POTASH AND PEARL-ASH, in commerce. See POTASSIUM. The chief source of this important article in Britain is Canada, where it is derived from the vast quantities of wood cut down and burned in clearing the forest for culture, and also from the branches of the trees felled for timber. The ashes, mixed with a small quantity of quick-lime, are put into large Wooden cisterns, and covered with water. The whole is well stirred up, and allowed to settle; the next day the clear liquor is drawn off and evaporated to dryness in iron pots, whence it is called potash. When a sufficient quantity is got to fill a cask of 5 cwt. it is fused at a red heat and poured into the cask. The mass when cold is colored gray externally, but when broken shows a pinkish tint internally. It is very deliquescent, and consequently the casks require to be nearly air-tight. In this state potash contains a large quantity of foreign materials, amounting to about 40 per cent, among which sulphur and carbonaceous matter predominate. This is the crude American potash of commerce. If it is calcined by a reverberatory furnace the sulphur is driven off, and the carbonaceous matter burned out; the carbonic acid, however, combines with the potash, and forms it into a carbonate. To form it into pearl-ash, it is
then broken up and dissolved in water in a wooden cistern, having a perforated bottom, covered with straw, through which it filters, and is afterward evaporated in flat-bottomed iron pans. As it approaches dryness it is stirred with irod rods, which break it up into round lumpy masses of a pearly-white color, and in this state it is the pearl-ash of com merce, and contains about 0 per cent of pure potassst. All land-plants yield potash when burned, and many in much greater proportions than the timber-trees of North America; but the circumstances in which the materials are obtained give an advantage to our colonial manufacturers, which hitherto has enabled them to compete with the whole world. The quantity imported annually of "pots" and "pearls," as they are technically called, reaches the value of nearly half a million sterling. See POTASSIUM.