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In Lassaigne's test for nitrogen , the blue colour is due to the formation of

(a) Potassium ferricyanide (b) Sodium cyanide (c) Sodium ferrocyanide (d) ferri-ferrocyanide

1 Answer

$Na +C+N \underrightarrow{\Delta} NaCN$
$2NaCN +FeSO_4 \longrightarrow Fe(CN)_2 +Na_2SO_4$
$Fe(CN)_2+4 NaCN \longrightarrow Na_4 [Fe(CN)_6]$
$3 Na_4 [Fe(CN)_6 ]+4 Fe^{3+} \longrightarrow Fe_4 [Fe(CN)_6]_3+12Na^{+}$
It is ferri-ferrocyanide
Hence d is the correct answer.
answered Mar 5, 2014 by meena.p
edited Mar 26 by sharmaaparna1

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