Process for the manufacture of ammonium nitrilotrisulfonate

In a process for the manufacture of ammonium nitrilotrisulfonate in a reaction vessel by reacting an aqueous ammonium sulfite solution having a pH in the range of 5.0 to 7.5 with gaseous nitric oxides the improvement which comprises maintaining a suspension in said sulfite solution of 20 to 800 g/l of solid nitrilotrisulfonate by continuously withdrawing from said reaction vessel a portion of said suspension, removing from a portion of said withdrawn suspension the solid nitrilotrisulfonate therein to form a mother liquor free of solid nitrilotrisulfonate and recycling at least a portion of said mother liquor together with the remaining portion of said withdrawn suspension containing nitrilotrisulfonate to the reaction vessel.