might have a variety of purposes, such as to: * Determin ...

used for detecting the presence of bile pigments in

urine Urine is a liquid by-product of metabolism in humans and in many other animals. Urine flows from the kidneys through the ureters to the urinary bladder. Urination results in urine being excreted from the body through the urethra. Cellular ...

. It is named after

Leopold Gmelin Leopold Gmelin (2 August 1788 – 13 April 1853) was a German chemist. Gmelin was a professor at the University of Heidelberg He worked on the red prussiate and created Gmelin's test, and wrote his ''Handbook of Chemistry'', which over successi ...

, who introduced the test. Five millilitres of urine is slowly added to five millilitres of concentrated

nitric acid Nitric acid is the inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but older samples tend to be yellow cast due to decomposition into oxides of nitrogen. Most commercially available nitri ...

in a test-tube. Different coloured rings between the two layers are visible if bile pigments are present as they are oxidised to various chemical products. Nitric acid is used as the

oxidising agent An oxidizing agent (also known as an oxidant, oxidizer, electron recipient, or electron acceptor) is a substance in a redox chemical reaction that gains or " accepts"/"receives" an electron from a (called the , , or ). In other words, an oxid ...

. Blue, green and violet rings are seen if bilirubin is present. Gmelin's test is not sensitive so a positive result always indicates the presence of bile pigments but a negative result does not exclude the presence of small quantities of bile pigments.

References

Chemical tests {{analytical-chemistry-stub