Sodium Bicarbonate: Soda Crystals Exposed to Carbonic Acid in Chambers (the Old Process)

Before the ammonia-soda works, baking soda was made by simply letting carbonic acid gas soak into soda crystals, as Thorpe's Dictionary (1913) describes. The crystals stand in layers on a lath false bottom; the gas comes in below, nine of the crystals' ten molecules of water drain away as mother liquor, carrying the impurities with it, and after 6 to 9 days the crystals have turned into loose, damp bicarbonate in their own shape. It is dried at no more than 45 °C. The picture: our diagram.