GB/T 6150.14-2008Methods for chemical analysis of tungsten concentrates - Determination of manganese content - The ammonium ferrous sulfate volumetric method and flame atomic absorption spectrometric method (English PDF)

3.1 parathion mixed acid solution

preparation methods. 5% (volume fraction) solution of sulfuric acid and 5% (volume fraction) of phosphoric acid solution by 1.1

Mixing ratio.

3.2

phosphoric acid (rho1.69g/mL).

3.3

Disodium hydrogen phosphate solution (100g/L).

3.4

solution of ammonium persulfate (200g/L), the time is now equipped with.

3.5

silver nitrate solution (20g/L), stored in brown bottles.

3.6

diphenylamine sulfonate indicator solution (5g/L).

3.7

sulfuric acid solution (1 + 9).

3.8

standard potassium dichromate solution (0.01mol/L). Weigh 2.9417g by 150 °C baking 1h drying baseline potassium dichromate, dissolved in water,

Move 1000mL volumetric flask, constant volume, and mix.

3.9

standard ferrous ammonium sulfate solution (0.1mol/L). Weigh ferrous ammonium sulfate 39g, dissolved in sulfuric acid solution (3.7) and treated with a solution of sulfuric acid (3.7) diluted to 1000mL, and mix, stored in a brown bottle, with calibration time.

Ferrous ammonium sulfate standard solution for calibration.

Pipette accurately 20.00mL ferrous ammonium sulfate standard solution (3.9) in a triangular pyramid 300mL flask, 100mL parathion mixed acid solution (3.1), add 2 to 3 drops of sodium diphenylamine sulfonate indicator solution (3.6), with standard potassium dichromate solution (3.8), titrated to a stable blue end

Point, note the number of volume Vp 1.

According to formula (1) to calculate the concentration of ammonium ferrous sulfate solution, in units of moles per liter.

Ba Ba 1 × 2 = 2 Vp 1 Vp (1)

Where.

Ba 2 --- molar concentration of ferrous ammonium sulfate, expressed in moles per liter (mol/L);

Ba 1 --- potassium bichromate standard solution molarity units per liter (mol/L);

Volume Vp 1 --- consumption of potassium dichromate standard solution, in milliliters (mL);