Sodium aluminum phosphate

A process for the preparation of an improved potassium modified 1:3:8 sodium aluminum phosphate which comprises:

• a. contacting, at a temperature above 40.degree. C., a food grade phosphoric acid having a concentration of about 85.0 to about 88.0 weight percent H.sub.3 PO.sub.4 with a sufficient amount of potassium ion to provide an analysis of about 0.5 to about 1.2 weight percent K.sub.2 O in the final product, and a sufficient amount of sodium ion to provide an analysis of about 2.4 to about 3.2 weight percent of Na.sub.2 O in the final product;
• b. contacting the sodium-potassium treated phosphoric acid with a sufficient amount of alumina to provide a concentration of about 15 to about 17% by weight A1.sub.2 O.sub.3 in the final product;
• c. cooling the slurry of potassium modified sodium aluminum phosphate thereby formed to a temperature varying from about 60 to about 75.degree. C;
• d. drying and granulating the potassium modified sodium aluminum phosphate;
• e. milling and classifying the potassium modified sodium aluminum phosphate to obtain the following particle size distribution:
• from about 0.1 to about 5% retained on 60 mesh;
• from about 3 to about 20% through 60 on 100 mesh;
• from about 9 to about 50% through 100 on 140 mesh.