Some standard content:
Chemical Industry Standard of the People's Republic of China
Calcium Magnesium Phosphate Potassium
Subject Content and Scope of Application
HG 2598-94
This standard specifies the technical requirements, test methods, inspection rules, as well as marking, packaging, transportation and storage of calcium magnesium phosphate potassium fertilizers. This standard applies to calcium magnesium phosphate potassium fertilizers made by melting phosphate ore, potassium feldspar (or potassium-containing ore) and magnesium and silicon-containing ores in a blast furnace or electric furnace at high temperature, quenching with water, drying and grinding. Calcium magnesium phosphate potassium fertilizers are a series of phosphate fertilizer products, which are used as fertilizers and soil conditioners in agriculture. 2 Reference standards
GB/T 601
GB/T 603
GB1250
Chemical reagents
Preparation of standard solutions for titration analysis (volumetric analysis) Preparation of preparations and products used in test methods Chemical reagents
Methods for expressing and determining limit values Test sieves
GB 6003
GB/T 6678
General rules for sampling of chemical products
Specifications and test methods for water used in analytical laboratories GB/T 6682
GB8569
3 Technical requirements
Packaging of solid chemical fertilizers
3.1 Appearance: Calcium magnesium phosphorus potassium fertilizer is off-white, grey-green or grey-black powder. 3.2 Calcium magnesium phosphorus potassium fertilizer should meet the requirements of Table 1: Table 1
Total nutrient (P,; + K,0) content, %
Effective potassium (K,0) content, %
Water content, %
Fineness: through 250μm standard sieve, %
4 Test method
Technical index of calcium magnesium phosphorus potassium fertilizer
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In the analysis, unless otherwise specified, analytical reagents are used, and the water used should meet the third-level water specifications in GB/T6682. 4.1 Determination of effective phosphorus pentoxide content, quinoline phosphomolybdic acid gravimetric method This method is equivalent to the international standard ISO6598:1985 "Determination of phosphorus content in fertilizers-quinoline phosphomolybdic acid gravimetric method". This method is an arbitration method for determining the effective phosphorus pentoxide content. Approved by the Ministry of Chemical Industry of the People's Republic of China on September 5, 1994. 244
Implementation on July 1, 1995
4.1.1 Scope of application
HG 2598-94
This method is applicable to the determination of test solutions with phosphorus pentoxide content in the range of 10 to 20 mg. 4.1.2 Summary of the method
Orthophosphate ions in phosphorus-containing solutions react with quinoline reagent in an acidic medium to form a yellow phosphomolybdic acid oxazoline precipitate, which is then filtered, washed, dried and weighed.
4.1.3 Reagents and materials
4.1.3.1 Nitric acid (GB/T626), 1+1 solution. 4.1.3.2 Citric acid (GB/T9855) solution, 20g/L, pH value is about 2.1, add 0.5g salicylic acid preservative to this solution, easy to store.
4.1.3.3 Quinoline molybdate reagent:
Solution A: Dissolve 70g sodium molybdate in a 400mL beaker containing 100mL water. Solution B: Dissolve 60g citric acid in a 1000mL beaker containing 100mL water, add 85mL concentrated nitric acid (GB/T626). Solution C: Add solution A to solution B and mix well. Solution D: Mix 35mL concentrated nitric acid and 100mL water in a 400mL beaker, and add 5mL quinoline. Add solution D to solution C, mix, let stand overnight, filter with filter paper or cotton, add 280mL acetone (GB/T686) to the filtrate, dilute with water to 1000mL, store the solution in a polyethylene bottle, place in a dark place, away from light and heat. 4.1.4 Instruments and equipment
· General laboratory glass instruments and:
Glass crucible filter, No. 4 (pore size 4-16μm), volume 30mL, a.
b. 35-40r/min up and down rotary oscillator or other horizontal reciprocating oscillator with the same effect; electric constant temperature drying oven, capable of maintaining a temperature of (180±2)℃; c.
d. Water bath.
4.1.5 Analysis steps
4.1.5.1 Preparation of sample solution
Weigh 1g of sample (accurate to 0.001g), place in a dry 250mL conical flask or 250mL volumetric flask, accurately add 150mL of citric acid solution (4.1.3.2) preheated to 28~30℃, plug the bottle tightly, keep the solution temperature between 28 and 30℃, and place on an oscillator (4.1.4b) for 1h. Dry filter immediately and discard the first few milliliters of filtrate. This is the test solution for phosphorus content determination. 4.1.5.2 Determination
Put a certain amount of test solution (4.1.5.1) (containing 10-20 mg of phosphorus pentoxide) into a 500 mL beaker, add 10 mL of nitric acid solution (4.1.3.1), dilute to 100 mL with water, preheat to near boiling, add 35 mL of quinoline molybdate reagent, cover with surface III, slightly boil on a hot plate for 1 min or keep warm in a near-boiling water bath until precipitation and stratification, take out the beaker and cool to room temperature, rotating the beaker 3-4 times during the cooling process. Filter through a No. 4 glass filter that has been dried to constant weight at (180 ± 2) ° C in advance, and filter out the upper clear liquid first. Then wash the precipitate 1-2 times by pouring method (about 25 mL of water each time), transfer the precipitate to the filter, and continue washing with water, using a total of about 125-150 mL of water. Place the filter with the precipitate in a drying oven at (180 ± 2)°C, dry for 45 minutes after the temperature reaches the required value, transfer to a desiccator, cool to room temperature, and weigh. 4.1.5.3 Blank test
During the determination, perform the analysis according to the same analytical steps, reagents, and dosages as in 4.1.5.1 and 4.1.5.2, except that no sample is added.
4.1.6 Expression of analysis results
The effective phosphorus pentoxide (POs) content X1, expressed as mass percentage (%), is calculated according to formula (1): X1=(m1=m)X0.03207×100
mo×150
(mlmz)X481.05
Wherein: mi
mass of quinoline phosphomolybdic acid precipitate, g;
HG 2598--94
mass of quinoline phosphomolybdic acid precipitate obtained in the blank test, g; mass of sample, g;
V-volume of sample solution taken, mL;
0.03207-
-coefficient for converting the mass of oxadiazole phosphate into the mass of phosphorus pentoxide. 4.1.7 Allowable difference
The arithmetic mean of the parallel determination results is taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.20%. The absolute difference of the determination results of different laboratories shall not exceed 0.30%. 4.2 Determination of effective phosphorus pentoxide content Phosphomolybdic acid oxazoline volumetric method 4.2.1 Scope of application
The scope of application of this method is within Article 4.1.1.
4.2.2 Summary of the method
After washing away the adsorbed acid solution, the yellow precipitate obtained by the phosphomolybdic acid oxazoline weight method is dissolved in an excess of a standard alkali titration solution and then back-titrated with a standard acid titration solution.
4.2.3 Reagents and materials
Same as 4.1.3 Reagents and:
4.2.3.1 Sodium hydroxide (GB/T629) standard titration solution, c(NaOH)=0.5mol/L Prepare, calibrate and compare according to 4.1 of GB/T601. 4.2.3.2 Hydrochloric acid (GB/T 622) standard titration solution, c(HCI)=0.25mol/L.
Measure 22mL of hydrochloric acid and slowly pour it into a 1000mL volumetric flask with about 500mL of water added in advance, cool, dilute with water to the scale, mix, calibrate and compare according to 4.2.2 and 4.2.3 of GB/T601. 4.2.3.3 Carbon dioxide-free water
Prepare according to 4.1.1 of GB/T603.
4.2.3.4 Thymol blue (HG/T3-1223): 1g/L ethanol solution Dissolve 0.1g thymol blue in 2.2mL c(NaOH)=0.1mol/L sodium hydroxide solution, dilute to 100mL with 60% (V/V) ethanol solution.
4.2.3.5 Phenolic acid (GB/T10729): 1g/L ethanol solution Dissolve 0.1g phenolic acid in 60mL ethanol (GB/T678), dilute to 100mL. 4.2.3.6 Mixed indicator
Take 3 volumes of thymol blue solution (4.2.3.4) and 2 volumes of phenolic acid solution (4.2.3.5) and mix well. 4.2.4 Instruments and equipment
General laboratory glassware and
4.2.4.135~~40r/min vertical rotary oscillator or other horizontal reciprocating oscillator with the same effect. 4.2.4.2 Water bath.
4.2.5 Analysis steps
Prepare the sample solution in 4.1.5.1 and the determination in 4.1.5.2 until "··Turn the beaker 3~4 times during the cooling process". The following operations are carried out according to the following procedures:
First filter the upper clear liquid with medium-speed filter paper or absorbent cotton, then wash the precipitate 3~4 times by pouring method, each time with about 25mL of water, transfer the precipitate to the filter, continue to wash with water until about 20mL of filtrate is obtained, add a drop of mixed indicator and 2~3 drops of sodium hydroxide solution (4.2.3.1), until the color of the filtrate is similar to the color of the same volume of water. Transfer the precipitate together with the filter paper or absorbent cotton to the original beaker, add sodium hydroxide standard titration solution (4.2.3.1) and stir thoroughly until the precipitate dissolves, then add about 10 mL excess. Add 100 mL of water without carbon dioxide, stir the precipitate, add 5 drops of mixed indicator, and use hydrochloric acid standard titration solution (4.2.3.2) to titrate the solution from purple to gray-blue to slightly yellow as the end point. At the same time, perform a blank test. Except for not adding the sample, all the steps of the blank test are the same as those in 4.2.5. 4.2.6 Expression of analysis results
The effective phosphorus pentoxide (P,O,) content X2, expressed as mass percentage (%), is calculated according to formula (2): X,(g(VV)(V×0. 002 730 100
mo×150
[c;(Vi-V)-c2(V2-V)) X 40. 95moV
Wherein: Ci—concentration of sodium hydroxide standard titration solution, mol/L; C2
concentration of hydrochloric acid standard titration solution, mol/L, volume of sodium hydroxide standard titration solution, mL, volume of hydrochloric acid standard titration solution, mL;
V3——volume of sodium hydroxide standard titration solution for blank test, mL, V——volume of hydrochloric acid standard titration solution for blank test, mL; mo—mass of sample, g;
V—volume of sample solution taken, mL;
0. 002 730-
（2）
The mass of phosphorus pentoxide in grams equivalent to 1.00mL of sodium hydroxide standard titration solution [c(NaOH)=1.000mol/L].
4.2.7 Allowable difference
The arithmetic mean of the parallel determination results shall be taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.20%. The absolute difference of the determination results of different laboratories shall not exceed 0.30%. 4.3 Determination of effective potassium oxide content Potassium tetraphenylborate gravimetric method 4.3.1 Applicable range
This method is suitable for the determination of samples with potassium oxide content in the range of 1% to 4%. 4.3.2 Method Summary
Use sodium tetraphenylborate solution to precipitate potassium ions in the test solution. The resulting precipitate is filtered, washed, dried and weighed. 4.3.3 Reagents and Materials
4.3.3.1 Nitric acid (GB/T626): 1+1 solution. 4.3.3.2 Citric acid (GB/T9855) solution, 20g/L, pH value is about 2.1. 0.5g salicylic acid preservative is added to this solution for easy storage. | |tt||4.3.3.3 Sodium tetraphenylborate: 15g/L solution. Take 15g of sodium tetraphenylborate and dissolve it in about 960mL of water, add 4mL of 400g/L sodium hydroxide solution and 20mL of 100g/L magnesium chloride hexahydrate solution, stir for 15min, let it stand and filter it with filter paper. The solution is stored in a brown bottle or plastic bottle, generally not more than 1 month. If turbidity is found, it should be filtered before use. 4.3.3.4 Sodium tetraphenylborate washing solution: dilute 1 volume of sodium tetraphenylborate solution with 10 volumes of water ( 4.3.3.3). 4.3.3.5 Thymol blue (HG/T3-1223) indicator: 1g/L ethanol solution, prepared according to 4.2.3.4. 4.3.4 Instruments and equipment
General laboratory glassware and
Glass crucible filter, No. 4 (pore size 4~16um), volume 30mL; 35~40r/min up and down rotary oscillator or other horizontal reciprocating oscillator with the same effect; b.
Electric constant temperature drying oven, capable of maintaining a temperature of (120±2)℃; water bath.
4.3.5 Analysis steps
4.3.5.1 Preparation of sample solution
HG 2598-94
Weigh 2.5g of sample (accurate to 0.001g) and place it in a dry 250mL conical flask. Accurately add 200 mL of citric acid solution (4.3.3.2) preheated to 28~30℃, plug the bottle tightly, keep the solution temperature between 28 and 30℃, place it on an oscillator (4.3.4b) for 1 hour, dry filter immediately, and discard the first few milliliters of filtrate. This is the test solution for potassium content determination. 4.3.5.2 Determination
Put 150mL of the test solution (4.3.5.1) in a 500mL beaker, add 5 drops of thymol blue indicator (4.3.3.5), adjust the solution to yellow-red (pH 2.0~～2.5) with 1+1 nitric acid solution, add sodium tetraphenylborate solution (4.3.3.3) dropwise to the sample solution under constant stirring, the amount added is 0.5mL of sodium tetraphenylborate solution for every 1mg of potassium oxide, and the excess is about 7mL, continue stirring for 1min, let stand for 15min (not more than 30min), filter the precipitate by pouring method into a No. 4 glass crucible filter that has been pre-weighed at 120℃, wash the precipitate with washing solution for 5~～7 times, each time using about 5mL, and finally wash it with water twice, each time using 5mL. Place the filter containing the precipitate in a drying oven at (120 ± 2)°C and dry for 1.5 hours, then transfer it to a desiccator to cool to room temperature and weigh it. 4.3.5.3 Blank test
During the determination, perform the analysis according to the same analytical steps, reagents and dosages as in 4.3.5.1 and 4.3.5.2, except that no sample is added.
4.3.6 Expression of analysis results
The effective potassium oxide (K,0) content X3, expressed as mass percentage (%), is calculated according to formula (3): X:=(m=m)X0.131 4×100
mo×200
_17.52X(mlmz)
Wherein: m-
0. 131 4-
The mass of potassium tetraphenylborate precipitate, g; mo
The mass of potassium tetraphenylborate precipitate obtained from the reagent blank test, name; The mass of the sample, g;
-The coefficient for converting the mass of potassium tetraphenylborate into the mass of potassium oxide. 4.3.7 Allowable difference
The arithmetic mean of the parallel determination results is taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.12%. The absolute difference between the results of different laboratories is not greater than 0.24%. 4.4 Determination of moisture by weight method
4.4.1 Scope of application
This method is applicable to the sample with a moisture loss greater than 0.001g. 4.4.2 Summary of the method
In an electric constant temperature drying oven at a certain temperature, the mass of the sample reduced by drying within a specified time is the moisture content. 4.4.3 Instruments and equipment
4.4.3.1 Electric constant temperature drying oven: capable of maintaining a temperature of (130 ± 2)°C. 4.4.3.2 Ground-mouth weighing bottle with lid: 50mm in diameter and 30mm in height. 4.4.4 Analysis steps
（3）
Weigh 10g of calcium magnesium phosphorus potassium fertilizer (accurate to 0.001g), place it in a weighing bottle (4.4.3.2) that has been dried to constant weight at (130±2)℃ in advance, open the lid of the weighing bottle slightly, place the weighing bottle in a drying oven and keep it close to the level of the mercury ball of the thermometer, dry it for 20 minutes when the temperature reaches (130±2)℃, take it out, cover the weighing bottle, cool it in a desiccator and weigh it. 4.4.5 Expression of analysis results
Water content (H,O)X4, expressed as mass percentage (%), calculated according to formula (4): 248
Where: m-
HG 2598—94
Weighing bottle and sample mass before drying, g; weighing bottle and sample mass after drying, g; sample mass, g.
4.4.6 Allowable difference
The arithmetic mean of the parallel determination results shall be taken as the determination result. The absolute difference of the parallel determination results shall not exceed 0.03%. The absolute difference of the determination results of different laboratories shall not exceed 0.06%. 4.5 Determination of fineness Sieving method
4.5.1 Method summary
The mass percentage of the sample passing through the specified sieve hole is calculated by the sieving method. 4.5.2 Instruments and equipment
4.5.2.1 Standard sieve: pore size 250μm, should meet the requirements of R40/3 series in GB6003, with sieve cover and chassis. 4.5.2.2 Balance: sensitivity 0.5g.
4.5.2.3 Electric vibrating sieve machine.
4.5.3 Analysis steps
(4)
Put the standard sieve with pore size 250μm on the chassis, weigh about 100g of sample (accurate to 0.5g), put it in the sieve, cover the sieve cover, clamp it on the vibrating sieve machine (4.5.2.3), vibrate for 10 minutes, then carefully brush the sample that passes through the specified sieve hole on the surface blood with a brush and weigh it. Note: If there is no vibrating sieve machine, the screening operation can be performed manually, that is, it is fully shaken manually for 10 minutes, but the vibrating sieve machine must be used for arbitration. 4.5.4 Expression of analysis results
The fineness Xs passing through the 250um standard sieve is expressed as mass percentage (%) and calculated according to formula (5): mx100
Where: m-
The mass of the sample passing through the sieve hole, g;
The mass of the sample, g.
5 Inspection rules
(5)
5.1 Calcium magnesium phosphate and potassium fertilizers shall be inspected by the quality inspection department of the manufacturer. The manufacturer shall ensure that all products leaving the factory meet the requirements of this standard. Each batch of products leaving the factory shall be accompanied by a quality certificate in a certain format, including: manufacturer name, factory address, product name, product grade, batch number, production date, product net weight and this standard number. 5.2 The user has the right to conduct quality inspection on the calcium magnesium phosphate and potassium fertilizers received in accordance with the provisions of this standard to verify whether its indicators meet the requirements of this standard.
5.3 Calcium magnesium phosphate and potassium fertilizers shall be inspected in batches, and the weight of each batch shall not exceed 300t. Users may regard products of uniform quality with the same quality certificate as one batch.
5.4 The number of sampling bags for bagged calcium magnesium phosphate and potassium fertilizers shall be selected in accordance with the provisions of GB/T6678, as shown in Table 2.249
Total number of packaging bags
65~81
82~101
102~125
126~151
152~181
HG2598—94
Table 2 Provisions for selecting the number of sampling bags
Number of sampling bags||tt ||Total number of bags
Total number of packaging bags
182~216
217~254
255~296
297~343
344~394
395450
451~512
Number of sampling bags
When the number of sampling bags exceeds 500, the number of sampling bags shall be calculated according to the provisions of 3×N (N is the total number of packaging bags of each batch of products). In the calculation, if there is a decimal, it shall be rounded up to an integer.
When sampling, use a sampler to obliquely insert from one side of the bag opening to 3/4 of the depth of the opposite bag to take a uniform sample. Each time, no less than 100g of sample is taken, and the total amount of sample taken shall not be less than 2kg.
5.5 Combine the samples, mix them carefully, and use a divider or quartering method to reduce them to about 0.5kg (no re-sampling is allowed), and pack them in two clean, dry wide-mouth bottles or polyethylene bottles with ground stoppers. Label them and indicate: manufacturer name, product name, batch number, sampling date and name of the sampler. One copy is for inspection, and the other is a reserved sample with a retention period of 2 months for inspection. 5.6 If one of the indicators in the test results does not meet the requirements of this standard, re-samples should be taken from twice the amount of packaging bags for re-inspection. If the re-inspection results show that even if only one indicator does not meet the requirements of this standard, the entire batch of calcium magnesium phosphorus potassium fertilizers is unqualified. 5.7 This standard adopts the "rounded value comparison method" in GB1250 to determine whether the test results meet the standard. 5.8 When the supply and demand parties have disputes over product quality and need arbitration, they should be conducted in accordance with the relevant product quality arbitration provisions of the "Product Quality Law of the People's Republic of China".
6 Packaging, marking, transportation and storage
6.1 Calcium magnesium phosphate fertilizers should be packaged in composite bags or multi-layer bags. The technical requirements of the packaging and the packaging materials should comply with the relevant provisions of GB8569 on "calcium magnesium phosphate fertilizers".
6.2 The net weight of each bag is (25±0.5) kg, (40±0.8) kg or (50±1.0) kg. The average net weight of each bag of each batch of products should reach 25 kg, 40 kg or 50 kg.
6.3 The packaging bag of calcium magnesium phosphate fertilizer should be marked with the manufacturer's name, factory address, product name, production date or production batch number, trademark, grade, net weight and this standard number.
6.4 Calcium magnesium phosphate and potassium fertilizers can be transported by vehicles, trains, ships and other means of transportation. During transportation, moisture and packaging bags should be prevented from being damaged. 6.5 Calcium magnesium phosphate and potassium fertilizers should be stored in warehouses with flat ground, cool, ventilated and dry conditions. The stacking height of packages should not exceed 7m. Additional notes:
This standard is proposed by the Technical Supervision Department of the Ministry of Chemical Industry. This standard is under the jurisdiction of the Shanghai Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard was drafted by the Shanghai Chemical Industry Research Institute of the Ministry of Chemical Industry. The main drafters of this standard are Xie Ruiming and Han Tingzhan. From the date of implementation of this standard, the former Ministry of Chemical Industry standard HG1-1384-81 "Uniform Analysis Method for Calcium Magnesium Phosphorus and Potassium Fertilizers" shall be invalid. 2507 This standard adopts the "rounded value comparison method" in GB1250 to judge whether the test results meet the standard. 5.8 When the supply and demand parties have disputes over product quality and need arbitration, the arbitration provisions on product quality in the "Product Quality Law of the People's Republic of China" shall be followed.
6 Packaging, marking, transportation and storage
6.1 Calcium magnesium phosphate fertilizers should be packaged in composite bags or multi-layer bags. The technical requirements and packaging materials of the packaging should comply with the relevant provisions of "calcium magnesium phosphate fertilizers" in GB8569.
6.2 The net weight of each bag is (25±0.5) kg, (40±0.8) kg or (50±1.0) kg. The average net weight of each bag of each batch of products is 25 kg, 40 kg or 50 kg.
6.3 The packaging bag of calcium magnesium phosphate fertilizer should be marked with the manufacturer's name, address, product name, production date or production batch number, trademark, grade, net weight and this standard number.
6.4 Calcium magnesium phosphate and potassium fertilizers can be transported by vehicles, trains, ships and other means of transportation. During transportation, moisture and packaging bags should be prevented from being damaged. 6.5 Calcium magnesium phosphate and potassium fertilizers should be stored in warehouses with flat ground, cool, ventilated and dry conditions. The stacking height of packages should not exceed 7m. Additional notes:
This standard is proposed by the Technical Supervision Department of the Ministry of Chemical Industry. This standard is under the jurisdiction of the Shanghai Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard was drafted by the Shanghai Chemical Industry Research Institute of the Ministry of Chemical Industry. The main drafters of this standard are Xie Ruiming and Han Tingzhan. From the date of implementation of this standard, the former Ministry of Chemical Industry standard HG1-1384-81 "Uniform Analysis Method for Calcium Magnesium Phosphorus and Potassium Fertilizers" shall be invalid. 2507 This standard adopts the "rounded value comparison method" in GB1250 to judge whether the test results meet the standard. 5.8 When the supply and demand parties have disputes over product quality and need arbitration, the arbitration provisions on product quality in the "Product Quality Law of the People's Republic of China" shall be followed.
6 Packaging, marking, transportation and storage
6.1 Calcium magnesium phosphate fertilizers should be packaged in composite bags or multi-layer bags. The technical requirements and packaging materials of the packaging should comply with the relevant provisions of "calcium magnesium phosphate fertilizers" in GB8569.
6.2 The net weight of each bag is (25±0.5) kg, (40±0.8) kg or (50±1.0) kg. The average net weight of each bag of each batch of products is 25 kg, 40 kg or 50 kg.
6.3 The packaging bag of calcium magnesium phosphate fertilizer should be marked with the manufacturer's name, address, product name, production date or production batch number, trademark, grade, net weight and this standard number.
6.4 Calcium magnesium phosphate and potassium fertilizers can be transported by vehicles, trains, ships and other means of transportation. During transportation, moisture and packaging bags should be prevented from being damaged. 6.5 Calcium magnesium phosphate and potassium fertilizers should be stored in warehouses with flat ground, cool, ventilated and dry. The stacking height of packages should not exceed 7m. Additional remarks:
This standard is proposed by the Technical Supervision Department of the Ministry of Chemical Industry. This standard is under the jurisdiction of the Shanghai Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard was drafted by the Shanghai Chemical Industry Research Institute of the Ministry of Chemical Industry. The main drafters of this standard are Xie Ruiming and Han Tingzhan. From the date of implementation of this standard, the former Ministry of Chemical Industry standard HG1-1384-81 "Uniform Analysis Method for Calcium Magnesium Phosphorus and Potassium Fertilizers" shall be invalid. 250
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