TECHNOLOGY FOCUS - INORGANIC CHEMISTRY - Preferred Components: The particles: have an average particle size of 10-500 nm, preferably 50-300 nm; contains hydroxy groups (present on their surfaces), ammonium cations and nitrogen oxides; have a nitrogen content of 0.2-8 wt.%, preferably 2.5-7 wt.% and a hydrogen content of 0.05-4 wt.%, preferably 1.5-2.5 wt.%; and comprise the fluorine which is essentially present on their surfaces, where at least 80 %, preferably at least 90 % of the fluorine is present in a surface layer on the same. The surface layer has a mean thickness of 0.3-20 nm, preferably 0.6-10 nm. The titanium dioxide is in the form of anatase. The ammonium bifluoride aqueous solution is present at a concentration of 10-37 wt.%, preferably 30 wt.%. Preferred Process: The stage (a1) is performed at: 100-110 degrees C, preferably 105 degrees C, and/or for 40-80 minutes; and a pressure of 1-2 bar and/or at a pH of 6.5-7. The filtration in stages (a2) and/or (a4) is performed using meshes having holes of 2-3 nm, preferably 2.5 nm. The step (a3) is performed through the addition of a solution of ammonium hydroxide or with stirring, the first stage at a speed of 40-60 rpm, preferably 50 rpm, and/or the second stage at 10 rpm. The first stage of hydrolysis is performed at a pH of 7-8 and/or in that the second stage of hydrolysis is performed at a pH of 10-11. The step (a4) is performed at a maximum temperature of 330-470 degrees C, preferably 350-450 degrees C, for 2-6 hours, preferably 5 hours, where the maximum temperature is maintained for 1-3 hours, preferably 2 hours. The solid residue from stage (a2) is subjected to pyrohydrolysis at a maximum temperature of 450 degrees C, preferably 360-380 degrees C, for 2-4 hours, preferably 3 hours. The process further comprises (a5) in which heating the filtrate obtained from stage (a4) to 150-170 degrees C, preferably 160 degrees C for 0.5-2 hours, consequently obtaining ammonium bifluoride which once re-dissolved in water can be recycled to stage (a1). EXAMPLE - Water (7 l), ammonium bifluoride salt (3 kg) and ilmenite sand (1341 g) sieved to a particle size of less than 200 microns were placed in a stirred reactor having a volume of 10 l. The mixture was then brought to boiling at atmospheric pressure, and kept for 1 hour. After this stage of reaction with the ore, solution (4 l) were drawn off through the valve in the bottom of the reactor and then filtered. Concentrated 30% ammonia solution (1.5 l) was added to the solution thus filtered containing the titanium and iron fluoride salts, thermostated to 70 degrees C, increasing its pH to 7.3. The white precipitate was separated out by filtration and a further concentrated solution of 30% ammonia (2 l) was added to the filtrate to obtain a pH of 9.5. The white precipitate was separated out by filtration and subjected to the subsequent stage of pyrohydrolysis to give a wet intermediate and the wet intermediate (30 g) was placed in an aluminum tube. The tube was inserted into a furnace chamber, then heated at 4.7 degrees C/minute up to 450 degrees C and kept for 2 hours. Slow cooling was followed to give fluorine-doped titanium dioxide.