In Carius method for estimation of halogens,$180 \ mg$ of an organic compound produced $143.5 \ mg$ of $AgCl$. The percentage composition of chlorine in the compound is $............. \%$.
[Given : molar mass in $g \ mol^{-1}$ of $Ag = 108$,$Cl = 35.5$]

Describe the Kjeldahl's method and the principles for the estimation of nitrogen present in an organic compound.

Describe the Carius method and its principle for the estimation of sulphur in an organic compound.

$0.5 \ g$ of an organic compound containing phosphorus was heated with conc. $HNO_3$ in a Carius tube. The phosphoric acid thus formed was precipitated with magnesia mixture $[MgNH_4PO_4]$,which on ignition gave a residue of $1.0 \ g$ of magnesium pyrophosphate $(Mg_2P_2O_7)$. The percentage of phosphorus in the organic compound is:

In sulphur estimation,$0.471 \ g$ of an organic compound gave $1.4439 \ g$ of barium sulphate. The percentage of sulphur in the compound is $.............$ (Nearest Integer) (Given: Atomic mass $Ba: 137 \ u, S: 32 \ u, O: 16 \ u$)

What is the reason for passing dry air through the combustion tube during the estimation of $C$ and $H$?