Potash and Pearl-Ash From Wood Ash: Leaching Tun, Evaporation, Calcining and Recrystallising (Tomlinson, 1854)

"Plants which grow near the sea mostly contain soda; inland plants potash. The ashes of the latter are lixiviated with water in a large cask or tun."

Fit a large cask with a false perforated bottom covered with straw, a plugged hole (o) between it and the real bottom, and a pipe (p) from the top down through the false bottom to let the air escape (Fig. 1667).

Fill with ashes of inland plants (wood ash), add water, and after some hours draw off the liquid; add more water until all the soluble matter is out. Pour the weakest solutions onto fresh ash instead of water.

Boil the leys to dryness and heat the residue to redness to burn off the brown organic matter: this is crude potash, or pearl-ash when white and pearly.

Treat the crude potash with its own weight of cold water and leave it several days, stirring now and then; the less soluble sulphate and chloride stay behind. Syphon off the liquor, boil it fast until small crystals appear, take it off the fire and stir as it cools so only small crystals form. Drain them on a filtering bed, wash with a little pure carbonate of potash, and dry at a stove.

From Charles Tomlinson (ed.), **Cyclopaedia of Useful Arts** (London, 1854), vol. II, "Potassium" (checked on the archive.org scan cyclopdiaofuse02tomlrich, pp. 434-435). He gives no quantities for the leaching; the tools are ours.