ammonium carbonate Also known as ammonium hydrogen carbonate E 503 Used in bakeries as a leavening agent for flat baked goods, usually in combination with potash. The contents of the package are sufficient for 4 kg of flour. In its pure form, this salt is also known as ABC drive, derived from the old pharmaceutical name of the main component ammonium bicarbonate (ammonium hydrogen carbonate). Harthorn salt was originally obtained by dry distillation of grated deer antler, from which the name originates.