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

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 ¡Ü 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). YS/T 273.9-2020 www.ChineseStandard.net ? Buy True-PDF ? Auto-delivery. Page 6 of 9 3.6 Sodium hydroxide solution (200 g/