A method for continuous determination of zinc, lead and tin in tin bronze

Abstract

The invention discloses a method for continuously determining zinc, lead and tin in tin bronze, comprising the following steps: weighing a sample in a glass beaker, adding hydrochloric acid-nitric acid mixed acid to dissolve the sample, separating tin, lead and zinc by precipitation with ammonia water, filtering and washing the filtrate for determining zinc; after dissolving the precipitate with hydrochloric acid, determining the total amount of lead and tin by back titration under certain acidity conditions, and then determining the amount of tin by fluoride salt substitution method. The purpose of the invention is to provide a method for continuously determining zinc, lead and tin in tin bronze, which not only shortens the analysis time, but also saves a large amount of drugs, and has high precision and accuracy.

Description

Technical Field

[0001] The invention relates to the technical field of iron and steel metallurgy analysis, and in particular to a method for continuously determining zinc, lead and tin in tin bronze. Background Art

[0002] Tin bronze is hard, fusible, and can be cast well. It is generally used to make elastic copper alloy components. Leaded tin bronze is often used as wear-resistant parts and sliding bearings. Therefore, in order to improve casting performance, zinc, tin, lead and other main elements are added to copper to improve the wear resistance and cuttability of the product. The amount of zinc, tin and lead directly affects the organization and mechanical properties of tin bronze. Therefore, accurate and effective measurement of zinc, tin and lead content is one of the important links in tin bronze quality control.

[0003] The analysis methods of zinc, tin and lead content in general copper alloys include spectrophotometry, chemical titration, atomic absorption spectrometry, hydride atomic fluorescence spectrometry, inductively coupled plasma atomic emission spectrometry, X-ray fluorescence spectrometry, photoelectric direct reading spectrometry, etc. Atomic absorption and hydride atomic fluorescence are suitable for the determination of samples containing trace or trace amounts of tin. There are many interference factors, especially when hydride atomic fluorescence is used to measure zinc, tin and lead, it is easy to generate volatile compounds and gas phase interference of coexisting elements. Moreover, tin has strict requirements on acidity and is not easy to master. At the same time, zinc is prone to memory effect, which causes the sensitivity to be reduced when measuring zinc. Since the amount of zinc, tin and lead added to tin bronze is relatively high, generally more than 4% (mass fraction, the same below), when inductively coupled plasma atomic emission spectrometry is used for determination, the copper spectrum will affect the zinc, tin and lead spectrum, so the determination error is relatively large. Although X-ray fluorescence spectrometry and photoelectric direct reading spectrometry have fast analysis speed, they require that the sample and the standard sample matrix for making the curve must match, have similar organizational structure and similar composition, otherwise the accuracy of the determination result is low. Although the classical chemical titration method is cumbersome to operate, it is highly accurate for the determination of zinc, tin and lead above 2%. Although there have been reports on the determination of zinc, lead and tin in tin bronze by chemical titration, it is not a continuous determination of the three elements, requires a wide variety of chemicals and has cumbersome steps. Summary of the invention

[0004] The purpose of the present invention is to provide a method for continuously determining zinc, lead and tin in tin bronze. The method adopts HCl and HNO3 mixed acid to dissolve the sample, and EDTA is used to continuously determine zinc, tin and lead after ammonia separation. A large number of tests are carried out on tin bronze, which not only shortens the analysis time, but also saves a large amount of drugs. At the same time, the method has high precision and accuracy.

[0005] In order to solve the above technical problems, the present invention adopts the following technical solutions:

[0006] The invention discloses a method for continuously determining zinc, lead and tin in tin bronze, comprising the following steps: weighing a sample in a glass beaker, adding hydrochloric acid-nitric acid mixed acid to dissolve the sample, using ammonia water to precipitate and separate tin, lead and zinc, filtering and washing the filtrate to determine zinc; after using hydrochloric acid to dissolve the precipitate, using a back titration method to determine the total amount of lead and tin under certain acidity conditions, and then using a fluoride salt substitution method to determine the amount of tin.

[0007] Further, the specific steps include:

[0008] Step 1: Weigh the tin bronze standard sample and the tin bronze test sample into a beaker, add hydrochloric acid-nitric acid mixture, dissolve at low temperature, cool to room temperature, rinse the beaker wall with water, and maintain an appropriate volume;

[0009] Step 2: Use ammonia water to adjust the solution acidity to pH 5, then add a certain amount, then add sodium carbonate solution, heat to boil, remove and cool slightly;

[0010] Step 3: Filter, wash the beaker with 45-55°C hot ammonia-ammonium chloride washing solution to transfer all the precipitate to the funnel, and then wash the precipitate until there is no obvious blue color;

[0011] Blank test: Conduct a reagent blank test along with the sample;

[0012] Step 4: Solution 1: Add the copper ammine complex ions to the above filtrate to dissolve them completely, cool to room temperature and transfer to a volumetric flask, dilute the filtrate with water and make up to volume for the determination of zinc;

[0013] Step 5: Solution 2: Wash the above precipitate with water into the original beaker, add hydrochloric acid to dissolve it, transfer it into a volumetric flask, dilute and fix the volume, and use it to determine lead and tin;

[0014] Step 6: Determination of zinc

[0015] Take solution 1 in a beaker, adjust the solution acidity to pH 4.5-5.0, add thiourea solution to mask copper, add acetic acid-ammonium acetate buffer solution to control the solution acidity, use xylenol orange as indicator, add EDTA standard solution until it turns bright yellow, and record the consumed volume V. The EDTA volume V consumed by the reagent blank in the synchronous operation 空白 , the mass fraction of zinc w Zn / %Calculation formula is shown in formula (1):

[0016]

[0017] Where: T Zn / EDTA is the titration degree of EDTA to Zn, that is, the mass of Zn equivalent to the unit volume of EDTA standard solution, g / mL; m is the sample weight, g; f is the liquid separation ratio; V is the volume of EDTA standard solution consumed, mL; V 空白: Volume of EDTA standard solution consumed in the titration blank test, mL;

[0018] Step 7: Determination of lead and tin

[0019] Take Solution 2 in a beaker, first adjust the acidity of the solution to pH 0.5 - 1.0 with ammonia water, add thiourea solution, add EDTA standard solution, boil and cool, then adjust the acidity of the solution to pH 5.0 - pH 6.0, add thiourea solution to mask copper, add EDTA standard solution and record V 总 , heat to boiling, remove and cool to room temperature, add hexamethylenetetramine solution, PAN indicator, titrate with bismuth nitrate standard solution until it turns red, record the consumed volume and record V 1 , this is the amount of EDTA in excess of the titration, continue to add ammonium fluoride solution, and then titrate with bismuth nitrate standard solution to the red end point, record the consumed volume and record V 2 , this is the volume consumed by bismuth nitrate in titrating the EDTA displaced from Sn - EDTA by ammonium fluoride; the mass fraction w Sn / % calculation formula is shown in Equation (2); the volume of EDTA consumed by lead is V 总 -(V 1 +V 2 ), the mass fraction (w Pb / % ) calculation formula is shown in Equation (3);

[0020]

[0021] In the formula: T Sn / EDTA is the titration degree of EDTA to Sn, that is, the mass of Sn equivalent to the unit volume of EDTA standard solution, g / mL; m: sample weighing amount, g; f is the separation ratio; V 2 is the volume of bismuth nitrate standard solution consumed, mL; F EDTA / BiNO3 is the comparison coefficient, that is, the number of milliliters of EDTA standard solution equivalent to 1.00 mL of 0.015 mol / L bismuth nitrate standard solution; V 2空白 : Volume of bismuth nitrate standard solution consumed in the titration blank test, mL;

[0022]

[0023] In the formula: T Pb / EDTA is the titration degree of EDTA to Pb, that is, the mass of Pb equivalent to the unit volume of EDTA standard solution, g / mL; V 总 is the volume of EDTA added, mL; m is the sample weighing amount, g; f: separation ratio; V 1 、V 2 : Volume of bismuth nitrate standard solution consumed, mL; F EDTA / BiNO3is the comparison coefficient, that is, 1.00mL 0.015 mol / L bismuth nitrate standard solution is equivalent to the milliliters of EDTA standard solution V 3空白 : The volume of EDTA standard solution consumed in the titration blank test (V 3空白 = Total amount of EDTA standard solution added in blank test - amount of bismuth nitrate standard solution consumed × F EDTA / BiNO3 ), mL.

[0024] Furthermore, in the hydrochloric acid-nitric acid mixed acid, hydrochloric acid: nitric acid: water = 1:1:1.

[0025] Furthermore, in step 3, the beaker is washed with 50° C. hot ammonia-ammonium chloride washing solution to transfer all the precipitates to the funnel.

[0026] Furthermore, the detection range is: Zn, Sn, Pb 1.00at~50.00at%.

[0027] Compared with the prior art, the beneficial technical effects of the present invention are:

[0028] The invention is used for the continuous determination of zinc, lead and tin in tin-copper, and utilizes the characteristics that zinc forms complex ions with ammonia water and lead and tin form precipitation with ammonia water to separate tin, lead and zinc, thereby avoiding mutual interference during the determination of tin, lead and zinc and improving the accuracy of the determination.

[0029] Since tin and lead react slowly with EDTA, this patent adopts back titration to determine the content of tin and lead, and adopts fluoride salt substitution method to determine the content of tin, so as to improve the stability of determination, and make the results of quantitative determination of tin and lead highly sensitive and more accurate.

[0030] The method is used to continuously determine zinc, tin and lead in tin bronze. The sample is decomposed by using 20mL (hydrochloric acid: nitric acid: water = 1:1:1) mixed acid, thiourea is used to mask copper, acetic acid-ammonium acetate is used to control acidity, and EDTA volumetric method is used to determine zinc; bismuth nitrate back titration method is used to determine the total amount of tin and lead, and fluoride salt substitution method is used to titrate tin. The continuous determination of the three elements is completed within 4 hours, shortening the analysis time and saving a large amount of chemical reagents. The present invention does not use inflammable and explosive drugs such as perchloric acid and inflammable and combustion-supporting gases such as acetylene and oxygen, and the range of the analysis method can reach 1.00-50.00%.

[0031] The invention has good application effect through multiple tests on tin bronze samples. It has a higher upper limit than the photometric method, atomic absorption spectrometry, ICP-AES spectrometry and X-ray fluorescence spectrometry and a wider measurement range. The invention has small matrix interference, only uses a burette in the measurement process, the device is easy to operate and easy to master, and the analysis result is accurate and reliable. This invention can create economic benefits of more than 200,000 yuan. DETAILED DESCRIPTION

[0032] A method for continuously determining zinc, lead and tin in tin bronze specifically comprises the following steps:

[0033] Step 1: Weigh 1.000 g of tin bronze standard sample and tin bronze test sample into a 300 mL beaker, add 20 mL of hydrochloric acid-nitric acid (hydrochloric acid: nitric acid: water = 1:1:1) mixed acid, dissolve at low temperature on a hot plate, cool to room temperature, rinse the beaker wall with water, and keep the volume at about 40 mL;

[0034] Step 2: Use ammonia (1+1) to adjust the solution acidity to pH 5, and then add 15 mL. Add 3 mL of 50 g / L sodium carbonate solution, heat and boil for 10 seconds, remove and cool slightly;

[0035] Step 3: Filter, wash the beaker three times with hot ammonia-ammonium chloride solution (about 50°C) to transfer all the precipitate to the funnel, and then wash the precipitate until there is no obvious blue color;

[0036] Blank test: Conduct a reagent blank test along with the sample;

[0037] Step 4: Solution 1: Add 25 mL of hydrochloric acid (1+1) to the above filtrate to dissolve all the copper ammine complex ions, cool to room temperature and transfer to a 250 mL volumetric flask, dilute the filtrate with water and make up to volume for the determination of zinc.

[0038] Step 5: Solution 2: Wash the above precipitate with water into the original beaker, add 20mL of hydrochloric acid (1+1) to dissolve it, transfer it into a 250mL volumetric flask, dilute and fix the volume, and use it to determine lead and tin;

[0039] Step 6: Determination of zinc Take 50mL of solution 1 in a 300mL beaker, adjust the solution acidity to pH 4.5-5.0, add 20mL of 200g / L thiourea solution to mask copper, add 20mL of acetic acid-ammonium acetate buffer solution to control the solution acidity, add 5 drops of 2g / L xylenol orange indicator, add 0.015mol / L EDTA standard solution until it turns bright yellow, and record the consumed volume V. (The EDTA volume V consumed by the reagent blank in the simultaneous operation 空白 ) Mass fraction of zinc (w Zn / %) calculation formula is shown in formula (1);

[0040]

[0041] Where: T Zn / EDTA is the titration degree of EDTA to Zn, that is, the mass of Zn equivalent to the unit volume of EDTA standard solution, g / mL; m is the sample weight, g; f is the liquid separation ratio; V is the volume of EDTA standard solution consumed, mL; V 空白 : The volume of EDTA standard solution consumed in the titration blank test, mL;

[0042] Step 7: Determination of lead and tin Take 50 mL of solution 2 in a 300 mL beaker, adjust the solution acidity to pH 0.5-1.0 with ammonia (1+1), add 1.0 mL of 200 g / L thiourea solution, add 20 mL of 0.015 mol / L EDTA standard solution, boil and cool, then adjust the solution acidity to pH 5.0-pH 6.0, add 1.0 mL of 200 g / L thiourea solution to mask copper, and add 20 mL of 0.015 mol / L EDTA standard solution (note V 总 ), heat to boil, remove and cool to room temperature, add 20mL 200g / L hexamethylenetetramine solution, 5 drops of PAN indicator, add 0.015mol / L bismuth nitrate standard solution until it turns red, and record the consumed volume (record V 1 ), which is the amount of EDTA in excess. Continue to add 10mL of 200g / L ammonium fluoride solution, and then add 0.015mol / L bismuth nitrate standard solution until the red end point, and record the consumed volume (recorded as V 2 ), which is the volume consumed by bismuth nitrate to titrate ammonium fluoride to replace EDTA in Sn-EDTA. The mass fraction of tin (w Sn / %) is calculated as shown in formula (2); the volume of EDTA consumed by lead is V 总 -(V 1 +V 2 ), mass fraction of lead (w Pb / %) calculation formula is shown in formula (3);

[0043]

[0044] Where: T Sn / EDTA is the titration degree of EDTA to Sn, that is, the mass of Sn equivalent to the unit volume of EDTA standard solution, g / mL; m: sample weight, g; f is the liquid separation ratio; V 2 is the volume of bismuth nitrate standard solution consumed, mL; F EDTA / BiNO3 V is the comparison coefficient, that is, 1.00mL of 0.015mol / L bismuth nitrate standard solution is equivalent to the number of milliliters of EDTA standard solution; 2空白 : The volume of bismuth nitrate standard solution consumed in the titration blank test, mL;

[0045]

[0046] Where: T Pb / EDTA V is the titration degree of EDTA to Pb, that is, the mass of Pb equivalent to the unit volume of EDTA standard solution, g / mL; 总 is the volume of EDTA added, mL; m is the sample weight, g; f: liquid separation ratio; V 1 、V 2 : Volume of bismuth nitrate standard solution consumed, mL; FEDTA / BiNO3 is the comparison coefficient, that is, 1.00mL 0.015mol / L bismuth nitrate standard solution is equivalent to milliliters of EDTA standard solution V 3空白 : The volume of EDTA standard solution consumed in the titration blank test (V 3空白 = total amount of EDTA standard solution added in blank test - amount of bismuth nitrate standard solution consumed × FEDTA / BiNO3), mL;

[0047] The detection range of this method: Zn, Sn, Pb 1.00at~50.00at%;

[0048] The present invention is further described in detail below in conjunction with specific embodiments:

[0049] In the embodiments of the present invention, the reagents used are preferably:

[0050] Tin bronze standard substance; Thiourea solution: 200g / L; 1-(-2-pyridyl azo)-2-naphthol (PAN) solution: 5g / L, ethanol as solvent; Xylenol orange solution: 2g / L water; Hexamethylenetetramine solution: 300g / L; Sodium carbonate solution: 50g / L; Acetic acid-ammonium acetate buffer solution: Dissolve 136g ammonium acetate in 500mL high-purity water, add 40mL acetic acid, and dilute to 1L with high-purity water; Hydrochloric acid (1+1); Ammonia water (1+1); Hydrochloric acid-nitric acid mixed acid (the volume ratio of hydrochloric acid: nitric acid: water is 1:1:3); Ammonia water-ammonium chloride washing solution: 2g ammonium chloride, 5mL ammonia water, diluted to 500mL with water; Ammonium fluoride solution: 200g / L; EDTA standard solution: 0.015mol / L, weigh 5.63g EDTA standard reagent, add 0.5g potassium hydroxide, dissolve in water, filter into a 1000mL volumetric flask, and dilute to scale; bismuth nitrate standard solution: 0.015mol / L, weigh 7.28g bismuth nitrate standard reagent, dissolve with 6mol / L nitric acid and dilute to a 1000mL volumetric flask.

[0051] The water used in the experiment was high-purity water.

[0052] Example 1

[0053] Detection limit of the method

[0054] According to the experimental method, 11 reagent blank solutions were prepared. After determining Zn, Pb and Sn, 3 times the standard deviation was calculated as the detection limit. The detection limits of Zn, Pb and Sn were 0.045%, 0.050% and 0.050%, respectively.

[0055] Example 2

[0056] Precision experiment

[0057] Select Tin Bronze 1 #For the sample, 11 sample solutions were prepared in parallel under the selected experimental method to determine tin, lead and zinc for precision investigation. The standard deviation (SD) and relative standard deviation (RSD) of the determination results of each component were calculated, as shown in Table 1.

[0058] Table 1 Precision test results

[0059] Table 1 Results of precision test

[0060]

[0061] Example 3

[0062] Accuracy experiment

[0063] Three tin bronze standard samples, ZQSn678, ZQSn3-12-5, and ZQSn4-4-4, were selected for verification, and a spike recovery experiment was carried out. The measurement results were compared with the certified values. The results are shown in Table 2.

[0064] Table 2 Accuracy and spike recovery test

[0065] Table 2 Test results of accuracy and recovery

[0066]

[0067] The embodiments described above are only descriptions of the preferred modes of the present invention, and are not intended to limit the scope of the present invention. Without departing from the design spirit of the present invention, various modifications and improvements made to the technical solutions of the present invention by ordinary technicians in this field should all fall within the protection scope determined by the claims of the present invention.

Claims

1. A method for continuous determination of zinc, lead and tin in tin bronze. It is characterized in that The specific steps include: Step 1: Weigh the tin bronze standard sample and the tin bronze test sample into a beaker, add hydrochloric acid-nitric acid mixture, dissolve at low temperature, cool to room temperature, rinse the beaker wall with water, and maintain an appropriate volume; Step 2: Use ammonia water to adjust the solution acidity to pH 5, then add a certain amount, then add sodium carbonate solution, heat to boil, remove and cool slightly; Step 3: Filter, wash the beaker with 45-55°C hot ammonia-ammonium chloride solution to transfer all the precipitate to the funnel, and then wash the precipitate until there is no obvious blue color; Blank test: Conduct a reagent blank test along with the sample; Step 4: Solution 1: Add the copper ammine complex ions to the above filtrate to dissolve them completely, cool to room temperature and transfer to a volumetric flask, dilute the filtrate with water and make up to volume for the determination of zinc; Step 5: Solution 2: Wash the above precipitate with water into the original beaker, add hydrochloric acid to dissolve it, transfer it into a volumetric flask, dilute and fix the volume, and use it to determine lead and tin; Step 6: Determination of zinc Take solution 1 in a beaker, adjust the solution acidity to pH 4.5-5.0, add thiourea solution to mask copper, add acetic acid-ammonium acetate buffer solution to control the solution acidity, use xylenol orange as indicator, add EDTA standard solution until it turns bright yellow, record the consumed volume V, and the EDTA volume V consumed by the reagent blank in the synchronous operation 空白 , the mass fraction of zinc w Zn / %Calculation formula is shown in formula (1): Where: T Zn / EDTA is the titration degree of EDTA to Zn, that is, the mass of Zn equivalent to the unit volume of EDTA standard solution, g / mL; m is the sample weight, g; f is the liquid separation ratio; V is the volume of the EDTA standard solution consumed, mL; V 空白 : the volume of the EDTA standard solution consumed in the titration blank test, mL; Step 7: Determination of lead and tin Take solution 2 in a beaker, adjust the solution acidity to pH 0.5-1.0 with ammonia water, add thiourea solution, add EDTA standard solution, boil, cool, adjust the solution acidity to pH 5.0-pH 6.0, add thiourea solution to mask copper, add EDTA standard solution and record V 总 , heat to boil, remove and cool to room temperature, add hexamethylenetetramine solution, PAN indicator, drip bismuth nitrate standard solution until red, record the consumed volume and record V 1 This is the amount of excess EDTA titrated. Continue to add ammonium fluoride solution, and then use bismuth nitrate standard solution to drop to the red end point. Record the consumed volume and record V 2 , which is the volume consumed by bismuth nitrate to titrate ammonium fluoride to replace EDTA in Sn-EDTA; the mass fraction of tin w Sn / % The calculation formula is shown in formula (2); the volume of EDTA consumed by lead is V 总 -(V 1 +V 2 ), mass fraction of lead (w Pb / %) calculation formula is shown in formula (3); Where: T Sn / EDTA is the titration degree of EDTA to Sn, that is, the mass of Sn equivalent to unit volume of EDTA standard solution, g / mL; m: sample weight, g; f is the liquid separation ratio; V 2 is the volume of bismuth nitrate standard solution consumed, mL; F EDTA / BiNO3 V is the comparison coefficient, that is, 1.00mL 0.015 mol / L bismuth nitrate standard solution is equivalent to the number of milliliters of EDTA standard solution; 2空白 : The volume of bismuth nitrate standard solution consumed in the titration blank test, mL; Where: T Pb / EDTA V is the titration degree of EDTA to Pb, that is, the mass of Pb equivalent to the unit volume of EDTA standard solution, g / mL; 总 is the volume of EDTA added, mL; m is the sample weight, g; f: liquid separation ratio; V 1 、V 2 : Volume of bismuth nitrate standard solution consumed, mL; F EDTA / BiNO3 is the comparison coefficient, that is, 1.00mL 0.015 mol / L bismuth nitrate standard solution is equivalent to the milliliters of EDTA standard solution V 3空白 : The volume of EDTA standard solution consumed in the titration blank test (V 3空白 = Total amount of EDTA standard solution added in blank test - amount of bismuth nitrate standard solution consumed × F EDTA / BiNO3 ), mL.

2. The method for continuously determining zinc, lead and tin in tin bronze according to claim 1, It is characterized in that In the hydrochloric acid-nitric acid mixed acid, hydrochloric acid: nitric acid: water = 1:1:

1.

3. The method for continuously determining zinc, lead and tin in tin bronze according to claim 1, It is characterized in that In step 3, the beaker is washed with 50° C. hot ammonia-ammonium chloride solution to transfer all the precipitate to the funnel.

4. The method for continuously determining zinc, lead and tin in tin bronze according to claim 1, It is characterized in that Detection range: Zn, Sn, Pb 1.00at~50.00at%.

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