GB/T 19226-2003Determination of vanadium in coal (English PDF)

4.1 Sodium peroxide

granular.

4.2 Sodium hydroxide (GB 629)

granular.

4.3 Sodium hydroxide solution

c(NaOH)=1 mol/L.

Weigh and take 40 g of sodium hydroxide; dissolve it in the water of 1L.

4.4 Sulfuric acid solution

c (1/2H2SO4) = 1 mol/L.

6.2.1 Ashing of coal samples

Accurately weigh and take 1 g of air-dried coal samples of which the particle size is less than 0.2 mm (the accuracy of weigh shall be 0.0002 g); put it into the crucible (5.3);

place it into the muffle furnace (5.1); heat it gradually from room temperature to (600±10°C); burn it at this temperature for at least 1 h until there is no black carbon particles; remove the crucible and cool it to room temperature.

Note. The amount of sample can be appropriately increased or decreased according to the content of vanadium.

6.2.2 Treatment of ash samples

In corundum crucible which contains ash sample, add 4 g of sodium hydroxide (4.2) and 1 g of sodium peroxide (4.1); place it in the muffle furnace. Under the condition of ensuring that the melt sample does not splatter or spill, gradually heat it from the room temperature until (650 ± 10) °C. Under this temperature, melt it for 10 min ~ 15 min;

remove the crucible and cool it to room temperature.

Place the crucible in the beaker (5.6); add 50 mL ~ 60 mL of boiling water; boil for 1 min to 2 min on the electric furnace (5.8). Remove the beaker; wash it with hot water.

Transfer the solution to 100 mL volumetric flask (5.5); cool it to room temperature;

dilute it with water until the scale, shake it evenly; place it for overnight or use qualitative filter paper (4.13) to perform dry filtration.

Note. Dry filtration refers to the filtration under the condition that the using instruments and materials (e.g..

funnels, beakers and filter paper, etc.) are both dry and clean.

6.2.3 Preparation of sample blank solution

When decomposing a batch of samples, it shall prepare a sample blank solution at the same time. The preparation method shall be the same as 6.2.2, but the ash sample shall not be added.

6.2.4 Determination

Accurately pipette 10 mL of the upper clear solution or filtrate of the sample AND 10 mL of the sample blank solution (6.2.3); respectively place them into 50 mL volumetric flask; add 5 mL of mixed masking agent and 2 drops of p-nitrophenol indicator; use sulfuric acid solution (4.5) to carefully adjust it from yellow to colorless. Follow 6.1.2 and 6.1.3, except that - use sample blank solution as the reference to determine the absorbance of the sample solution. Find-obtain the content of vanadium pentoxide (µg) in sample solution from working curve.

Note. According to the content of vanadium in sample's total solution, the amount of liquid absorption can be appropriately increased or decreased. […]