ARM & HAMMER® Ammonium Bicarbonate ARM & HAMMER® Ammonium Bicarbonate is unique because of its ability to completely convert to leavening gasses – ammonia, carbon dioxide and steam -.with heat alone, leaving no alkaline salt behind. Normally use of ABC without a leavening acid is limited to products with a final moisture lower than 5%. Ammonium bicarbonate can be used to increase the spread of cookies rather than the height where this is desirable and can be used in combination with other leavening systems. ARM & HAMMER® Ammonium Bicarbonate is available as is, or treated with a flow aid to improve its handling properties.