ISO 5378:1978 Preview
Starches and derived products -- Determination of nitrogen content by the Kjeldahl method -- Spectrophotometric method
This standard was last reviewed and confirmed in 2013. Therefore this version remains current.
Destruction of organic matter by sulphuric acid in the presence of a compound catalyst (see ISO 1871), alkalization of the reaction products, destillation of the liberated ammonia and collection in a sulphuric acid solution, followed by measuring of the ammonium salt formed after the addition of Nessler reagent. The method is provided for contents less than 0,025 % (m/m). For greater contents, see ISO 3188.