Clear and stable basic, neutral, or acid solutions of aluminium phosphate sulphate containing more than 1 mol. of Al2(PO4)2 to 2 mols. of Al2(SO4)3, i.e. more than 0,33 mols. P2O5 to each mol. of Al2O3, are obtained by bringing together the three components alumina, phosphoric acid, and sulphuric acid in the necessary proportions under the requisite conditions of concentration and temperature. By evaporating the final solutions, for instance under reduced pressure, water-soluble solid products may be obtained. The solutions may be decomposed by heat, especially when diluted, to precipitate a basic aluminium phosphate, and precipitation may be assisted by addition of a neutralizing agent such as sodium carbonate; by virtue of this property the solutions are adapted for use as textile mordants. The precipitated basic phosphate may be used as a base for colour lakes. In examples, a hot solution of trisodium phosphate or the solid salt may be added to a hot aluminium sulphate solution to give a mixed solution having a ratio of 0,5 to 0,66 mols. P2O5 to each mol. Al2O3; or tricalcium phosphate may be added to an aluminium sulphate solution to give a ratio of 0,5 mol. P2O5 to 1 mol. Al2O3, the solution may be heated to effect double decomposition, and the precipitated calcium sulphate be separated from the resulting solution; or hydrated aluminium phosphate may be dissolved in an aluminium sulphate solution to give a ratio of 0,5 to 0,66 mols. p P2O5 to each mol. Al2O3. The P2O5 ratio in the above solutions may be increased to about 0,75 mol. P2O5 per mol. Al2O3 by addition of phosphoric acid, or by using disodium phosphate or di- or mono-calcium phosphate. Reference has been directed by the Comptroller to Specification 275,891, [Class 121].ALSO:Clear and stable basic, neutral, or acid solutions of aluminium phosphate sulphate containing more than 1 mol. of Al2(PO4)2 to 2 mols. of Al2(SO4)3, i.e., more than 0.33 mols. P2O5 to each mol. of Al2O3, are obtained by bringing together the three components alumina, phosphoric acid, and sulphuric acid in the necessary proportions under the requisite conditions of concentration and temperature. Thus a hot solution of trisodium phosphate or the solid salt may be added to a hot aluminium sulphate solution to give a mixed solution having a ratio of 0.5 to 0.66 mols P2O5 to each mol. Al2O3; or tricalciu phosphate may be added to an aluminium sulphate solution to give a ratio of 0.5 mol. P2O5 to 1 mol. Al2O3, the solution be heated to effect double decomposition, and the precipitated calcium sulphate be separated from the resulting solution; or hydrated aluminium phosphate may be dissolved in an aluminium sulphate solution to give a ratio of 0.5 to 0.66 mols. P2O5 to each mol. Al2O3. The P2O5 ratio in the above solutions may be increased to about 0.75 mol. P2O5 per mol. Al2O3 by addition of phosphoric acid, or by using disodium phosphate or di- or mono-calcium phosphate. By evaporating the final solutions, for instance under reduced pressure, water-soluble solid products may be obtained. The solutions may be decomposed by heat, especially when diluted, to precipitate a basic aluminium phosphate, and precipitation may be assisted by addition of a neutralizing agent such as sodium carbonate; by virtue of this property the solutions are adapted for use as textile mordants, in the sizing of paper, the mineral tannage of leather, and the purification of water. The precipitated basic phosphate may be used as a base for colour lakes. Reference has been directed by the Comptroller to Specification 275,891, [Class 121].ALSO:Clear and stable basic, neutral, or acid solutions of aluminium phosphate sulphate containing more than 1 mol. of Al2(PO4)2 to 2 mols. of Al2(SO4)3, i.e. more than 0.33 mols. P2O5 to each mol. of Al2O3, are obtained by bringing together the three components alumina, phosphoric acid, and sulphuric acid in the necessary proportions under the requisite conditions of concentration and temperature. By evaporating the final solutions, for instance under reduced pressure, water-soluble solid products may be obtained. The solutions may be decomposed by heat, especially when diluted, to precipitate a basic aluminium phosphate, and precipitation may be assisted by addition of a neutralizing agent such as sodium carbonate; by virtue of this property the solutions are adapted for use in the purification of water. In examples, a hot solution of trisodium phosphate or the solid salt may be added to a hot aluminium sulphate solution to give a mixed solution having a ratio of 0,5 to 0,66 mols. P2O5 to each mol. Al2O3; or tricalcium phosphate may be added to an aluminium sulphate solution to give a ratio of 0,5 mol. P2O5 to 1 mol. Al2O3, the solution be heated to effect double decomposition, and the precipitated calcium sulphate be separated from the resulting solution; or hydrated aluminium phosphate may be dissolved in an aluminium sulphate solution to give a ratio of 0,5 to 0,66 mols. P2O5 to each mol. Al2O3. The P2O5 ratio in the above solutions may be increased to about 0,75 mol. P2O5 per mol. Al2O3 by addition of phosphoric acid, or by using disodium phosphate or di- or mono-calcium phosphate. Reference has been directed by the Comptroller to Specification 275,891, [Class 121].ALSO:Clear and stable basic, neutral, or acid solutions of aluminium phosphate sulphate containing more than 1 mol. of Al2\(PO4)2 to 2 mols. of Al2(SO4)3, i.e. more than 0,33 mols. P2O5 to each mol. of Al2O3, are obtained by bringing together the three components alumina, phosphoric acid, and sulphuric acid in the necessary proportions under the requisite conditions of concentration and temperature. By evaporating the final solutions, for instance under reduced pressure, water-soluble solid products may be obtained. The solutions may be decomposed by heat, especially when diluted, to precipitate a basic aluminium phosphate, and precipitation may be assisted by addition of a neutralizing agent such as sodium carbonate; by virtue of this property the solutions are adapted for use in the sizing of paper. In examples, a hot solution of trisodium phosphate or the solid salt may be added to a hot aluminium sulphate solution to give a mixed solution having a ratio of 0,5 to 0,66 mols. P2O5 to each mol. Al2O3; or tricalcium phosphate may be added to an aluminium sulphate solution to give a ratio of 0,5 mol. P2O5 to 1 mol. Al2O3, the solution be heated to effect double decomposition, and the precipitated calcium sulphate be separated from the resulting solution; or hydrated aluminium phosphate may be dissolved in an aluminium sulphate solution to give a ratio of 0,5 to 0,66 mols. P2O5 to each mol. Al2O3. The P2O5 ratio in the above solutions may be increased to about 0,75 mol. P2O5 per mol. Al2O3 by addition of phosphoric acid, or by using di-sodium phosphate or di- or mono-calcium phosphate. Reference has been directed by the Comptroller to Specification 275,891, [Class 121].