YS/T 575.6-2007Methods for chemical analysis of bauxite. Part 6: Determination of titanium dioxide content. Diantipyrylmethane photometric method (English PDF)

3.1 Sodium peroxide.

NOTE: Sodium peroxide should prevent moisture absorption and it cannot be used once it is

agglomerated.

3.2 Sodium carbonate and sodium tetraborate flux: use 3 parts of anhydrous sodium

carbonate (Na2CO3) and 1 part of anhydrous sodium tetraborate (Na2B4O7) to mix

thoroughly.

3.3 Hydrofluoric acid.

3.4 Sulfuric acid (1+1).

3.5 Sulfuric acid (1+9).

3.6 Hydrochloric acid (1+1).

3.7 Mixed acid: pipette 225 mL of water into a 1000 mL beaker; carefully add 175 mL

of sulfuric acid, and mix well. Cool to room temperature; add 150mL of hydrochloric

acid and 50mL of nitric acid; and mix well (prepared when it is used).

3.8 Ascorbic acid solution: 100g/L (prepared on the day when this solution is used).

3.9 Diantipyrylmethane solution (15g/L): dissolve 15g of diantipyrylmethane

(C23H24N4O2) into 1L of sulfuric acid (1+49); prepare on the day of use.

3.10 Ammonium ferric sulfate solution: Dissolve 6 g of ferric ammonium sulfate [Fe2

(NH4)2 (SO4) 4 - 24H2O] in 1L of water containing 10mL sulfuric acid solution (3.5).

3.11 Titanium standard storage solution: 1mL solution contains 1mg titanium dioxide.

In use, any of the following methods can be used:

3.11.1 Take 0.300g of high-purity titanium (99.9%), accurate to 0.001g. Put in a conical

flask; add 50mL of water and 50mL sulfuric acid solution (3.4); dissolved by heating.

Add nitric acid (1+4) drop by drop to oxidize the solution until the purple color

disappears. Cool off, transfer to a 500mL volumetric flask; dilute to the scale and mix

evenly.

3.11.2 Take 0.500g of high-purity titanium dioxide (99.9%), accurate to 0.001g (burned

in a platinum crucible at 980°C for 30min before cooling in a dryer). Put it into a 250mL

conical flask; add 8g of ammonium sulfate and 25mL of sulfuric acid (3.4). Insert a

short-neck glass funnel on the bottle mouth; carefully heating continuously to a slight

boiling; continue heating to complete dissolution; and cool to room temperature. Add

200mL of water in one portion and cool. Quantitatively transfer 100mL of sulfuric acid

If the specimen is decomposed by acid; it shall be performed according to analytical

procedure 6.5.1.1. If the specimen is decomposed by alkaline sintering, it shall be

performed by analytical procedure 6.5.1.2. If the specimen is decomposed by melting,

it shall be performed by the analysis steps of 6.5.1.3.

6.4.1.1 Acid decomposition

Put the specimen (6.1) in a 400mL beaker; moisten it with water. Add 60mL of mixed

acid (3.7); cover with a watch glass and decompose by heating at 80°C (when the

amount of Fe2O3 in the specimen is greater than 15%, heating time shall be extended

a bit). After the brown smoke is gone, wash the watch glass and the wall of the beaker.

Remove the watch glass; heat and evaporate until the thick sulfuric acid smoke

appears. Cover the watch glass again; and heat it on hot plate to keep the temperature

of the solution at 210°C±10°C. Heat the strong reflow for 60min. In another beaker

containing sulfuric acid, measure the temperature by inserting a thermometer and

immersing it at 10 mm in sulfuric acid.

6.4.1.2 Alkaline sintering decomposition

Put the specimen (6.1) in a dry zirconium crucible; add 10 g of sodium peroxide (3.1);

mix thoroughly by a dry metal spoon; and then put it in a muffle furnace for sintering at

490°C for 45 minutes. Remove the crucible and material from the furnace; heat the

molten sintered material (about 30s) on a torch. In the molten state, heat the crucible

for 2min as rotate it; cool it to room temperature. Place the crucible side in a 400mL

beaker and cover the watch glass; carefully add 140mL of sulfuric acid solution (3.5)

to the back of the crucible; and then add 20mL of sulfuric acid solution (3.4); heat and

leach the molten material in the crucible. When the specimen in crucible is completely

leached, take out the crucible and wash the watch glass and beaker wall; remove the

watch glass; heat and evaporate the solution to emit thick sulfuric acid smoke; cover

the watch glass; and heat the solution on a hot plate to keep the temperature of the

solution at 210°C±10°C, strongly reflux for 60min.

6.4.1.3 Melting decomposition

Place the specimen (6.1) in a dry platinum-yellow alloy crucible; add 2g of sodium

carbonate and sodium tetraborate mixed flux (3.2); mix thoroughly by a dry metal

spoon; then cover the platinum lid. Put it in a muffle furnace, keep it at 480°C~500°C

for 5min; then move it into another muffle furnace; maintain it at 900°C for 10min; take

out the crucible; put it in a 400mL beaker after cooling; add 40mL water and 35mL

sulfuric acid solution(3.4). Cover the watch glass, heat and leach the specimen in the

crucible. After the specimen in the crucible is completely leached, take out the crucible

and wash the watch glass and the beaker wall. Heat and evaporate solution to emit

thick sulfuric acid smoke; cover the watch glass; heat on the hot plate and keep the

solution temperature at 210°C±10°C, strongly reflux for 60min.

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