GB/T 5686.2-2022Ferromanganese, ferromanganese-silicon, nitrogen-bearing ferromanganese and manganese metal—Determination of silicon content—Molybdenum blue spectrophotometric method, silicon potassium fluoride titrimetric method and perchloric acid dehydration gravimetric method (English PDF)

4.1 Principle

The test portion is dissolved with sodium peroxide-sodium carbonate and acidified with sulfuric acid.

4.2 Reagents and Materials

Unless otherwise specified, only reagents that are confirmed to be analytically pure are used in the analysis.

4.2.1 Water, GB/T 6682, Grade-3.

4.2.6 Sodium sulfite solution, 100 g/L. Weigh-take 100 g of anhydrous sodium sulfite, dissolve it in water (see 4.2.1), then, use water (see 4.2.1) to dilute it to 1,000 mL.

4.2.7 Ammonium molybdate solution, 40 g/L. Weigh-take 40 g of ammonium molybdate [(NH4)6Mo7O24 - 4H2O], place it in a 400 mL beaker, add 200 mL of water (see 4.2.1), warm to dissolve it, filter it, then add 800 mL of water (see 4.2.1), and mix it well.

4.2.11 Iron solution, 4 mg/mL. Weigh-take 3.5 g of iron sulfate into a 500 mL beaker, add 200 mL of water (see 4.2.1) and heat to dissolve it. After the sample is completely dissolved, transfer it to a 250 mL volumetric flask, use water (see 4.2.1) to dilute to the scale, and mix it well. 1 mL of this solution contains approximately 4 mg of iron.

4.3 Instruments

In the analysis, only common laboratory instruments are used. The one-mark volumetric flasks, graduated pipettes and one-mark pipettes used shall respectively comply with the requirements of GB/T 12806, GB/T 12807 and GB/T 12808.

4.4 Sampling and Sample Preparation

In accordance with the provisions of GB/T 4010, conduct sampling and sample preparation. The specimens shall all pass the 0.125 mm sieve mesh.

4.5 Analytical Steps

4.5.4 Determination

4.5.4.1 Decomposition of test portion

Place the test portion (see 4.5.2) in a nickel crucible containing 3 g of sodium peroxide (see 4.2.3) and 1 g of anhydrous sodium carbonate (see 4.2.4), evenly stir it and place it in a high-temperature furnace at 700 °C to melt for 7 minutes ~ 8 minutes. Take it out and let it slightly cool. Use hot water (see 4.2.1) to leach it into a 200 mL plastic beaker containing 80 mL of hot water (see 4.2.1), clean the crucible and take it out. While using a plastic rod to stir it, slowly add 35 mL of sulfuric acid (see 4.2.5), add 10 mL of sodium sulfite solution (see 4.2.6), stir it, until the solution is clear. Transfer it into a 200 mL volumetric flask, use running water to cool it to room temperature. Use water (see 4.2.1) to dilute it to the scale and mix it well.

4.6 Calculation of Analysis Results

In accordance with Formula (1), calculate the silicon content wSi in the specimen, expressed in mass fraction (%).

5.1 Principle

The test portion is decomposed with nitric acid and hydrofluoric acid, convert silicon into fluorosilicic acid, add potassium fluoride and potassium nitrate to generate a precipitate of potassium fluorosilicate. After filtering and washing, use alkali to neutralize the free acid remaining on the filter paper and the precipitate.

5.2 Reagents and Materials

Unless otherwise specified, only reagents that are confirmed to be analytically pure are used in the analysis.

5.2.1 Water, GB/T 6682, Grade-3.

5.2.2 Nitric acid, rho is approximately 1.42 g/mL.

5.2.3 Hydrofluoric acid, rho is approximately 1.15 g/mL.

5.2.7 Urea solution, 50 g/L.

5.2.8 Potassium nitrate solution, 50 g/L

Intra-laboratory Allowable Difference (r) Inter-laboratory Allowable Difference (R) Silicon Content (mass fraction)

5.2.9 Potassium nitrate-ethanol solution, 40 g/L. Weigh-take 40 g of potassium nitrate and dissolve it in 1,000 mL of ethanol solution (1 + 4).

5.2.10 Phenolphthalein indicator solution, 5 g/L, prepared with ethanol solution (1 + 1).

5.2.11 Sodium hydroxide standard titration solution, c (NaOH) = 0.18 mol/L. Weigh-take 7.2 g.

5.3 Instruments

In the analysis, only common laboratory instruments are used. The burettes used shall comply with the provisions of GB/T 12805.

5.4 Sampling and Sample Preparation

In accordance with the provisions of GB/T 4010, conduct sampling and sample preparation. The specimens shall all pass the 0.125 mm sieve mesh.

5.5 Analytical Steps

5.6 Calculation of Analysis Results

In accordance with Formula (3), calculate the silicon content wSi in the specimen, expressed in mass fraction (%).

6.1 Principle

The test portion is dissolved with nitric acid, hydrochloric acid or sodium peroxide. Use perchloric acid to evaporate and smoke to dehydrate silicic acid. After filtering and washing, burn the precipitate at 1,100 °C to a constant mass. Add hydrofluoric acid to volatilize and eliminate the silicon as silicon tetrafluoride, then, burn it to a constant mass. Based on the mass difference before and after hydrofluoric acid treatment, calculate the mass fraction of silicon.

6.2 Reagents and Materials

Unless otherwise specified, only reagents that are confirmed to be analytically pure are used in the analysis.

6.2.9 Hydrochloric acid, 1 + 1.

6.2.10 Hydrochloric acid, 1 + 10.

6.2.11 Sulfuric acid, 1 + 3.

6.2.12 Ammonium thiocyanate solution, 50 g/L.

6.2.13 Silver nitrate solution, 10 g/L.

6.3 Instruments

In the analysis, only common laboratory instruments are used.

6.4 Sampling and Sample Preparation

In accordance with the provisions of GB/T 4010, conduct sampling and sample preparation. The specimens shall all pass the 0.125 mm sieve mesh.

6.5 Analytical Steps

6.5.4 Determination

6.5.4.2.1 Place the test portion (see 6.5.2) in a 300 mL beaker, use a small amount of water (see 6.2.1) to moisten it, use a watch glass to cover it, and slowly add 20 mL of nitric acid (see 6.2.8) and 5 mL ~ 10 mL of hydrochloric acid (see 6.2.4).

6.5.4.1 Decomposition of ferromanganese-silicon test portion

6.6 Calculation of Analysis Results

In accordance with Formula (4), calculate the silicon content wSi in the specimen, expressed in mass fraction (%).

6.7 Allowable Difference

The difference in the analysis results shall be not greater than the allowable difference listed in Table 5. Otherwise, the number of additional measurements and the analysis results shall be determined as specified in Appendix A.