In a complexometric titration of metal ion with ligand
M(Metal ion) + L(Ligand) $$ \to $$ C(Complex) end point is estimated spectrophoto - metrically (through light absorption). If 'M' and 'C' do not absorb light and only 'L' absorbs, then the titration plot between absorbed light (A) versus volume of ligand 'L' (V) would look like :

Which of the following compounds will be suitable for Kjeldahl’s method for nitrogen estimation?

A solution containing a group-IV cation gives a precipitate on passing H₂S. A solution of this precipitate in dil.HCl produces a white precipitate with NaOH solution and bluish-white precipitate with basic potassium ferrocyanide. The cation is :

Sodium extract is heated with concentrated HNO₃ before testing for halogens because :