ISO 900:1977 pdf download.Aluminium oxide primarily used for the production of aluminium - Determination of titanium content一Diantipyrylmethane photometric method
4.8.1 In a platinum dish of suitable capacity, weigh, to the nearest 0,000 1 g，0,601 5g of dipotassium hexafluoro-titanate (K2TiFg) previously dried at about 50 'C and cooled in a desiccator. Moisten the product with a few drops of water and then add 15ml of sulphuric acid solution, ρ approximately 1,84 g/ml. Evaporate carefully almost to dryness in a well-ventilated fume cupboard.
Repeat the operation until the fluorine is completely expelled, using each time 5 to 6 ml of the same sulphuric acid solution. Finally, add 3 ml of the same sulphuric acid solution and heat until the residue is completely dissolved.
Allow to cool, immerse the dish and its contents in a beaker containing 95 ml of water and 5 ml of the same sulphuric acid solution and heat on a boiling water bath until the solution is completely clear.
Remove the platinum dish, wash it carefully with water,transfer the solution and the washings quantitatively to a 500 ml one-mark volumetric flask, dilute to the mark and mix.
Cool and transfer the solution quantitatively to a beaker of suitable capacity containing 100 ml of water. Add, drop
by drop, approximately 0,1 N potassium permanganate solution until the colour of the solution is permanently pink. Transfer the solution quantitatively to a 500 ml one-mark volumetric flask, dilute to the mark and mix.
1 ml of this standard solution contains the equivalent of 0,400 mg of TiO2.
NOTE - If dipotassium hexafluorotitonate or dipotassium titanyl dioxalate dihydrate is not available, the following alternative procedure may be adopted :
In a platinum crucible of suitable capacity, weigh, to the nearest 0,0001 9, 0,200 0 g of titanium dioxide (TiO2) previously calcined at 1 200°C and cooled in a desiccator. Add 4g of potassium pryosulphate (K2S20z) and fuse carefully at about 1 200。C.
Allow to cool and place the crucible and contents in a beaker of suitable capacity. Add 100 ml of the sulphuric acid solution (4 .4) and heat gently to dissolve the melt. Remove the crucible and wash it with hot water, collecting the washings in the beaker. Transfer the solution and the washings quantitatively to a 500 ml one-mark volumetric flask, dilute to the mark and mix.
Add 25ml of the sulphuric acid solution (4.4) to each flask. Dilute with water to about 70 ml, add 3 mI of the ascorbic acid solution (4.5) and 3 drops of the copper(I) sulphate solution (4.6) and mix. Allow to stand for 20 min,add 10 ml of the diantipyrylmethane solution (4.7), dilute to the mark and mix.
6.3.2 Photometric measurements
After at least 40 min, carry out the photometric measure-ments using the spectrophotometer (5.2) at a wavelength of about 420 nm or the photoelectric absorptiometer (5.3) fitted with suitable filters, after having adjusted the in-strument to zero absorbance against the compensation solution.ISO 900 pdf download