GB/T 4702.7-1984 Chemical analysis of chromium metal - Determination of iron content by atomic absorption spectrophotometry

GB/T 4702.7-1984 Chemical analysis of chromium metal - Determination of iron content by atomic absorption spectrophotometry GB/T4702.7-1984 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemical analysis of chromium metal
Determination of iron content by atomic absorption spectrophotometry
Methods for chemical analysis of chromium metalThe atomic absorption spectrophotomtetric methodfor the determination of iron contentThis standard is applicable to the determination of iron content in chromium metal. Determination range: less than 1.00%. This standard complies with GB1467-78 "General Principles and General Provisions for Chemical Analysis Standards for Metallurgical Products". 1 Method Summary
UDC 669.26: 543
422: 546.72
GB 4702.7-84
The sample is decomposed with perchloric acid to generate smoke, then diluted with water to a certain volume, and the absorbance of iron is measured with an atomic absorption spectrophotometer.
2 Reagents
2.1 Perchloric acid (specific gravity 1.67).
2.2 Chromium standard solution: Weigh 1.0000g electrolytic chromium, place in a 500ml beaker, cover with a watch glass, add 15ml perchloric acid (2.1), heat to decompose, continue heating for about 10min to make it smoke, add about 50ml warm water to dissolve the salt after cooling, transfer to a 100ml volumetric flask, cool to room temperature, dilute to scale with water, and mix. This solution contains 10.0mg chromium per ml. 2.3 Iron standard solution: Weigh 0.1000g iron (99.9% or more), place in a 300ml beaker, cover with a watch glass, add 30ml hydrochloric acid (1+1), heat to decompose, add 12ml nitric acid (11) and boil for about 10min, cool and transfer to a 1000ml volumetric flask, dilute to scale with water, and mix. This solution contains 0.1mg iron per ml.
3 Instruments
Atomic absorption spectrophotometer with an iron hollow cathode lamp. Under the best operating conditions of the instrument, any atomic absorption spectrophotometer that meets the following indicators can be used. The instrument operating conditions are shown in Appendix B (reference).
Minimum sensitivity: 1. Among the standard solutions of equal concentration used in the curve, the absorbance of the highest concentration standard solution should not be less than 0.35. Curve linearity: Among the standard solutions of equal concentration, the absorbance difference between the two highest concentration standard solutions should not be less than 0.9 times the absorbance difference between the lowest concentration standard solution and the empty solution. Minimum stability: The highest concentration used in the working curve The coefficient of variation of the absorbance obtained by multiple measurements of the concentration standard solution and the blank solution relative to the average absorbance of the highest concentration standard solution should be less than 1.3% and 0.6% respectively. The calculation of the coefficient of variation is shown in Appendix A (Supplement).
4 Sample
The sample should pass through a 1.68mm sieve.
5 Analysis steps
5.1 Determination data
Published by the National Bureau of Standards on October 4, 1984
Implemented on September 1, 1985
GB 4702.7 -84
The same sample solution should be tested twice and the average value should be taken. 5.2 Sample quantity
Weigh 1.000g of sample.
5.3 Empty test
Carry out an empty test with the sample.
5.4 Determination
5.4.1 Place the sample (5.2) in a 500ml beaker, cover with a cover, add 15ml of perchloric acid (2.1), heat to decompose, and continue heating to evaporate for about 10 minutes to make it If smoke is generated, remove the bottle and cool to room temperature. 5.4.2 Add 50 ml of warm water to dissolve the soluble salts, filter the solution into a 100 ml volumetric flask with quantitative filter paper, wash the beaker and filter paper with warm water, cool to room temperature, dilute to the mark with water, and mix. 5.4.3 Transfer 10.00 ml of solution (5.4.2) into a 100 ml volumetric flask, dilute to the mark with water, and mix. 5.4.4 Adjust the original absorption spectrophotometer to the best working state, take the test solution (5.4.3) and place it in the original On the absorption spectrophotometer, at the analytical line of 248.3 nm, in an air-diyne flame, use water to adjust the zero point to measure its absorbance, subtract the absorbance of the air accompanying the sample from the measured absorbance, and find out the corresponding iron content from the curve. 5.51 Plotting the curve
5.5.1 Take 0, 0.50, 1.00, 1.50, 2.00 ml of the iron standard solution (2.3) and place them in ten groups of 100 ml volumetric flasks, respectively, and add 10 ml of the chromium standard solution (2.3) to each group. 2) Dilute with water to the scale and mix well. Measure its absorbance as follows in 5.4.4. 5.5.2 Draw a curve with the amount of iron as the horizontal axis and the absorbance (minus the absorbance of the reagent blank) as the vertical axis. 6 Calculation of analysis results
Calculate the iron content according to the following formula:
Where: m,--the amount of iron obtained from the curve, mg; mo\--the amount of sample, g;
the ratio of the test solution to the sample.
The analysis results are expressed to the decimal point. The allowable difference
ma -r× 1000
The difference in the analysis results between laboratories is not less than the allowable difference listed in the following table. Iron
0.50~1.00
GB4702.7—~84
Appendix A
Calculation of the minimum stability coefficient of variation
(Supplement)
The coefficient of variation of the absorbance reading of the empty solution of the highest concentration standard solution is calculated as follows: S.
Formula: Ss-
Z (o- a)2
-Percent coefficient of variation of the absorbance of the highest concentration standard solution; S,-Percent coefficient of variation of the absorbance of the empty solution; C———Absorbance of the highest concentration standard solution;-Average value of the absorbance of the most distant concentration standard solution; C
o—Absorbance of the empty solution;
c——Average value of the absorbance of the empty solution; n
-Number of measurements.
·（A2）
GB 4702.7—B4
Appendix B
Instrument working conditions
（reference）
Use WYX-401 atomic absorption spectrophotometer to determine the iron content, analysis line
Additional instructions:
Lamp current
Working conditions are shown in the following table:
0.5kgf/cm2(0.049MPa)
1.8kgf/cm2(0.177MPa)
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. Fire
3.2~3.41/minWww.bzxZ.net
13.31/min
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB582--65 "Methods for Chemical Analysis of Chromium" shall be invalid.
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