ISO 900:1977 pdf download – Aluminium oxide primarily used for the production of aluminium – Determination of titanium content – Diantipyrylmethane photometric method
4.8.1 In a platinum dish of suitable capacity, weigh, to the nearest 0,000 1 g, 0,601 5 g of dipotassium hexafluoro- titanate (K,TiF,) previously dried at about 50 “C and cooled in a desiccator. Moisten the product with a few drops of water and then add 15 ml of sulphuric acid solution, p approximately I,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. 1 ml of this standard solution contains the equivalent of 0,400 mg of TiO
Cool and transfer the solution quantitatively to a beaker of suitable capacity containing 1 00 ml of water. Add, drop by drop, approximately 0,l 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 TiO,. NOTE – If dipotassium hexafluorotitanate or dipotassium titanyf dioxalate dihydrate is not available, the following alternative procedure may be adopted : In a platinum crucible of suitable capacity, weigh, to the nearest 0,000 1 g, 0,200 0 g of titanium dioxide (TiOg) previously calcined at 1 200 “C and cooled in a desiccator. Add 4 g of potassium pryosulphate  and fuse carefully at about 1 2OO’C. Allow to cool and place the crucible and contents in a beaker of suitable capacity. Add 1 00 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 25 ml of the sulphuric acid solution (4.4) to each flask. Dilute with water to about 70 ml, add 3 ml of the ascorbic acid solution (4.5) and 3 drops of the copper 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. NOTE – The absorbance of the solution is stable for about 24 h.