Greiss test
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The Griess test is a chemical analysis test which detects the presence of organic nitrite compounds. As such it was used in forensics for many years to test for the traces of explosive materials, although recent discoveries have found that the test can give false positive results in many circumstances.
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 Greiss reagent; if the solution turns pink within ten seconds, this indicates the presence of nitrites. The test itself is positive if, after adding only Greiss reagent to the second bowl, the solution there remains clear. The Greiss reagent is a prepared solution of equivolumes of 0.2% naphthylenediamine dihydrochloride, 2% sulphanilamide in 5% Phosphoric acid.
As the Greiss test detects both organic nitrites and nitrates, which might be found in many household chemicals, it eventually proved of limited value and British police forces had practically stopped using it by the mid-1980s. However, the convictions of the Birmingham Six and Maguire Seven, which were assisted by evidence that Greiss tests on some of the accused had been positive, were not overturned until many years later.
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