GB 4333.6-1988 Chemical analysis methods for ferrosilicon - The diphenylcarbohydrazide photometric method for the determination of chromium content

This standard specifies the determination of chromium content by diphenylcarbazide photometric method. This standard is applicable to the determination of chromium content in ferrosilicon. Determination range: 0.10 0% - .60 0% GB 4333.6-1988 Chemical analysis method for ferrosilicon Determination of chromium content by diphenylcarbazide photometric method GB4333.6-1988 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemical analysis of ferrosiliconbZxz.net
The diphenylcarbazide photometric method forthe determination of chromium contentSubject content and scope of application
This standard specifies the diphenylcarbazide photometric method for the determination of chromium content. This standard is applicable to the determination of chromium content in ferrosilicon. Determination range: 0.100%～0.600%. 2 Method summary
UDC 669.15/782
:543.42:546
GB 4333.6-- 88
Replaces GB4333.6—84
The sample is dissolved with nitric acid and fluoric acid, and perchloric acid is fumed. Sodium carbonate is used to separate interfering elements such as iron and manganese. Chromium reacts with diphenylcarbonyl in a sulfuric acid medium to form a soluble purple-red complex, and its absorbance is measured at a wavelength of 550nm on a spectrophotometer. 3 Reagents
3.1 Nitric acid (pl.42g/mL).
3.2 Hydrofluoric acid (pl.15g/mL).
3.3 Perchloric acid (pl.67g/mL).
3.4 ​​Sulfuric acid (1 +4).
3.5 Silver nitrate solution (5mg/mL).
3.6 Ammonium persulfate solution (0.2g/mL). Sodium carbonate solution (0.2g/mL).
Manganese sulfate solution (10 mg/mL).
Diphenylcarbohydrazide ethanol solution (2mg/mL): Weigh 0.20g diphenylcarbohydrazide, place in a 150mL beaker, add 10mL acetic acid and 90mL anhydrous acetic acid, stir to dissolve, and prepare when needed. 3.10 Phenol ethanol solution (1mg/mL).
3.11 Iron solution: Weigh 86.34g ammonium ferric sulfate [NH,FeSO,)·12HzO], place in a 300mL beaker, dissolve with water, add 50mL sulfuric acid (3.4), transfer to a 1000mL volumetric flask, dilute with water to the mark, and mix. This solution contains 10mg iron in 1mL. 3.12 Manganese solution: Weigh 2.749g manganese sulfate, place in a 300mL beaker, dissolve with water, transfer to a 1000mL volumetric flask, dilute with water to the mark, and mix. This solution contains 1mg manganese in 1mL. 3.13 Chromium standard solution: Weigh 0.2829g of potassium dichromate standard reagent that has been dried at 150C and constant, place it in a 150mL beaker, dissolve it with water, transfer it to a 1000mL volumetric flask, dilute it to the mark with water, and mix it. This solution contains 100μg chromium in 1mL. 4 Sample
The sample should pass through a 0.125mm sieve.
Approved by the Ministry of Metallurgical Industry of the People's Republic of China on September 8, 1988 10G
Implemented on January 1, 1990
5 Analysis steps
5.1 Sample quantity
Weigh 0.2000g of sample.
5.2 Blank test
Perform a blank test with the sample.
5.3 Determination
GB 4333.6--88
5.3.1 Place the sample (5.1) in platinum III, add 5mL nitric acid (3.1), add 3~5mL hydrofluoric acid (3.2) dropwise, until the sample is completely dissolved, add 5mL perchloric acid (3.3), heat on an electric furnace and evaporate until perchloric acid smoke appears for about 3 minutes. Remove and cool slightly, rinse the dish wall with water, continue heating and evaporating until perchloric acid smoke appears for about 1 minute. Remove and cool slightly, add about 20mL water, heat again to dissolve the salts, transfer to a 200mL beaker, and adjust the volume to about 80mL with water.
5.3.2 Add 3mL silver nitrate solution (3.5) and 5mL ammonium persulfate solution (3.6), heat and boil on an electric furnace to fully oxidize the chromium and completely decompose the ammonium persulfate. Remove and cool slightly, carefully add sodium carbonate solution (3.7) to make the solution about pH 9 (check with pH test paper), heat to boiling, remove and cool. Add manganese sulfate solution (3.8) dropwise until the red color disappears. Transfer to a 200mL volumetric flask, dilute to scale with water, and mix well. Dry filter and discard the first 5-10mL solution that flows out. Transfer 20.00mL of filtrate (if the chromium content is greater than 0.40%, transfer 10.00mL of filtrate), place in a 100mL volumetric flask, add 1 drop of phenol anhydride ethanol solution (3.10), neutralize with sulfuric acid (3.4) until the red color disappears and 1-2 drops are in excess, add 3mL of sulfuric acid (3.4), 60mL of water, and 5mL of diphenylcarbazide ethanol solution (3.9), mix, dilute to scale with water, and mix. 5.3.3 Transfer part of the solution into 1cm colorimetric III, and measure its absorbance at a wavelength of 550nm on a spectrophotometer using the blank solution prepared with the sample as a reference. Find the corresponding chromium content from the working curve. 5.4 Drawing of working curve
5.4.1 Transfer 0, 1.00, 3.00, 5.00, 7.00, and 9.00mL of chromium standard solution (3.13) to a set of 200mL beakers, add 15mL of iron solution (3.11), 1.5mL of manganese solution (3.12), and 4mL of perchloric acid (3.3), and adjust the volume to about 80mL with water. Proceed as in 5.3.2.
5.4.2 Transfer part of the solution into 1cm colorimetric III, and measure its absorbance at a wavelength of 550nm on a spectrophotometer using the reagent blank as a reference. Draw a working curve using the chromium content as the abscissa and the absorbance as the ordinate. 6 Calculation of analysis results
Calculate the percentage of chromium according to the following formula:
Cr(%) = 3
× 100
Wherein: m---the amount of chromium found from the working curve, g; V——total volume of test solution, mL;
i-volume of test solution taken, mL;
n——sample volume, g.
7 Allowable difference
The difference in analysis results between laboratories should not be greater than the allowable difference listed in the following table. 107
Additional instructions:
0.100~0.250
0.2500.600
This standard was drafted by Nanjing Ferroalloy Factory.
Who drafted this standard? Wang Rude Wan Meiju 108
GB4333.6-88
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