YS/T 509.3-2008Methods for Chemical Analysis of Spodumene and Lepidolite Concentrates - Determination of silicon dioxide content - Gravimetric-molybdenum blue photometric method (English PDF)

3.1 Potassium hydroxide (superior grade pure).

3.2 Sodium hydroxide (superior grade pure).

3.3 Absolute ethanol.

3.4 Hydrofluoric acid (rho1.15g/mL).

3.5 Hydrochloric acid (rho1.19g/mL).

5.1 Spodumene concentrate shall pass through a sieve with an aperture of

0.074mm. Lepidolite concentrate shall pass through a sieve with an aperture of

0.105mm.

5.2 The specimen is pre-baked at 105°C~110°C for 2h. Place in a desiccator to

cool to room temperature.

6.1 Test material

Weigh 0.50g of specimen, to the nearest of 0.0001g.

6.2 Number of determinations

Make parallel determinations of two test materials. Take the average value.

6.3 Blank test

Along with spodumene and lepidolite concentrates, conduct blank test of test

material respectively.

6.4 Determination

6.4.1 Place the test material (6.1) in a 30mL nickel crucible. Add 3 drops of

absolute ethanol (3.3) to moisten. Add 2g of potassium hydroxide (3.1) and 2g

of sodium hydroxide (3.2). Put the lid on the crucible and leave a little gap.

Remove water on a low temperature electric furnace. Place in a high

temperature furnace of 600°C~650°C. Melt for 10min~15min. Take out. Cool.

6.4.2 Use filter paper to wipe the outer wall of the crucible. Place in a 125mL

porcelain evaporating dish with handle. Cover the watch glass. Use hot water

to leach the melt. Wash the crucible. Take it out.

6.4.3 In the test solution (6.4.2) of lepidolite concentrate, add 20mL of boric acid

saturated solution (3.12). The test solution of spodumene concentrate does not

need to add saturated solution of boric acid.

6.4.4 Add 20mL of hydrochloric acid (3.5). Place on a boiling water bath and

evaporate to a volume of about 10mL~15mL. Remove. Cool.

6.4.5 Add 5mL of polyredoxane solution (3.15). Use a glass rod to stir well. Let

stand for 5min~10min.

6.4.6 Use medium-speed quantitative filter paper to filter. The filtrate is accepted

by a 250mL volumetric flask. Add a small amount of hot hydrochloric acid (3.7)

to the porcelain evaporating dish. Use a wiper rod to wipe. Use hot hydrochloric

acid to wash the evaporating dish. Wash the precipitate 7~8 times. Then use

hot water to wash the precipitate. Use silver nitrate solution (3.11) to check that

there is no chloride ion.

6.4.7 Place the precipitate and filter paper in a platinum crucible. After ashing

on the electric stove, place in a high temperature furnace at 950°C~1000°C for

1.5h. Take out. Cool for a while. Place in a desiccator to cool to room

temperature. Weigh. Then put the crucible into a high temperature furnace of

950°C~1000°C and burn for 0.5h. Take out. Cool for a while. Place in the

desiccator to cool to room temperature. Weigh. Repeat the operation until the

amount becomes constant.

6.4.8 Add 3~5 drops of water along the wall of the crucible to wet the

precipitation. Add 4 drops of sulfuric acid (3.8), 10mL of hydrofluoric acid (3.4).

Evaporate on a low-temperature electric stove until there is white smoke.

Remove. Cool for a while. Add 5mL of hydrofluoric acid (3.4). Continue to heat

until all white smoke is emitted.

6.4.9 Place the residue together with the crucible in a high temperature furnace

of 950°C~1000°C for 0.5h. Take out to cool for a while. Place in the desiccator

to cool to room temperature. Weigh. Repeat the operation until the amount

becomes constant.

6.4.10 Cool the filtrate (6.4.6) to room temperature. Use water to dilute to the

graduation of scale. Mix well. Pipette 10.00mL of solution into a 100mL

volumetric flask. Add water to a volume of about 35mL.

6.4.11 Add 1 drop of p-nitrophenol solution (3.13). Use potassium hydroxide

solution (3.14) to adjust to yellow. Then use sulfuric acid (3.9) to adjust till the

yellow disappears and exceed by 5mL. Mix well. Add 10mL of ammonium

molybdate solution (3.10). Mix well. Let stand for 10min. Add 5mL of reducing

solution (3.16.3). Mix well. Let stand for 15min. Use water to dilute to the

graduation of scale. Mix well.

6.4.12 Move part of the solution (6.4.11) into a 2cm cuvette. Take the blank of

the accompanying specimen of spodumene or lepidolite as reference. Measure

the absorbance at a wavelength of 700nm of the spectrophotometer. Find the

corresponding amount of silicon dioxide from the working curve.

6.5 Drawing of working curve

6.5.1 Pipette 0mL, 0.50mL, 1.00mL, 1.50mL, 2.00mL, 2.50mL, 3.00mL of silicon

dioxide standard solution (3.17). Respectively place in a set of 100mL

......