| 摘要 |
In the preparation of composite titanium oxide-calcium sulphate pigments made by heating and hydrolizing a mineral acid solution of titanium salts containing a suspension of calcium sulphate upon which the titanium oxide is precipitated, the calcium sulphate is made by adding quick or slaked lime, calcium carbonate or other calcium compound to concentrated sulphuric acid. An aqueous slurry of lime is added to 78 per cent sulphuric acid, and the resulting pulp of calcium sulphate is mixed while still hot with an acid solution of ilmenite containing 6 per cent of TiO2. The mixture was boiled and the resulting precipitate filtered, washed with a small amount of water and ignited at 700-1200 DEG C. Pigments containing 30 and 75 per cent of titanium oxide are described. By this process the pigment is made free from iron. The form of calcium sulphate used is stated to be anhydrite, which partly dissolves in acid solutions, yielding a suspension of fine particles whereby the formation of colloidal titanium salts is prevented.
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