Gmelin's test is a

chemical test In chemistry, a chemical test is a qualitative property, qualitative or Quantitative property, quantitative procedure designed to identify, quantify, or characterise a chemical compound or substituent, chemical group. Purposes Chemical testing m ...

used for detecting the presence of bile pigments in

urine Urine is a liquid by-product of metabolism in humans and many other animals. In placental mammals, urine flows from the Kidney (vertebrates), kidneys through the ureters to the urinary bladder and exits the urethra through the penile meatus (mal ...

. 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 Potassium ferricyanide, red prussiate and created Gmelin's test, and wrote his ''Handbook of Chemistry ...

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

nitric acid Nitric acid is an inorganic compound with the formula . It is a highly corrosive mineral acid. The compound is colorless, but samples tend to acquire a yellow cast over time due to decomposition into nitrogen oxide, oxides of nitrogen. Most com ...

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 ''electron donor''). In ot ...

. Blue, green and violet rings are seen if

bilirubin Bilirubin (BR) (adopted from German, originally bili—bile—plus ruber—red—from Latin) is a red-orange compound that occurs in the normcomponent of the straw-yellow color in urine. Another breakdown product, stercobilin, causes the brown ...

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