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

Differentiate between the principle of estimation of nitrogen in an or

1.	Differentiate between the principle of estimation of nitrogen in an organic compound by (i) Dumas method (ii) Kjeldahl's method.
Answer» Solution :(i) In Dumas method, a known mass of the ORGANIC compound is heated with excess of CUO in an atmosphere of `CO_(2)`, when nitrogen of the organic compound is converted into `N_(2)` gas. The volume of `N_(2)` thus obtained is converted into NTP and the percentage of nitrogen determined by applying the equation. `%N = (28)/(22400) xx ("Vol. of " N_(2) " at NTP")/("Mass of the substance taken")` (ii) In Kjeldahl's method, a known mass of the organic substance is digested (heated) with conc. `H_(2)SO_(4)` in PRESENCE of `K_(2)SO_(4)` (raises the b.p. of `H_(2)SO_(4)`) and little `CuSO_(4)` or Hg (catalyst) in a long necked flask called Kjeldahl's flask when nitrogen in the organic compound is quantitatively converted into `(NH_(4))_(2)SO_(4). (NH_(4))_(2)SO_(4)` thus obtained is boiled with excess of NaOH solution to LIBERATE `NH_(3)` gas which is absorbed in a known excess of a standard acid such as `H_(2)SO_(4)` or HCl. The volume of acid unused is formed by titration against a standard alkali solution. From the volume of the acid used, the percentage of nitrogen is determined by applying the equation, `%N = (1.4 xx "Molarity of the acid" xx "Basicity of the acid" xx "Vol. of the acid used")/("Mass of the substance taken")`