HG 2958.5-1988 Determination of silicon content in celestite ore Molybdenum blue spectrophotometry HG2958.5-1988 standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determinatien of silicon cantent- Molybdenurblum spectrophotamctric method
Celestite ores
Determinatien of silicon cantent- Molybdenurblum spectrophotamctric method1 Subject content and scope of application
This standard specifies the molybdenum blue spectrophotometric method for the determination of silicon content in celestite ores. This standard is applicable to celestite ores with a silicon dioxide content of less than 20%. 2 Method Summary
UDC 549. 761. 3
GB 9018, 588
2958.5-1788
The sample is melted with sodium hydroxide, leached with water and then acidified. Under the condition of pH 1.1 ± 0.2, sodium molybdate and silicate form silicate, which is reduced to a blue complex by ascorbic acid in oxalic acid-sulfuric acid medium. Its absorbance is measured at 700-800 nm by spectrophotometer. 3 Reagents and solutions
This method uses single distilled water or water of equivalent purity. 3.1 Sodium hydroxide (GB 629-81);
3.2 Sodium hydroxide: 10% solution. Store in plastic bottles; 3.3 Sodium perfluoride;
3.4 ​​Anhydrous sodium carbonate (OB639-77);
p-Nitrophenol: 0.5% ethanol solution;
Hydrochloric acid (GB 622-77); 1+1 solution;
Hydrochloric acid: 1+2 solution:
3.8 Hydrochloric acid: 1-19 solution:
3.9 Sulfuric acid (GB 62577): 1+3 solution;
Oxalic acid (HG 3--988-76): 5% solution; bzxZ.net
Ascorbic acid: 2.5% solution (prepare before use); 3. 113
3.12 Sodium hydroxide (Na,MoD-2H,0) (HGB3401-62), 14% solution. Weigh 35g of sodium platinate into a plastic beaker, add 250mL of 50°C hot water, dissolve completely, and cool to room temperature. Transfer the solution to a plastic bottle (prepare and filter when using); 3.13 Silicon dixenide (high purity reagent);
3.14 Silicon dioxide standard solution: 20.0mg/1. Weigh 0.5000g of silicon dioxide (3.13) pre-calcined at 1000°C for 30min into a beaker. Add 5g of anhydrous sodium carbonate (3.1) and mix. Cover with 1g of anhydrous sodium carbonate (3.4), melt at 100°C in a muffle furnace for 30 min, remove, and cool. Place the beaker in a polytetrafluoroethylene beaker containing 100 mL of hot water, heat and gently remove the melt until the solution is clear. Wash the crucible and lid with hot water, cool to room temperature, transfer to a 1000L container, dilute to the mark with water, and shake. Immediately transfer the solution to a plastic bottle.
Put 20.00 mL of the above solution in a 500 mL volumetric flask, dilute with water to the mark, and mix well. Each mL of this solution contains 20 ug of silicon dioxide (applied when used).
4 Instruments
Spectrophotometer.
5 Sample
GB9018.5-88
The sample passes through a (.075 mm sieve) (GBti003-81), and is dried at 105-110°C until it is heavy, and then placed in a desiccator to cool to room temperature. 6 Analysis steps
6.1 Weigh the sample according to Table 1 (accurate weighing 0.0002 g) and add 3B sodium hydroxide (3.1) and a small amount of sodium peroxide (3.3) to the crucible, and cover the crucible. (Leave a gap) Place the crucible in a muffle furnace: heat from low temperature to 300°C, stay for 10 minutes, continue to heat to 700°C: keep for 30 minutes, take out and cool. Place the crucible in a polytetrafluoroethylene beaker containing 50mL hot water, heat at low temperature, leaching out the molten material, wash the crucible with hot water [if necessary, 2-3 drops of hydrochloric acid (3.8) to dissolve the residue of the whole glass], transfer to the corresponding volumetric flask according to Table 1, quickly add the specified amount of hydrochloric acid (3.6), shake, cool, dilute with water to the scale, and shake. Dry filter with double-layer medium-speed filter paper. Table 1
Dihydrogen content, service
~ : 0 -~20
Dilution with narrow volume, mL.
Add 5.00ml of filtrate in a 100mL volumetric bottle and dilute with water to 30mL. Add 1 drop of p-nitrophenol indicator solution (3.5), sodium hydroxide solution (3.2) and hydrochloric acid (3.8) to make the solution turn from yellow to colorless, 6.34.0mL of 4-nitrophenol (3.7). Shake well. Add 10.0mL of sodium hydroxide solution (3.12) and shake well. Let stand for 10min (the pH of the solution is now 1.1±0.2). Add 10mL of oxalic acid solution (3.10) while shaking and let stand for 5min. Add 5ml of sulfuric acid (3.9) to probe. Add 2mL of ascorbic acid solution (3.11). Dilute with water to the mark and shake. 6. After 40 min, select 1 Cin absorption cell: In the spectrophotometer, select a suitable wavelength in the range of 700-800 nm, use the blank test solution as the reference solution, and Measure the absorbance within min. Perform a white test at the same time.
7 Drawing of standard curve
Use a microburette to take 0.00, 1.00, 2.00, 4.00, 6.00, 8.00, 10.00 ml of silicon dioxide standard solution (3.14) and place them in a group of 100 ml volumetric flasks, dilute with water to 30 ml, and add 1 drop of p-nitrophenol indicator solution (3.5). Use hydrochloric acid (3.8) to adjust the solution until the yellow color turns white. The following is carried out according to the analysis steps 6.3 and 6.4, using the reagent blank as the reference solution to measure its absorbance. Use the micrograms of silicon dioxide contained in 1001L of the standard colorimetric solution as the horizontal axis and the corresponding absorbance as the vertical axis to draw a standard curve.
8 Calculation of results
The content (X) of silicon monoxide (SiO2) is calculated as follows: X- ×10-
Where: m: silica obtained from a standard curve, g; total volume of test solution, mL;
Tolerance
The mass of the sample, B.
GB 9018. 5—88
The difference in the results of the same laboratory should be less than the value shown in Table 2. Table 2
Additional Notes:
>1. 00~ 5. 00
25. 00 ~20. 00
(sio,)
This standard is under the jurisdiction of the Chemical Industry Design and Research Institute of the Ministry of Chemical Industry. This standard was drafted by the Chemical Industry Design and Research Institute of the Ministry of Chemical Industry. This standard was mainly drafted by artificial peace, Dilihua, and
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