GB/T 4702.3-1984 Chemical analysis method for chromium metal - Determination of phosphorus content by molybdenum blue photometry GB/T4702.3-1984 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Methods for chemical analysis of chromium metalThe molybdenum blue photometric method forthe determinatlon of phosphorus contentThis standard applies to the determination of phosphorus content in chromium metal. Determination range: 0.002~0.040%. UDC 669.26: 543
.4: 546.18
GB 4702. 8—84
This standard complies with GB1467-78 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". 1 Summary of the method
The sample is dissolved in perchloric acid and heated until white smoke is emitted to oxidize phosphorus to orthophosphoric acid. Chromium is dispersed with perchloric acid and sodium chloride, and then iron is reduced with sodium bisulfite. Phosphorus reacts with ammonium sulfate and hydrazine sulfate to form molybdenum blue, and its absorbance is measured. 2 Reagents
2.1 Sodium chloride, use after drying.
2.2 Homoic acid (specific gravity 1.67).
2.3 Hydrochloric acid (specific gravity 1.19).
2.4 Sodium bisulfite solution (10%).
2.5 Color developer solution;
2.5.1 Weigh 20g ammonium molybdate [(NH.)MoO2g·4H,O], dissolve in 100ml warm water, add 700ml sulfuric acid (1+1), cool to room temperature, dilute to 1000ml with water, and mix. 2.5.2 Weigh 1.5g sodium sulfate, dissolve in water and dilute to 1000ml, mix. 2.5.3 When using, take 25ml (2.5.1) solution, 10m! (2.5.2) solution and 65ml water, mix. Use 25ml each time. 2.6 Phosphorus standard solution:
2.6.1 Weigh 0.4394g of potassium dihydrogen phosphate (KH2PO4) which has been dried to constant weight at 110℃ and stored in a desiccator, dissolve it in water and transfer it to a 1000ml volumetric flask, dilute it to the mark with water and mix it. This solution contains 0.1mg phosphorus in 1ml. 2.6.2 Transfer 25.00ml of phosphorus standard solution (2.6.1) to a 500ml volumetric flask, dilute it to the mark with water and mix it. This solution contains 5μ phosphorus in 1ml.
3 Instruments
Spectrophotometer.
4 Sample
The sample should pass through a 1.68mm sieve.
5 Analysis steps
6.1 Sample quantity
Weigh the sample according to Table 1.
National Bureau of Standards Issued on October 4, 1984
Implemented on September 1, 1985
5.2 Empty test
Each company's sample is tested empty.
5.3 Determination
GB 4702. 3-84
Sample,
5.9.1 Place the sample (5.1) in a 1300ml beaker and cover it with a beaker. Add 20ml perchloric acid (2.2), heat and dissolve the sample until perchloric acid smoke appears, continue heating to make the perchloric acid smoke reflux in the beaker for about 10 minutes, slowly add 5ml hydrochloric acid (2.3) to disperse the chromium, continue heating to oxidize the reduced chromium, repeatedly add 5ml hydrochloric acid (2.3) to volatilize the chromium, add 1g sodium chloride (2.1) while heating, repeatedly volatilize the chromium several times until it is exhausted and continue to use smoke to drive out chlorine. Remove and cool, add about 40ml of water, and heat to dissolve soluble salts. Filter with filter paper containing a small amount of filter paper pulp into a 250ml volumetric flask, and wash with warm water 4 to 5 times. Cool to room temperature with running water. Dilute to scale with water and mix. 5.8.2 Transfer 25.00ml of solution to a 100ml volumetric flask, add 10ml of sodium bisulfite solution (2.4), and heat in a boiling water bath until the solution becomes colorless. Add 25ml of color developer solution (2.5.3), and heat in a boiling water bath for 15 minutes. Cool to room temperature with running water, dilute to scale with water, and mix.
5.3.3 Transfer part of the solution (5.3.2) to an appropriate colorimetric medium, and measure its absorbance at a wavelength of 825nm on a spectrophotometer using the blank test solution accompanying the sample as a reference. Find the corresponding phosphorus content from the curve drawn above. 5.4 Drawing of working curve
6.4,1 Take 0, 1.00, 2.00, 3.00, 4.00, 5.00 ml of phosphorus standard solution (2.6.1) and place them in 100 ml beakers respectively. Add 5 ml of perchloric acid (2.2) to each beaker. Heat and evaporate until white perchloric acid smoke appears for 10 minutes. Remove and cool. Add about 40 ml of water and heat to dissolve soluble salts. Filter into a 250 ml volumetric flask with filter paper with a little mouse filter paper pulp and wash with warm water 4 to 5 times. Cool to room temperature with running water. Dilute with water to the scale and mix well. The following is carried out according to 5.3.2 to 5.3.3 (only with the reagent blank as the reference). Measure its absorbance, and draw a line L with phosphorus as the horizontal coordinate and absorbance as the vertical coordinate. 6 Calculation of analysis results
Calculate the phosphorus content according to the following formula:
Where: m
P(%)) =
The maximum phosphorus value found from the E curve, g
Sample volume, g,
Test solution ratio.
Analysis results are expressed to the decimal place.
Tolerance
ml×100
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 2. 2
n.002 - 0.00.
0.005~0,010
0.010~0.040www.bzxz.net
GB 4702. 3—84
Additional remarks:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is issued by Hunan Ferroalloys. From the date of implementation of this standard, the original metallurgical industry standard YR582-65 "Methods for Chemical Analysis of Chromium" shall be invalidated.
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