Potassium hydrogen carbonate — potassium bicarbonate, the potassium analogue of ordinary bicarbonate of soda — is a white powder or granular material used in baking powders for sodium-free leavening and in medicine as an antacid. It releases carbon dioxide when heated or combined with acids to leaven batters and doughs. Its advantage over sodium bicarbonate is sodium-free leavening, valuable in products formulated for sodium-restricted diets and in low-sodium baking powders. As an antacid it neutralises excess stomach acid, and in effervescent formulations it provides the fizz. The compound is also used in fire extinguishers and as a fungicide in organic agriculture. At food-use levels it is considered safe, contributing potassium rather than sodium, a meaningful nutritional difference in an era of sodium reduction targets.