Manufacturer and builder 12, 1872
There is no secret at all in this proceeding. The ashes are simply leeched - that means, they are placed in long cylinders, provided with small perforations below, and water percolated through them, which water will then dissolve out all what is soluble. In order to concentrate this solution, or lye, as it is called, the same water may be consentively passed through different portions of ashes, taking, however, care not to reject any which has not been submitted to the action of a fresh quantity of water. The succeeding treatment of the lye is evaporation by the heat, when the soluble salts, chiefly carbonate of potash, will remain. To change this into caustic potash, the solution is treated with quicklime, which will combine with the carbonic acid of the potash, forming an insoluble carbonate of lime, while the solluble potash remains in solution, and is then afterwards obtained by evaporation of the water by heat. There are some practical peculiarities to be observed, especially if this process is to be executed on a large scale and paying basis; htis, however, would require a separate treatise to describe it all. Coal ashes contain little or no potash, while different kinds of wood differ considerably in this respect, especially when grown in different kinds of soil, as the wood, of course, must take all the potash from the soil on which it grows.