A detection method for the chlorine content of a snow melting agent

Abstract

The invention discloses a method for detecting the chlorine content of a snow melting agent, belonging to the technical field of analytical chemistry. It is applicable to the detection of the chloride content in a snow melting agent mainly produced from sodium formate, and includes the following steps: Weigh a certain amount of the raw material sodium formate snow melting agent sample, place it in a muffle furnace for calcination treatment at a temperature above 500 °C. Utilizing the thermal decomposition characteristics of sodium formate, sodium formate is thermally decomposed into sodium carbonate and a small amount of carbon. Filter off the carbon generated during calcination with filter paper. Then, after adjusting the pH value to a certain acidic range (3.0 - 3.5) with nitric acid according to the mercury method, the sodium carbonate generated by the thermal decomposition of sodium formate volatilizes into carbon dioxide under acidic conditions, while chlorine exists in the form of chloride ions in the sample after calcination. Then, the chlorine content is titrated by the mercury nitrate method using diphenylcarbazone as an indicator, so as to quickly and accurately determine the chloride ion content in the test. This method is a rapid chloride ion content analysis method and is applicable to sodium formate snow melting agent products.

Description

Technical Field

[0001] The present invention relates to the technical field of analytical chemistry, and particularly relates to a method for detecting the chlorine content of a snow melting agent. Background Art

[0002] According to the national standard GB / T23851-2017 "Snow Melting Agent", snow melting agents are divided into non-chloride types and chloride types. For non-chloride snow melting agents, according to the requirements of the national standard GB / T23851-2017 "Snow Melting Agent", the chloride content ≤ 1.0%, and according to the American standards AMS1431E "Runway Deicing and Anti-Icing Solid Deicing Agent" and AMS1435C "Runway Deicing and Anti-Icing Liquid Deicing Agent", the chlorine content is required to be less than 250 ppm. Therefore, in order to prevent the chlorine content in the snow melting agent from exceeding the standard, the detection of chloride ions is a very important indicator.

[0003] The national standard GB / T23851-2017 "Snow Melting Agent" stipulates that the detection of chloride ions is carried out according to GB / T11896 "Determination of Chloride in Water - Silver Nitrate Titration Method", which is a direct silver nitrate titration method. This method is a volumetric method, and the equipment used is simple to operate and widely used. However, we found that there are many limitations in the actual operation process, specifically manifested as follows: The silver nitrate titration method is a precipitation titration method. Silver nitrate reacts with chloride ions to form silver chloride precipitate. When the titration end point is reached, silver nitrate reacts with the indicator potassium chromate to form a brick-red silver chromate precipitate to indicate the end point. Due to the interference of silver chloride precipitate, the end point color change is not sharp, with a large degree of empiricism, and the measurement result is inaccurate.

[0004] Similarly, according to the formate chemical industry standard HG / T5390-2018 "Formate", the detection of chloride ions in formate is also carried out according to the above silver nitrate titration method. We used the silver nitrate titration method to determine the chloride ions in formate and formate snow melting agent, and found the following problems: ① The judgment of the titration end point is fuzzy, and the error of parallel measurement results is large; ② There are many interference factors, and the measurement results are generally much higher. Since the main raw material formate for producing formate snow melting agent contains many impurity components (synthetic formate contains sodium carbonate, and by-product formate contains organic impurities such as formaldehyde), in addition, additives for preventing metal corrosion (such as orthophosphate / metaphosphate / polyphosphate, etc.) need to be added during the production of formate snow melting agent. The silver nitrate titration method requires titration under neutral to weakly alkaline (pH 6.5 - 10.5) conditions. Under these conditions, these impurity components can react with silver ions. For example, formaldehyde reacts with silver ions to form a silver mirror reaction, and phosphate and sodium carbonate react with silver ions to form a precipitate reaction, resulting in a higher result.

[0005] For the conventional method of detecting chloride ions by volumetric method, in addition to the silver nitrate titration method, there is also the mercury nitrate titration method. Compared with the silver nitrate titration method, which has the problems of insensitive endpoint color change, large empirical nature and errors, the mercury nitrate titration method has the characteristics of very sensitive color change, easy judgment and high accuracy. Therefore, we considered using the mercury nitrate titration method to test the chlorine content in the sodium formate snow melting agent. Referring to GB / T3051-2000 "General method for the determination of chloride content in inorganic chemical products - mercury method", the sodium formate snow melting agent sample is not treated, and the solution is adjusted to slightly acidic (pH = 3.0 - 3.5) with sodium hydroxide solution and nitric acid solution, and directly titrated with a mercury nitrate standard solution. The color change at the endpoint is not obvious, very difficult to judge, and the accuracy cannot be guaranteed. The inventor speculated that the reason is: when the sample sodium formate is adjusted to slightly acidic (the pH value needs to be adjusted to acidic during detection), a very strong buffer of formic acid - sodium formate buffer is formed, which affects the endpoint color change. Therefore, a method must be found to eliminate this interference. Summary of the Invention

[0006] The present invention discloses a method for detecting the chlorine content in a snow melting agent, which improves the existing mercury nitrate titration method. The interference of formic acid - sodium formate can be eliminated through a simple method, ensuring the detection accuracy. The detection result is close to that of the ion chromatography method and is better than the conventional silver nitrate titration method and mercury nitrate titration method.

[0007] The method includes the following steps:

[0008] (1) Burn the sodium formate snow melting agent sample at 500 - 800 °C for 30 - 60 minutes.

[0009] (2) According to visual inspection; if the sample after burning is white, rinse the sample with deionized water to obtain a test solution; if the sample after burning is gray - black, rinse the sample with deionized water and filter it, with the number of times being greater than or equal to three (preferably 3 - 5 times), and stop until the filtrate is free of alkalinity or chloride ions, and combine the filtrates to obtain a test solution; the volume of the test solution is 100 - 200 mL. (3) Use the mercury nitrate titration method to detect the chloride ion content of the test solution.

[0010] In step (1), the inventor found through experiments that the sodium formate has the following thermal decomposition behavior:

[0011] At 25 - 330 °C, it melts.

[0012] At 330 - 400 °C, there are 2 reactions:

[0013] 2HCOONa = NaC2O2 + H2;

[0014] 2HCOONa = Na2CO3 + H2 + CO.

[0015] At 330 - 400 °C, there are three reactions:

[0016] 2HCOONa = NaC2O2 + H2;

[0017] 2HCOONa = Na2CO3 + H2 + CO;

[0018] NaC2O2 = Na2CO3 + CO.

[0019] At 420 - 500 °C, sodium formate is completely consumed and a small amount of sodium oxalate decomposes:

[0020] NaC2O2 = Na2CO3 + CO.

[0021] At 500 - 580 °C, sodium oxalate decomposes rapidly:

[0022] NaC2O2 = Na2CO3 + CO.

[0023] 7NaC2O2 = 7Na2CO3 + CO + 3CO2 + 3C.

[0024] At 580 - 600 °C, sodium oxalate completely decomposes into sodium carbonate.

[0025] In the actual operation process, carbon may appear between 500 - 800 °C, possibly due to insufficient time, uneven heating, etc. However, at this temperature and after a certain time, there is no sodium formate. During the thermal decomposition of sodium formate, the decomposition product sodium carbonate is alkaline, and the chloride ions in the sample always exist as sodium chloride and will not be lost or consumed. When the thermal decomposition temperature reaches above 500 °C, the reaction only takes 30 - 60 minutes to complete.

[0026] In step (2), it is a conventional process. In this embodiment, if filtration is required, a chloride ion test paper or a pH test paper can be used to determine whether all the chloride ions in the sample are washed off; preferably, the inventor found that chloride ions are more easily washed off than carbonate ions. If the washing solution is not alkaline, it can be defaulted that all the chloride ions are washed off, which is more convenient for judgment.

[0027] In step (3), the process is similar to the mercuric nitrate titration method. In the mercuric nitrate titration method, the pH value of the test solution needs to be adjusted to 3.0 - 3.5. Under this condition, carbonate ions can be removed to make the result more accurate. Through experimental tests and research, it is found that for the sodium formate snow melting agent sample, without sample treatment, directly determined according to GB / T 3051-2000 General Method for the Determination of Chloride Content in Inorganic Chemical Products - Mercurimetric Method, the indicator color change is not sensitive, the analysis is inaccurate, and basically the test cannot be completed. However, as long as it is treated by the thermal decomposition step and then the chlorine content is determined according to GB / T 3051-2000 General Method for the Determination of Chloride Content in Inorganic Chemical Products - Mercurimetric Method, the indicator color change is very sensitive and the test is fast and accurate.

[0028] Among them, in step (1), weigh a solid or liquid sodium formate snow melting agent sample and place it in a crucible of 30 - 100 mL; based on the solid snow melting agent, the weight of the sample is greater than or equal to 0.5 g, and the weighing accuracy is 0.0001 g; put the crucible into a muffle furnace, start timing after heating to 500 - 800 °C, and burn for 30 - 60 minutes. After burning is completed, take out the crucible. Among them, the crucible is selected from a silver crucible, a nickel crucible, a high-temperature porcelain crucible, etc.; preferably, the crucible is a volatile porcelain crucible. Preferably, if it is expected that the chloride ion content of the sample is low (such as less than or equal to 100 ppm), the sample weight is preferably greater than or equal to 3 g.

[0029] Preferably, the burning temperature is 500 - 600 °C; more preferably, the burning temperature is 580 °C. When the temperature is low, the carbon content is high; when the temperature is high, the energy consumption is high and the operation difficulty is great.

[0030] Specifically, in step (2), if the sample after burning is grayish-black, each time rinse the sample in the crucible with 20 - 30 mL of deionized water and pour it into a glass funnel with filter paper for filtration, stop until the filtrate is non-alkaline or free of chloride ions, combine the filtrates and transfer them to a 250 mL Erlenmeyer flask; if the sample after burning is white, rinse the sample in the crucible with deionized water and then transfer it to a 250 mL Erlenmeyer flask.

[0031] Among them, in step (2), the filter paper is a qualitative filter paper with a diameter of φ12 - 15 cm; preferably, the filter paper is a qualitative filter paper with a diameter of φ12 cm.

[0032] Among them, in step (3), the detection method can refer to the description in GB / T 3051-2000 General Method for the Determination of Chloride Content in Inorganic Chemical Products - Mercurimetric Method, including the following steps:

[0033] S301: Adjust the pH value of the test solution to 3.0 - 3.5.

[0034] S302: Add about 1 mL of diphenylcarbazone indicator solution to the test solution, and titrate with the mercury nitrate standard solution until the color changes from yellow to purplish red as the end point. The concentration of the mercury nitrate standard solution is 0.01 - 0.1 mol / L; meanwhile, conduct a blank experiment.

[0035] S303: Calculate the concentration of chloride ions according to the following formula: CL - % =(V - V0)*C*0.03545*100 / M;

[0036] In the formula: V is the volume of the mercury nitrate standard solution consumed in the titration of the sample, in mL;

[0037] V0 is the volume of the mercury nitrate standard solution consumed in the blank experiment, in mL;

[0038] C is the concentration of the mercury nitrate standard solution, in mol / L;

[0039] 0.03545 is the millimolar mass of chlorine, in g / mmol;

[0040] M is the mass of the sample, in g.

[0041] Among them, this embodiment is optimized on the basis of GB / T3051 - 2000 "General method for the determination of chloride content in inorganic chemical products - Mercurimetric method", making the detection more accurate and convenient. Then step S301 includes: Add 2 - 3 drops of bromophenol blue indicator to the test solution. The solution is blue. First, add a high - concentration nitric acid solution until it turns yellow, then add sodium hydroxide solution until it turns blue, and then add a low - concentration nitric acid solution until it turns yellow and then add 2 - 3 more drops in excess.

[0042] Specifically, in step (3), the bromophenol blue is a 0.1% ethanol solution; the high - concentration nitric acid solution is a 1:1 (specifically, volume ratio, the same hereinafter) solution; the low - concentration nitric acid solution is a 1:7 solution; the diphenylcarbazone indicator solution is a 0.5% ethanol solution; the concentration of the sodium hydroxide solution is 1.0 mol / L; the concentration of the mercury nitrate standard solution is 0.05 mol / L, 0.025 mol / L or 0.01 mol / L, and the concentration of the mercury nitrate standard solution can be adjusted according to the expected chlorine content; if the expected chlorine content is high, then use a 0.05 mol / L mercury nitrate standard solution; if the expected chlorine content is low, then use a 0.025 mol / L mercury nitrate standard solution.

[0043] Specifically, the method for detecting the chlorine content of the deicing salt provided by the present invention includes the following steps:

[0044] (1) Weigh a solid or liquid sodium formate deicing agent sample and place it in a 30 - 100 mL volatile porcelain crucible. Based on the solid deicing agent, the weight of the sample is greater than or equal to 0.5 g, and the weighing accuracy is 0.0001 g. Place the volatile porcelain crucible in a muffle furnace, heat it to 500 - 600 °C and then start timing. Burn for 30 - 60 minutes, and after burning is completed, take out the volatile porcelain crucible.

[0045] (2) According to visual inspection; if the sample after burning is gray - black, each time rinse the sample in the crucible with 20 - 30 mL of deionized water and pour it into a glass funnel with a φ12 - 15 cm qualitative filter paper for filtration. Stop when the filtrate is no longer alkaline. Combine the filtrates and transfer them to a 250 mL Erlenmeyer flask. If the sample after burning is white, rinse the sample in the crucible with deionized water and then transfer it to a 250 mL Erlenmeyer flask. The volume of the test solution in the Erlenmeyer flask is 100 - 200 mL.

[0046] (3) Add 2 - 3 drops of bromophenol blue indicator to the test solution. The solution is blue. First, add a high - concentration nitric acid solution until it turns yellow, then add a sodium hydroxide solution until it turns blue, and then add a low - concentration nitric acid solution until it turns yellow and then add 2 - 3 more drops in excess. Add 1 mL of diphenylcarbazone indicator solution to the test solution and titrate with a mercury nitrate standard solution until the color changes from yellow to purple - red as the end point. The concentration of the mercury nitrate standard solution is 0.01 - 0.1 mol / L. At the same time, conduct a blank experiment. Calculate the chloride ion concentration according to the following formula: CL - %=(V - V0)*C*0.03545*100 / M.

[0047] The present invention provides a method for detecting the chlorine content of a deicing agent. This method utilizes the thermal decomposition characteristics of sodium formate. Through burning and filtration measures, and then using the mercury method to determine the chloride content in the sodium formate deicing agent. The indicator has a sharp color change, is not interfered by common impurity ions such as sulfate, phosphate, carbonate, and other organic substances such as formaldehyde. It has good reproducibility, and its sensitivity and accuracy are better than the detection methods for the chlorine content in sodium formate deicing agents provided by the national standard GB / T 23851 - 2017 "Deicing Agent" and the industry standard HG / T 5390 - 2018 "Sodium Formate". In addition, the operation of the present invention is simple and practical. The present invention only requires a muffle furnace heating device and several porcelain crucibles, and then it can be detected according to the conventional volumetric method, which is fast and accurate, and can complete the testing of more than 40 samples per hour. Specific embodiments

[0048] The protection scope of the present invention is not limited to the following embodiments. Those skilled in the art can adjust one or several steps, and all changes made without departing from the essence of the present invention are within the protection scope of this application.

[0049] Example 1:

[0050] Example 1 discloses a method for detecting the chlorine content of a deicing agent, comprising the following steps:

[0051] 1.1 Accurately weigh 2.5361 g of solid sodium formate de-icing agent sample into a 30 mL volatile content porcelain crucible.

[0052] 1.2 Place the above sample porcelain crucible into the muffle furnace, turn on the muffle furnace and start heating it to 500℃ for burning. Start timing when the temperature reaches the set 500℃. The burning time at this temperature is 60 minutes, and then carefully take out the crucible.

[0053] 1.3 After the crucible has cooled to room temperature, rinse the sample in the crucible with 20-30 mL of deionized water each time and pour it into a glass funnel with φ12 cm qualitative filter paper for filtration. Each time the rinsing water is filtered dry, the next rinsing water can be filtered only after the previous rinsing water has been filtered. After filtering four times, the alkalinity of the filtrate is detected to disappear. The total volume of the filtrate collected in the conical beaker is about 200 mL.

[0054] 1.4 Prepare analytical reagents in accordance with GB / T603-2002 "Preparation of preparations and products used in chemical reagent test methods":

[0055] 1.4.1 Nitric acid: 1:1 solution;

[0056] 1.4.2 Nitric acid: 1:7 solution;

[0057] 1.4.3 Bromophenol blue: 0.1% ethanol solution;

[0058] 1.4.4 Diphenylazocarbohydrazide indicator solution: 0.5% ethanol solution, re-prepare if color change is not sensitive;

[0059] 1.4.5 Sodium hydroxide solution: C(NaOH) = 1.0 mol / L;

[0060] 1.4.6 Mercuric nitrate standard solution: C(Hg(NO3)2) = 0.05 mol / L, 0.025 mol / L, 0.01 mol / L.

[0061] 1.5 pH adjustment:

[0062] Add 2-3 drops of bromophenol blue indicator (1.4.3) to the solution in the beaker in step 1.3 to develop a blue color. Adjust the pH of the solution to 3.0-3.5 as follows:

[0063] 1.5.1 If the solution is blue, first add nitric acid solution (1.4.1) dropwise until it turns yellow, then add sodium hydroxide solution (1.4.5) dropwise until it turns blue, and then add nitric acid solution (1.4.2) dropwise until it turns yellow and then add 2-3 drops in excess.

[0064] 1.6 Solution titration:

[0065] Add 1 mL of diphenylcarbazone indicator solution (1.4.4) to the test solution (1.5) with adjusted pH value, and titrate with mercuric nitrate standard solution (1.4.6) until the color changes from yellow to purplish red as the end point.

[0066] Perform a blank test simultaneously.

[0067] 1.7 Calculate the chloride ion content based on the titration volume of the sample, the titration volume of the blank, and the sample weight.

[0068] The following comparative tests are conducted on this sample simultaneously:

[0069] (1) Entrust the authoritative testing agency CTi Huace Testing to conduct testing and comparison according to the ion chromatography method (US EPA 3500C:2007 & USEPA 9056A:2007).

[0070] (2) According to the chlorine content detection method specified in GB / T 23851-2017 "Snow Melting Agent" and HG / T 5390-2018 "Sodium Formate", GB / T11896 "Water Quality - Determination of Chloride - Silver Nitrate Titration Method", simply referred to as the direct silver nitrate titration method for determination and comparison.

[0071] (3) Without using the calcination and filtration treatment of the present invention, directly use the mercuric nitrate method, simply referred to as the direct mercuric nitrate titration method for determination and comparison.

[0072] Example 2:

[0073] Example 2 discloses a method for detecting the chlorine content of a snow melting agent, including the following steps:

[0074] 2.1 Accurately weigh 3.5812 g of solid sodium formate snow melting agent sample in a 30 mL volatile matter porcelain crucible.

[0075] 2.2 Place the above sample porcelain crucible into a muffle furnace, start heating the muffle furnace to 520 °C for calcination. When the temperature reaches the set 520 °C, start timing. The calcination time at this temperature is 55 minutes, and then carefully take out the crucible.

[0076] 2.3 After the crucible cools to room temperature, each time rinse the sample in the crucible with 20 - 30 mL of deionized water and pour it into a glass funnel with a φ12 cm qualitative filter paper for filtration. Each filtration should wait until the previous rinse water has drained before filtering the next rinse water. After filtering 5 times, detect that the alkalinity of the filtrate disappears, and collect the total volume of the filtrate in a triangular flask, approximately 200 mL.

[0077] The remaining steps are the same as in Example 1.

[0078] Perform a blank test and a comparative test according to the method of Example 1 simultaneously.

[0079] Example 3:

[0080] Example 3 discloses a method for detecting the chlorine content of a snow melting agent, comprising the following steps:

[0081] 3.1 Accurately weigh 2.6274 g of a solid sodium formate snow melting agent sample in a 30 mL volatile porcelain crucible.

[0082] 3.2 Place the above sample porcelain crucible into a muffle furnace, start heating the muffle furnace to 540 °C for burning. When the temperature reaches the set 540 °C, start timing. The burning time at this temperature is 50 minutes, and then carefully take out the crucible.

[0083] 3.3 After the crucible cools to room temperature, rinse the sample in the crucible with 20 - 30 mL of deionized water each time and pour it into a glass funnel with a φ12 cm qualitative filter paper for filtration. Each filtration should wait until the previous rinse water has drained before filtering the next rinse water. After 4 filtrations, detect that the alkalinity of the filtrate disappears, and the total volume of the filtrate collected in the Erlenmeyer flask is about 200 mL.

[0084] The remaining steps are the same as those in Example 1.

[0085] At the same time, conduct a blank experiment and a comparative experiment according to the method in Example 1.

[0086] Example 4:

[0087] Example 4 discloses a method for detecting the chlorine content of a snow melting agent, comprising the following steps:

[0088] 4.1 Accurately weigh 2.7290 g of a solid sodium formate snow melting agent sample in a 30 mL volatile porcelain crucible.

[0089] 4.2 Place the above sample porcelain crucible into a muffle furnace, start heating the muffle furnace to 560 °C for burning. When the temperature reaches the set 560 °C, start timing. The burning time at this temperature is 40 minutes, and then carefully take out the crucible.

[0090] 4.3 After the crucible cools to room temperature, rinse the sample in the crucible with 20 - 30 mL of deionized water each time and pour it into a glass funnel with a φ12 cm qualitative filter paper for filtration. Each filtration should wait until the previous rinse water has drained before filtering the next rinse water. After 4 filtrations, detect that the alkalinity of the filtrate disappears, and the total volume of the filtrate collected in the Erlenmeyer flask is about 200 mL.

[0091] The remaining steps are the same as those in Example 1.

[0092] At the same time, conduct a blank experiment and a comparative experiment according to the method in Example 1.

[0093] Example 5:

[0094] Example 5 discloses a method for detecting the chlorine content of a snow melting agent, comprising the following steps:

[0095] 5.1 Accurately weigh 1.7669 g of a solid sodium formate snow melting agent sample in a 30 mL volatile porcelain crucible.

[0096] 5.2 Place the above sample porcelain crucible into a muffle furnace, start heating the muffle furnace to 580 °C for burning. When the temperature reaches the set 580 °C, start timing. The burning time at this temperature is 30 minutes, and then carefully take out the crucible.

[0097] 5.3 After the crucible cools to room temperature, each time rinse the sample in the crucible with 20 - 30 mL of deionized water and pour it into a glass funnel with a φ12 cm qualitative filter paper for filtration. Each filtration should wait until the previous rinse water has drained before filtering the next rinse water. After filtering 4 times, detect that the alkalinity of the filtrate disappears, and the total volume of the filtrate collected in the triangular flask is about 200 mL.

[0098] The remaining steps are the same as those in Example 1.

[0099] At the same time, conduct blank experiments and comparative tests according to the method in Example 1.

[0100] Example 6:

[0101] Example 6 discloses a method for detecting the chlorine content of a snow melting agent, comprising the following steps:

[0102] 6.1 Accurately weigh 4.0511 g of a solid sodium formate snow melting agent sample in a 30 mL volatile porcelain crucible.

[0103] 6.2 Place the above sample porcelain crucible into a muffle furnace, start heating the muffle furnace to 600 °C for burning. When the temperature reaches the set 600 °C, start timing. The burning time at this temperature is 30 minutes, and then carefully take out the crucible.

[0104] 6.3 After the crucible cools to room temperature, each time rinse the sample in the crucible with 20 - 30 mL of deionized water and pour it into a glass funnel with a φ12 cm qualitative filter paper for filtration. Each filtration should wait until the previous rinse water has drained before filtering the next rinse water. After filtering 5 times, detect that the alkalinity of the filtrate disappears, and the total volume of the filtrate collected in the triangular flask is about 200 mL.

[0105] The remaining steps are the same as those in Example 1.

[0106] At the same time, conduct blank experiments and comparative tests according to the method in Example 1.

[0107] Verification Example

[0108] Verify the test results of Examples 1 - 6 by means of self - inspection and submission for inspection. The results are shown in Tables 1 and 2:

[0109] Table 1 Test Data and Results of Embodiments of the Present Invention

[0110]

[0111] Table 2 Comparative Test Results of Embodiments of the Present Invention

[0112]

[0113] As can be seen from Table 1 and Table 2 above, the test results of the present invention are relatively close to the results detected by the entrusted authoritative testing institution (CTi Huace Testing) using ion chromatography. However, there are significant differences in the test results of the direct titration method with silver nitrate, and the direct titration method with mercuric nitrate cannot obtain relatively accurate test results.

[0114] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims

1. A method for detecting the chlorine content of a snow melting agent, characterized in that, The steps include the following: (1) Weigh a solid or liquid sodium formate deicing agent sample and place it in a 30 - 100 mL porcelain crucible for volatile matter; Based on the solid deicing agent, the weight of the sample is greater than or equal to 0.5 g, and the weighing accuracy is 0.0001 g; Place the porcelain crucible for volatile matter in a muffle furnace, heat it to 500 - 600 °C and then start timing, burn for 30 - 60 minutes, and take out the porcelain crucible for volatile matter after burning is completed; (2) According to visual inspection; If the sample after burning is gray - black, rinse the sample in the crucible with 20 - 30 mL of deionized water each time and pour it into a glass funnel with a qualitative filter paper of φ12 - 15 cm for filtration, stop when the filtrate has no alkalinity, combine the filtrates and transfer them to a 250 mL Erlenmeyer flask; If the sample after burning is white, rinse the sample in the crucible with deionized water and then transfer it to a 250 mL Erlenmeyer flask; The volume of the test solution in the Erlenmeyer flask is 100 - 200 mL; (3) Add 2 - 3 drops of bromophenol blue indicator to the test solution. The solution is blue. First, add a high - concentration nitric acid solution until it turns yellow, then add a sodium hydroxide solution until it turns blue, and then add a low - concentration nitric acid solution until it turns yellow and then add 2 - 3 more drops in excess; Add 1 mL of diphenylcarbazone indicator solution to the test solution, and titrate with a mercury nitrate standard solution until the color changes from yellow to purple - red as the end point. The concentration of the mercury nitrate standard solution is 0.01 - 0.1 mol / L; At the same time, conduct a blank experiment; Calculate the chloride ion concentration according to the following formula: CL - %=(V - V0)*C*0.03545*100 / M; In the formula: V is the volume of the mercury nitrate standard solution consumed in the titration of the sample, with the unit of mL; V0 is the volume of the mercury nitrate standard solution consumed in the blank experiment, with the unit of mL; C is the concentration of the mercury nitrate standard solution, with the unit of mol / L; 0.03545 is the millimolar mass of chlorine, with the unit of g / mmol; M is the mass of the sample, with the unit of g.

2. The detection method of the chlorine content of the snow melting agent according to claim 1, characterized in that, In step (3), bromophenol blue is a 0.1% ethanol solution; The high - concentration nitric acid solution is a 1:1 solution; The low - concentration nitric acid solution is a 1:7 solution; The diphenylcarbazone indicator solution is a 0.5% ethanol solution; The concentration of the sodium hydroxide solution is 1.0 mol / L; The concentration of the mercury nitrate standard solution is 0.05 mol / L, 0.025 mol / L or 0.01 mol / L.

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