This standard specifies the formaldehyde method for determining the ammoniacal nitrogen content in fertilizers. This standard is applicable only when the sample does not contain urea or its derivatives, cyanamides and organic nitrogen compounds, and can also be applied to corresponding industrial products. This method is not applicable to ammonium bicarbonate and ammonia water. GB/T 3600-2000 Determination of ammoniacal nitrogen content in fertilizers Formaldehyde method GB/T3600-2000 standard download decompression password: www.bzxz.net

GB/T3600—2000
This standard adopts the former Soviet Union national standard rOCT2--1985 "Ammonium Nitrate". Differences in content:
This standard and GB/T3600—1983 "Determination of Ammonia Nitrogen Content in Fertilizers" a) Added "Foreword"
b) Added Chapter 2 "Reference Standards". c) Chapter 4 "Test Methods" stipulates the preparation of reagents, water and solutions used. When the specifications and preparation methods are not indicated, they should comply with the provisions of HG/T2843.
d) Deleted "Appendix A" of the original standard. This standard replaces GB/T3600-1983 from the date of implementation. This standard is proposed by the State Administration of Petroleum and Chemical Industry. This standard is under the jurisdiction of the National Technical Committee for Standardization of Fertilizers and Soil Conditioners. Drafting unit of this standard: Shanghai Chemical Industry Research Institute. Drafter of this standard: Zhu Tao.
This standard was first issued in 1983.
1 Scope
National Standard of the People's Republic of China
Determination of ammoniacal nitrogen content in fertilizers-Formaldehyde method
This standard specifies the method for determining ammoniacal nitrogen content in fertilizers by formaldehyde method. GB/T3600—2000
Replaces GB/T3600---1983bzxz.net
This standard is applicable only when the sample does not contain urea or its derivatives, cyanamides and organic nitrogen compounds, and can also be applied to corresponding industrial products. This method is not applicable to ammonium bicarbonate and ammonia water. 2 Referenced Standards
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. HG/T2843-1997 Common standard titration solutions, standard solutions, reagent solutions and indicator solutions for chemical analysis of fertilizer products 3 Method Summary
In a neutral solution, ammonium salt reacts with formaldehyde to generate hexamethylenetetramine and an acid equivalent to the content of ammonium salt. In the presence of an indicator, titrate with a standard sodium hydroxide titration solution.
4 Test method
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. 4.1 Reagents
4.1.1 Boric acid.
4.1.2 Potassium chloride.
4.1.3 Standard sulfuric acid titration solution: c (1/2H, SO.) = 0.1 mol/L. 4.1.4
Standard sodium hydroxide titration solution: c (NaOH) = 0.1 mol/L. 4.1.5 Standard sodium hydroxide titration solution: c(NaOH)=0.5mol/L. 4.1.6
Formaldehyde solution: 250g/l.
4. 1.7 Ethanol: 95% (V/V).
4.1.8 Methyl red indicator solution: 1g/L.
4.1.9 Phenol indicator solution: 10g/l.
4.1.10 Color reference solution of pH 8.5.
In a 250ml conical flask, add 15.15ml 0.1mol/l sodium hydroxide standard solution, 37.50mL 0.2mol/l boric acid-potassium chloride solution (weigh 6.138g boric acid and 7.455g potassium chloride, dissolve in water, transfer to a 500mL volumetric flask, dilute to scale), then add 1 drop of methyl red indicator solution and 3 drops of phenolphthalein indicator solution, dilute to 150mL. 4.2 Instruments
Approved by the State Administration of Quality and Technical Supervision on July 31, 2000 118
Implemented on March 3, 2001
General laboratory instruments and pH meters.
4.3 Analysis steps
4.3.1 Preparation of sample solution
GB/T 3600—2000
Weigh 1g of sample, accurate to 0.001g, place in a 250mL conical flask, add 100ml.~120mL of water to dissolve, then add 1 drop of methyl red indicator solution (4.1.8), and adjust with sodium hydroxide standard titration solution (4.1.4) or sulfuric acid standard titration solution (4.1.3) until the solution turns orange. 4.3.2 Determination
Add 15mL of formaldehyde solution (4.1.6) to the sample solution (4.3.1), then add 3 drops of phenolphthalein indicator solution (4.1.9), and mix well. After 5 minutes, titrate with sodium hydroxide standard solution (4.1.5) to pH 8.5. The color of the color reference solution (4.1.10) does not disappear after 1 minute (or titrate to pH 8.5 indicated by the pH meter). 4.3.3 Blank test
During the determination, except for not adding the sample, the same analytical steps, reagents and dosages are used for parallel operation. 4.4 Expression of analytical results
Nitrogen content, expressed as mass percentage X of nitrogen (N), is calculated according to formula (1): X(%) = (V;-V)c×0. 014 01 × 100m
Wherein: V
The volume of sodium hydroxide standard titration solution consumed by the test sample, mL; -The volume of sodium hydroxide standard titration solution consumed by the blank, mL; (1)
The concentration of sodium hydroxide standard titration solution, mol/L.; The mass of nitrogen in grams equivalent to 1.00 ml of sodium hydroxide standard titration solution [c(NaOH)=1.000moi/1.];
m~The mass of the test sample, g.
The arithmetic mean of the parallel determination results is taken as the determination result. 4.5 Allowable difference
The absolute difference of parallel determinations shall not exceed 0.06%; the absolute difference of determination results of different laboratories shall not exceed 0.08%. 119
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