ISO 937:1978 Preview
Meat and meat products -- Determination of nitrogen content (Reference method)
This standard was last reviewed and confirmed in 2018. Therefore this version remains current.
The method consists in digesting of a test portion with concentrated sulphuric acid, using copper(II) sulphate as a catalyst, to convert organic nitrogen to ammonia ions. Then alkalisation, distillation of the liberated ammonia into an excess of boric acid solution, titration with hydrochloric acid to determine the ammonia bound by the boric acid, and calculation of nitrogen content of the sample from the amount of ammonia produced.
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