This standard specifies the determination of chromium in high-purity quartz sand. This standard is applicable to the analysis of various grades of high-purity quartz sand. SJ 3228.7-1989 Determination of chromium in high-purity quartz sand SJ3228.7-1989 Standard download decompression password: www.bzxz.net
This standard specifies the determination of chromium in high-purity quartz sand. This standard is applicable to the analysis of various grades of high-purity quartz sand.

Standard of the Ministry of Machinery and Electronics Industry of the People's Republic of China Determination of chromium in high-purity quartz sand
1 Subject content and scope of applicationbZxz.net
1.1 Subject content
This standard specifies the determination of chromium in high-purity quartz sand. 1.2 Scope of application
This standard is applicable to the analysis of high-purity quartz sand of various grades. Reference standard
SJ3228.2—89 General rules for analysis of high-purity quartz sand. 3 Method summary
SJ3228.7-89
After the sample is treated with hydrofluoric acid and sulfuric acid, the trivalent chromium is oxidized to a hexavalent complex with ammonium persulfate using a silver nitrate catalyst in a dilute sulfuric acid medium. The hexavalent chromium reacts with an acidic solution and diphenylcarbazide to form a brown-red complex, which is used for colorimetric determination.
4 Reagents
4.1 Hydrofluoric acid, 40%
4.2 Sulfuric acid: 1:1,
4.3 Silver nitrate: 0.5%,
4.4 Ammonium persulfate: solid,
4.5 Diphenylcarbohydrazide: 0.25% ethanol solution4.6 Chromium standard solution: 0.001mg·ml-1. Weigh 0.1414g of dried potassium dichromate, use water solution, and dilute to 11 volumetric flask, the concentration of chromium is 0.05mg·ml-1. This solution is liquid A, take 2ml of liquid A and dilute it with water to a 100ml volumetric flask, the concentration of Cr+ in this solution is 0.001mg·m1-1, for colorimetric analysis. 5 Analysis steps
Accurately weigh 1g of the sample dried at 110℃, place it in the lining of a high-pressure crucible, moisten it with water, and add 6ml of hydrofluoric acid. 1:1 sulfuric acid 1ml, shake gently, cover the liner, put it in a stainless steel sleeve, tighten the lid, place it in a constant temperature drying oven at 145℃ and dissolve it for 2h. After cooling to room temperature, open the lid, gently push out the liner, and place it on a 120℃ hot plate to evaporate until dry. Heat 20ml of water, add 10 drops of silver nitrate, 1ml of sulfuric acid, 0.5g of ammonium persulfate, stir well, boil for 3min, add 50ml of water, boil for another 12min, transfer to a 100ml colorimetric tube after cooling, dilute to 90ml with water (Approved by the Ministry of Machinery and Electronics Industry of the People's Republic of China on March 20, 1989-03-25, implemented on March 25, 1989
SJ3228.7--89
) and add 3ml of diphenylcarbazide solution. Dilute to the scale with water, shake well, and place it for 10min before colorimetric comparison of the purple-red test solution. At the same time, the reagent blank is prepared under the same conditions, and a standard series is prepared for comparison with the sample solution. Note: The purpose of boiling the sample is to decompose ammonium persulfate and oxidize Cr+ to ammonium C acid. The decomposition is complete.
6 Calculation
Cr (%) =
m·1000
Where: V-the volume of the consumed chromium standard solution. ml, C-—chromium standard solution concentration. mg·ml-\mSample weight. g.
Additional remarks:
This standard is proposed by the Electronic Standardization Research Institute of the Ministry of Machinery and Electronics Industry. . Usually, the small bubbles in the test solution indicate that the persulfate has been completely removed. This standard was drafted by the 18th Research Institute of the Ministry of Machinery and Electronics Industry and the Hubei Guangshui Quartz Powder Factory. The main drafters of this standard: Qin Guozhen and Sheng Jianguo. 2—
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