Process for the manufacture of zeolites 4A having a high crystallinity and a fine granulometry and being particularly suitable for the formulation of detergent compositions

A batch process for the synthesis of a zeolite 4A having a coarse fraction equal to zero, an exchange power with Mg.sup.++ equal to or higher than 45 mg CaO/g, and a granulometric modulation index equal to or higher than 85, wherein, in a first stage, an aqueous solution of Na silicate, in which the SiO.sub.2 :H.sub.2 O molar ratio is from 0.60 to 0.150 and the SiO.sub.2 /Na.sub.2 O molar ratio is from 1.95 to 2.30, is added to an aqueous solution of Na aluminate containing an excess of NaOH, preheated at 70.degree.-75.degree. C., and wherein, in a second stage, the thus-obtained mixture is crystallized at 70.degree.-105.degree. C., the global dilution factor, .tau., being from 8 to 15, said process being characterized in that the temperature of the silicate solution is at least 20.degree. C. lower than the temperature of the aluminate solution, the crystallization time being at least 50 minutes, whereby said silicate solution can be added within a time equal to or less than 15 minutes without using any Venturi tube or any ultra-rapid stirrer, and wherein the crystallization is subdivided into three sub-stages, the first sub-stage being characterized by the temperature of approximately 70.degree. C., the second sub-stage including a gradual rising of the temperature between the first and third sub-stages of from approximately 70.degree. C. to 95.degree.-105.degree. C., and the third sub-stage being characterized by a temperature of from 95.degree. to 105.degree. C.