GB/T 4324.7-1984 Chemical analysis method for tungsten - Determination of cobalt content by photometric method with cobalt reagent GB/T4324.7-1984 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Chemical analysis method of tungsten
Determination of cobalt content by photometric method with cobalt reagent
Methodsfor chemicalanalystsoftungstenThef-cl-PADABphotometricmethodforthedeterminati on of cobalt contentUDC 669.27 : 543
.42:546.73
GB 4324.7--84
This standard is applicable to the determination of cobalt content in pigeon powder, tungsten bar, tungsten trioxide, tungstic acid and ammonium paratungstate. Determination range: 0.0007~0.012%. This standard complies with GB1467-78 "General Principles and General Provisions of Chemical Analysis Methods for Metallurgical Products": 1 Method Summary
The sample is decomposed with hydrogen peroxide or sodium hydroxide, and the main tungsten is complexed with potassium sodium tartrate. The cobalt reagent forms an orange-red complex with cobalt in a phosphate buffer solution with a pH of 6 to 7. Its absorbance is measured in a phosphoric acid medium. 2 Reagents
Hydrogen peroxide (specific gravity 1,10).
2.2 Sulfuric acid (1 + 1).
2.3 Phosphoric acid (6 M).
2.4 Sodium hydroxide solution (20%).
2.5 Potassium sodium tartrate solution (40%).
2.64 ~ [(5-chloro-2-pyridyl) azo] -1,3-diaminobenzene (cobalt reagent) ethanol solution (0.05%). Store in a brown bottle.
2.7 Buffer solution: weigh 35.5g disodium hydrogen phosphate and dissolve it in 500ml water; weigh 34g potassium dihydrogen phosphate and dissolve it in 500ml water, mix the two evenly (pH6 ~ 7), and set aside.
2.8 Phenol-ethanol solution (0.1%).
2.g pH test paper (pH1 ~ 14).
Bis-distilled water (this water is used in this method). 2.11 Cobalt standard solution
2.11.1 Weigh 0.1000g metal cobalt (more than 99.9%), put it in a 250ml beaker, add 10ml nitric acid (1+1) to dissolve it, add 10ml sulfuric acid (2.1), heat until white sulfuric acid smoke appears, remove and cool, wash the surface with water, add 30ml water, boil, cool, transfer to a 1000ml volumetric flask with water, dilute to the scale, and mix evenly. 1 ml of this solution contains 0.1 mg of cobalt. .11.2 Take 50.00 ml of the cobalt standard solution (2.11.1) and place it in a 500 ml volumetric flask, dilute to the mark with water and mix well. 1 ml of this solution contains 0.010 mg of cobalt.
3 Sample
The tungsten bar should be crushed and pass through a 120-month sieve.
4 Analysis steps
4. 1 Quantity to be measured
National Bureau of Standards 1984-04-12 Issued
1985-03-01 Implementation
- GB 4324.7-84
Three samples should be weighed for measurement during analysis. The measured values ​​should be within the allowable difference in the room and the average value should be taken. 4.2. Sample section
Weigh the sensitive sample cover according to Table 1.
Drill, along
0.0007 ~0. (0)20
0.0020~0.0080bzxz.net
0. 0080 ~ 0., 012
4.a Blank test
Carry out blank test together with the sample.
4. 4 Determination
Tungsten powder, pigeon
Sample amount: g
:: 0:4600
Put the sample (4.2) in a 250ml beaker, add 1-2ml water to moisten it, cover it with a beaker, and slowly add 10ml hydrogen peroxide (2.1) twice while shaking continuously. Leave it to decompose. After the violent reaction stops, add 5m hydrogen peroxide (2.1) and heat it at a low temperature to decompose the sample completely (the solution is clear). Rinse the beaker III and the wall of the beaker with water (no longer cover it), continue heating and evaporating it to dryness, and repeat this process for times. Remove it and cool it. Add 5ml sodium hydroxide solution (2.4) and heat to dissolve it until the solution is clear. Add 10ml sodium hydroxide solution (2.5) and 3ml sulfuric acid (2.2), cool it down. Add 1-2 drops of phenol ethanol solution (2.8), add sodium hydroxide solution (2.4) to neutralize it until the solution turns slightly red, and then add sulfuric acid (.2) to remove the red color (pH 6-8). Check it with pH test paper. Dilute the blanket with water to about 40ml, add 1.50ml cobalt reagent ethanol solution (2.6); mix well, add 5ml of the rinse solution 4.4.1,3
(2.7), stir, place the beaker in a boiling water bath and heat for 5min, cool to room temperature, transfer to a 100ml colorimetric tube with water and control the volume not to exceed ml, add 40ml phosphoric acid (2.3), dilute to the scale with water, and mix. Transfer part of the solution to a 2cm colorimetric tube.
4.4.1.4 Take the blank made with the sample as a reference, measure its absorbance at a wavelength of 550nm with a spectrophotometer, and find the corresponding cobalt maximum from the working curve.
4.42 Tungsten trioxide, tungstic acid, ammonium paratungstate Place the sample (4.2) in a 250ml beaker, add 5ml sodium hydroxide solution (2.4), heat and dissolve until the solution is clear, add 10ml potassium sodium tartrate solution (2.5) and 3ml sulfuric acid (2.2), and cool. The following is carried out according to 4.4.1.2 to 4.4.1.4. 4. 5 Drawing of working curve
: Take 0.00, 0.25, 0.50, 1.00, 1.50, 2.00ml of cobalt standard solution (2.11.2), respectively, and place them in a group of 250ml beakers, dilute them with water to about 10ml, add 10ml potassium sodium tartrate solution (2.5), and the following is carried out according to 4.4.1.2 to 4.4.113, using the reagent blank as a reference to measure its absorbance. With the amount of cobalt as the horizontal axis and the absorbance as the vertical axis, draw a working curve. 5 Calculation of analysis results
Calculate the percentage of cobalt according to the following formula
Where mi
is the amount of cobalt found from the working curve, name
: m-amount of sample, g.
Allowable difference
GB 4324.7--84
The difference in analysis results between laboratories should not be greater than the allowable difference listed in Table 2. Table 2
0.0007~0.0015
>0.0015~0.0025
>0, 0025 ~0. 0050
>0.00500,0080
>0.0080~0.0120
Additional remarks,
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. This standard is drafted by Zhuzhou Cemented Carbide Factory. This standard is drafted by Zhuzhou Cemented Carbide Factory.
The main drafters of this standard are Liu Tingzhu and Yang Jinge. Allowable difference
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