GB/T 4324.21-1984 Chemical analysis of tungsten - Determination of chromium content by diphenylcarbohydrazide photometric method GB/T4324.21-1984 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis methods of tungsten
The diphenylcarbazide photometric method forthe determination of chromium content UDC 669.27: 543
.52: 546.76
GB 4324.21—84
Applicable to the standard for the determination of chromium content in pigeon powder, hook strips, tungsten trioxide, pigeon acid, and ammonium para-piperate. Determination range: 0.0002-0.030%. This standard complies with GB1467-78 "General Principles and General Provisions for Chemical Analysis Methods of Metallurgical Products". 1 Method Summary
The sample is decomposed with sulfuric acid and ammonium sulfate, and beryllium hydroxide is used as a carrier to coprecipitate chromium at pH 8-9 and separate it from the upper body tungsten. Dissolve the precipitate with sulfuric acid, add chromium disulfide to form a purple-red complex with chromium, and measure its absorbance. 2 Reagents
Ammonium sulfate (superior grade).
Anhydrous sodium sulfate.
Sulfuric acid (specific gravity 1.84)
Sulfuric acid (1N),
Phosphoric acid (1+1).
Sodium hydroxide (superior grade) solution (40%). Sodium azide solution (5%).
Beryllium sulfate solution (2%)
Washing liquid: 1% ammonium sulfate solution, reduced to pH 9 with sodium hydroxide solution (2.6). Potassium permanganate solution (0.3%).
Phenol 7 alcohol solution (0.1%).
Phenylcarbonyl diacetone solution (0.5%), prepared at the same time. Subdistilled water (this method uses this water). 2.14
Chromium standard solution
Take 0.2263g of potassium dichromate pre-dried at 140-150°C, dissolve it in water, transfer it to a 1000ml volumetric flask with water, 2. 14.1
and dilute to the mark, swirl. This solution contains 80μg chromium in 1ml. 2.14.2Take 5.00ml of chromium standard solution (2.14.1), place it in a 100ml beaker, add 20ml of water, 5ml of sulfuric acid (2.4), and a few grains (about 3m) of sodium sulfite (2.2), boil to remove sulfur oxides, cool, transfer it to a 200ml volumetric flask, dilute to the mark with water, and mix well. This solution contains 2μg chromium in 1ml. 3 Sample
Tungsten bar should be crushed and pass through a 120 mesh.
National Bureau of Standards Issued on April 12, 1984
Implementation on March 1, 1985
Analysis steps
GB 4324.21--84
4.1 Determination quantity
One sample should be weighed for determination during analysis. The measured value should be within the allowable difference in the case, and the median value should be taken. 4.2 Sample quantity
Weigh the sample quantity according to Table 1.
.00026-0.0010
2.0010~0.010
2-0.010~0,030
4.3 Blank test
Carry out a blank test together with the sample.
Sample,
4.4 Determination
4.41 Place the sample (4.2) in a 1300ml beaker, add 6g ammonium sulfate (2.1), 10ml sulfuric acid (2.3, heat to dissolve. 4.4.2 Remove and cool slightly, add 150ml water, mix well, add a drop of phenol ethanol solution (2.1), use sodium hydroxide solution (2.6) ift and the whole solution just turns red, add 12 drops in excess, heat, add 5ml sulfuric acid plating solution (2.8), Boil and wash for 2-3 minutes (the solution is pH 8-9), cool and let stand for 1 hour, filter, wash the precipitate and beaker with hot washing solution (2.9) 5 times each, dissolve the precipitate in a 50-ml volumetric flask with hot 25 ml sulfuric acid (2.), and wash the filter paper once with hot water. 4.4.3 Add 2 ml phosphoric acid (2.5), mix, add 6 drops of potassium permanganate solution (2.10), mix, heat in a water bath for 15-20 minutes, and add sodium azide solution (2.7) until the red color of the solution disappears (drops Add the mixture for 15 seconds), cool, dilute with water to 40 ml, and keep the mixture. Add 2 ml of phenylcarbazide solution (2.12), dilute with water to the mark, mix well, and transfer the solution to a 3 cm colorimetric area.
4.4.4 Take the white sample prepared with the figure as a reference, measure its absorbance at a wavelength of 540 nm on a spectrophotometer, and find the corresponding path from the curve 1.
4.5 Drawing of the working curve
Pipette 0.00, 1. 00, 2.00, 3.00, 4.00, 5.00, 6.00, 7.50 ml of chromium standard solution (2.11.2) are respectively placed in a 300 ml beaker and ammonium sulfate (2.1) is added. The following is carried out according to 4.4.2 to 4.4.3, using the reagent as a reference and measuring its absorbance. Using the chromium content as the horizontal axis and the absorbance as the vertical axis, draw a working curve. 5 Calculation of analysis results
The following formula allows the chromium content to be calculated:
Cr (%) =
Formula: m, the amount of chromium obtained from the above curve, gm-sample,.
6 Allowable difference
× 100
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 2. Additional period:
0.00020 ~0.00050
20.00150
20.00150~0.00400
-0.0040~0.0080
.>0.008 ~ 0.015
-0.01 5~0.030
GB4324.21-84wwW.bzxz.Net
This standard was proposed by the Ministry of Metallurgy of the People's Republic of China. It was drafted by Zhuzhou Cemented Carbide Co., Ltd. This standard was drafted by Zhuzhou Cemented Carbide Co., Ltd. The main drafter of the standard was Chen Guohua.
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