This standard specifies the determination of silicon dioxide content by molybdenum blue spectrophotometry. This standard is applicable to the determination of silicon dioxide content in limestone products for chemical use, with a range of 0.05%-S%> GB/T 15057.5-1994 Determination of silicon dioxide content in limestone for chemical use Molybdenum blue spectrophotometry GB/T15057.5-1994 Standard download decompression password: www.bzxz.net

National Standard of the People's Republic of China
Determination of silicon dioxide content in limestone for chemical industry---Molybdenum blue spectrophotometric method
Linestone for chemical industry-Determination of silicon dioxide content---Molybdenum blue spectrophotometric method1 Subject content and scope of application
This standard specifies the determination of silicon dioxide content by molybdenum blue spectrophotometric method. GB/T15057.5-94
This standard is applicable to the determination of silicon dioxide content in limestone products for chemical industry, with a determination range of 0.05%-5%. 2 Reference standards
GB6682 Specifications and test methods for water used in analytical laboratories GB/T9721 Chemical reagent molecular absorption spectrophotometric method (ultraviolet and visible light part) 3 Method summary
The sample is melted with sodium carbonate-boric acid mixed flux and leached with dilute hydrochloric acid. Under the acid condition of pH about 1.1, ammonium sulfate and silicic acid form silicic acid heteropolyacid, and ethanol is used as a stabilizer. It is reduced to silicic acid blue with ammonium ferrous sulfate in oxalic acid-sulfuric acid medium, and the absorbance is measured at a wavelength of 680 mm on a spectrophotometer.
4 Reagents and solutions
The water used in this standard shall comply with the specifications of secondary water in GB6682. The listed reagents, unless otherwise specified, are analytically pure reagents. 4.1 Mixed flux: grind 2 parts of anhydrous sodium carbonate (GB639) and 1 part of boric acid (GB628) and mix well. 4.2 Hydrochloric acid (GB622), 1+6 solution
4.3 Hydrochloric acid: 1+29 solution.
4.4 95% ethanol (GB679).
4.5 Ammonium molybdate L (NH) MO,O24·411:OJ (GB657): 60g/L solution. Weigh 6g of ammonium molybdate and soak it in 50mL of hot water, cool it, dilute it with water to 100ml, filter it and store it in a plastic bottle. 4.6 Oxalic acid-sulfuric acid mixed solution: Weigh 3g of oxalic acid (GB9854) and dissolve it in 100m sulfuric acid (GB625) 1+9 solution. 4.7 Ammonium ferrous sulfate [FeSO.* (NH.>SO, ·6H2OJ (GB661): 60g/L solution. Weigh 6g of ammonium ferrous sulfate and dissolve it in 50mL of water, add 5-6 drops of sulfuric acid (GB625), dilute with water to 100mL, filter and use (use period is one week). 4.8 Silicon dioxide standard solution: 200mg/m1. Weigh 0.2000g of silicon dioxide (high purity reagent) that has been burned at 9501000C for 30m and placed in a dryer to cool to room temperature, add 3g of mixed flux (4.1), mix well, and then cover with 1g of mixed flux. Cover with orange Cover the crucible and leave a gap, place it in a high-temperature furnace and melt it at 950℃ for 20 minutes, take it out and cool it. Place the crucible in a polytetrafluoroethylene plastic beaker A containing 100mL of hot water, heat it and diffuse the melt until the solution is clear. Wash out the glass volute and the lid with hot water, cool it to room temperature, transfer the solution to a 1000mL volumetric flask, dilute it to the scale with water, shake it, and store it in a plastic bottle. This solution contains 200g of silicon dioxide in 1ml (the shelf life is one month). National Technical Supervision Kitchen Approved on May 5, 1994 194
Far low holding
Implemented on February 1, 1995
GB/T 15057.5--94
4.9Silicon dioxide standard solution: 20μg/mLPipette 50.00mL of silicon dioxide standard solution (4.8) into a 500mL volumetric flask, dilute to the mark with water, shake and store in a plastic bottle. 1mL of this solution contains 20μg of silicon dioxide (prepared before use). 5 Instruments
Spectrophotometer: It should comply with the provisions of GB9721. 6 Samples
Laboratory samples pass through a 125um test sieve (GB6003), dry at 105~110°C for more than 2h, and cool to room temperature in a desiccator.
7 Analysis steps
7.1 Weigh the sample according to the provisions of Table 1, accurate to 0.0001g, and place it in a platinum crucible. Perform a blank test at the same time. Table 1
Silicon dioxide content, %
0. 05~ 0. 25
≥0. 25~1.0
>1. 0~5. 0
Weigh the sample amount·more
Add hydrochloric acid solution (4.2)
Volume, mL
Use a container for dissolution
Volume, rnL
Thickness of the absorption cell, cm
7.2Add 2-3g of mixed flux (4.1), mix well, and then cover with 1g of mixed flux. Cover with a lid and leave a gap, place in a high-temperature furnace and raise the temperature from low temperature to 950℃, keep for 10 minutes, take out, and cool. Place the crucible in a polytetrafluoroethylene plastic sintering In the cup, add hydrochloric acid solution (4.2) according to the amount specified in Table 1, cover the surface, heat at low temperature to leach the molten material, and wash out the snail and cover with water. Continue to heat until the solution is clear, cool to room temperature, transfer to the corresponding volumetric flask according to the provisions of Table 1, dilute with water to the scale, and shake well. 7.3 Pipette 10.00mL of the test solution into a 100mL volumetric flask, add 10.0mL of ethanol (4.4), add water to 40ml7.4 Add 5.0mL of ammonium molybdate solution (4.5), spread evenly, and let it stand for 10min. Add 20.0mL of oxalic acid-sulfuric acid mixed solution (46), shake well, and let it stand for 5min. Add 5.0mL of ammonium ferrous sulfate solution (4.7), dilute with water to the scale, and shake well. 7.5 Select the corresponding absorption cell according to the provisions of Table 1, and measure the absorbance at the wavelength of 680mm on the spectrophotometer with the blank test solution as the reference.
8 Drawing of working curve
Measure 0.00, 1.00, 2.50, 5.00, 7.50, 10.00mL of silica standard solution (4.9) and place them in a 100mL volumetric flask pre-filled with 10.0mL of hydrochloric acid solution (4.3), add 10.0mL of ethanol (4.4), and add water to 40mL. The following steps are carried out according to 7.4 and 7.5, in which the reagent blank is used as a reference and the absorbance is measured. Draw the working curve with the amount of silica as the horizontal axis and the corresponding absorbance as the vertical axis.
9Description of the analysis results
The silicon dioxide (SiO2) content (z) expressed as mass percentage is calculated as follows: m mX10~6
wherein?mThe amount of silicon dioxide obtained from the working curve, V,-the volume of the sample solution absorbed, ml
VThe total volume of the sample solution, m.
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10Allowable difference
The mass of the sample,.
GB/T 15057. 5--94www.bzxz.net
Take the arithmetic mean of the parallel analysis results as the final analysis result. The absolute difference of the parallel analysis results should not be greater than the allowable difference listed in Table 2.
Silicon dioxide (SiO2) content
0.05~0.25
>0.25~～1.00
>1.00~5.00
Additional notes:
This standard is proposed by the Ministry of Chemical Industry of the People's Republic of China. This standard is under the jurisdiction of the Chemical Industry and Mining Design Institute of the Ministry of Chemical Industry. This standard is drafted by the Chemical Industry and Mining Design Institute of the Ministry of Chemical Industry. The main drafters of this standard are Wang Zhaowen and Li Donghao. Allowable difference
This standard refers to the German standard DIN52240-3-1985 "Inspection of raw materials for glass products-Chemical analysis of limestone with a minimum calcium carbonate content of 95%-Determination of silicon dioxide content". 196
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