If on adding $FeCl_3$ solution to acidified Lassaigne solution of an organic compound a blood red colouration is produced,it indicates the presence of

Which compound is responsible for the formation of a blue precipitate when ferric ions react with a Lassaigne's extract or potassium ferrocyanide solution?

Given below are two statements :
Statement $I :$ In Lassaigne's test,the covalent organic molecules are transformed into ionic compounds.
Statement $II :$ The sodium fusion extract of an organic compound having $N$ and $S$ gives prussian blue colour with $FeSO_4$ and $FeCl_3$.
In the light of the above statements,choose the correct answer from the options given below.

In the detection test of nitrogen,the Prussian blue colour is due to which compound?

Which of the following substances will give the Lassaigne's test for nitrogen?

The Lassaigne's extract is boiled with dilute $HNO_3$ before testing for halogens because,