GB/T 4702.6-1984 Chemical analysis of chromium metal - EDTA volumetric method for determination of aluminum content GB/T4702.6-1984 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemical analysis of chromium metalThe EDTA volumetric method for thedetermination of aluminium contentThis standard is applicable to the determination of aluminium content in metallic chromium, with a determination range of 0.20-1.00%. UDC 669.244.6
: 546.721
GB 4702.6--84
This standard complies with GB1467-1978 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". 1 Summary of the method
The sample is decomposed with perchloric acid and adjusted to alkalinity with ammonium hydroxide to separate most of the chromium. Use perchloric acid and nitric acid to dissolve the hydroxide precipitate, use sodium chloride to volatilize chromium in the form of chromyl chloride while smoking, dissolve the salt with water, adjust the pH, use sulfosalicylic acid as an indicator, use EDTA standard solution to titrate iron, adjust the pH and heat, use Cu-PAN as an indicator, and use EDTA standard solution to titrate. 2 Reagents
2.1 Sodium chloride: Use after heating and drying.
Nitric acid (specific gravity 1.42).
Hydrochloric acid (1+4).
Perchloric acid (specific gravity 1.67).
Ammonium hydroxide (specific gravity 0.90).
Ammonium chloride solution (2%).
Ammonium acetate solution (25%).
Ammonium acetate solution (2%).
Sulfosalicylic acid.
Ammonia buffer solution (pH 10): weigh 67.5g ammonium chloride and place it in a 1000ml volumetric flask, add 570ml ammonia water, dilute with water 2.10
to the mark, and mix.
Cu-PAN solution: dissolve 1g Cu-PAN [mixture of Cu-EDTA and 1-2-pyridyl azo-2-naphthol] 2.11
in 100ml isopropanol (50%). Because the null value of Cu-PAN indicator is sometimes negative, the Cu-PAN solution should not be negative.
2.12 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 dissolve it completely, cool to room temperature, transfer to a 1000ml volumetric flask, dilute to scale with water, and mix well. 2.13 EDTA standard solution (0.01M)
2.13.1 Preparation
Weigh 3.7225g sodium ammonium acetate (CHO, N, Na2·2, O), dissolve in 400ml water, transfer to a 1000ml volumetric flask, dilute to scale with water, and mix well.
2.13.2 Calibration
Pipette 25.00ml EDTA standard solution (2.13.1), place in a 250ml conical flask, add 75ml water, 10ml ammonia buffer solution (2.10), add 3 drops of chrome black T solution*, and titrate with zinc standard solution (2.12) until it turns red. Calculate the concentration of EDTA standard solution according to the following formula: Where: Mi——concentration of zinc standard solution, M; Mz=Mi·i
-concentration of EDTA standard solution after calibration, M; M2
Vl is the volume of zinc standard solution consumed, ml; V2 is the volume of EDTA standard solution, ml. 3 Sample
The sample should pass through a 1.68mm sieve.
4 Analysis steps
4.1 Sample quantitywwW.bzxz.Net
Weigh 1.000g of sample.
4.2 Empty test
Perform an empty test with the sample.
4.3 Determination
4.3.tPlace the sample (4.1) in a 500ml beaker, cover with a beaker cover, add 40ml of perchloric acid (2.4) and heat to decompose. When heated to produce white smoke, continue heating for 15 minutes while the perchloric acid vapor refluxes along the inner wall of the beaker, remove and cool. 4.3.2 Add about 200 ml of water, neutralize with ammonium hydroxide (2.5) to slightly alkaline, boil and let stand for 1-2 minutes, filter with quantitative filter paper, wash the precipitate and filter paper with warm ammonium chloride solution (2.6), and move the precipitate and filter paper to the original beaker 1. 4.3.3 Add 20 ml of perchloric acid (2.4) and 10 ml of nitric acid (2.2), heat until smoking, continue heating until the vapor of perchloric acid refluxes along the inner wall of the beaker, and add 2 g of sodium chloride (2.1) several times while heating to volatilize the remaining chromium, and then smoke for 10 minutes. Remove and cool.
4.3.4 Add about 200 ml of warm water to dissolve the salts, add 20 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 (2.9), and titrate with EDTA standard solution (2.13) until the solution changes from reddish purple to colorless or light yellow.
4.3.5 Add ammonium acetate solution (2.8) to adjust the solution to pH 2.9-3.1, heat to above 90°C, immediately add 2-3 drops of CuPAN solution (2.11), and titrate with EDTA standard solution (2.13) until the solution changes from purple-red to yellow. Boil the solution, and if it turns purple-red, continue titrating until it turns yellow. 5 Calculation of analysis results
Calculate the percentage of aluminum by the following formula:
Al(%) =
M2 : V× 0.02698
Formula 41: M2---Concentration of EDTA standard solution after calibration, M; V---Volume of EDTA standard solution consumed by titrating aluminum in the test solution, ml; mo---Sample volume, g,
0.02698---Amount of aluminum equivalent to 1ml1MEDTA standard solution, g. The analysis results are expressed to one decimal place. ×100
*Preparation of chrome black T solution: Weigh 0.2g of chrome black T in a 50ml beaker, add 15ml of triethanolamine and 5ml of ethanol (95%), and mix. 212
Allowable difference
GB4702.6-84
The difference between the analysis results of laboratories should not exceed the allowable difference listed in the following table. Aluminum 1
0.20~0.50
:0.501.00
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 Factory. Supplement
From the date of implementation of this standard, the original Ministry of Metallurgical Industry Standard YB582-65 "Methods for Chemical Analysis of Chromium" shall be invalidated. 213
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