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# In Lassaigne's test when both N and S are present, blood red colour is due to the formation of

(a) ferric sulphocyanide
(b) ferric cyanide
(c) ferric ferrocyanide
(d) none of these

Nitrogen, Sulphur and halogens, if present in an organic compound are detected by Lassaigne's test. The elements present in the compound aer converted from covalent form into the ionic compound are converted from covalent form into the ionic form by fusing the compound with sodium metal.

In case, N & S both are present in the organic compound, sodium thiocyanate is formed. It gives blood red colour.
$Na + N + C + S \overset{Fuse}{\longrightarrow} Na^+CNS^-$
$F^{3+} + 3CNS^- \longrightarrow Fe(CNS)_3$
Ferric sulphocyanide
(blood red colouration)