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

(N/A) Estimation of halogens: Halogens are estimated by the Carius method. $A$ known quantity of organic compound is heated with fuming nitric acid in the presence of silver nitrate in a Carius tube. Carbon and hydrogen are oxidized to $CO_2$ and $H_2O$,and the halogen is converted to $AgX$. The mass of $AgX$ is measured. The percentage of halogen is calculated as: $\frac{\text{Atomic mass of } X \times m_1 \times 100}{\text{Molecular mass of } AgX \times m}$.
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,which is then precipitated as barium sulphate $(BaSO_4)$ by adding barium chloride. The percentage of sulphur is calculated as: $\frac{32 \times m_1 \times 100}{233 \times m}$.
Estimation of phosphorus: $A$ known quantity of organic compound is heated with fuming nitric acid to oxidize phosphorus to phosphoric acid. It is then precipitated as ammonium phosphomolybdate by adding ammonia and ammonium molybdate. The percentage of phosphorus is calculated as: $\frac{31 \times m_1 \times 100}{1877 \times m} \%$. Alternatively,it can be precipitated as $MgNH_4PO_4$ and ignited to yield $Mg_2P_2O_7$,where the percentage of phosphorus is: $\frac{62 \times m_1 \times 100}{222 \times m} \%$.