Baking soda is derived from soda ash. Soda ash is obtained through the Solvay process – combining sodium chloride, ammonia, and carbon dioxide in water – or from trona ore, which is refined into slurry that contains both soda ash and baking soda.
While mining trona ore produces both soda ash and sodium bicarbonate, the Solvay process to make soda ash, which dates to 1861 and Belgian chemist Ernest Solvay, is a safe and economical way to extract soda ash by mixing carbonated water with ammonia brine. The solution precipitates sodium bicarbonate, which is then heated to form soda ash.
Next, the soda ash solution is placed in a centrifuge to separate out the crystals. The soda ash crystals are then dissolved in another bicarbonate solution to make a saturated solution of soda ash that is filtered and pumped into a carbonating tower.
As the soda ash solution moves down the carbonating tower, it reacts with pressurized carbon dioxide at the bottom to form sodium bicarbonate crystals. These crystals collect at the bottom of the carbonating tower. They are then transferred to another centrifuge. Once the liquid is removed, the remaining crystals are again washed in a bicarbonate solution, forming a “cake-like” substance that’s flashed-dried, powdered and sold as baking soda.