'$$\mathrm{X}$$' is :

In a reaction,

reagents 'X' and 'Y' respectively are :

Given below are two statements :

Statement I : Sulphanilic acid gives esterification test for carboxyl group.

Statement II : Sulphanilic acid gives red colour in Lassigne's test for extra element detection.

In the light of the above statements, choose the most appropriate answer from the options given below :

Which element is not present in Nessler's reagent?