This standard specifies the determination method of nitrate nitrogen content in fertilizers Nitrogen reagent gravimetric method. This standard applies to various fertilizers. GB/T 3597-2002 Determination of nitrate nitrogen content in fertilizers Nitrogen reagent gravimetric method GB/T3597-2002 Standard download decompression password: www.bzxz.net

ICS65.080
National Standard of the People's Republic of China
GB/T3597—2002
Replaces GB/T3597--1983
Determination of nitrate nitrogen content in fertilizers
Nitrogen reagent gravimetric method
Fertilizer---Determination of nitrate nitrogen content-Nitron gravimetric method
(ISO 4176:1981,Ferlilizers-Determination of nitrate nitrogen content-Nitron gravimetric method ,MOD)2002-09-24 Issued
General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China
Implementation on April 1, 2003
GB/T3597-2002
This standard is a revision of GB/T3597-1983 "Determination of nitrate nitrogen content in fertilizers-Nitrogen reagent gravimetric method". The consistency of this standard with the international standard ISO4176:1981 "Determination of nitrate nitrogen content in fertilizers - Nitrogen reagent gravimetric method" is modified adoption. The main differences are as follows:
Some formatting of ISO4176:1981 has been modified according to the structure and writing rules of Chinese standards; some expressions applicable to international standards have been changed to expressions applicable to Chinese standards; there are slight technical differences in the determination steps between ISO4176:1981 and my country's national conditions; Chapter 2 "Reference Materials" and Chapter 10 "Test Report" in ISO4176:1981 have been deleted; the explanation of the source of statistical data in Chapter 9 "Precision" in ISO4176:1981 has been listed in the footnotes. This standard has modified the formatting of the previous version of the standard according to GB/T1.1-2000 "Guidelines for Standardization Work Part 1: Structure and Writing Rules of Standards".
This standard was proposed by the China Petroleum and Chemical Industry Association. This standard is under the jurisdiction of the National Technical Committee for Standardization of Fertilizers and Soil Conditioners and is responsible for interpretation. This standard was drafted by the Shanghai Research Institute of Chemical Industry. The main drafters of this standard are Fan Bin and Sun Xiuhong. This standard was first issued in 1983.
1 Scope
Determination of nitrate nitrogen content in fertilizers
Nitrogen reagent gravimetric method
This standard specifies the method for determining nitrate nitrogen content in fertilizers Nitrogen reagent gravimetric method. This standard applies to various fertilizers:.
Note: When an excess of chloride 9 times the nitrogen content is present, the result will be 0.4% higher. 2 Normative references
GB/T3597—2002
The clauses in the following documents become the clauses of this standard through reference in this standard. For any dated referenced document, all subsequent amendments (excluding errata or revised versions) are not applicable to this standard. However, parties to an agreement based on this standard are encouraged to study whether the latest versions of these documents can be used. For any undated referenced document, the latest version applies to this standard. HG/T2843 Commonly used standard titration solutions, standard solutions, reagent solutions and indicator solutions in chemical analysis of fertilizer products 3 Principle
In an acidic solution, nitrate ions react with nitrogen reagents to form a complex and precipitate. The precipitate is filtered, washed, dried and weighed to calculate the nitrate nitrogen content.
4 Reaction formula
5 Reagents and materials
CN-!-C,Hs
: HNO3
5.1 The preparation of reagents, water and solutions used in this standard shall comply with the provisions of HG/T2843 when the specifications and preparation methods are not specified; 5.2
Mass fraction of acetic acid solution: 28.5%. Dilute 285mL of glacial acetic acid to 1000mL with water; 5.3 Sulfuric acid solution: 1+3;
5.4 Nitrogen reagent (nitric acid) solution: 100g/L. 6 Instruments
6.1 Common laboratory instruments;
6.2 Glass crucible filter: No. 4, 30mL; 6.3 Drying oven: capable of maintaining a temperature of 110℃±2℃; 1
GB/T3597—2002
6.4 Oscillator: reciprocating oscillator or gyroscopic oscillator; 6.5 Ice bath: capable of maintaining a temperature of 0C~0.5CAnalysis steps
7.1 Sample
Weigh 2g~5g of sample (accurate to 0.001g) into a 500mL volumetric flask. 7.2 Preparation of sample solution
7.2.1 Water-soluble products
Add about 400mL of 20C water to the sample, vibrate the volumetric flask continuously for 30 minutes with an oscillator, dilute to the mark with water, and mix. 7.2.2 Contains products that may retain nitric acid Add 50mL of water and 50mL of acetic acid solution to the sample, mix the contents in the volumetric flask, let it stand until the release of carbon dioxide stops, add about 300mL of 20°C water, vibrate the volumetric flask continuously for 30min with an oscillator, dilute with water to the scale, and mix well. 7.3 Determination
7.3.1 Filtration
Dry filter the sample bath liquid with medium-speed filter paper into a clean and dry conical flask, discard the first 50mL of filtrate, accurately take a certain amount of filtrate containing 11mg~23mg of nitrate nitrogen (preferably 17mg) and place it in a 250mL beaker and dilute with water to 10 0mL. 7.3.2 Precipitation
Add 10~12 drops of sulfuric acid solution to make the solution pH 1~1.5, quickly heat to boiling point, but do not allow the solution to boil, and immediately remove from the heat source. Check whether there is calcium sulfate precipitation. If there is, add a few drops of sulfuric acid solution to dissolve it. Add 10mL12mL nitrogen reagent solution at a time, place the beaker in an ice bath, stir the dissolved content for 2min, and place it in the ice bath for 2h. Add enough ice cubes to the ice bath frequently to ensure that the temperature of the contents Jcoo
remains at 0C~
Note 1: Urea and urea-formaldehyde condensates will decompose in boiling acid.
will lead to a higher result, while a temperature above 0.5C will lead to a lower result. Note 2: When the temperature is below 00°C, filter with a glass crucible filter that has been dried in a drying oven at 110°C to constant weight (accurate to 0.001). The filter should be cooled in an ice bath in advance. Use the filtrate to transfer the remaining trace precipitate from the beaker to the filter. Finally, wash the precipitate with 10mL to 12mL of water at 0°C to 0.5°C, place the filter and the washed precipitate in a drying oven at 110°C ± 2°C, and dry for 1 hour. Cool in a desiccator and weigh until constant weight.
7.4 Blank test
Take 100mL of water. If acetic acid solution is used to dissolve the sample, take the same amount of acetic acid solution as that in the test solution during the determination, dilute with water to 100mL, and follow the procedure in 7
3.2 above. The mass of the precipitate should not exceed 1mg. If it exceeds, a new nitrogen reagent must be used to repeat the blank test. It is known that old nitrogen reagent will cause the blank test result to be too high. 8. Expression of analytical results
Nitrate nitrogen content is expressed as mass fraction W (%) and calculated according to formula (1): W = (m)-m.) × 14: 017375- × 100-1866x (wl-m.) mg × V/500
Wherein:
mass of precipitate, in grams (g);
mass of precipitate obtained in blank test, in grams (g); atomic weight of nitrogen:
molecular weight of nitrogen reagent nitrate complex: mass of sample, in grams (g);
volume of sample solution absorbed, in milliliters (mL); mv
. (1)
500-total volume of sample solution, in milliliters (mL). The arithmetic mean of the parallel determination results is taken as the determination result. 9 Precision 1
9.1 Repeatability
GB/T3597—2002
When the difference between the results of consecutive measurements of the same sample under the same conditions (analysis performed simultaneously by the same operator and the same laboratory) is greater than 0.4% of the average value, the measurement result will be questioned. 9.2 Reproducibility
When the individual analysis results of the same sample under different conditions (different operators, different laboratories, different equipment and different time) measured by this method are different by more than 1.8%, the analysis result will be doubted. 1) The statistical data of precision are from the analysis results of 30 groups of 7 national laboratories. GB/T3597-2002
People's Republic of China
National Standard
Determination of Nitrate Nitrogen Content in Fertilizers
Nitrogen Reagent Gravimetric Method
GB/T3597—2002
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