The Middleton test is used for the detection of which element?

Lassaigne's test for nitrogen is negative for which compound?

The Kjeldahl's method for the estimation of nitrogen can be used to estimate the amount of nitrogen in which one of the following compounds?

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.

Why is nitric acid added to sodium extract before adding silver nitrate for testing halogens?

Lassaigne's test is used for the detection of which of the following?