Discuss the principle of estimation of halogens,sulphur and phosphorus present in an organic compound.

(N/A) Estimation of halogens by Carius method:
$A$ known quantity of organic compound is heated with fuming nitric acid in the presence of silver nitrate in a hard glass tube (Carius tube) in a furnace. Carbon and hydrogen are oxidized to $CO_2$ and $H_2O$. The halogen is converted to silver halide $(AgX)$,which is filtered,washed,dried,and weighed.
Percentage of halogen $= \frac{\text{Atomic mass of } X \times m_1 \times 100}{\text{Molecular mass of } AgX \times m}$,where $m$ is the mass of the organic compound and $m_1$ is the mass of $AgX$.
Estimation of sulphur:
$A$ known quantity of organic compound is heated with fuming nitric acid or sodium peroxide in a Carius tube. Sulphur is oxidized to sulphuric acid $(H_2SO_4)$. Excess barium chloride $(BaCl_2)$ is added to precipitate barium sulphate $(BaSO_4)$.
Percentage of sulphur $= \frac{32 \times m_1 \times 100}{233 \times m}$,where $m_1$ is the mass of $BaSO_4$.
Estimation of phosphorus:
$A$ known quantity of organic compound is heated with fuming nitric acid,oxidizing phosphorus to phosphoric acid $(H_3PO_4)$. It is precipitated as ammonium phosphomolybdate by adding ammonia and ammonium molybdate,or as $MgNH_4PO_4$ which on ignition yields $Mg_2P_2O_7$.
Percentage of phosphorus $= \frac{31 \times m_1 \times 100}{1877 \times m}$ (as ammonium phosphomolybdate) or $\frac{62 \times m_1 \times 100}{222 \times m}$ (as $Mg_2P_2O_7$).