Method for rapidly measuring content of effective phosphorus pentoxide in compound fertilizer

Abstract

The invention relates to the technical field of fertilizer detection, and discloses a method for rapidly determining the content of effective phosphorus pentoxide in a compound fertilizer, which comprises the following steps: 1) sample treatment, 2) precipitation filtration, 3) precipitation titration, and 4) result analysis. According to the method, test data can be obtained within half an hour, the accuracy of a measurement result can still be ensured, and for the nutrient control process of the produced compound fertilizer, the production decision-making process is accelerated, and the quality of the compound fertilizer is ensured.

Description

Technical Field

[0001] The invention relates to the technical field of fertilizer detection, and in particular to a method for quickly determining the content of effective phosphorus pentoxide in a compound fertilizer. Background Art

[0002] The phosphorus sources in compound fertilizers are mostly monoammonium phosphate and superphosphate, which are usually produced by the reaction of phosphate rock and ammonia or by sulfuric acid treatment. The method for detecting phosphorus pentoxide in phosphate rock is the quinoline phosphomolybdic acid volumetric method. Similarly, for compound fertilizers produced using monoammonium phosphate and superphosphate as raw materials, the phosphorus pentoxide content in the compound fertilizer can also be obtained by this method.

[0003] The quinoline phosphomolybdate volumetric method is to transfer the sample solution and heat it on a hot plate for 10 minutes, add the reagent and then boil it for 1 minute, cool it to room temperature and filter the precipitate, place the precipitate in a drying oven (180±2°) and dry it for 45 minutes, take it out and cool it for 40 minutes, weigh it, and calculate it. The operation is relatively cumbersome and takes 3 hours, which is not conducive to quickly obtaining the data required for production. A rapid determination method for the content of effective phosphorus pentoxide in compound fertilizers is urgently needed to solve the above problems. Summary of the invention

[0004] The purpose of the present invention is to provide a method for quickly determining the content of effective phosphorus pentoxide in compound fertilizer.

[0005] The scheme of the present invention is:

[0006] A method for quickly determining the effective phosphorus pentoxide content in a compound fertilizer, characterized in that it comprises the following steps:

[0007] 1) Sample treatment: weigh 0.05-0.1 g of the sample to be tested and put it in a beaker. Rinse the beaker wall with 20-40 ml of distilled water. Add 10 ml of concentrated nitric acid under the ventilation device. Boil it on the heating device for 3-5 minutes. Slowly add 35 ml of quinoline molybdate reagent and continue to keep boiling for 3 minutes. Remove the beaker containing the treated sample;

[0008] 2) Precipitation and filtration: Place absorbent cotton in a funnel for filtration, transfer the treated sample in the beaker to the funnel, wash the treated sample in the funnel, and wash until the pH of the droplets filtered out of the lower tube outlet of the funnel is neutral. After washing, transfer the absorbent cotton in the funnel and the washed precipitate back to the beaker for titration;

[0009] 3) precipitation titration, titrating the beaker with a sodium hydroxide standard solution until the color turns yellow to colorless, recording V1, where V1 is the volume of the sodium hydroxide standard solution consumed, then adding 7 to 10 drops of thymol blue-phenolphthalein indicator for coloring, and then titrating with a hydrochloric acid standard solution until the color turns from purple to colorless, recording V2, where V2 is the volume of the hydrochloric acid standard solution consumed;

[0010] 4) Analysis results: The effective phosphorus pentoxide content is expressed as mass percentage and is calculated according to the following formula:

[0011]

[0012] Where:

[0013] C NaOH is the concentration of sodium hydroxide standard solution mol / L;

[0014] C HCl is the concentration of hydrochloric acid standard solution mol / L;

[0015] V1 is the volume of sodium hydroxide standard solution consumed, in milliliters;

[0016] V2 is the volume of the hydrochloric acid standard solution sample consumed, in milliliters;

[0017] m is the mass of the sample weighed, in grams.

[0018] 0.00273 and 1.00ml sodium hydroxide standard solution (C NaOH =1.0000 mol / L) is equivalent to the mass of phosphorus pentoxide expressed in grams.

[0019] As a preferred technical solution, the sodium hydroxide standard solution in step 4) is C NaOH =0.3mol / L; hydrochloric acid standard solution is C HCl =0.1 mol / L; thymol blue-phenolphthalein indicator is a mixture of 3 volumes of thymol blue solution (1 g / L) and 2 volumes of phenolphthalein (1 g / L).

[0020] As a preferred technical solution, the quinoline molybdate reagent in step 1) includes sodium molybdate, water, citric acid, nitric acid, quinoline and acetone.

[0021] The method for preparing the quinoline molybdate reagent comprises the following steps:

[0022] Solution a: weigh 70g sodium molybdate (Na2MoO4·2H2O) and dissolve it in 100ml water;

[0023] Solution b: Weigh 60g of citric acid (C6H8O7·H2O) into a 1L beaker, add 100mL of water to dissolve, and then add 85ml of nitric acid;

[0024] Solution c: Add solution a to solution b and mix well;

[0025] Solution d: Add 100 ml of water and 35 ml of nitric acid into a 500 ml beaker, and add 5 ml of quinoline, and mix well;

[0026] Add solution d to solution c, mix well, let stand overnight, filter with absorbent cotton, add 280 ml of acetone to the filtrate, and dilute with water to 1 L. Stir and mix well, store the solution in a polyethylene bottle in a dark place, away from light and heat. If the solution of the quinoline molybdate reagent turns light blue, add potassium bromate solution (10 g / L) until the color disappears.

[0027] As a preferred technical solution, in step 1), the sample is passed through a 1.0 mm test sieve and weighed; and the beaker wall is rinsed with 30 ml of distilled water.

[0028] As a preferred technical solution, broken filter paper soaked in pure water is laid on the absorbent cotton in the funnel in 2).

[0029] As a preferred technical solution, the processing sample in the funnel is washed with water in 2), and the amount of water used for each washing is ≤30 ml.

[0030] A rapid determination method for the effective phosphorus pentoxide content in a compound fertilizer is adopted, comprising the following steps: 1) sample treatment, weighing 0.05-0.1 g of the sample to be tested, putting it in a beaker, washing the beaker wall with 20-40 ml of distilled water, adding 10 ml of concentrated nitric acid under an open ventilation device, boiling it on a heating device for 3-5 minutes, slowly adding 35 ml of quinoline molybdate reagent, continuing to keep boiling for 3 minutes, and removing the beaker containing the treated sample; 2) precipitation filtration, placing absorbent cotton in a funnel for filtration, transferring the treated sample in the beaker to the funnel, washing the treated sample in the funnel The sample is washed until the pH of the droplets filtered out from the lower tube outlet of the funnel is neutral, and the washing is completed. The absorbent cotton in the funnel and the washed precipitate are transferred back to the beaker for titration; 3) Precipitation titration, the beaker is titrated with a sodium hydroxide standard solution until it turns yellow to colorless, and V1 is recorded. V1 is the volume of the sodium hydroxide standard solution consumed, and then 7 to 10 drops of thymol blue-phenolphthalein indicator are added to color it, and then titrated with a hydrochloric acid standard solution. The titration is from purple to colorless as the end point, and V2 is recorded. V2 is the volume of the hydrochloric acid standard solution consumed; 4) Analysis results, the effective phosphorus pentoxide content is expressed as mass percentage, calculated according to the following formula,

[0031]

[0032] Where:

[0033] C NaOH is the concentration of sodium hydroxide standard solution mol / L;

[0034] C HCl is the concentration of hydrochloric acid standard solution mol / L;

[0035] V1 is the volume of sodium hydroxide standard solution consumed, in milliliters;

[0036] V2 is the volume of the hydrochloric acid standard solution sample consumed, in milliliters;

[0037] m is the mass of the sample weighed, in grams.

[0038] Advantages of the present invention:

[0039] The method of the present invention can obtain test data in half an hour and still ensure the accuracy of the test results, thereby accelerating the production decision-making process for the nutrient control process of compound fertilizer production and ensuring the quality of compound fertilizer.

[0040] The present invention can be used as a reliable analytical method for detecting phosphorus content in the production process of compound fertilizers, which speeds up the determination of phosphorus content in the production process of compound fertilizers, thereby helping producers to make production decisions faster, optimize production plans and improve fertilizer quality. At the same time, the simplified determination method also helps to reduce production costs and improve production efficiency. DETAILED DESCRIPTION

[0041] In order to make the technical means, creative features, objectives and effects achieved by the present invention easy to understand, the present invention is further described below in conjunction with specific embodiments.

[0042] The following examples are only used to further illustrate the present invention in detail, but do not constitute any limitation to the present invention; the materials used in the following examples, unless otherwise specified, were purchased from conventional chemical reagent companies and raw material suppliers.

[0043] Embodiment 1:

[0044] A method for quickly determining the content of effective phosphorus pentoxide in a compound fertilizer comprises the following steps:

[0045] 1) Sample treatment: weigh 0.05 g of the sample to be tested and put it in a beaker. Rinse the beaker wall with 20 ml of distilled water. Add 10 ml of concentrated nitric acid under the ventilation device. Boil it on the heating device for 3 min. Slowly add 35 ml of quinoline molybdate reagent. Keep boiling for 3 min. Remove the beaker containing the treated sample.

[0046] 2) Precipitation and filtration: Place absorbent cotton in a funnel for filtration, transfer the treated sample in the beaker to the funnel, wash the treated sample in the funnel, and wash until the pH of the droplets filtered out of the lower tube outlet of the funnel is neutral. After washing, transfer the absorbent cotton in the funnel and the washed precipitate back to the beaker for titration;

[0047] 3) precipitation titration, titrating the beaker with a sodium hydroxide standard solution until the color turns yellow to colorless, recording V1, where V1 is the volume of the sodium hydroxide standard solution consumed, then adding 7 drops of thymol blue-phenolphthalein indicator for coloring, and then titrating with a hydrochloric acid standard solution until the color turns from purple to colorless, recording V2, where V2 is the volume of the hydrochloric acid standard solution consumed;

[0048] 4) Analysis results: The effective phosphorus pentoxide content is expressed as mass percentage and is calculated according to the following formula:

[0049]

[0050] Where:

[0051] C NaOH is the concentration of sodium hydroxide standard solution mol / L;

[0052] C HCl is the concentration of hydrochloric acid standard solution mol / L;

[0053] V1 is the volume of sodium hydroxide standard solution consumed, in milliliters;

[0054] V2 is the volume of the hydrochloric acid standard solution sample consumed, in milliliters;

[0055] m is the mass of the sample weighed, in grams.

[0056] 0.00273 and 1.00ml sodium hydroxide standard solution (C NaOH =1.0000 mol / L) is equivalent to the mass of phosphorus pentoxide expressed in grams.

[0057] In the step 4), the sodium hydroxide standard solution is C NaOH =0.3mol / L; hydrochloric acid standard solution is C HCl =0.1 mol / L; thymol blue-phenolphthalein indicator is a mixture of 3 volumes of thymol blue solution (1 g / L) and 2 volumes of phenolphthalein (1 g / L).

[0058] The method for preparing the quinoline molybdate reagent comprises the following steps:

[0059] Solution a: weigh 70g sodium molybdate (Na2MoO4·2H2O) and dissolve it in 100ml water;

[0060] Solution b: Weigh 60g of citric acid (C6H8O7·H2O) into a 1L beaker, add 100mL of water to dissolve, and then add 85ml of nitric acid;

[0061] Solution c: Add solution a to solution b and mix well;

[0062] Solution d: Add 100 ml of water and 35 ml of nitric acid into a 500 ml beaker, and add 5 ml of quinoline, and mix well;

[0063] Add solution d to solution c, mix well, let stand overnight, filter with absorbent cotton, add 280 ml of acetone to the filtrate, and dilute with water to 1 L. Stir and mix well, store the solution in a polyethylene bottle in a dark place, away from light and heat. If the solution of the quinoline molybdate reagent turns light blue, add potassium bromate solution (10 g / L) until the color disappears.

[0064] In the step 1), the sample is passed through a 1.0 mm test sieve and weighed.

[0065] In the above 2), broken filter paper soaked in pure water is laid on the absorbent cotton in the funnel.

[0066] The processing sample in the funnel is washed with water in 2), and the amount of water used for each washing is ≤30 ml.

[0067] Embodiment 2:

[0068] A method for quickly determining the content of effective phosphorus pentoxide in a compound fertilizer comprises the following steps:

[0069] 1) Sample treatment: weigh 0.08 g of the sample to be tested and put it in a beaker. Rinse the beaker wall with 40 ml of distilled water. Add 10 ml of concentrated nitric acid under the ventilation device. Boil it on the heating device for 5 min. Slowly add 35 ml of quinoline molybdate reagent. Keep boiling for 3 min. Remove the beaker containing the treated sample.

[0070] 2) Precipitation and filtration: Place absorbent cotton in a funnel for filtration, transfer the treated sample in the beaker to the funnel, wash the treated sample in the funnel, and wash until the pH of the droplets filtered out of the lower tube outlet of the funnel is neutral. After washing, transfer the absorbent cotton in the funnel and the washed precipitate back to the beaker for titration;

[0071] 3) precipitation titration, titrating the beaker with a sodium hydroxide standard solution until the color turns yellow to colorless, recording V1, where V1 is the volume of the sodium hydroxide standard solution consumed, then adding 10 drops of thymol blue-phenolphthalein indicator for coloring, and then titrating with a hydrochloric acid standard solution until the color turns from purple to colorless, recording V2, where V2 is the volume of the hydrochloric acid standard solution consumed;

[0072] 4) Analysis results: The effective phosphorus pentoxide content is expressed as mass percentage and is calculated according to the following formula:

[0073]

[0074] Where:

[0075] C NaOH is the concentration of sodium hydroxide standard solution mol / L;

[0076] C HCl is the concentration of hydrochloric acid standard solution mol / L;

[0077] V1 is the volume of sodium hydroxide standard solution consumed, in milliliters;

[0078] V2 is the volume of the hydrochloric acid standard solution sample consumed, in milliliters;

[0079] m is the mass of the sample weighed, in grams.

[0080] 0.00273 and 1.00ml sodium hydroxide standard solution (C NaOH =1.0000 mol / L) is equivalent to the mass of phosphorus pentoxide expressed in grams.

[0081] In the step 4), the sodium hydroxide standard solution is C NaOH =0.3mol / L; hydrochloric acid standard solution is C HCl =0.1 mol / L; thymol blue-phenolphthalein indicator is a mixture of 3 volumes of thymol blue solution (1 g / L) and 2 volumes of phenolphthalein (1 g / L).

[0082] The method for preparing the quinoline molybdate reagent comprises the following steps:

[0083] Solution a: weigh 70g sodium molybdate (Na2MoO4·2H2O) and dissolve it in 100ml water;

[0084] Solution b: Weigh 60g of citric acid (C6H8O7·H2O) into a 1L beaker, add 100mL of water to dissolve, and then add 85ml of nitric acid;

[0085] Solution c: Add solution a to solution b and mix well;

[0086] Solution d: Add 100 ml of water and 35 ml of nitric acid into a 500 ml beaker, and add 5 ml of quinoline, and mix well;

[0087] Add solution d to solution c, mix well, let stand overnight, filter with absorbent cotton, add 280 ml of acetone to the filtrate, and dilute with water to 1 L. Stir and mix well, store the solution in a polyethylene bottle in a dark place, away from light and heat. If the solution of the quinoline molybdate reagent turns light blue, add potassium bromate solution (10 g / L) until the color disappears.

[0088] In the step 1), the sample is passed through a 1.0 mm test sieve and weighed.

[0089] In the above 2), broken filter paper soaked in pure water is laid on the absorbent cotton in the funnel.

[0090] The processing sample in the funnel is washed with water in 2), and the amount of water used for each washing is ≤30 ml.

[0091] Embodiment 3:

[0092] A method for quickly determining the content of effective phosphorus pentoxide in a compound fertilizer comprises the following steps:

[0093] 1) Sample treatment: weigh 0.1 g of the sample to be tested and put it in a beaker. Rinse the beaker wall with 30 ml of distilled water. Add 10 ml of concentrated nitric acid under the ventilation device. Boil it on the heating device for 3 to 5 minutes. Slowly add 35 ml of quinoline molybdate reagent and continue to keep boiling for 3 minutes. Remove the beaker containing the treated sample;

[0094] 2) Precipitation and filtration: Place absorbent cotton in a funnel for filtration, transfer the treated sample in the beaker to the funnel, wash the treated sample in the funnel, and wash until the pH of the droplets filtered out of the lower tube outlet of the funnel is neutral. After washing, transfer the absorbent cotton in the funnel and the washed precipitate back to the beaker for titration;

[0095] 3) precipitation titration, titrating the beaker with a sodium hydroxide standard solution until yellow to colorless, recording V1, wherein V1 is the volume of the sodium hydroxide standard solution consumed, then adding color with thymol blue-phenolphthalein indicator, and then titrating with a hydrochloric acid standard solution until the titration changes from purple to colorless as the end point, recording V2, wherein V2 is the volume of the hydrochloric acid standard solution consumed;

[0096] 4) Analysis results: The effective phosphorus pentoxide content is expressed as mass percentage and is calculated according to the following formula:

[0097]

[0098] Where:

[0099] C NaOH is the concentration of sodium hydroxide standard solution mol / L;

[0100] C HCl is the concentration of hydrochloric acid standard solution mol / L;

[0101] V1 is the volume of sodium hydroxide standard solution consumed, in milliliters;

[0102] V2 is the volume of the hydrochloric acid standard solution sample consumed, in milliliters;

[0103] m is the mass of the sample weighed, in grams.

[0104] 0.00273 and 1.00ml sodium hydroxide standard solution (C NaOH =1.0000 mol / L) is equivalent to the mass of phosphorus pentoxide expressed in grams.

[0105] In the step 4), the sodium hydroxide standard solution is C NaOH =0.3mol / L; hydrochloric acid standard solution is C HCl =0.1 mol / L; thymol blue-phenolphthalein indicator is a mixture of 3 volumes of thymol blue solution (1 g / L) and 2 volumes of phenolphthalein (1 g / L).

[0106] The method for preparing the quinoline molybdate reagent comprises the following steps:

[0107] Solution a: weigh 70g sodium molybdate (Na2MoO4·2H2O) and dissolve it in 100ml water;

[0108] Solution b: Weigh 60g of citric acid (C6H8O7·H2O) into a 1L beaker, add 100mL of water to dissolve, and then add 85ml of nitric acid;

[0109] Solution c: Add solution a to solution b and mix well;

[0110] Solution d: Add 100 ml of water and 35 ml of nitric acid into a 500 ml beaker, and add 5 ml of quinoline, and mix well;

[0111] Add solution d to solution c, mix well, let stand overnight, filter with absorbent cotton, add 280 ml of acetone to the filtrate, and dilute with water to 1 L. Stir and mix well, store the solution in a polyethylene bottle in a dark place, away from light and heat. If the solution of the quinoline molybdate reagent turns light blue, add potassium bromate solution (10 g / L) until the color disappears.

[0112] In the step 1), the sample is passed through a 1.0 mm test sieve and weighed.

[0113] In the above 2), broken filter paper soaked in pure water is laid on the absorbent cotton in the funnel.

[0114] The processing sample in the funnel is washed with water in 2), and the amount of water used for each washing is ≤30 ml.

[0115] experiment,

[0116] The method of the present invention is compared with the quinoline phosphomolybdic acid weight method for determining the effective phosphorus content in compound fertilizers in the prior art, and ten kinds of compound fertilizers are taken to determine the effective phosphorus pentoxide using the prior art and the method of the present invention respectively.

[0117] Quinoline phosphomolybdic acid weight method:

[0118] This is a method for determining phosphorus content by forming a precipitate and weighing it. Phosphorus reacts with quinoline molybdate to form an insoluble quinoline phosphomolybdate precipitate, which is then filtered, washed, dried and weighed to determine the phosphorus content.

[0119] The method of the present invention:

[0120] This is a method for determining phosphorus content by titration. Phosphorus reacts with quinoline molybdate to form a soluble complex, which is then titrated to determine the amount of quinoline molybdate consumed in the reaction, thereby inferring the phosphorus content. Reagents:

[0121] Nitric acid (analytical grade)

[0122] Cotton wool

[0123] PH test paper (measurement range pH 1~14)

[0124] Sodium hydroxide standard titration solution: C(NaOH)=0.3mol / L

[0125] Hydrochloric acid standard titration solution: C(HCl)=0.1mol / L

[0126] Thymol blue-phenolphthalein: Take 3 volumes of thymol blue solution (1 g / L) and 2 volumes of phenolphthalein (1 g / L) and mix well.

[0127] Quinmolybdate reagent:

[0128] Solution a: Weigh 70 g of sodium molybdate (Na2MoO4·2H2O) and dissolve it in 100 ml of water.

[0129] Solution b: Weigh 60 g of citric acid (C6H8O7·H2O) and place it in a 1 L beaker, add 100 mL of water to dissolve it, and then add 85 mL of nitric acid.

[0130] Solution c: Add solution a to solution b and mix well.

[0131] Solution d: Add 100 ml of water and 35 ml of nitric acid to a 500 ml beaker, and add 5 ml of quinoline, and mix well. Add solution d to solution c, mix well, let stand overnight, filter with absorbent cotton, add 280 ml of acetone to the filtrate, and dilute with water to 1 L. Stir and mix well, and store the solution in a polyethylene bottle in a dark place, away from light and heat. Note: If the solution of quinoline molybdenum citric acid reagent turns light blue, add potassium bromate solution (10 g / L) until the color disappears.

[0132] instrument:

[0133] Usually required laboratory equipment.

[0134] Heating device: The heating device can be a 1000-watt adjustable temperature electric furnace, or other types of adjustable temperature electric furnaces or adjustable temperature electric heating plates.

[0135] Analysis steps:

[0136] Sample preparation

[0137] The laboratory samples were prepared according to GB / T 8571 standard and passed through a 1.0 mm test sieve.

[0138] Sample processing of effective phosphorus pentoxide:

[0139] According to the different proportions of compound fertilizer in the sample, weigh 0.05g to 0.1g (accurate to 0.02000) of the sample into a 300ml beaker 1. Add about 30ml of distilled water to rinse the wall of beaker 1, place it under ventilation equipment, add 10ml of concentrated nitric acid (be careful with this step, concentrated nitric acid and the sample will react violently), put it on a heating device and boil for 3-5 minutes, slowly add 35ml of quinolyphosphine reagent, reduce the heat and continue boiling (keep it in a slightly boiling state for 3 minutes), and remove beaker 1.

[0140] Quinoline phosphomolybdic acid precipitation filtration:

[0141] Use a little absorbent cotton to filter in a funnel (lay broken filter paper soaked in pure water on the absorbent cotton), transfer the filtrate and quinoline phosphomolybdate precipitate in beaker 1 to the funnel, wash the quinoline phosphomolybdate precipitate in the funnel (use no more than 30 ml of water each time), check the droplets at the outlet of the lower tube of the funnel with pH test paper, and end the washing when the droplets are neutral, transfer the precipitate and absorbent cotton to beaker 1 for titration.

[0142] Titration of Quinoline Phosphomolybdic Acid Precipitate

[0143] At this time, the solution is yellow, and sodium hydroxide standard solution C (NaOH) = 0.3 mol / L is titrated until yellow to colorless, and V1 is the volume of sodium hydroxide solution consumed. Then add 7 to 10 drops of thymol blue-phenolphthalein indicator, and then titrate with hydrochloric acid standard solution C (HCl) = 0.1 mol / L, and the end point is when the purple disappears to colorless, and V2 is the volume of hydrochloric acid standard solution consumed.

[0144] Result description:

[0145] Calculation of analysis results

[0146] The effective phosphorus pentoxide content (P2O5) is expressed as mass percentage (%) and is calculated according to formula 1:

[0147]

[0148] Where:

[0149] C(NaOH)—Concentration of sodium hydroxide standard solution (mol / L)

[0150] C(HCl)—Concentration of hydrochloric acid standard solution (mol / L)

[0151] V1—Volume of sodium hydroxide standard solution consumed (ml)

[0152] V2—Volume of the hydrochloric acid standard solution sample consumed (ml)

[0153] m—is the mass of the sample (g)

[0154] 0.00273 is equivalent to the mass of phosphorus pentoxide expressed in grams, which is equivalent to 1.00 ml of sodium hydroxide standard solution [C(NaOH)=1.0000 mol / L]. (0.00273 is completely reacted with 1.00 ml of 1.0000 mol / L sodium hydroxide standard solution The mass of phosphorus pentoxide. That is, from the stoichiometric relationship of the chemical reaction, phosphorus pentoxide and a given volume and concentration of hydroxide The sodium solution reacts completely. It also means that the volume and concentration of the consumed sodium hydroxide solution can be used to calculate the The mass of phosphorus pentoxide reacted. Therefore, the conversion factor of 0.00273 is introduced into the calculation formula to calculate the mass of phosphorus pentoxide reacted. The number of moles of sodium hydroxide used in the phosphorus dissolving reaction.

[0155] Conclusion of analysis results:

[0156] The comparison of the analysis results of Appendix A of GB / T 15063-2020 for the determination of effective phosphorus pentoxide and this method is shown in Table 1.

[0157] Table 1 Analysis results of effective phosphorus pentoxide %

[0158]

[0159] In the above Table 1, after ten measurements, the error of the quinoline phosphomolybdic acid weight method and the method of the present invention is ±0.4%. It can be seen that the measurement results of the method of the present invention can be used as a reliable analysis method for detecting phosphorus content in the production process of compound fertilizers. The method of the present invention can speed up the determination of phosphorus content in the production process of compound fertilizers, thereby helping producers to make production decisions faster, optimize production plans and improve the quality of fertilizers. At the same time, the simplified measurement method also helps to reduce production costs and improve production efficiency.

[0160] The above shows and describes the basic principles, main features and advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A method for rapidly determining the content of effective phosphorus pentoxide in compound fertilizer, characterized in that: The following steps are involved: 1) Sample treatment: weigh 0.05-0.1 g of the sample to be tested and put it in a beaker. Rinse the beaker wall with 20-40 ml of distilled water. Add 10 ml of concentrated nitric acid under the ventilation device. Boil it on the heating device for 3-5 minutes. Slowly add 35 ml of quinoline molybdate reagent and continue to keep boiling for 3 minutes. Remove the beaker containing the treated sample; 2) Precipitation and filtration: Place absorbent cotton in a funnel for filtration, transfer the treated sample in the beaker to the funnel, wash the treated sample in the funnel, and wash until the pH of the droplets filtered out of the lower tube outlet of the funnel is neutral. After washing, transfer the absorbent cotton in the funnel and the washed precipitate back to the beaker for titration; 3) precipitation titration, titrating the beaker with a sodium hydroxide standard solution until the color turns yellow to colorless, recording V1, where V1 is the volume of the sodium hydroxide standard solution consumed, then adding 7 to 10 drops of thymol blue-phenolphthalein indicator for coloring, and then titrating with a hydrochloric acid standard solution until the color turns from purple to colorless, recording V2, where V2 is the volume of the hydrochloric acid standard solution consumed; 4) Analysis results: The effective phosphorus pentoxide content is expressed as mass percentage and is calculated according to the following formula: Where: C NaOH is the concentration of sodium hydroxide standard solution mol / L; C HCl is the concentration of hydrochloric acid standard solution mol / L; V1 is the volume of sodium hydroxide standard solution consumed, in milliliters; V2 is the volume of the hydrochloric acid standard solution sample consumed, in milliliters; m is the mass of the sample weighed, in grams.

2. A method for rapidly determining the content of effective phosphorus pentoxide in a compound fertilizer as claimed in claim 1, characterized in that: In the step 4), the sodium hydroxide standard solution is C NaOH =0.3mol / L; hydrochloric acid standard solution is C HCl =0.1 mol / L; thymol blue-phenolphthalein indicator is a mixture of 3 volumes of thymol blue solution and 2 volumes of phenolphthalein.

3. A method for rapidly determining the effective phosphorus pentoxide content in a compound fertilizer as claimed in claim 1, characterized in that: In the step 1), the quinoline molybdate reagent comprises sodium molybdate, water, citric acid, nitric acid, quinoline and acetone.

4. A method for rapidly determining the effective phosphorus pentoxide content in a compound fertilizer as claimed in claim 1, characterized in that: In step 1), the sample is passed through a 1.0 mm test sieve and weighed; 30 ml of distilled water is used to rinse the beaker wall.

5. A method for rapidly determining the content of effective phosphorus pentoxide in a compound fertilizer as claimed in claim 1, characterized in that: In the above 2), broken filter paper soaked in pure water is laid on the absorbent cotton in the funnel.

6. A method for rapidly determining the content of effective phosphorus pentoxide in a compound fertilizer as claimed in claim 1, characterized in that: The processing sample in the funnel is washed with water in 2), and the amount of water used for each washing is ≤30 ml.

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