GB/T 4702.4-1984 Chemical analysis of chromium metal - EDTA volumetric method for determination of iron content GB/T4702.4-1984 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chermical analysis of chromium metalThe EDTA volumetric method forthe determination of Iron contentThis standard is applicable to the determination of chromium metal content, with a determination range of less than 1.00%. UDC 669.26 : 543
.244.6:546bzxZ.net
GB 4702. 484
This standard complies with GB1467-1978 "General Principles and General Provisions of Standards for Chemical Analysis Methods of Metallurgical Products". 1 Method Summary
The sample is decomposed with perchloric acid, and ammonium hydroxide is used to adjust the alkalinity to separate most of the chromium. The hydroxide is dissolved and precipitated with perchloric acid and nitric acid. Sodium chloride is added while the chromium is volatile as chromyl chloride. The salt is dissolved with water. After adjusting the pH, sulfosalicylic acid is used as an indicator and titrated with EDT A standard solution. The percentage of iron is calculated based on the consumption of the standard solution. 2 Reagents
2.1 Sodium chloride, used after heating and drying.
2.2 Nitric acid (specific gravity 1.42).
2.3 Hydrochloric acid (1 + 4).
2.4 Pernitrogen acid (specific gravity 1.67).
2.5 Ammonium hydroxide (specific gravity 0.90).
2.6 Ammonium chloride solution (2%).
2.7 Ammonium acetate solution (25%).
2.8 Sulfosalicylic acid.
2.9 Ammonia buffer solution (pH 10): Weigh 67.5g ammonium chloride, place in a 1000ml volumetric flask, add 570ml hydrogen water, dilute to scale with water, and mix well.
2.10 Zinc standard solution (0.01000M)
Weigh 0.6538g pure zinc (99.99%), place in a 300ml conical flask, install a funnel, add 15ml hydrochloric acid (1+1), wait for the violent reaction to stop, slowly heat to completely dissolve, cool to room temperature, transfer to a 1000ml volumetric flask, dilute to scale with water, and mix well. 2.11 EDTA standard solution (0.01M)
2.11.1 Preparation
Weigh 3.7225g monosodium ethylenediaminetetraacetic acid [C. Hl, ON, Naz2H, O], dissolved in 400ml water, transferred to a 1000 volumetric flask, diluted to scale with water, and mixed.
2.11.2 Calibration
Pipette 25.00ml EDTA standard solution (2.11.1), put it into a 250ml conical flask, add 75ml water, 10ml ammonia buffer solution (2.9), add 3 drops of chrome black T solution*, and titrate with zinc standard solution (2.10) until red. : Weigh 0.2g chrome black T in a 50ml beaker, add 15ml 1-ethanolamine, 5m ethanol (95%), and mix well. Issued by the National Bureau of Standards on October 4, 1984
Implemented on September 1, 1985
Calculate the concentration of the EDTA standard solution according to the following formula: Where: A——Concentration of zinc standard solution, M; GB4702.4
M2——Concentration of EDTA standard solution after calibration: M[-—Volume of zinc standard solution consumed, m!V,—Volume of EDTA standard solution, ml. 3 Sample
The sample should pass through a 1.68mm sieve
4 Analysis steps
4.1 Sample
Weigh 1.000g of sample.
4.2 Empty test
The test sample is tested with an empty door.
4.3 Determination
4.3.1 Place the sample (4.1) in a 500ml beaker, cover the surface, add 40ml perchloric acid (2.4) and heat to decompose. When the sample is heated and evaporated to produce smoke, the perchloric acid vapor flows along the inner wall of the beaker. Continue heating for 15 minutes, remove and cool. 4.3.2 Add about 200ml water, neutralize with ammonium hydroxide (2.5) to slightly alkaline, boil and let stand for 1 to 2 minutes, filter with quantitative filter paper, wash the precipitate and filter paper with warm ammonium chloride solution (2.6), and transfer the precipitate and filter paper to the original beaker. 4.3.3 Add 20 ml of perchloric acid (2.4) and 10 m nitric acid (2.2), heat until smoke is generated, continue heating until the vapor of perchloric acid refluxes along the inner wall of the beaker, add 2% sodium chloride (2.1) several times while heating, volatilize the remaining chromium, and then smoke for about 10 minutes. Cool.
4.3.4 Add about 200 ml of warm water to dissolve the salts, add 2 ml of ammonium acetate solution (2.7), adjust the solution to pH 2.0-2.2 with hydrochloric acid (2.3) or ammonium hydroxide (2.5), add about 0.1 g of sulfosalicylic acid (2.8), and titrate with FDTA standard solution (2.11) until the solution changes from reddish purple to dark brown or light yellow. 5 Calculation of analysis results
Calculate the percentage of iron as follows:
Mz·Vx0.05585
Fe(%) =
Wherein: M——concentration of EDTA standard solution after calibration, M; V——volume of EDTA standard solution consumed, mlmo——sample volume. gt
0.05585-1ml1MEDTA standard solution is equivalent to the amount of iron, g. The analysis results are expressed to the decimal place.
6 Tolerance
The difference in analysis results between laboratories should not be greater than the tolerance specified in the following table. ×100
20.50 -1.00
GB 4702. 4—B4
Additional remarks:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard was drafted by Hunan Ferroalloys. From the month of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB582-65 "Methods for Chemical Analysis of Metallic Chromium" will be invalidated.
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