Abstract: A one-stage method for production of free-flowing, absorptive particles of Wegscheider's Salt (Na.sub.2 CO.sub.3 .multidot.3NaHCO.sub.3), having a low bulk density, low alkalinity and low friability, by reaction of higher bulk density, anhydrous sodium carbonate particles with carbon dioxide and steam at superatmospheric pressure is disclosed. Particles of high bulk density anhydrous sodium carbonate are introduced into a preheated reaction zone and heated to a temperature of at least about 100.degree. F., and thence continuously contacted therein with a gaseous mixture containing from about 45 to 70 weight percent steam and 30 to 55 weight percent carbon dioxide. By preheating the reaction zone and delaying the introduction of the gaseous mixture thereto until the temperature of the particles of sodium carbonate therein is at least about 100.degree. F., caking and coagulation of the contacted particles is substantially eliminated. The exothermic reaction mixtue is maintained at a temperature from about 240.