Process for the production of an aluminum hydroxy Al(OH).sub.3 having rounded grain surfaces

A process for the production of aluminum hydroxide Al(OH).sub.3 with rounded grain surfaces, comprising grinding and grading an aluminum hydroxide derived from the Bayer process, having a grain diameter in the 50 percent range d.sub.50 of 30 to 100 .mu.m, and consisting of primary crystals having a grain diameter in the 50 percent range d.sub.50 of 5 to 25 .mu.m, to obtain aluminum hydroxide having a grain diameter in the 50 percent range d.sub.50 of 5 to 25 .mu.m, in the 90 percent range d.sub.90 of 10 to 50 .mu.m and in the 10 percent range of d.sub.10 of 1.0 to 4.5 .mu.m, seeding an alkaline solution which is derived from the Bayer process and which has a molar ratio of Na.sub.2 O to Al.sub.2 O.sub.3 of 2.0 to 2.3 with 25 to 500 g/l with said ground and graded aluminum hydroxide, the continuing after seeding precipitation until a molar ratio of Na.sub.2 O to Al.sub.2 O.sub.3 of 2.6 to 3.1 has been reached, and then filtering the resultant solid aluminum hydroxide with rounded grain surfaces from said solution, said aluminum hydroxide having a grain diameter in the 50 percent range d.sub.50 of 5 to 25 .mu.m, in the 90 percent range d.sub.90 of 10 to 50 .mu.m and in the 10 percent range d.sub.10 of 1.0 to 4.5 .mu.m.