ISO 7408:1983 Preview
Fertilizers -- Determination of ammoniacal nitrogen content in the presence of other substances which release ammonia when treated with sodium hydroxide -- Titrimetric method
This standard was last reviewed and confirmed in 2017. Therefore this version remains current.
The method consists in entraining, by means of a strong current of air, of the ammonia from a moderately alkaline test mixture at ambient temperature into standard volumetric sulfuric acid solution, and back-titrating of the excess sulfuric acid solution with standard volumetric sodium hydroxide solution.
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