Some standard content:
Chemical Industry Standard of the People's Republic of China
HG2095-91
Coated Urea
Published on July 17, 1991
Ministry of Chemical Industry of the People's Republic of China
Implementation on January 1, 1992
Chemical Industry Standard of the People's Republic of China
1 Subject Content and Scope of Application
HG209591
This standard specifies the technical requirements, test methods, inspection rules, and marking, packaging, transportation and storage of coated urea. This standard applies to coated urea obtained by synthesizing urea from ammonia and carbon dioxide and coating it with an organic chelate of iron or other coating materials approved by the competent industry department. This product is used as a fertilizer in agriculture. 2
Reference standards
GB601 Preparation of standard solutions for titration analysis (volume analysis) of chemical reagents GB6283 Determination of moisture content in chemical products by Karl Fischer method (general method) GB603 Preparation of preparations and products used in test methods for chemical reagents GB6003
Test sieves
GB8569
9 Packaging of solid chemical fertilizers
3 Technical requirements
3.1 Appearance: brown or yellow granules.
3.2 Coated urea shall meet the requirements of Table 1. Table 1 Technical indicators of coated urea
Total nitrogen (N) content (dry basis), %
Diamine content, %
Water (H20), %
Coating material (chelated iron) content, %
Particle size (@0.85~2.80mm), %
Note: 1) Other coating materials can be used, but they must be approved by the competent department of the ministry. In this case, the indicators of the coating material are determined separately. Qualified products
3.3 Coated urea should have long-lasting and slow-acting effects (compared with ordinary urea), and should not be easy to agglomerate and absorb moisture. This characteristic is tested by type.
3.4 In the coating material, the arsenic (As) content is <0.001%; the heavy metal (Pb) content is <0.005%. Type inspection is carried out according to Appendix B and Appendix C.
3.5 Coating inspection of coated urea: Using an electron microscope, it can be observed that the coating material is deposited on the surface of urea particles. This inspection is a type inspection. 4 Test method
In the analysis, unless otherwise specified, only analytical reagents, distilled water or water of equivalent purity shall be used. 4.1 Determination of total nitrogen content Titration after distillation Approved by the Ministry of Chemical Industry of the People's Republic of China on July 17, 1991 and implemented on January 1, 1992
HG2095-91
The determination method is equivalent to ISO1592-77 "Industrial urea-Determination of nitrogen content-Titration after distillation". 4.1.1 Principle
In the presence of copper sulfate, the amide nitrogen in the sample is converted into ammonia nitrogen by heating in concentrated sulfuric acid, which is distilled and absorbed in an excess of sulfuric acid standard solution. In the presence of an indicator solution, it is back-titrated with a sodium hydroxide standard solution. 4.1.2 Reagents and solutions
4.1.2.1 Copper sulfate (CuSO·5H20, GB665); 4.1.2.2 Sulfuric acid (GB625);
4.1.2.3 Sodium hydroxide (GB629) solution: 450g/L solution, weigh 45g sodium hydroxide, dissolve in water, and dilute to 100mL; 4.1.2.4 Mixed indicator solution: methyl red-methylene blue ethanol solution. Add 0.10g methyl red (HG3-958) and 0.05g methylene blue to about 50mL 95% ethanol (GB679), dissolve, dilute to 100mL with ethanol of the same specification, and mix well; Sulfuric acid standard solution: c (No.
HSO) = 0.5mol/L. Prepare and calibrate according to GB601; 4.1.2.5
4.1.2.6 Standard sodium hydroxide titration solution: c(NaOH)=0.5mol/L. Prepare and calibrate according to GB601; 4.1.2.7 Silicone grease.
4.1.3 Instruments
General laboratory instruments and
4.1.3.1 Steaming stuffing instruments
It is best to use a complete set of instruments with standard ground mouths or any instrument that can ensure quantitative distillation and absorption. The various components of the distillation instrument are connected with rubber stoppers and rubber tubes, or with spherical ground glass joints. To ensure the sealing of the system, the spherical glass joints should be clamped with spring clips.
The instrument recommended for use in this standard is shown in the figure, including the following parts: a. Distillation flask: volume is 1L;
Single-ball splash-proof tube and cylindrical dropping funnel with top opening, volume of about 50mL and parallel to the inlet and outlet of the splash-proof ball; b.
c. Straight condenser: effective length is about 400mm; d. Receiver: conical flask with volume of 500mL, with double balls connected to the side of the flask; 4.1.3.2 Pear-shaped glass funnel.
4.1.4 Analysis steps
4.1.4.1 Sample
Weigh about 5g of sample, accurate to 0.001g, and transfer it into a 500mL conical flask. 4.1.4.2 Preparation of test solution
In the conical flask containing the sample, add 25mL of water, 50mL of sulfuric acid, and 0.5g 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 white smoke is emitted, continue heating for 20 minutes, remove, and after cooling, carefully add 300mL of water to cool.
Quantitatively transfer the solution in the conical flask into a 500mL volumetric flask, dilute to the scale, and shake to hook. 4.1.4.3 Steaming stuffing
Pipette 50.0mL of solution from the volumetric flask into a distillation flask, add about 300mL of water, a few drops of mixed indicator solution, and a small amount of explosion-proof zeolite or porous porcelain chips.
HG209591
Distillation apparatus diagram
A—distillation flask; B—splash-proof bulb; C—dropping funnel, D—condenser; E—conical flask with double-connected bulbs. Use a burette or pipette to transfer 40.0mL of sulfuric acid standard solution into the receiver, add water so that the solution can submerge the neck of the double-connected bulb of the receiver, and add 4 to 5 drops of mixed indicator liquid.
Apply silicone grease to the instrument interface, install the distillation instrument as shown in the diagram, and ensure that all connecting parts of the instrument are sealed. Add enough sodium hydroxide solution (4.1.2.3) 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 collection volume in the receiver reaches 250-300mL. Stop heating, remove the splash-proof bulb, wash the condenser with water, and collect the washing liquid in the receiver.
4.1.4.4 Titration
HG2095—91
Mix the solution in the receiver and back-titrate the excess acid with sodium hydroxide standard titration solution until the indicator solution turns gray-green. Stir carefully during titration to ensure that the solution is mixed. 4.1.5 Blank test
Perform a blank test according to the above steps. Except that no sample is used, the operating procedures and reagents used are the same as those for determination. 4.1.6 Calculation of analysis results
The total nitrogen content X in the sample, expressed as nitrogen (N) and expressed as mass percentage (%), is calculated according to formula (1): (V.-V).cX0.01401X100_(V,-V).c×1401X=9
5%·m.10000c
m100-X0）
When determining, the volume of the sodium hydroxide standard titration solution is used, mL; where.V|| tt||——the volume of sodium hydroxide standard titration solution used in blank test, mL; c——the concentration of sodium hydroxide standard titration solution used in determination and blank test, mol/L; m——the mass of sample, g;
0.01401——the mass of nitrogen equivalent to 1.00mL sodium hydroxide standard titration solution (c(NaOH)=1.000mol/L), expressed in grams,
XBO—the water content in the sample, %.
The result should be expressed to two decimal places.
4.1.7 Allowable difference
The absolute difference of parallel determinations shall not exceed 0.10%; the absolute difference of determination results of different laboratories shall not exceed 0.15%; the arithmetic mean of the parallel determination results shall be taken as the determination result. 4.2 Determination of biuret content Spectrophotometric method The determination method shall refer to ISO2754-73 "Industrial urea-Determination of biuret content-Spectrophotometric method". 4.2.1 Principle
Biuret generates a purple-red complex in an alkaline solution of copper sulfate and potassium sodium tartrate, and its absorbance is measured at a wavelength of 550nm. 4.2.2 Reagents and solutions
4.2.2.1 Copper sulfate (CuSO4·5H20, GB665) solution: 15g/L solution. Weigh 15g of copper sulfate and dissolve it in water, dilute to 1000mL;
4.2.2.2 Sodium potassium tartrate (NaKC,H,Og·4H20, GB1288): 50g/L alkaline solution. Weigh 50g sodium potassium tartrate and dissolve it in water, add 40g sodium hydroxide, and dilute to 1000mL; ÷HSO,) = 0.1mol/L. Prepared according to GB601; 4.2.2.3 Sulfuric acid (GB625) solution: about c(4.2.2.4 Sodium hydroxide (GB629): about c(NaOH) = 0.1mol/L solution, prepared according to GB601; 4.2.2.5 Ammonia water (GB631): 100g/L solution. Measure 220mL of ammonia water and dilute it to 500mL with water. 4.2.2.6 Biuret standard solution: 2.00g/L; a. Biuret purification:
First wash the biuret with ammonia water, then wash it with water, and then wash it with acetone to remove water, and finally dry it in a drying oven at about 105℃. b. Preparation of 2.00g/L biuret standard solution: Weigh 1.000g of purified biuret and dissolve it in 450mL of water, Use sulfuric acid or sodium hydroxide solution to adjust the solution to pH = 7, transfer quantitatively into a 500mL volumetric flask, dilute to the scale, and mix. This solution contains 2.00mg of biuret in 1mL.
4.2.3 Instruments
General laboratory instruments and water bath.
4.2.4 Analysis steps
4.2.4.1 Drawing of standard curve
HG2095--91
4.2.4.1.1 Preparation of standard colorimetric solution, suitable for photometric measurement of 3cm light path length cuvette. Measure as shown in Table 2 and inject the biuret standard solution into 8 100mL volumetric flasks. Table 2
Volume of biuret standard solution
Corresponding amount of biuret
Each Dilute the volumetric flask with water to 50mL, then add 20.0mL potassium sodium tartrate alkaline solution and 20.0mL copper sulfate solution in turn, shake well, dilute to the scale, immerse the volumetric flask in a 30±5℃ water bath for about 20min, and shake from time to time. 4.2.4.1.2 Photometric determination
Within 30min, use the solution with zero biuret as the reference solution and use a spectrophotometer to determine the absorbance of the standard colorimetric solution (4.2.4.1.1) at a wavelength of 550nm. www.bzxz.net
4.2.4.1.3 Drawing of the standard curve
Use the mass (mg) of biuret contained in 100mL of the standard colorimetric solution as the horizontal axis and the corresponding absorbance as the vertical axis to draw a graph. 4.2.4.2 Determination||tt| |4.2.4.2.1 Preparation of sample and test solution
Weigh about 50g of sample, accurate to 0.01g, put it in a 250mL beaker, add about 100mL of water to dissolve, then add 10mL of sodium hydroxide solution, heat to boil, filter the precipitate with filter paper and wash with hot water, collect the filtrate and washing liquid in another 250mL beaker, adjust the pH of the solution to 7 with sulfuric acid solution, transfer quantitatively to a 250mL volumetric flask, dilute to scale, and shake well. Take the above test solution containing 20-50mg of biuret in a 100mL volumetric flask, then add 20.0mL of potassium sodium tartrate alkaline solution and 20.0mL of copper sulfate solution in turn, shake well, dilute to scale, immerse the volumetric flask in a water bath at 30±5℃ for about 20min, and shake from time to time. 4.2.4.2.2 Blank test
Carry out a blank test according to the above steps. Except for not using the sample, the operating procedures and reagents used are the same as those for the determination. 4.2.4.2.3 Photometric determination
The procedure is the same as that for drawing the standard curve. The test solution and the blank test solution are photometrically determined to determine their absorbance. Note: ① If the test solution is colored or turbid and colored, in addition to determining the absorbance according to (4.2.5), add 20.0mL of potassium sodium tartrate alkaline solution to each of two 100mL volumetric flasks, add the same volume of test solution as that used for color development to one of them, dilute the solution to the mark with water, and shake well. Use the solution without the test solution as the reference solution, determine the absorbance of the other solution under the same conditions as the determination, and deduct it from the calculation. ② If the test solution is only turbid, before adjusting the pH value of the test solution, add 2mL of hydrochloric acid solution with c(HCI)=1mol/L to the test solution, shake vigorously, filter with medium-speed filter paper, wash with a small amount of water, collect the filtrate and washing solution quantitatively in a beaker, and then adjust the pH and dilute according to the preparation of the test solution. Calculation of analysis results
Find out the amount of biuret corresponding to the measured absorbance from the standard curve. The biuret content X2 in the sample is expressed as mass percentage (%) and is calculated according to formula (2): X
(m-m2).DX100
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Wherein: m1——the mass of biuret measured by the sample solution, g; m2——the mass of biuret measured by the sample solution, g; m——the mass of the sample, g;
D——the ratio of the total volume of the sample to the volume of the sample solution used for the color reaction. The result should be expressed to two decimal places.
4.2.6 Allowable error
The absolute difference of the parallel determination results shall not exceed 0.05% and the absolute difference of the determination results of different laboratories shall not exceed 0.08%; the arithmetic mean of the parallel determination results shall be taken as the determination result. 4.3 Determination of moisture content by Karl Fischer method
The determination method is equivalent to ISO2753-73 "Industrial urea - Determination of water content - Karl Fischer method". 4.3.1 Principle
The water present in the sample reacts quantitatively with the Karl Fischer reagent with a known water equivalent, and the reaction formula is as follows:H20+I2+SO2+3CH.N-2CHN·HI+CHN·SOsC.H,NSO:+CH.OH--CH,NH·OSO,OCHs4.3.2 Reagents
4.3.2.1 Karl Fischer reagent, prepared in accordance with GB62834.3.2.2 Karl Fischer reagent without pyridine, prepared as follows:Put 63g iodine (GB675) in a dry 1L brown bottle with a stopper, add 600mL methanol (GB683), then add 25g anhydrous sodium iodide and 85g sodium acetate (GB694) which have been dried to constant weight at 120℃, plug the bottle, and shake until the iodine and its salts are dissolved (solution A). Pass sulfur dioxide gas through methanol cooled by ice water to make the concentration of sulfur dioxide gas c(SO2)-4 mol/L (solution B). Add 90 mL of solution B (containing 23 g of sulfur dioxide) to solution A, dilute to 1 L with methanol, mix well, and place in a dark place for later use. 4.3.2.3 Methanol (GB683);
4.3.2.4 Sodium tartrate dihydrate (HG3-1101). 4.3.3 Instrument
Karl Fischer direct coulometric titration instrument, its typical device is in accordance with GB6283. 4.3.4 Analysis steps
4.3.4.1 Calibration of Karl Fischer reagent
a. Calibration of universal Karl Fischer reagent containing pyridine: According to the steps specified in GB6283, use sodium tartrate dihydrate or water to calibrate the water equivalent T of Karl Fischer reagent.
b. Calibration of Karl Fischer reagent without pyridine: Use water to calibrate the water equivalent T of the reagent according to the steps specified in GB6283. 4.3.4.2 Determination
Use a weighing tube to weigh 2 to 5 g of the sample, accurate to 0.001 g. The volume of Karl Fischer reagent consumed by the weighed sample shall not exceed 20 mL. Drain the residual liquid in the titration container through the discharge nozzle of the Karl Fischer instrument, add 50 mL of methanol to the titration container, the amount of methanol must be enough to submerge the electrode, turn on the electromagnetic stirrer, and titrate with Karl Fischer reagent as in the calibration of Karl Fischer reagent (4.3.2.1 or 4.3.2.2. During arbitration, use Karl Fischer reagent containing pyridine), until the current meter produces the same deflection as during calibration, and keep it stable for 1 minute. Open the rubber stopper of the feed port, quickly pour the sample in the weighing tube into the titration vessel, immediately cover the rubber stopper, stir until the sample dissolves, and titrate to the endpoint with Karl Fischer reagent as above, recording the volume of Karl Fischer reagent consumed (V). Weigh the mass of the weighing tube before and after adding it to the titration vessel to determine the mass of the sample used (m). 4.3.5 Calculation of analysis results
Instructions for use:
1 The international standard uses Karl Fischer reagent containing pyridine, and this standard uses Karl Fischer reagent without pyridine. 6
HG2095--91
The water content Xs in the sample is expressed as mass percentage (%) and is calculated according to formula (3): Xs=T.VX100
m×1000
Wherein: V is the volume of Karl Fischer reagent used for titration, mL; T is the water equivalent of Karl Fischer reagent, mg/mL; m
is the mass of the sample, g.
The result should be expressed to two decimal places.
4.3.6 Allowable difference
The absolute difference of the parallel determination results shall not be greater than 0.03%; the arithmetic mean of the parallel determination results is taken as the determination result. T·V
4.4 Determination of coating material content (calculated as chelated iron) 1,10-phenanthroline spectrophotometric method (3)
The determination method refers to ISO6685-82 "Industrial chemical products-General method for determination of iron content-1,10-phenanthroline spectrophotometric method".
4.4.1 Principle
Ascorbic acid is used to reduce the trivalent iron ions in the test solution to divalent iron ions. At pH 2-9, the divalent iron ions and 1,10-phenanthroline form an orange-red complex. The absorbance is determined by a spectrophotometer at the maximum absorption wavelength of 510nm. This standard selects the condition of pH=4.5 to form a complex. 4.4.2 Reagents and solutions
4.4.2.1 Hydrochloric acid (GB622): 1+1 solution; 4.2.2.2
Ammonia water (GB631): 1+1 solution;
Sodium acetate (GB693);
Acetic acid-sodium acetate buffer solution: pH=4.5, prepared according to GB603; Ascorbic acid solution: 2% solution, the solution can be used for 10 days; 4.4.2.5
4.4.2 .61,10-phenanthroline (GB1293) solution: 0.2% solution; Iron standard solution: 1mL contains 0.100mg iron; 4.4.2.7
Weigh 0.863g of ammonium ferric sulfate [NH,Fe(SO4),·12H0), accurate to 0.001g, place in a 200mL beaker, add 100mL water and 10mL sulfuric acid, transfer quantitatively to a 1000mL volumetric flask after dissolution, dilute with water to scale, and shake well. 4.4.2.8 Iron standard solution: 1mL contains 0.010mg iron; dilute 10 times with (4.4.2.7) iron standard solution, only for use on the same day. 4.4.3 Instruments
General laboratory instruments and
4.4.3.1 Spectrophotometer: with a cuvette with a light path length of 3cm or 1cm; 4.4.3.2 pH meter.
4.4.4 Analysis steps
4.4.4.1 Preparation of standard curve
4.4.4.1.1 Preparation of standard colorimetric solution
According to Table 3, add the given volume of iron standard solution (4.4.2.8) to a series of 100mL volumetric flasks. Table 3
Amount of iron standard solution
Corresponding iron content
Amount of iron standard solution
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Continued Table 3
Each volumetric flask is treated in the same way as follows: Corresponding iron content
Add about 40mL of water, use a pH meter, adjust the pH of the solution to close to 2 with hydrochloric acid solution, add 2.5mL of ascorbic acid solution, 10mL of acetic acid-sodium acetate buffer solution, 5mL of 1,10-phenanthroline solution, dilute to the scale with water, and shake well. 4.4.4.1.2 Photometric determination
Use a solution with zero iron content as the reference solution and determine the absorbance of the standard colorimetric solution (4.4.4.1.1) at a wavelength of 510 nm using a spectrophotometer.
4.4.4.1.3 Plotting of the standard curve
Plot a graph with the iron content (ug) in 100 mL of the standard colorimetric solution as the horizontal axis and the corresponding absorbance as the vertical axis. 4.4.4.2 Determination
4.4.4.2.1 Preparation of sample and test solution
Transfer the precipitate of iron separated from the determination of dihydrogen phosphate (4.2.4.2) together with the filter paper to the original beaker (or directly weigh 50g of the sample), add a small amount of water and 10mL of hydrochloric acid solution, heat to boil, smash the filter paper with a glass rod, and keep boiling for 3min, filter after cooling, and wash with water several times, collect the solution quantitatively in a 500mL volumetric flask, add water to the scale, and mix well. Pipette 5.0mL of the test solution into a 100mL beaker, add water to 40mL, use a pH meter, adjust the pH of the solution to about 2 with ammonia solution, transfer the solution quantitatively to a 100mL volumetric flask, add 2.5mL of ascorbic acid solution, 10mL of acetic acid-sodium acetate buffer solution, and 5mL of 1,10 phenanthroline solution, dilute with water to the scale, and mix well. 4.4.4.2.2 Blank test
Carry out a blank test according to the above steps. Except that no sample is used, the operation procedures and reagents used are the same as those for the sample determination. 4.4.4.2.3 Photometric determination
Carry out photometric determination of the sample and blank test solution in the same manner as the standard curve drawing procedure to determine their absorbance. 4.4.5 Calculation of analytical results
Find out the iron content corresponding to the measured absorbance from the standard curve. The coating material content X (calculated as chelated iron (Fe)) in the sample is expressed as mass percentage (%) and calculated according to formula (4): X, = m = m2 ×
Where: m1——the mass of iron measured in the sample, g; - the mass of iron measured in the blank test, ug;
——the mass of the sample,.
The obtained result is expressed to four decimal places.
4.4.6 Allowable difference
The absolute difference of parallel determination results shall not exceed 0.0010%; the absolute difference of determination results of different laboratories shall not exceed 0.0020%; the arithmetic mean of parallel determinations shall be taken as the determination result. 4.5 Determination of particle size Sieving method
4.5.1 Summary of method
Use sieving method to separate the coated urea into different particle sizes and weigh them, and calculate the percentage. 4.5.2 Instrument
(4)
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4.5.2.1 One set of experimental sieves (GB6003R40/3 series) with aperture of 0.85mm and 2.80mm (with sieve cover and bottom plate); 4.5.2.2 Balance with a sensitivity of 0.5g,
4.5.2.3 Oscillator, which can oscillate vertically and horizontally. 4.5.3 Analysis steps
Stack the sieves in order of aperture size, weigh about 100g of sample, accurate to 0.5g, and place it on a sieve with an aperture of 2.80mm, cover the sieve cover, place it on an oscillator, clamp it, and oscillate for 3 minutes. Weigh the sample that passes through the 2.80mm aperture sieve and does not pass through the 0.85mm aperture sieve, and measure the particles sandwiched in the sieve holes as the part that does not pass through this aperture. 4.5.4 Calculation of analysis results
The particle size X5 in the aperture range of 0.85 to 2.80mm in the sample is expressed as mass percentage (%) and calculated according to formula (5): X=mX100
Where: m1—the mass of the sample that passes through the 2.80mm sieve and does not pass through the 0.85mm sieve, g; m
—the mass of the sample.
The result should be expressed to one decimal place.
5 Inspection rules
5.1 Coated urea shall be inspected by the quality inspection department of the manufacturer. The manufacturer shall ensure that each batch of fertilizers shipped out of the factory meets the requirements of this standard. Each batch of coated urea shipped out of the factory shall be accompanied by a quality certificate in a certain format, which shall include the following contents: manufacturer name, product name or trade name), trademark, product grade, batch number, production date, product net weight and this standard number and name. 5.2 The user has the right to conduct quality inspection on the received coated urea in accordance with the provisions of this standard to verify whether its indicators meet the requirements of this standard.
5.3 Coated urea shall be inspected in batches, with the shift output as one batch. The user shall regard the uniform quality products with one quality certificate as one batch. 5.4 Sampling method
For packaged products, when the total number of packaging bags is less than 512, the number of sampling bags shall be selected according to the provisions of Table 4; when it is greater than 512, it shall be selected according to the provisions of 3×N (N is the total number of packaging bags). When sampling, use a sampler to vertically insert 3/4 of the bag from the center to take a uniform sample. Or use an automatic sampler, spoon or other suitable tools to take cross-sectional samples from the belt conveyor at certain time intervals. 5.5 Use a reducer or quartering method to quickly reduce the sample taken to 600-1200g of uniform test samples, and divide them into two clean, dry, wide-mouth bottles with ground stoppers or other airtight containers. Label the containers and indicate: manufacturer name, product name, batch number, sampling date and name of the sampler. One copy is for testing: the other is used as a reserved sample, which is retained for one month for inspection. 5.6 If one of the indicators in the test results does not meet the requirements of this standard, samples should be taken from twice the number of bags for re-testing. If the sample is taken on a belt conveyor, it should be re-tested according to 5.4 Provisions on sampling in bagsRetest after sampling. Table 4 Provisions on the number of sampling bags
Total number of packaging bags
102~125
126151
152~181
Minimum number of sampling bags selected
Total number of packaging bags
182~216
217~254
255~296
297~343
344~394
395~450
451~512
Minimum number of sampling bags selected
As a result of the retest, if any one indicator does not meet the requirements of this standard, the entire batch of products shall be deemed unqualified. 5.7 The type inspection of harmful elements in coating materials shall be carried out by the manufacturer every three months; the coating of coated urea shall be inspected by the manufacturer when it is put into production.
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5.8 When the supply and demand parties have objections to the product quality, the two parties shall negotiate to add test items for arbitration. Packaging, marking, transportation and purchase and storage
6.1 Coated urea is packaged in plastic woven bags (the inner bag is a polyethylene film bag) and composite plastic woven bags. The net weight of each bag is 40±0.2 or 50±0.2kg. The average net weight of each batch of product bags is 40 or 50kg. The quality of coated urea packaging should comply with the relevant provisions of GB8569. 6.2 The packaging bag of coated urea should clearly indicate: manufacturer name, product name (or trade name), trademark, product net weight and the number and name of this standard.
6.3 Coated urea can be transported by vehicles, trains, ships and other means of transportation. The means of transportation and loading and unloading tools should be clean, flat and free of protruding sharp objects to avoid puncturing or scratching the packages.
6.4 Coated urea should be stored in a warehouse with a flat, cool, ventilated and dry site. The packages should be stacked neatly and the stacking height should be less than 7m. 10
A1 Subject content and scope of application
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Appendix A
Calculation method for determination of total nitrogen content
(reference)
This appendix specifies the calculation method for determining the total nitrogen content in coated urea. This appendix is only applicable to routine analytical product inspections by manufacturers. A2
Except for water and biuret nitrogen, the content of other impurities in coated urea can be ignored. Therefore, its total nitrogen content can be regarded as the sum of urea and biuret nitrogen. Urea nitrogen can be obtained by 100% water content reduction (H0) and diuretic nitrogen (Biu%), and diuretic nitrogen can be obtained by diuretic nitrogen content calculation. The sum of the two is the total nitrogen.
Calculation method
Total nitrogen content X, expressed as mass percentage of nitrogen (N), is calculated according to formula (A1) and formula (A2): X= [100 -(A + B)) 0- 466 5 ± B× 0. 407×100100-A
46. 65 - 0. 466 5 XA - 0. 059 XB × 100..100—A
Q-46.65-0.4665XA
β=0.059×B
Wherein: A—water content, %;
B—biuret content, %;
Listed in Table A1
Listed in Table A2
100—A
0.4665—coefficient of urea converted to nitrogen; 0.407——coefficient of biuret converted to nitrogen. The result should be expressed to two decimal places.
Calculation Table
1α value
H20,
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