In Duma’s method of estimation of nitrogen 0.35 of an organic compound gave 55 mL of nitrogen collected at 300 K temperature and 715 mm pressure. The percentage composition of nitrogen in the compound would be -
(Aqueous tension at 300K= 15 mm)

1.  16.45
2.  17.45
3.  14.45
4.  15.45

The Lassaigne’s extract is boiled with conc. ${\mathrm{HNO}}_3$ while testing for halogens, because it- 

1. Helps in the precipitation of $\mathrm{AgCl}$
2. Increases the solubility product of $\mathrm{AgCl}$
3. Increases the concentration of ${\mathrm{NO}}_3^{-}$ ions
4. Decomposes ${\mathrm{Na}}_2\mathrm{S}$ and $\mathrm{NaCN}$, if formed