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1. $Fe^{2+}$ (Brown ring reaction) |
(Fill into a test tube 2 mL of a solution of nitrate slide in 2 mL of conc $H_2SO_4$, let cool in the water bath, carefully add a few drops of fresh iron(II) sulphate solution) $2NO_3^-$ $+$ $8H^+$ $+$ $6Fe^{2+}$ $\rightarrow$ $ 6Fe^{3+}$ $+$ $4H_2O$ $+$ $2NO$ $2NO+2FeSO_4$ $\rightarrow$ $2Fe(NO)SO_4$ (-> Brown ring, unstable complex if heated) |
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2. Diphenylamine in the presence of conc. $H_2SO_4$ |
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Navy blue color (Wet the inside a test tube with the reactant, thereafter introduce a few drops of nitrate) This reaction is very sensitive, but not specific; nitrite and chlorate do the same. |
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3. Diazotation (Griess reaction) in the presence of $Zn/CH_3COOH$ |
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Mix in a test tube: 1-2 mL of acetic solution of sulfanilic acid 1-2 mL of acetic solution of α - naphthylamine Add several drops of the nitrate solution Add one piece of zinc p.a. which operates the reduction: $Zn$ $+$ $2H^+$ $+$ $NO_3^-$ $\rightarrow$ $Zn^{2+}$ $+$ $H_2O$ $+$ $NO_2^-$ Nitrite forms a cherry-red compound. ) |
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4. Reagent "Nitron" (1,4-diphényl-2,5-endoanilo-1,3,4-triazoline) |
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- White crystalline precipitate - Forms slowly in dilute solution |