GB/T 4324.28-1984 Chemical analysis of tungsten - Determination of molybdenum content by thiocyanate photometry
Some standard content:
National Standard of the People's Republic of China
Chemical analysis method of tungsten
Thiocyanate photometric method for thedetermimation of molybdenum content in tungsten powder, tungsten bar, tungsten trioxide, pigeon acid and ammonium paratungstate. Determination range: 0.0015~0.35%. This standard complies with GB1467-78 "General Principles and General Provisions of Chemical Analysis Methods for Metallurgical Products". 1 Method Summary
Tungsten powder and tungsten bars are decomposed with hydrogen peroxide, tungsten dioxide, tungstic acid and ammonium paratungstate are dissolved with sodium hydrocyanide, and then tungsten is complexed with citric acid. In sulfuric acid medium, iron sulfate is used as catalyst, and ascorbic acid is used to reduce molybdenum (V) to molybdenum (V), so that pyromethane thiocyanate forms a colored complex, and its absorbance is measured. 2 Reagents
2.1 Citric acid.
Sulfuric acid (specific gravity 1.84).
Sulfuric acid (1 + 1).
Sulfuric acid (4 + 96).
Hydrogen peroxide (specific gravity 1.10).
Butyl acetate.
Sodium hydroxide solution (20%).
Ammonium thiocyanate solution (50%).
Ascorbic acid solution (20%), prepare when needed. Ferrous sulfate solution; weigh 0.100g of metallic iron, place in a beaker, add 10ml of sulfuric acid (1+2), heat until completely dissolved, cool, transfer to a 1000ml volumetric flask, dilute to scale with water, and mix. This solution contains 100μg of iron per ml. 2. 11
Phenol ethanol solution (0.1%).
Bis-distilled water (this method uses this water), 2.18 Molybdenum standard solution
2.13.1 Weigh 0.1500g of molybdenum trioxide (99.9% or more), place in 250ml of beaker, add 20ml of sodium hydroxide solution (10%), heat until dissolved, cool, transfer to a 1000ml volumetric flask, dilute to scale with water, and mix. This solution contains 100μg of molybdenum per ml. 2.13.2 Take 100.0ml of molybdenum standard solution (2.13.1) and place it in a 1000ml volumetric flask, dilute to the mark with water and mix well. This solution contains 10μg of molybdenum per ml.
8 Sample
The tungsten bar should be crushed and passed through a 120-mesh screen.
National Bureau of Standards Issued on April 12, 1984
Implementation on March 1, 1985
4 Analysis steps
GB 4$24.28-84www.bzxz.net
4.1 Determination quantity
Three samples should be weighed for determination during analysis. The measured values should be within the indoor allowable difference and the average value should be taken. 4.2 Sample quantity
Weigh the sample quantity according to Table 1.
Lead, %
>0.008 ~0.10
0.10~0,20
2:0,20~0.30
>0.30~0.35
4.3 Blank test
Carry out a blank test on any sample.
4, 4 Determination
Sample, more
4.4.1 Tungsten powder, tungsten bar
4.4.1.1 Place the sample (4.2) in a 250ml beaker, add 2~3ml water to moisten it, add 5ml hydrogen peroxide (2.5) twice with constant shaking, wait until the violent reaction weakens, then add 10~15ml hydrogen peroxide (2.5) in 23 times), heat at low temperature to completely decompose the sample and evaporate to nearly ten, then remove it. 4.4.1.2 Add 20ml (slowly wash from the blood on the surface into the beaker) of sodium hydroxide solution (2.7), rinse the surface 1 and the wall of the beaker with water, heat to dissolve the pertungstic acid until the solution is clear, boil for several minutes, drive out the hydrogen peroxide, remove and cool, transfer to a 100ml volumetric flask, dilute to the mark with water, and mix. "
4.4.1.3 Transfer 10.00ml of the clear solution (if there is precipitation in the solution, it must be filtered before taking it out), place it in a 50l colorimetric glass containing 3g of citric acid (2.1), shake to dissolve the citric acid, then add 4ml of sulfuric acid (2.3) while shaking, immediately cool with water, add 0.5m ferric sulfate solution (2.10), mix well. Add 1 person 2.0ml of ammonium sulffluoride solution (2.8), mix well, add 2.5m ascorbic acid solution (2.9) is diluted with water to 25.00ml, mixed and left for 30min. 4.4.1.4 Pour part of the solution into a 1cm colorimetric tube, use water as reference, measure its absorbance at a wavelength of 460nm on a spectrophotometer, subtract the absorbance of the blank sample made with the sample, and find the sales volume of the plant from the curve above. 4.4.1.5 For samples with a feed rate less than 0.0080%, follow the steps below Extraction: transfer the solution (4.4.1.3) to a 125ml separatory funnel, wash the original colorimetric tube with 25ml sulfuric acid (2.4) and combine them in a separatory funnel (total volume is 50ml), add 10.0ml of n-acetic acid (2.6), shake for 3min, let stand to separate, discard the aqueous phase, transfer part of the organic phase to a 1cm colorimetric III, and measure the absorbance with n-acetic acid as a reference. Subtract the absorbance of the blank made with the same sample and find the corresponding amount from the working curve. 4.4.2 Pigment trioxide, tungstic acid, ammonium paratungstate Place the sample (4.2) in a 250ml beaker, add 20ml of sodium hydroxide solution (2.7), heat until the sample is completely dissolved, transfer to a 100ml volumetric flask, dilute to the mark with water, and mix. The following is carried out according to 4.4.1.3 to 4.4.1.5. 4.5 Drawing of working curve
GB 4324.28--84
"Drawing curve A": Applicable to samples with a volume of not less than 0.008%. 4.5.1
Pipette 0.00, 0.10, 0.30, 0.50, 1.00, 1.50, 2.00 ml of the standard solution (2.13.1), respectively, into 50 ml colorimetric tubes, rinse the colorimetric tubes with water until the volume of the solution is 10 ml, and measure its absorbance according to 4.4.1.3 to 4.4.1.4, and subtract the absorbance of the reagent space. Draw the curve with the display as the horizontal axis and the absorbance as the vertical axis. 4.5.21 Drawing curve (B): Applicable to samples with a volume of less than 0.0080%. Pipette 0.00, 0.3 0, 0.50, 1.00, 2.00, 3.00 ml of standard solution (2.13.2) are placed in a 50 ml colorimetric tube respectively, and water is added to the colorimetric tube to make it 10 ml, and then proceed to 4.4.1.3 and 4.4.1.5, measure its absorbance, and subtract the absorbance of the reagent tube. Draw a graph with the absorbance as the horizontal axis and the absorbance as the vertical axis. 5
Calculation of analysis results
Calculate the percentage of molybdenum according to the above formula
Where: m is the amount of molybdenum found from the graph, g; VF
·total volume of test solution, mT;
6 Allowable difference
Take the volume of test solution, .ml;
Sample is displayed.
The difference between the analysis results of laboratories should not be greater than the allowable difference listed in Table 2. Table 2
Allowance
0.0015~0.0060
0.0060.012
>0.012~0.020
0.020~0.060
Additional remarks:
This standard is proposed by the Ministry of Metallurgical Industry of the People's Republic of China. Zhuzhou Cemented Carbide Factory is responsible for drafting this standard. This standard is drafted by Zhuzhou Cemented Carbide Factory. The main drafter of this standard is Zhou Xinhua.
Allowance
2*0.060-0.150
>0.150 ~ 0. 250
0.25~0.35
From the date of implementation of this standard, the former Ministry of Metallurgical Industry Standard YB895-77 "Tungsten Chemical Analysis Method" shall be invalid. 100
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