YS/T 273.9-2020 English PDF (YST273.9-2020)

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YS/T 273.9-2020: Methods for chemical analysis and physical properties test of cryolite - Part 9: Determination of phosphorous pentoxide content - Molybdenum blue photometric method
YS/T 273.9-2020
YS
NON-FERROUS METAL INDUSTRY STANDARD
OF THE PEOPLE’S REPUBLIC OF CHINA
ICS 71.100.10
H 30
Replacing YS/T 273.9-2006
Methods for Chemical Analysis and Physical Properties
Test of Cryolite – Part 9: Determination of Phosphorous
Pentoxide Content – Molybdenum Blue Photometric Method
ISSUED ON: DECEMBER 09, 2020
IMPLEMENTED ON: APRIL 1, 2021
Issued by: Ministry of Industry and Information Technology of the People’s
Republic of China
Table of Contents
Foreword ... 3
1 Scope ... 5
2 Method Summary ... 5
3 Reagents ... 5
4 Apparatus ... 6
5 Specimen ... 6
6 Test Procedures ... 6
7 Calculation of Test Results ... 8
8 Precision ... 8
9 Quality Assurance and Control ... 9
10 Test Report ... 9
Methods for Chemical Analysis and Physical Properties
Test of Cryolite – Part 9: Determination of Phosphorous
Pentoxide Content – Molybdenum Blue Photometric Method
1 Scope
This Part specifies the method for determination of phosphorous pentoxide in cryolite.
This Part applies to the determination of phosphorous pentoxide in cryolite. The determination
range: 0.0030%~0.50%.
2 Method Summary
The test material is melted by a mixed solvent of anhydrous sodium carbonate and boric acid,
and acidified by sulfuric acid. Use sodium hydroxide to adjust the acidity. When the pH value
is ≤ 0.3, add molybdic acid to form phosphomolybdenum heteropoly acid with phosphorus.
After being reduced by ascorbic acid to phosphomolybdenum blue, measure its absorbance at
a wavelength of 815nm with a spectrophotometer. The content of phosphorus pentoxide is
calculated using the standard curve method.
3 Reagents
Unless otherwise stated, use only reagents confirmed to be of analytically pure and distilled
water or water of equivalent purity.
3.1 Sodium carbonate anhydrous.
3.2 Boric acid.
3.3 Sulfuric acid (1+1).
3.4 Acidic solution of ammonium molybdate (25 g/L): Weigh 25g of ammonium molybdate
tetrahydrate [(NH4)6Mo7O24• 4H2O] and dissolve it in 200 mL of hot water. After cooling, add
about 434mL of sulfuric acid (3.3); dilute to 1L with water; and mix well. This solution is stored
in polyethylene bottles.
3.5 Ascorbic acid solution (20 g/L).
3.6 Sodium hydroxide solution (200 g/L).
3.7 Phosphorus pentoxide standard storage solution: Weigh 0.1944g of sodium dihydrogen
phosphate monohydrate [NaH2PO4•H2O], dissolve it in water and transfer it to a 1L volumetric
flask; dilute to the mark and mix well. 1 mL of this solution contains 100μg of phosphorus
pentoxide.
3.8 Phosphorus pentoxide standard solution: Pipette 50.00mL of phosphorus pentoxide
standard storage solution (3.7) into a 500 mL volumetric flask; dilute to the mark with water;
and mix well. 1 mL of this solution contains 10μg of phosphorus pentoxide.
3.9 Phenolphthalein ethanol solution (10 g/L).
4 Apparatus
4.1 Platinum dish: diameter 70 mm, height 35 mm, with platinum lid.
4.2 High temperature furnace: capable of controlling the temperature at 850°C±20°C.
4.3 Water bath: capable of controlling the temperature at 80°C±2°C.
4.4 Spectrophotometer.
5 Specimen
The specimen is ground and mixed, and passed through a 75μm standard sieve; baked in an
oven at 110°C ± 5°C for 2 h; and cooled to room temperature in a desiccator.
6 Test Procedures
6.1 Test material
Weigh the specimen (5) according to Table 1, accurate to 0.0001 g.
6.2 Parallel test
Do two experiments in parallel and take the average.
6.3 Blank test
Do a blank test along with the test material.
6.4 Determination