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Which of the following is an incorrect statement regarding the Griess-I test for nitrite ions?

1. The diazotised acid couples with 1-Naphthylamine to form a red azo dye.
2. Acidification with acetic acid ensures formation of HNO2 which then causes diazotisation of sulphanilic acid.
3. The red azo dye forms regardless of the concentration of the test solution.
4. The red azo dye molecule contains three nitrogen atoms in a single molecule.

Correct answer: The red azo dye forms regardless of the concentration of the test solution.

Solution

In the Griess-I test: sulphanilic acid is diazotised by HNO2 (formed from nitrite under acidic conditions), and the diazonium salt couples with 1-naphthylamine to give a red azo dye. Statements A, B, and D are correct. Statement C is incorrect because the test has a sensitivity limit; very dilute nitrite solutions do not produce detectable azo dye colour.

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