NEDA (N-(1-Naphthyl)ethylenediamine Dihydrochloride)
Definition
The azo coupling component in the modified Griess test. After diazotisation of sulphanilic acid with nitrous acid, NEDA couples with the diazonium salt to produce the visible orange-pink azo dye that maps propellant residue deposition.
- Full name
- N-(1-naphthyl)ethylenediamine dihydrochloride
- Role
- Azo coupling component in the modified Griess test
- Reacts with
- Diazotised sulphanilic acid
- Visible result
- Orange-pink azo dye
Common questions
What does the colour NEDA produces actually reveal about a shooting?+
The orange-pink dye maps the spatial pattern of nitrite-containing propellant residue deposited around a bullet entry hole on a target such as clothing, and the density and spread of that pattern is compared against test firings from the suspect weapon to estimate firing distance.
Why is a two-step Griess test with NEDA used rather than a single-reagent colour test?+
Diazotisation of sulphanilic acid first forms a diazonium salt selectively from nitrite in the residue, and only then does NEDA couple with that salt to form the visible dye, a two-step sequence that gives more specific and reproducible results than a single combined reagent would.
Related terms
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