| 摘要 |
Water-soluble crystalline silicophosphoric acid containing SiO2 : P2O5 in the molar ratio of 1 : 1 is produced by mixing finely-divided amorphous silica with phosphoric acid having a concentration of at least 70% by weight P2O5 in such proportions as to have a molar ratio SiO2 : P2O5 within the range 0.3 : 1 to 1.5 : 1, ripening the mixture at 50 DEG to 300 DEG C., removing excess or unreacted phosphoric acid by means of an organic solvent inert towards silicophosphoric acid. The ripening may be assisted by seeding with crystals of the product and/or by kneading. The organic solvent preferably has a boiling-point below 200 DEG C. and may contain a carbonyl, ether, or sulphoxy group, e.g. di-isopropyl ether, di-ethyl ether, formic acid, acetic anhydride, methyl acetate, dimethyl sulphoxide, dioxan, or tetrahydrofuran. The solubility of the product in water may be altered by heating the product for a period of time. |
