YS/T 252.5-2007 English PDF (YST252.5-2007)

This Part specifies the method for determination of sulfur content in high nickel matte. This Part is applicable to the determination of sulfur content in high nickel matte. Measuring range: 15% ~ 25%. 2 Method summary The sample uses copper wire as flux and burns in air flow at 1250 ¡ãC ~ 1300 ¡ãC, to convert sulfur into sulfur dioxide. It is absorbed and oxidized into sulfuric acid by hydrogen peroxide. Methyl red-methylene blue solution is used as a mixed indicator. Use sodium hydroxide standard titration solution to make titration, until the solution changes from purple to bright green, which is taken as the end point. 3 Reagents 3.1 Copper wire (mass fraction of copper ¡Ý 99.95%, diameter 0.25 mm ~ 0.5 mm). 3.2 Acid absorption solution (potassium dichromate-sulfuric acid solution): Heat and dissolve 5 g of potassium dichromate with a small amount of water. After cooling, add 100 mL of sulfuric acid. 3.3 Desiccant: Anhydrous calcium chloride. 3.4 Alkali absorption solution: Sodium hydroxide (50 g/L). 3.5 Phenolphthalein indicator (10 g/L), ethanol solution. 3.6 Methyl red-methylene blue mixed indicator: Weigh 0.3 g of methyl red and 0.25 g of methylene blue. Dissolve in 500 mL of absolute ethanol. 3.7 Hydrogen peroxide absorption solution (pre