Crystalline zeolite powder of type A (III)

A process of preparing a crystalline zeolite powder of Type A with the composition

• 1.0.+-.0.2M.sub.2/n O:Al.sub.2 O.sub.3 :1.85.+-.0.5SiO.sub.2.yH.sub.2 O
• where M is a sodium cation, n is its valence and y has a value up to 6 with 50 weight % of the particles not over 4.3.mu. and with a particle spectrum:
• ______________________________________ Fraction (.mu.) Portion (weight %) ______________________________________ <3 18 to 38 <5 70 to 82 <10 93 to 99 <15 96 to 100 ______________________________________
• comprising hydrothermally crystallizing a SiO.sub.2, Al.sub.2 O.sub.3, M.sub.2 O and water containing alkali aluminate, water, alkali silicate synthesis mixture where M is sodium, said process including the steps of providing an aqueous alkali aluminate liquor having a temperature of 30.degree. to 100.degree. C. and containing 0.1 to 100 grams of Al.sub.2 O.sub.3 /l and 1 to 200 grams of Na.sub.2 O/l, feeding in sodium silicate solution containing 50 to 150 grams of Na.sub.2 O/l and 200 to 450 grams of SiO.sub.2 /l within 10 to 200 minutes to obtain a clear reaction solution having the composition SiO.sub.2 /Al.sub.2 O.sub.3 =50 to 1000:1, Na.sub.2 O/SiO.sub.2 =0.2 to 20:1 and H.sub.2 O/Na.sub.2 O=4 to 300:1, adding with stirring to the synthesis mixture an aqueous sodium aluminate containing 10 to 200 grams/l of Al.sub.2 O.sub.3 and 10 to 250 grams/l of Na.sub.2 O having a temperature of 30.degree. to 100.degree. C., the aqueous sodium aluminate having 10 to 200 grams/l of Al.sub.2 O.sub.3 and 10 to 250 grams/l of Na.sub.2 O being added to the synthesis mixture in two steps, the speed of addition in the second step being 2 to 10 time higher than in the first step, and allowing the thus obtained synthesis mixture to crystallize at a temperature between 20.degree. and 170.degree. C. for at least 15 minutes.