- Griess test
The Griess test is a chemical analysis test which detects the presence of organic
nitrite compounds. The "Griess diazotization reaction" on which the Griess reagent relies was first described in 1858 byPeter Griess .Method
Nitrite is detected and analyzed by formation of a red pink colour upon treatment of a NO2−-containing sample with the Griess
reagent .When sulphanilic acid is added, the nitrites form a
diazonium salt . When theazo dye agent (alpha-naphthylamine) is added a pink colour develops [cite web |url=http://www.newscientist.com/article/mg13217944.400-forensic-science-goes-on-trial-even-senior-judges-can-beblinded-by-science-a-royal-commission-is-looking-for-better-ways-to-weighup-the-evidence-.html|title= Forensic science goes on trial: Even senior judges can be blinded by science |accessdate=2007-08-07 |author= Mick Hamer |authorlink= |coauthors= |date=1991-11-09 |year= |month= |format= |work= |publisher=NewScientist |pages= |language= |archiveurl= |archivedate= |quote= ] .A typical commercial Griess reagent contains 0.2% naphthylenediamine dihydrochloride, and 2% sulphanilamide in 5%
phosphoric acid .Forensics
The test was used in
forensics for many years to test for the traces ofnitroglycerine .Caustic soda is used to break down the molecule of
nitroglycerine to produce nitrite ions. The concentration of this caustic soda is crucial to the test.The test involves the taking of a
sample with ether and its division into two bowls.Sodium hydroxide is added to the first bowl followed by the Griess reagent; if the solution turns pink within ten seconds, this indicates the presence of nitrites. The test itself is positive if, after adding only Griess reagent to the second bowl, the solution there remains clearDue to the ability of many substances to produce nitrite ions, the test is not conclusive and eventually proved of limited value. British police forces had practically stopped using it by the mid-1980s.
The convictions of
Judith Ward and theBirmingham Six were assisted byFrank Skuse 's flawed interpretation of Griess test results.References
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