Gmelin's test

{{Short description|Chemical test}}

Gmelin's test is a chemical test used for detecting the presence of bile pigments in urine. It is named after Leopold Gmelin, who introduced the test.{{cite book|author1=Erwin Kuntz|author2=Hans-Dieter Kuntz|title=Hepatology: Textbook and Atlas|url=https://books.google.com/books?id=oL6d9KuVqLQC&pg=PA11|date=11 March 2009|publisher=Springer|isbn=978-3-540-76839-5|page=11}}{{cite book|author1=John Daintith|author2=Derek Gjertsen|title=A Dictionary of Scientists|url=https://books.google.com/books?id=AtngooiwXikC&pg=PA216|date=4 March 1999|publisher=Oxford University Press|isbn=978-0-19-280086-2|page=216}}{{cite book|author=John Daintith|title=Biographical Encyclopedia of Scientists, Third Edition|url=https://books.google.com/books?id=vqTNfnKJVPAC&pg=PA295|date=12 December 2010|publisher=CRC Press|isbn=978-1-4200-7272-3|page=295}} Five millilitres of urine is slowly added to five millilitres of concentrated nitric acid 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.{{cite book|author=Srinivas B Rao|title=Practical Biochemistry for Medical Students|url=https://books.google.com/books?id=FI-z0owfQEsC&pg=PA56|publisher=Academic Publishers|page=56}}{{cite book|author=Dandekar|title=Practicals And Viva In Medical Biochemistry|url=https://books.google.com/books?id=s9HEoJquruwC&pg=PA47|date=1 January 2004|publisher=Elsevier India|isbn=978-81-8147-025-6|page=47}} Nitric acid is used as the oxidising agent.{{cite book|author=D M Vasudevan|title=Textbook of Biochemistry for Medical Students|url=https://books.google.com/books?id=nQz8AAAAQBAJ&pg=PA279|year=2013|publisher=JP Medical Ltd|isbn=978-93-5090-530-2|page=279}} Blue, green and violet rings are seen if bilirubin is present.{{cite book|author=Malhotra|title=Practical Biochemistry for Students|url=https://books.google.com/books?id=LHa1G131MuYC&pg=PA46|date=1 January 2003|publisher=Jaypee Brothers Publishers|isbn=978-81-8061-109-4|page=46}}{{Dead link|date=June 2024 |bot=InternetArchiveBot |fix-attempted=yes }} 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.{{cite book|author=A.C. Croftan|title=Clinical Urinology|url=https://books.google.com/books?id=0_vvAgAAQBAJ&pg=PA123|publisher=Рипол Классик|isbn=978-1-275-01265-3|page=123}}