GB/T 4702.11-1985 Chemical analysis methods for chromium metal - Alizarin violet spectrophotometric method for determination of tin content

This standard is applicable to the determination of tin content in metallic chromium. Determination range: 0.0005～0.0020%. This standard complies with GB 1467-78 "General Principles and General Provisions of Chemical Analysis Methods for Metallurgical Products". GB/T 4702.11-1985 Chemical Analysis Method for Metallic Chromium - Alizarin Violet Spectrophotometric Method for Determination of Tin Content GB/T4702.11-1985 Standard Download Decompression Password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemical analysis of chromium metalThe alizarin yiolet spectrophotometric methodfor the determination of tin contentThis standard is applicable to the determination of tin content in metallic chromium. Determination range: 0.0005~0.0020%. This standard complies with GB1467--78 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". 1 Method Summary
UDC 669.26 : 543
42 : 546.811
GB 4702.11—85
This method is based on the oxidation of tin with ammonium persulfate to convert chromium into chromium (VI), and then the separation of tin from ammonium hydroxide by precipitation of tin hydroxide. In an aqueous solution at pH 1.4, the red complex formed by alizarin violet and tin (IV) is extracted with toluene, and the precipitate is dissolved with ethanol. The absorbance is measured at a wavelength of 490 nm using a spectrophotometer. 2 Reagents
2.1 Sulfuric acid (7N), high grade.
2.2 Sulfuric acid (7+93), high grade.
Sulfuric acid (1+3), high grade.
Nitric acid (specific gravity 1.42), high grade.
Hydrochloric acid (1+3), high grade.
Ammonium hydroxide (specific gravity 0.90), high-grade pure. Ammonium hydroxide (1+100), high-grade pure.
Silver nitrate solution (0.25%), high-grade pure. Ammonium persulfate solution (25%), high-grade pure. Hydrogen peroxide (specific gravity 1.10), high-grade pure. Ethanol (anhydrous), high-grade pure.
Toluene, high-grade pure.
Tartaric acid-ascorbic acid mixed solution: Weigh 5g tartaric acid (high-grade pure) and 5g ascorbic acid (high-grade pure) and dissolve them in 20-30ml water, transfer to a 100ml volumetric flask, dilute to the mark with water, and mix well. Prepare before use. 2.14 Alizarin violet ethanol solution (0.1%): Weigh 0.1g Alizarin violet (superior grade), place in a 100ml beaker, add 0.5ml hydrochloric acid (specific gravity 1.19), grind with a glass rod, add 50ml ethanol (2.11), mix and place overnight, filter the solution with fast filter paper into a 100ml volumetric flask, rinse the filter paper with ethanol (2.11) several times and dilute to the mark, mix. 2.15 Ferrous sulfate solution (5%): Weigh 50g ferrous sulfate (superior grade), add 500ml sulfuric acid (1+100), slowly heat to dissolve, filter into a 1000ml volumetric flask, dilute to the mark with water, and mix. This solution contains 14mg iron in 1ml. 2.16 Tin standard solution
2.16.1 Weigh 0.1000g of metallic tin (99.9% or more) and dissolve it in 20ml of hot sulfuric acid (specific gravity 1.84) 4i. After cooling, transfer the solution to a 1000ml volumetric flask, wash with sulfuric acid (2.1) and dilute to the mark, and mix. This solution contains 0.1mg tin per ml. 2.16.2 Transfer 10.00ml of the tin standard solution (2.16.1) to a 100ml volumetric flask, dilute to the mark with sulfuric acid (2.1), and mix. This solution contains 0.01mg tin per ml. Prepare when using. 3 Test specimens
All test specimens should pass through a 1.68mm sieve. bZxz.net
4 Analysis steps
4.1 Sample quantity
Weigh 1.0000g of sample.
4.2 Empty test
Carry out an empty self-test with the sample.
4.3 Determination
4.3.1 Place the sample (4.1) in a 500ml conical flask, add 20ml sulfuric acid (2.3), heat to dissolve, oxidize with 5ml nitric acid (2.4), add 2ml ferric sulfate solution (2.15) and evaporate until sulfuric acid fumes begin to appear, cool, add 50ml water, and heat to dissolve the salts. 4.3.2 Transfer the solution to a 500ml beaker, dilute to 300ml with water, add 25ml silver nitrate solution (2.8), 100ml ammonium persulfate solution (2.9), heat to oxidize the chromium, boil to decompose the excess ammonium persulfate, remove, and add ammonium hydroxide (2.6) until a precipitate is precipitated and 10ml in excess. Heat to condense the precipitate, keep it warm for 15 to 20 minutes. Filter with fast filter paper, rinse the precipitate with hot ammonium hydroxide (2.7) 4 or 5 times, and discard the filtrate. Dissolve the precipitate in the original beaker with 50ml hot sulfuric acid (2.2), and wash the filter paper. 4.3.3 Add 15ml silver nitrate solution (2.8) and 50ml ammonium persulfate solution (2.9) to the solution to oxidize the residual chromium. The following is carried out according to 4.3.2. Rinse the precipitate on the filter paper with hot water and put it into the original beaker. Wash the filter paper with 10ml hydrochloric acid (2.5) and water. Add 1ml hydrogen peroxide (2.10). Heat and evaporate the solution to 40ml. Cool to room temperature. Transfer to a 50ml volumetric flask. Dilute to scale with water and mix. 4.3.4 Take 25.00ml of solution (4.3.3) and place it in a 100ml beaker. Add 4ml of tartaric acid-ascorbic acid mixed solution (2.13). Stir and place for 1-2min. Add 2.00ml of Alizarin violet ethanol solution (2.14). Dilute to 50ml with water. Add ammonium hydroxide (2.6). Use a pH meter to adjust the solution to pH 1.4. Use a small amount of water to transfer the solution to a 100ml separatory funnel 4 and place for 30min. 4.3.5 Add 10 ml of toluene (2.12) to the separatory funnel, shake for 2 minutes, and discard the aqueous phase after standing and separating the layers. Add 7 ml of ethanol (2.11) to the organic phase. Shake to dissolve the precipitate in the separatory funnel 41. Transfer the solution to a 25 ml volumetric flask, wash the funnel wall with ethanol (2.11), add the washing liquid to the volumetric flask, dilute to the scale, and mix well. 4.3.6 Transfer part of the solution to a 2 cm colorimetric tube 1, and measure its absorbance at a wavelength of 490 nm on a spectrophotometer with a mixed solvent of 2 parts toluene (2.12) and 3 parts ethanol (2.11) as a reference. 4.3.7 Subtract the absorbance of the blank test accompanying the sample from the measured absorbance. Find the corresponding tin amount from the working curve. 4.4 Drawing of working curve
4.4.1 Add 80ml sulfuric acid (2.3) and 5ml nitric acid (2.4) to 6 500ml beakers respectively, heat, add 2ml ferric sulfate solution (2.15) while hot and add 0.00, 0.50, 1.00~1.50, 2.00ml tin standard solution (2.16.2) respectively, evaporate the solution until sulfuric acid smoke appears, cool it down, add 50ml water, heat to dissolve the salts, and measure the absorbance according to 4.3.2~4.3.6. 4.4.2 Draw a curve with the amount of tin as the horizontal axis and the absorbance (minus the absorbance of the reagent blank) as the vertical axis. 5 Calculation of analysis results
Calculate the percentage of tin according to the following formula:
Sn(%)=
Wherein: m——the amount of tin found from the working curve, g; mo-——the amount of sample, g;
r-——the ratio of test solution.
The analysis result is accurate to the fourth decimal place. 228
6 Allowable difference
GB4702.1185
The difference in analysis results between laboratories should not be greater than the allowable difference listed in the following table. Tin
0.0005~0.0010
0.00100.0020
Additional remarks:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is drafted by Hunan Ferroalloy Technology Co., Ltd. From the date of implementation of this standard, the former metallurgical industry standard YB582-65 "Methods for chemical analysis of metallic chromium" shall be invalidated.
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