YS/T 252.5-2007Methods for chemical analysis of nickel matte. Determination of sulfur content. Combustion-neutralization titrimetric method (English PDF)

3.1 Copper wire (mass fraction of copper >= 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

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 (prepared when used): Take 50 mL of

hydrogen peroxide. Use water to dilute it to 1 L. Add 10 mL of mixed indicator (3.6).

Use sodium hydroxide solution (3.8) to make adjustment, until bright green appears.

3.8 Sodium hydroxide standard titration solution [c(NaOH) ~ 0.065 mol/L]:

3.8.1 Preparation: Prepare sodium hydroxide into a saturated solution. Place it in a

plastic bottle until the solution is clear. Pipette 32 mL of supernatant. Use carbon

dioxide-free water to dilute it to 10 L. Mix well.

3.8.2 Calibration: Weigh four sets of 0.300 g (accurate to 0.0001 g) of potassium

hydrogen phthalate (standard reagent), that has been dried at 100 °C ~ 105 °C for 2

hours. Place it in a 300 mL Erlenmeyer flask. Use 60 mL of hot water, which does not

contain carbon dioxide, to dissolve it. After cooling, add 2 drops of phenolphthalein

indicator (3.5). Use sodium hydroxide standard titration solution to make titration, until

it shows light red, which is taken as end point.

Do a blank test along with the calibration.

Calculate the titration coefficient of sodium hydroxide standard titration solution for

sulfur, according to formula (1):

Where:

FS - Titration coefficient, the mass of sulfur equivalent to 1.00 mL of sodium

hydroxide standard titration solution, in milligrams per milliliter (mg/mL);

m1 - The mass of potassium hydrogen phthalate, in grams (g);

V1 - During calibration, the volume of sodium hydroxide standard titration solution

consumed in titrating potassium hydrogen phthalate solution, in milliliters (mL);

V0 - During calibration, the volume of sodium hydroxide standard titration solution

consumed by titrating the blank test solution, in milliliters (mL);

204.2 - Molar mass of potassium hydrogen phthalate [M(C8H5KO4)], in grams per

mole (g/mol);

16.03 - Molar mass of sulfur [M(1/2S)], in grams per mole (g/mol).

Take the average of four results. The range of the four calibration results is not greater

than 0.0060 mg/mL; otherwise, the measurement will be repeated.

4.1 Tubular combustion furnace: The maximum temperature 1350 °C, common

temperature 1300 °C, equipped with resistance furnace temperature controller (0 °C ~