Differentiate between the principle of estimation of nitrogen in an organic compound by $(i)$ Dumas method and $(ii)$ Kjeldahl's method.

(N/A) $(i)$ In Dumas method,a known mass of the organic compound is heated with excess of $CuO$ in an atmosphere of $CO_{2}$,where nitrogen of the organic compound is converted into $N_{2}$ gas. Based on the volume of $N_{2}$,the percentage of $N$ is calculated.
$(ii)$ In Kjeldahl's method,a known mass of the organic substance is heated with concentrated $H_{2}SO_{4}$ in the presence of $K_{2}SO_{4}$ and a little $CuSO_{4}$ or $Hg$ catalyst,where nitrogen is converted into ammonium sulphate. This is then boiled with excess of $NaOH$ solution to liberate $NH_{3}$,and the percentage of $N$ is calculated.