HG/T 2220-1991 Determination of phosphorus content in triple superphosphate-Quinoline phosphomolybdate gravimetric method
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Chemical Industry Standard of the People's Republic of China
HG2220-91
Determination of phosphorus content in triple superphosphate
Quinomaglyphophosphophosphate gravimetric method
Published on November 15, 1991
Ministry of Chemical Industry of the People's Republic of China
Implementation on July 1, 1992
Chemical Industry Standard of the People's Republic of China
Determination of phosphorus content in triple superphosphate
Quinomaglyphophosphophosphate gravimetric method
HG2220-91
This standard adopts the international standards ISO7497-84 "Fertilizers-Extraction of acid-soluble phosphorus (Method A)" and ISO6598-85 "Fertilizers-Determination of phosphorus content-Quinomaglyphophosphophosphate gravimetric method". 1 Subject content and scope of application
This standard specifies the extraction and determination methods of total phosphorus and available phosphorus in triple superphosphate. This standard applies to the determination of total phosphorus and available phosphorus content in triple superphosphate. 2 Principle
Use a mixed acid solution of hydrochloric acid and nitric acid to extract total phosphorus in triple superphosphate, and use water and neutral ammonium citrate solution to extract available phosphorus. The orthophosphate ions in the extract (if not completely present as orthophosphate ions, it can be heated and hydrolyzed first) react with quinoline molybdate reagent in an acidic medium to generate yellow quinoline phosphomolybdic acid precipitate, which is weighed after filtration, washing, and drying. 3 Reagents and solutions
In the analysis, unless otherwise specified, only analytical reagents, distilled water or water of equivalent purity can be used. 3.1 Nitric acid (GB626): 1+1 solution.
3.2 Mixed acid: Add 3 volumes of nitric acid (GB626) to 1 volume of hydrochloric acid (GB622), dilute with 4 volumes of water, and mix well. 3.3 Neutral ammonium citrate solution (pH=7.0, density 1.09 at 20℃): Dissolve 370g citric acid (CH:Oz·H2O) in 1.5L water, add 345mL ammonium hydroxide (GB631) to make the solution close to neutral. If the ammonia content is lower than 28%, the amount of ammonium hydroxide can be increased accordingly, and a smaller amount of water can be used to dissolve the citric acid. Cool, test the pH value of the solution with an acidometer, adjust the pH of the solution to 7.0 with 1+7 ammonium hydroxide or citric acid solution, and dilute with water to make its density 1.09 at 20℃. The prepared solution is stored in a sealed container. During use, check the pH value frequently. If there is any change, readjust the pH to 7.0. 3.4 Quinoline molybdate reagent:
Solution I Dissolve 70g sodium molybdate (Na2Mo0·2H20) in a 400mL beaker containing 100mL water; Solution I
Dissolve 60g citric acid in a 1000mL beaker containing 100mL water, add 85mL nitric acid (GB626); Solution Add solution I to solution I and mix well; Solution V Mix 35mL nitric acid (GB626) and 100mL water in a 400mL beaker, add 5mL quinoline (CHN) Solution V Add solution NV to solution III, mix well, let stand overnight, filter with filter paper, add 280mL acetone (GB686) to the solution, and dilute to 1000mL with water. The prepared solution is stored in a polyethylene bottle with a stopper in a cool place away from light. The shelf life is one month.
4 Instruments
Usual laboratory instruments and
4.1 Sintered glass crucible filter: No. 4 (pore size 4~16um), volume 30mL. 4.2 Drying oven: capable of maintaining a constant temperature of 180±2℃. Approved by the Ministry of Chemical Industry of the People's Republic of China on November 15, 1991 and implemented on July 1, 1992
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5 Operating steps
5.1 Weighing of sample
Weigh about 1g of sample, accurate to 0.001g. 5.2 Preparation of test solution
5.2.1 Extraction of total phosphorus
HG2220-91
Place the weighed sample (5.1) in a 200mL beaker, add 25mL of mixed acid (3.2), cover with surface blood, heat to boiling and keep it slightly boiling for 30min. Add 50mL of water, heat to boiling again, and keep it slightly boiling for 15min. Cool, transfer quantitatively into a 250mL volumetric flask, dilute with water to the scale, and mix well. Filter with dry filter paper and funnel, discard the initial part of the filtrate, and the resulting filtrate is used for the determination of total phosphorus. 5.2.2 Extraction of available phosphorus
Place the weighed sample (5.1) in 75mL of porcelain evaporating blood, add 25mL of water to grind, let it stand, and then pour and filter the clear liquid into a 500mL volumetric flask pre-added with 5mL of nitric acid (3.1). After the sample is treated as above three times, it is quantitatively transferred to the filter paper soil and washed with water until the filtrate in the volumetric flask reaches about 400mL. When washing the filter, rinse with a thin stream of water along the upper edge of the entire filter paper to ensure that the added water is in full contact with the sample. After the water in the added funnel is filtered out, continue to wash with water. Dilute the filtrate in the volumetric flask to the scale with water, mix well, and use it for the determination of available phosphorus. Transfer the water-insoluble residue together with the filter paper into a 250mL volumetric flask with 100mL of neutral ammonium citrate solution (3.3) preheated to 65±1℃, cover the bottle stopper, and shake until the filter paper breaks into fibers. Place the volumetric flask in a water bath at 65±1℃, keep warm and extract for 1h, and shake the volumetric flask once every 10min. Remove the volumetric flask from the water bath, cool to room temperature, dilute to the scale with water, and mix well. Filter with dry filter paper and funnel, discard the initial part of the filtrate, and the resulting filtrate is used for the determination of available phosphorus. 5.3 Determination of phosphorus content
After the drying process, part of the orthophosphate in the superphosphate is dehydrated and polymerized. The effective phosphorus test solution extracted with water and neutral ammonium citrate solution may contain metaphosphate, pyrophosphate or polyphosphate. Therefore, the extract for determination by pipette should be heated and boiled for several minutes before adding quinoline reagent (3.4) for hydrolysis. 5.3.1 Determination of total phosphorus content
Use a pipette to draw less than 20 mg of total phosphorus pentoxide extract (5.2.1), transfer it into a 400 mL beaker, add 10 mL of nitric acid solution (3.1), dilute with water to about 100 mL, heat to near boiling, and add 35 mL of quinoline reagent (3.4). Cover with surface III, place in a near-boiling water bath to keep warm until precipitation and stratification, take out, and cool to room temperature. Filter with a sintered glass crucible filter that has been dried to constant weight at 180 ± 2°C. First, filter out the supernatant in the beaker. Then wash the precipitate 1 to 2 times by pouring (about 25 mL of water each time). Transfer the precipitate to the filter and continue washing with water. The total amount of water used is about 125 to 150 mL. Place the filter together with the precipitate in a drying oven at 180 ± 2°C. When the temperature reaches the temperature, keep it warm for 45 minutes, transfer it to a desiccator, cool it to room temperature, and weigh it.
5.3.2 Determination of effective phosphorus content
Use a pipette to draw the water-soluble phosphorus and neutral ammonium citrate-soluble phosphorus extracts (5.2.2, volume ratio of 2:1) with a total of less than 20 mg of phosphorus pentoxide, transfer them to a 400 mL beaker, add 10 mL of nitric acid solution (3.1), and dilute with water to about 100 mL. Heat to near boiling (if hydrolysis is required, slowly heat and boil for several minutes), add 35mL quinoline molybdate reagent (3.4). The following procedures are the same as those in 5.3.1. 5.3.3 Blank test
For the determination of the above phosphorus contents, except that no sample is used, a blank test shall be carried out using the same reagent, solution and dosage and the same operating procedures.
6 Result Expression
6.1 Total Phosphorus Content
The total phosphorus (P20s) content X1 expressed as a mass percentage is calculated according to formula (1): 2
WW.bzsoso.cOm Various American Standard Industry Data Free Download In the formula: m1-
HG2220-91
Xi=(m1-m2)×0. 032 07,
(ml-m2)×801.75
The mass of the quinoline phosphomolybdic acid precipitate obtained by the determination, g; the mass of the quinoline phosphomolybdic acid precipitate obtained by the blank test, 8mo——the mass of the sample, g,
V——the volume of the total phosphorus extract absorbed during precipitation, mL, the coefficient for converting the mass of quinoline phosphomolybdic acid into the mass of phosphorus pentoxide. 0.03207
The result should be expressed to two decimal places.
6.2 Effective phosphorus content
The effective phosphorus (P20s) content X2 expressed as mass percentage is calculated according to formula (2): Xx=(m1m)X0.03207×10(m1m2)X2405.25.mo×750
Where: m
——mass of quinoline phosphomolybdic acid precipitate obtained by determination, name, -mass of quinoline phosphomolybdic acid precipitate obtained by blank test, 8mo—mass of sample, g,
V——total volume of water-soluble phosphorus and neutral ammonium citrate soluble phosphorus extracts absorbed at a volume ratio of 2:1 during precipitation, mL, 0.03207—coefficient for converting the mass of quinoline phosphomolybdic acid into the mass of phosphorus pentoxide. The result should be expressed to two decimal places.
6.3 Allowable difference
6.3.1 Take the arithmetic mean of the parallel determination results as the determination result. 6.3.2 The absolute difference of the parallel determination results shall not exceed 0.20%. 6.3.3 The absolute difference of the determination results of different laboratories shall not exceed 0.40%. Additional remarks:
This standard is proposed by the Science and Technology Department of the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Shanghai Chemical Industry Research Institute of the Ministry of Chemical Industry. This standard was drafted by Shanghai Chemical Industry Research Institute of the Ministry of Chemical Industry and Yunnan Phosphate Fertilizer Factory. The main drafters of this standard are Yin Yongkang, Chen Xuezhi, Xie Ruiming and Hua Xian. (1)
（2）Www.bzxZ.net
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