kjeldahls methodis used to determine nitrogen content in organic compounds in which nitrogen is attached to cabron and hydrogen (bt not in azo,nitro and azoxy)
principle:nitrogen is heated with conc sulphuric acid in copper sulphate which converts it into ammonium sulphate . this ammonium sulphate is treated with excess of alkali which decomposes to ammonia from which nitrogen content is calculated.
catalyst used is coppersulphate and mercury .
potassium sulphate is also added to raise the boiling point of sulphuric acid.