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Abstract

There is disclosed a process for producing an amorphous aluminosilicate having the formula: 2Na.sub.x O.Al.sub.2 O.sub.3.ySiO.sub.2 (wherein x is a number between 0.6 and 1.8 inclusive; and y is a number between 1.3 and 7 inclusive); which comprises: a step of maintaining an alkali solution (Solution-C), the alkalinity of which is within the range of 1.2-3.5N under stirring; a step of adding a sodium aluminate solution (Solution-A) containing free alkali and sodium silicate solution or colloidal silica solution (Solution-B) containing free alkali to the Solution-C, separately to prepare a slurry which contains an amorphous sodium aluminosilicate in the form of finely divided particles which are only slightly soluble in water; and a step of aging the slurry, characterized in that the addition of Solution-A and Solution-B into Solution-C is carried out so that the Si/Al ratio in the resultant mixture is kept within the range of 0.7 to 7.6 during and after the addition, and mixing effected at 55.degree. C. or lower, and Solution-A and Solution-B are prepared so that both the alkalinity of the aqueous solution phase during the formation of the slurry and during the maturing is kept within .+-.0.30N of the alkalinity of Solution-C.

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