YS/T 273.3-2020 English PDF (YST273.3-2020)

This Part specifies the method for determination of chlorine content in cryolite. This Part is applicable to the determination of chlorine content in cryolite. The determination range is: 40.00% ~ 60.00%. The and quot;Distillation - Thorium nitrate titration method and quot; is the arbitration method. 2 Distillation - Thorium nitrate titration method 2.1 Summary of methods Dissolve the sample with sodium carbonate. Separate the chlorine, through sulfuric acid (or perchloric acid)-steam distillation. Use sodium alizarin sulfonate-methylene blue as the indicator. Use thorium nitrate solution for titration, to calculate the fluorine content in the sample. 2.2 Reagents Unless otherwise stated, only reagents and deionized water determined to be of analytical grade are used in the analysis. 2.2.1 Anhydrous sodium carbonate, superior grade pure. 2.2.2 Perchloric acid (p ¡Ö l.60 g/mL). 2.2.3 Hydrochloric acid (1 + 199). 2.2.4 Sodium hydroxide solution (20 g/L). 2.2.5 Sulfuric acid (2 + 1). 2.2.6 Buffer solution (pH value 2.7): Weigh 9.45 g of monochloroacetic acid. Dissolve in 50 mL of sodium hydroxide (1 mol/L). Use water to dilute it to 100 mL. Mix well. 2.2.7 Thorium nitrate standard titration solution: - Preparation: Weigh 4.5 g of thorium nitrate tetrahydrate [Th(NO3)4 ? 4H2O]. Use YS/T 273.3-2020 www.ChineseStandard.net ? Buy True-PDF ? Auto-delivery. Page 6 of 14 water to dissolve it. Dilute it to 1 L. Mix well. - Calibration: Weigh 0.2800 g of anhydrous sodium chlorine (preliminarily burned at 600 ¡ãC and cooled to room temperature in a desiccator). Use 20 mL ~ 30 mL of w