Improved iodine oxidation-dimethylglyoxime spectrophotometric method for determining nickel content in steel

Abstract

The application discloses an improved iodine oxidation-dimethylglyoxime spectrophotometry for detecting the content of nickel in steel, which comprises the following steps: obtaining an acidolysis solution by acidolysis of the steel to be detected; then diluting the solution to obtain a mother liquor to be detected; mixing the mother liquor to be detected with an ammonium citrate solution, water, an iodine solution, ammonia water and a dimethylglyoxime solution to obtain a chromogenic solution to be detected; and placing the chromogenic solution to be detected below a critical temperature to perform spectrophotometry to obtain the content of nickel in the steel to be detected. The application controls the adding amount of the ammonium citrate and the dimethylglyoxime in the chromogenic solution to be detected and the chromogenic temperature, so that the stable time of the absorbance of the chromogenic solution to be detected is greater than or equal to 60 minutes, the detection of the content of copper in the steel to be detected is less than or equal to 0.2%, and the probability of the result of the detection of the content of nickel in the steel to be detected (0.10%-50%) exceeding the allowable error of a navigation mark is less than or equal to 5%.

Description

Technical Field

[0001] This invention relates to the field of chemical analysis technology, and in particular to an improved iodine oxidation-dimethylglyoxime spectrophotometric method for detecting nickel content in steel. Background Technology

[0002] There are two spectrophotometric methods for determining nickel content in steel: the sodium persulfate (ammonium) oxidation-methylglyoxime method and the iodine oxidation-methylglyoxime method in ammoniacal solution. The sodium persulfate (ammonium) oxidation-methylglyoxime method has a slower color development speed, higher sensitivity, and longer absorbance stabilization time, making it suitable for detecting nickel content in copper-containing steel. However, cobalt causes significant interference, making it unsuitable for detecting nickel content in high-cobalt steel. The iodine oxidation-methylglyoxime method in ammoniacal solution has a fast color development speed, completing color development instantaneously, and cobalt does not interfere. However, it has lower sensitivity and an extremely short absorbance stabilization time (less than 12 minutes), making it difficult to control on-site and resulting in a probability of the detection results exceeding the allowable tolerance (>60%).

[0003] Studies have shown that the absorbance stabilization time of the iodine oxidation-butanone oxime spectrophotometric method in ammoniacal solution is related to the amount of ammonium citrate butanone oxime added to the colorimetric test solution and the colorimetric temperature.

[0004] However, no relevant studies have been reported. It is necessary to improve the iodine oxidation-butanone oxime spectrophotometric method in ammoniacal solutions to increase the stability time for detecting nickel content in steel and reduce the probability of exceeding the allowable deviation. Summary of the Invention

[0005] To address the problems existing in the prior art, this invention provides an improved spectrophotometric method for detecting nickel content in steel using iodine oxidation-butanedione oxime, comprising:

[0006] The nickel-containing steel to be tested was acid-hydrolyzed to obtain an acid hydrolysate, which was then diluted to obtain the mother liquor to be tested.

[0007] The test stock solution is mixed with ammonium citrate solution, water, iodine solution, ammonia water and dimethylglyoxime solution to obtain the colorimetric test solution;

[0008] The nickel content in the nickel-containing steel is obtained by photometric testing below the critical temperature of the colorimetric test solution.

[0009] Further, the step of mixing the mother solution to be tested with ammonium citrate solution, water, iodine solution, ammonia water, and dimethylglyoxime solution to obtain the colorimetric test solution includes,

[0010] Mix 8-12 mL of the stock solution to be tested with 15-25 mL of ammonium citrate solution, 15-25 mL of water, 4-6 mL of iodine solution, 8-12 mL of ammonia water, and 15-25 mL of dimethylglyoxime solution to obtain the colorimetric test solution.

[0011] Furthermore, the concentration of the ammonium citrate solution is 500 g / L.

[0012] Furthermore, the iodine solution is a mixed solution of 25.4 g / L potassium iodide and 0.1 mol / L elemental iodine.

[0013] Furthermore, the concentration of the ammonia water is 0.9 g / mL.

[0014] Furthermore, the concentration of the dimethylglyoxime solution is 2.00 g / L.

[0015] Furthermore, the critical temperature is 26°C.

[0016] Furthermore, the copper content in the nickel-containing steel to be tested is ≤0.2%, and the nickel content is 0.10%-50%.

[0017] Furthermore, the acid hydrolysis solution obtained by acid hydrolyzing the nickel-containing steel to be tested includes,

[0018] Different types of acid solutions are used for acid hydrolysis depending on the nickel content in the nickel-containing steel;

[0019] The acid solution includes concentrated hydrochloric acid, concentrated nitric acid, a mixed acid solution of nitric acid, hydrochloric acid and water, a mixed acid solution of nitric acid and hydrochloric acid, and a mixed acid solution of sulfuric acid and phosphoric acid.

[0020] Furthermore, the step of placing the colorimetric test solution below the critical temperature for photometric testing to obtain the nickel content in the nickel-containing steel includes,

[0021] The colorimetric test solution was placed below the critical temperature and allowed to stand for 5-10 minutes, then transferred to a spectrophotometer to detect the absorbance at a wavelength of 530 nm.

[0022] The nickel content in the nickel-containing steel to be tested is calculated based on the absorbance.

[0023] Compared with the prior art, the present invention has the following beneficial effects:

[0024] This invention controls the amount of ammonium citrate and dimethylglyoxime added to the colorimetric test solution, as well as the colorimetric temperature, to ensure that the absorbance of the colorimetric test solution stabilizes for ≥60 minutes. The probability of the nickel content in steel with copper content ≤0.2% and nickel content 0.10%-50% exceeding the allowable difference of the navigation standard is ≤5%.

[0025] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the steps indicated in the description and the drawings. Attached Figure Description

[0026] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 A flowchart of an improved iodine oxidation-butanedione oxime spectrophotometric method for detecting nickel content in steel according to the present invention is shown. Detailed Implementation

[0028] The existing iodine oxidation-dimethylglyoxime spectrophotometric method for detecting nickel content in steel suffers from poor stability, resulting in a probability exceeding the allowable tolerance (>60%). This invention discovers that the amounts of ammonium citrate and dimethylglyoxime added to the chromogenic test solution, as well as the chromogenic temperature, significantly affect the chromogenic stability. By controlling the amounts of ammonium citrate and dimethylglyoxime added at a lower chromogenic temperature, the stabilization time of the absorbance of the chromogenic test solution can be significantly improved, thereby reducing the probability of exceeding the allowable tolerance.

[0029] Therefore, such as Figure 1 As shown, this invention provides an improved spectrophotometric method for detecting nickel content in steel using iodine oxidation-butanedione oxime, comprising the following steps:

[0030] S101. The nickel-containing steel to be tested is acidified to obtain an acidified solution, which is then diluted to obtain the mother liquor to be tested.

[0031] Preferably, the copper content in the nickel-containing steel to be tested is ≤0.2%, and the nickel content is 0.10%-50%.

[0032] Preferably, the nickel-containing steel to be tested can be pig iron, iron powder, carbon steel, alloy steel, high-temperature alloy, or precision alloy.

[0033] Preferably, different types of acid solutions are used for acid hydrolysis depending on the nickel content of the nickel-containing steel to be tested.

[0034] Preferably, the acid solution includes concentrated hydrochloric acid, concentrated nitric acid, a mixed acid solution of nitric acid, hydrochloric acid and water, a mixed acid solution of nitric acid and hydrochloric acid, and a mixed acid solution of sulfuric acid and phosphoric acid.

[0035] In an embodiment of the present invention, the acid hydrolysis of the nickel-containing steel to be tested uses a mixed acid solution of hydrochloric acid with a density of 1.19 g / mL, nitric acid with a density of 1.42 g / mL, and water, or a mixed acid solution of hydrochloric acid with a density of 1.19 g / mL and nitric acid with a density of 1.42 g / mL. The volume ratio of hydrochloric acid, nitric acid, and water in the mixed acid solution is different. Different types of mixed acid solutions are selected according to the different contents of tungsten, molybdenum, and niobium in the nickel-containing steel to be tested.

[0036] Preferably, the acid solution comprises a first mixed acid, a second mixed acid, a third mixed acid, a fourth mixed acid, a fifth mixed acid, and a sixth mixed acid. The first mixed acid is formed by mixing hydrochloric acid (density 1.19 g / mL), nitric acid (density 1.42 g / mL), and water in a volume ratio of 3:2:5; the second mixed acid is formed by mixing hydrochloric acid (density 1.19 g / mL), nitric acid (density 1.42 g / mL), and water in a volume ratio of 1:4:4; the third mixed acid is formed by mixing hydrochloric acid (density 1.19 g / mL), nitric acid (density 1.42 g / mL), and water in a volume ratio of 1:12:1; the fourth mixed acid is nitric acid (1+3); the fifth mixed acid is formed by mixing hydrochloric acid (density 1.19 g / mL) and nitric acid (density 1.42 g / mL) in a volume ratio of 12:1; and the sixth mixed acid is formed by mixing sulfuric acid (density 1.84 g / mL) and phosphoric acid (density 1.70 g / mL) in a volume ratio of 1:4.

[0037] In a preferred embodiment of the present invention, as shown in Table 1, depending on the different nickel content in the nickel-containing steel to be tested, a certain volume of acid solution is used to acidify the nickel-containing steel to be tested to obtain an acid solution, which is then diluted to obtain a mother liquor to be tested, and a small portion of the mother liquor to be tested is then taken for subsequent absorbance testing.

[0038] Table 1. Selection of parameters for acid-hydrolyzed nickel-containing steel.

[0039]

[0040] It should be noted that when acidifying the nickel-containing steel sample with a mixture of hydrochloric acid with a density of 1.19 g / mL and nitric acid with a density of 1.42 g / mL, the ratio of hydrochloric acid with a density of 1.19 g / mL to nitric acid with a density of 1.42 g / mL can be adjusted appropriately to ensure that the nickel-containing steel sample is completely dissolved.

[0041] In an embodiment of the present invention, if the nickel-containing steel to be tested is a high-tungsten sample, 0.1-0.2g of the high-tungsten sample is dissolved in 100-120mL of the fifth mixed acid, then 10mL of the sixth mixed acid is added and mixed well, followed by 25mL of nitric acid with a density of 1.42g / mL. The mixture is then heated until sulfuric acid fumes are emitted, cooled to room temperature, 50mL of water is added, and 10mL of hydrochloric acid with a density of 1.19g / mL is added. The mixture is then heated to boiling, cooled to room temperature, and diluted to 500mL to obtain the mother liquor to be tested.

[0042] In this invention, hydrochloric acid with a density of 1.19 g / mL, nitric acid with a density of 1.42 g / mL, sulfuric acid with a density of 1.84 g / mL, and phosphoric acid with a density of 1.70 g / mL are commonly used concentrated hydrochloric acid, concentrated nitric acid, concentrated sulfuric acid, and phosphoric acid.

[0043] S102. The test mother liquor is mixed with ammonium citrate solution, water, iodine solution, ammonia water and dimethylglyoxime solution to obtain a colorimetric test solution.

[0044] In an embodiment of the present invention, 8-12 mL of the test stock solution is mixed with 15-25 mL of ammonium citrate solution, 15-25 mL of water, 4-6 mL of iodine solution, 8-12 mL of ammonia water, and 15-25 mL of dimethylglyoxime solution to obtain a colorimetric test solution.

[0045] Preferably, the concentration of the ammonium citrate solution is 500 g / L.

[0046] Preferably, the iodine solution is a mixed solution of 25.4 g / L potassium iodide and 0.1 mol / L elemental iodine. The iodine solution can be prepared by weighing 25.4 g of potassium iodide and 12.7 g of elemental iodine into a 250 or 300 mL wide-mouth beaker, adding 100-150 mL of water, stirring until completely dissolved, transferring to a 1000 mL volumetric flask, and diluting with water to obtain the iodine solution.

[0047] Preferably, the concentration of the ammonia water is 0.9 g / mL.

[0048] Preferably, the concentration of the dimethylglyoxime solution is 2.00 g / L. The dimethylglyoxime solution can be prepared by adding 500 mL of water, 20 g of sodium hydroxide, and 4.00 g of dimethylglyoxime to a 1000 mL wide-mouth plastic beaker, stirring until completely dissolved, transferring to a 2000 mL volumetric flask, and diluting with water to obtain the dimethylglyoxime solution.

[0049] Preferably, multiple sets of colorimetric test solutions are prepared in parallel, and the average absorbance is calculated.

[0050] In an embodiment of the present invention, cobalt consumes iodine, thereby affecting the color development effect. The cobalt content in the transfer solution is controlled to be no more than 40 mg. When the cobalt content in the transfer solution is greater than 5 mg but not more than 40 mg, an iodine solution containing cobalt content in the transfer solution divided by 5.893 is added.

[0051] S103. The colorimetric test solution is placed below the critical temperature and the nickel content in the nickel-containing steel is obtained by photometric testing.

[0052] Preferably, the critical temperature is 26°C.

[0053] More preferably, the critical temperature is 25°C, and the color development temperature of the colorimetric test solution is controlled to be ≤25°C. When the temperature is >25°C, the colorimetric test solution can be transferred to an air-conditioned room with a temperature ≤25°C for color development and then the subsequent tests can be completed.

[0054] Preferably, the colorimetric test solution is placed below the critical temperature and allowed to stand for 5-10 minutes, then transferred to a spectrophotometer to detect the absorbance at a wavelength of 530 nm; the nickel content in the nickel-containing steel is calculated based on the absorbance.

[0055] Preferably, the reference solution used for detecting absorbance is water.

[0056] In the embodiments of this invention, the colorimetric test solution is allowed to stand at a temperature of 26°C or lower for 5-10 minutes, and then a portion is transferred to a cuvette and placed on a 722 type visible spectrophotometer. A reference solution is prepared without adding dimethylglyoxime solution, with all other operations identical to those for the colorimetric solution, and the absorbance is measured. The standard curve is established using a method commonly used in the art: 4-6 standard samples are weighed, ensuring the nickel content of the test sample is within the range specified for the standard samples. The analytical procedures are followed, and a series of absorbance values ​​are measured. A linear regression is performed on the nickel content of the standard samples against the corresponding absorbance values ​​to obtain the working curve function. The relationship between colorimetric temperature and absorbance stabilization time is shown in Table 2.

[0057] Table 2 Relationship between color development temperature and absorbance stabilization time

[0058]

[0059] As can be seen from the results in Table 2, this invention, by controlling the amounts of ammonium citrate, iodine solution, and dimethylglyoxime in the colorimetric test solution, maintains the colorimetric temperature at ≤26℃, thereby extending the absorbance stabilization time for nickel content testing to over 60 minutes. Furthermore, the lower the temperature during the colorimetric test, the longer the absorbance stabilization time.

[0060] Based on the results in Table 2, this invention provides guidance on color development temperature and recommended detection time: color development temperature 22.5-25℃, absorbance measurement to be completed within 60 minutes after color development; color development temperature 20.0-22.5℃, absorbance measurement to be completed within 90 minutes after color development; color development temperature 15-20℃, absorbance measurement to be completed within 120 minutes after color development; color development temperature <15℃, absorbance measurement to be completed within 180 minutes after color development.

[0061] Preferably, the nickel content in the nickel-containing steel to be tested is calculated according to the following formula:

[0062]

[0063] In the formula, W Ni m0 represents the nickel content in the nickel-containing steel to be tested, m0 represents the mass of nickel in the nickel-containing steel to be tested calculated based on the measured absorbance using the working curve function, and m represents the mass of the nickel-containing steel to be tested.

[0064] The technical solutions of the present invention will be clearly and completely described below with reference to specific embodiments. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0065] Example

[0066] This embodiment applies the improved iodine oxidation-dimethylglyoxime spectrophotometric method for detecting nickel content in steel to the testing of nickel content in standard samples. The specific processes for acid dilution to obtain the mother liquor and the establishment of the working curve function are not detailed here. The following steps are included:

[0067] Step 1: Acid hydrolyze the standard nickel-containing steel to be tested to obtain the acid hydrolysate, and then dilute it to obtain the mother liquor to be tested;

[0068] Step 2: The test solution is prepared by mixing 10 mL of the test stock solution with 20 mL of 500 g / L ammonium citrate solution, 20 mL of water, 5 mL of iodine solution (a mixed solution of 25.4 g / L potassium iodide and 0.1 mol / L elemental iodine), 10 mL of 0.9 g / mL ammonia solution and 20 mL of 2.00 g / L dimethylglyoxime solution.

[0069] Step 3: Place the colorimetric test solution at 25℃ and let it stand for 5 minutes to develop color. Take a small amount of the developed colorimetric test solution and transfer it to a cuvette. Load the sample onto a 722 type visible spectrophotometer. Use a solution prepared without adding dimethylglyoxime solution, with all other operations identical to the colorimetric solution preparation, as a reference solution for absorbance detection. Measure the absorbance at a wavelength of 530 nm. Calculate the mass of nickel in the standard sample based on the absorbance and the working curve function, thus obtaining the nickel content in the standard sample.

[0070] The test results of nickel content of a series of standard samples are shown in Table 3. Among them, for the standard samples in the table, the absorbance stability time of the colorimetric test solution is more than 70 minutes. It is recommended to detect the absorbance within 60 minutes.

[0071] Table 3. Test results of nickel content in standard samples.

[0072]

[0073] As can be seen from the test results in Table 3, the nickel content detection value of the improved iodine oxidation-dimethylglyoxime spectrophotometric method for detecting nickel content in steel in this embodiment is very close to the nickel content standard value, and the probability of exceeding the allowable difference of the navigation standard is less than 5%.

[0074] Comparative Example

[0075] The conventional iodine oxidation-dimethylglyoxime spectrophotometric method for detecting nickel content in steel suffers from poor stability due to the lack of specified colorimetric temperature and control range for divalent copper in the colorimetric solution. Furthermore, the concentrations of ammonium citrate and dimethylglyoxime added to the colorimetric solution are only half of those used in this invention. Specifically, the absorbance of the colorimetric solution stabilizes for 10-20 minutes at room temperature <15°C, 5-10 minutes at room temperature 15-25°C, and less than 5 minutes at room temperature >25°C. This low absorbance stability results in a probability exceeding the allowable tolerance by more than 60%.

[0076] In summary, this invention obtains an acid-hydrolyzed solution from nickel-containing steel by acid hydrolysis, which is then diluted to obtain a mother liquor for testing. This mother liquor is mixed with ammonium citrate solution, water, iodine solution, ammonia, and dimethylglyoxime solution to obtain a colorimetric test solution. The colorimetric test solution is then placed below a critical temperature for photometric testing to determine the nickel content in the nickel-containing steel. By controlling the amount of ammonium citrate and dimethylglyoxime added to the colorimetric test solution and the colorimetric temperature, this invention ensures that the absorbance of the colorimetric test solution stabilizes for ≥60 minutes, and the probability of the nickel content exceeding the allowable deviation in steel with copper content ≤0.2% and nickel content 0.10%-50% is ≤5%.

[0077] Finally, it should be noted that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art can still modify the technical solutions described in the foregoing embodiments or make equivalent substitutions for some of the technical features. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. An improved spectrophotometric method for detecting nickel content in steel using iodine oxidation-butanedione oxime, characterized in that, include, The nickel-containing steel to be tested is acid-electrolyzed to obtain an acid-electrolyte solution, which is then diluted to obtain a mother liquor for testing. The nickel-containing steel to be tested has a copper content of ≤0.2% and a nickel content of 0.10%-50%. Mix 8-12 mL of the stock solution to be tested with 15-25 mL of ammonium citrate solution, 15-25 mL of water, 4-6 mL of iodine solution, 8-12 mL of ammonia water, and 15-25 mL of dimethylglyoxime solution to obtain the colorimetric test solution. The concentration of the ammonium citrate solution is 500 g / L, the iodine solution is a mixture of 25.4 g / L potassium iodide and 0.1 mol / L elemental iodine, the concentration of the ammonia water is 0.9 g / mL, and the concentration of the dimethylglyoxime solution is 2.00 g / L. The nickel content in the nickel-containing steel was obtained by photometric testing at a critical temperature below 26°C. The absorbance of the colorimetric test solution stabilizes for no less than 60 minutes after color development at a critical temperature below 26°C.

2. The improved iodine oxidation-butanedione oxime spectrophotometric method for detecting nickel content in steel according to claim 1, characterized in that, The acid hydrolysis solution obtained by acid hydrolyzing the nickel-containing steel to be tested includes... Different types of acid solutions are used for acid hydrolysis depending on the nickel content in the nickel-containing steel; The acid solution includes concentrated hydrochloric acid, concentrated nitric acid, a mixed acid solution of nitric acid, hydrochloric acid and water, a mixed acid solution of nitric acid and hydrochloric acid, and a mixed acid solution of sulfuric acid and phosphoric acid.

3. The improved iodine oxidation-butanedione oxime spectrophotometric method for detecting nickel content in steel according to claim 1, characterized in that, The step of placing the colorimetric test solution below the critical temperature and performing photometric testing to obtain the nickel content in the nickel-containing steel to be tested includes... The colorimetric test solution was placed below the critical temperature and allowed to stand for 5-10 minutes, then transferred to a spectrophotometer to detect the absorbance at a wavelength of 530 nm. The nickel content in the nickel-containing steel to be tested is calculated based on the absorbance.

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