GB/T 2441.1-2001 Urea determination method Determination of total nitrogen content
Some standard content:
GB/T 2441. 1--2001
This standard is a revision of GB/T2441-1991 "Determination of total nitrogen content of urea - Titration after distillation". The main technical differences between this standard and GB/T2441-1991 are as follows: 1 The determination of total nitrogen content is divided into titration after distillation and calculation method, of which the titration after distillation is an arbitration method, which is equivalent to IS01592:1977 "Determination of fluorine content of industrial urea - Volumetric analysis after distillation". 2 Reference HG/T2843-1997 standard, no longer reference GB/T601 series standards. 3 Add the use of \ or sulfuric acid solution [c(1/2HzSO4）=1.0mol/L]\ in the reagent solution section. 4 In the calculation method, the calculation coefficient is corrected, and the calculation of total nitrogen content after adding formaldehyde is added. This standard is Part 1 of GB/T2441 "Determination of urea method". GB/T2441 also includes the following parts:
GB/T2441.2--2001 Determination method of urea-Determination of biuret content-Spectrophotometric method-Part 2
Part 3
Part 4
Part 5
Part 6
Part 7
Part 8
Part 9
GB/T2441.3-2001 Determination method of urea-Determination of water content-Karl Fischer method 1. Determination method of urea-Determination of iron content-O-phenanthroline spectrophotometric method GB/T 2441.4--2001
GB/T 2441.5--2001
GB/T 2441.6--2001
GB/T 2441.7
7—2001
GB/T2441.8
3—2001
GB/T 2441. 9--2001
Determination method of urea
Determination of alkalinity-Volumetric method
Determination of water-insoluble matter
Gravimetric method
Determination method of urea
Determination method of urea
Determination method of urea
Determination method of urea
This standard shall replace GB/T2441-1991 from the date of its implementation. This standard is proposed by the State Administration of Petroleum and Chemical Industry. Determination of particle size Sieving method
Determination of sulfate content Visual turbidimetry
Determination of methylene diamine content Spectrophotometric method This standard is under the jurisdiction of the National Technical Committee for Standardization of Fertilizers and Soil Conditioners and is responsible for interpretation. Drafting units of this standard: National Fertilizer Quality Supervision and Inspection Center (Shanghai), PetroChina Rumuqi Petrochemical Company Fertilizer Plant, Sinopec Jiujiang Branch, Hainan Fudao Chemical Co., Ltd. Main drafters of this standard: Zhang Qiuzhen, Jiang Jianxin, Li Zifen, Guo Zu, Sha Yanping, Yang Jiqun. This standard was first issued in 1981.
National Standard of the People's Republic of China
Determination of total nitrogen content
Determination of urea -Determination of total nitrogen content1 Scope
This standard specifies the determination of total nitrogen content in urea. This standard is applicable to the determination of total nitrogen content in urea synthesized from ammonia and carbon dioxide. 2 Reference standards
GB/T 2441. 1--2001
GB/T2441-1991
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 the parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T3595-2000 Determination of ammonia nitrogen content in fertilizers Titration after distillation HG/T2843-1997 Commonly used standard titration solutions, standard solutions, reagent solutions and indicator solutions in chemical analysis of fertilizer products 3 Determination of total nitrogen content
3.1 Titration after distillation (arbitration method)
3.1.1 Principle
In the presence of copper sulfate, heat in concentrated sulfuric acid to convert amide nitrogen in the sample into ammonia nitrogen, distill and absorb in excess sulfuric acid solution, and in the presence of indicator solution, titrate the remaining acid with sodium hydroxide standard titration solution. 3.1.2 Reagents and solutions
Unless otherwise specified, the reagents, solutions and water used in this test method shall comply with the requirements of HG/T2843. 3.1.2.1 Copper sulfate pentahydrate;
3.1.2.2 Sulfuric acid;
3.1.2.3 Sodium hydroxide solution, about 450g/L, 3.1.2.4 Methyl red-methylene blue mixed indicator solution; 3.1.2.5 Sulfuric acid solution: Ec(1/2HzSO)=0.5mol/LJ or Ee(1/2H,SO.)=1.0mol/LJ; 3.1.2.6 Standard sodium hydroxide titration solution: c(NaOH)=0.5mol/L; 3.1.2.7 Silicone grease.
3.1.3 Instruments
General laboratory instruments and
3.1.3.1 Distillation instruments
A complete set of instruments with a standard push-mill port or any instrument that can ensure quantitative distillation tanks and absorption. The components of the distillation apparatus are connected with rubber stoppers and rubber tubes, or with ball-shaped ground glass joints. To ensure the sealing of the system, the ball-shaped glass joints should be clamped with springs.
The apparatus recommended for use in this standard is shown in Figure 1, and includes the following parts: Approved by the General Administration of Quality Supervision, Inspection and Quarantine of the People's Republic of China on July 26, 200168
Implementation on January 1, 2002
GB/T2441.1--2001
000 mL
Unit: mm
dMeiMei
A Distillation flask, B splash-proof ball tube, C-dripping funnel; D-cold avoidance tube; E-male flask with double-connected balls Figure 1 Diagram of the distillation tank apparatus
3.1.3.1.1 Distillation flask, a round-bottom flask with a capacity of 1L; 3.1.3.1.2 A single-ball anti-splash tube and a circular dropping funnel with an opening at the top and a capacity of about 50mL parallel to the inlet and outlet of the anti-splash ball; 3.1.3.1.3 A straight condenser with an effective length of about 400mm; 3.1.3.1.4 A receiver, a conical flask with a capacity of about 500mL and a double ball connected to the side of the flask; 3.1.3.2 A pear-shaped glass abyss;
3.1.3.3 Anti-splash rod, a glass rod with a length of about 100mm and a diameter of about 5mm, one end of which is covered with a polyethylene tube with a length of about 25mm. 3.1.4 Analysis steps
3.1.4.1 Preparation of test solution
Weigh about 5g of laboratory sample (accurate to 0.001g), transfer it to a 500mL conical flask, add 25ml of water, 50ml of sulfuric acid, and 0.5ml of copper sulfate, insert a pear-shaped glass funnel, and slowly heat in a fume hood to allow carbon dioxide to escape, then gradually increase the heating temperature until smoke appears, and continue heating for 20 minutes before stopping the heating. After the test solution in the conical flask is fully cooled, carefully add 300ml of water and cool it. Transfer the test solution in the conical flask quantitatively into a 500mL volumetric flask, dilute to the scale, and shake well. 3.1.4.2 Distillationwww.bzxz.net
Pipette 50.0mL of the test solution from the volumetric flask into a steaming flask, add about 300mL of water, 4~5 drops of mixed indicator solution, and place a splash rod with the end of the polyethylene tube facing downward.
GB/T 2441.1—2001
Use a burette, pipette or automatic dosing device to add 40.0mL [c(1/2HSO.）=0.5mol/L] or 20.0mL [c(1/2HSO）1.0mol/L sulfuric acid solution to the receiver, add water so that the solution can submerge the double-ball bottleneck of the receiver, and add 4~5 drops of mixed indicator liquid. Apply silicone grease to the instrument interface, install the distillation instrument as shown in the figure, and ensure that all connecting parts of the instrument are sealed. Add enough sodium hydroxide solution to the distillation flask through the dropping funnel to neutralize the solution and add 25mL in excess. It should be noted that at least a few milliliters of solution remain in the dropping funnel. Heat and distill until the solution in the receiver reaches 250mL~300mL, stop heating, remove the splash-proof ball tube, wash the condenser with water, and collect the washing liquid in the receiver. 3.1.4.3 Titration
Mix the solution in the receiver and titrate with sodium hydroxide standard titration solution until the indicator solution turns gray-green. The solution should be fully mixed during titration.
3.1.5 Blank test
Carry out a blank test according to the above operating steps. Except that no sample is added, the operating steps and reagents used are the same as those for the determination. 3.1.6 Calculation of analysis results
The total nitrogen (dry basis) content (X) in the sample is expressed as the mass fraction (%) of nitrogen (N) and is calculated according to formula (1): X = c(V, - V) × 0.014 01 × 10050×m×
100-XH,0
c(V2-Vr) × 1 401
m(100-XH,0)
Wherein: V,
0. 014 01-
The volume of sodium hydroxide standard titration solution consumed in the determination, mL; The volume of sodium hydroxide standard titration solution consumed in the blank test, mL; The concentration of the sodium hydroxide standard titration solution used in the determination and blank test, mol/L; The mass of the sample, g;
（1）)
The mass of nitrogen equivalent to 1.00mL of sodium hydroxide standard titration solution [c(NaOH）=1.000mol/L], expressed in grams;
XH,o——Water content in the sample, %.
The arithmetic mean of the parallel determination results is taken as the determination result, and the obtained result is expressed to two decimal places. 3.1.7 Allowable difference
The absolute difference of the parallel determination results shall not exceed 0.10%; the absolute difference of the determination results of different laboratories shall not exceed 0.15%; 3.2 Calculation method
This method is only applicable to routine analysis and product inspection of the manufacturer. 3.2.1 Principle
When formaldehyde is added during the production process, the content of other impurities (heavy metals and by-products) in urea except water, dihydrogen urea and methylene diurea can be ignored. Therefore, its total nitrogen content can be regarded as the sum of urea nitrogen, dihydrogen urea and methylene diurea nitrogen. Urea nitrogen can be obtained by subtracting water, dihydrogen urea and methylene diurea content from 100%, dihydrogen urea nitrogen can be calculated by measuring dihydrogen urea content, and methylene diurea nitrogen can be calculated by measuring methylene diurea content. The sum of the three is the total nitrogen. 3.2.2 Calculation
The total nitrogen (dry basis) content (X) of formaldehyde added during the production process is expressed as the mass percentage (%) of nitrogen (N) and is calculated according to formula (2): X
[100-(XH,0%+XBu% +4.400XXHCHo%)J×0.4665+XBu%×0.4077+4.400×XHCHo%×0.4241100-XH,0
46.65-0.4665XXH,0%-0.0588XXBu%-0.186 6×XHcHo%100-XH,0%
Assume: α=46.65-0.4665×XH0% (listed in Table 1); 70
8=0.0588XXu% (listed in Table 2);
Y=0. 186 6XXHCHo% (listed in Table 3); GB/T 2441.1—2001
100 -- XH,0%
The total nitrogen (dry basis) content (X) without adding formaldehyde in the production process is expressed as the mass fraction (%) of nitrogen (N), calculated according to formula (3): αβ
100 - XH,0%
Wherein: XH,0%-water content;
Hydroxyl content:
XHCHo%
Methylene disulfide content;
Coefficient of urea converted to nitrogen;
Coefficient of hydroxyl conversion to nitrogen;
Coefficient of formaldehyde converted to methylene disulfide; Coefficient of methylene disulfide converted to nitrogen.
The result is expressed to two decimal places. | |tt | 77 ~ ~ 0.93 | | tt | 61
1.62~1.78
1. 79~1. 94
（2）
++*++++( 3)
Methylene diurea, %
(in HCHO))
0.14~0.18
0.25~0.29
0.30~0.34
0.35~0.40
0.41~~0.45
0.46~0.50
GB/T 2441. 1—2001
Table 3 Values
Methylene diurea, %
(in HCHO) Count)
0.51~0.56
0.57~0.61
0.62~0.67
0.68~0.72
0.73~0.77
0.78~0.83
0.84~0.8828~1.44
1. 45~1. 61
1.62~1.78
1. 79~1. 94
(2)
++ *++++( 3)
Methylenediurea,%
(as HCHO Count))
0.14~0.18
0.25~0.29
0.30~0.34
0.35~0.40
0.41~~0.45
0.46 ~0.50
GB/T 2441. 1—2001
Table 3 Values
Methylenediamine, %
(in terms of HCHO)
0.51~0.56
0.57~0.61| |tt||0.62~0.67
0.68~0.72
0.73~0.77
0.78~0.83
0.84~0.8828~1.44
1. 45~1. 61
1.62~1.78
1. 79~1. 94
(2)
++ *++++( 3)
Methylenediurea,%
(as HCHO Count))
0.14~0.18
0.25~0.29
0.30~0.34
0.35~0.40
0.41~~0.45
0.46 ~0.50
GB/T 2441. 1—2001
Table 3 Values
Methylenediamine, %
(in terms of HCHO)
0.51~0.56
0.57~0.61| |tt||0.62~0.67
0.68~0.72
0.73~0.77
0.78~0.83
0.84~0.88
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