12.22. Differentiate between the principle of estimation of nitrogen in an organic compound by
(ii) Kjeldahl’s method.
In Kjeldahl’s method, the nitrogen-containing organic compound is heated with concentrated sulphuric acid. Nitrogen is converted into ammonium sulphate. It is then passed into the known volume of sulphuric acid. The amount of ammonia produced can be estimated by the amount of consumed in the reaction.
It is done by estimating the amount of unreacted left after the absorption of ammonia by titrating it with a standard alkali solution. This method is not applicable for the compound contain nitrogen in -nitro form or nitrogen present in the ring structure.