The NY/T 1977-2010 standard specifies a method for the determination of the content of total nitrogen, phosphorus and potassium in water-soluble fertilizers. Suitable for the analysis of liquid or solid water-soluble fertilizers. The determination of total nitrogen content uses the post-distillation Titrimetric method, that is, nitrate is reduced to ammonia in alkaline medium, then the ammonia is distilled out and absorbed with excess sulfuric acid solution, and finally the standard sodiumhydrate titration solution is used for reverse titration. This method uses a mixed indicator of methyl red and methylene blue for end point indication, and the total nitrogen content in the sample is determined by calculating the amount of solution required for titration.