potash

• WordNet 3.6
  • n potash a potassium compound often used in agriculture and industry
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• • n Potash (Chem) The hydroxide of potassium hydrate, a hard white brittle substance, KOH, having strong caustic and alkaline properties; -- hence called also caustic potash.
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• • n potash A substance obtained by leaching wood-ashes, evaporating the solution obtained, and calcining the residuum; one of the fixed alkalis; the so-called vegetable alkali; more or less impure or crude potassium carbonate, or carbonate of potash as formerly generally (and still very frequently) designated; any combination of which potassium forms the base, whether containing oxygen or not. Potash-salts play a most important part in vegetable life, existing in all plants in various proportions, and in various combinations with both inorganic and organic acids. When plants are burned, the inorganic constituents remain behind in the ashes, and it is by the lixiviation or leaching of these ashes that potash was first obtained, a process with which the Greeks and Romans were acquainted, although they were unable clearly to distinguish potash from soda, calling them both by the same name (νιτρον, nitrum). The name potash is of comparatively modern origin, and is derived from the fact that the potassiferous solution from wood-ashes was boiled down or concentrated in pots. It was not until about the middle of the eighteenth century that the two alkalis, soda and potash, were clearly distinguished from each other; but they were considered to be simple substances until after the beginning of the nineteenth century, when their metallic bases were separated from them by Davy (1807-8). Up to comparatively recent times the potash compounds used in the arts—and they are numerous and of great importance—were chiefly obtained in the form of crude potash after the method indicated as having given origin to the name of this alkali, and this method is still in use, although much less important than it formerly was. Saltpeter, or the nitrate of potash, had been long known, and obtained in a very different way. (See saltpeter.) Since the beginning of the present century potash has been obtained in considerable quantity from the refuse of beet-root used in the manufacture of sugar, and from sheep's wool. It has also been got (in the form of the chlorid) from sea-water; but the most important source of supply is the region near Stassfurt in Prussia, where two minerals containing potassic compounds (carnallite, a double chlorid of potassium and magnesium, and cænite, containing sulphates of potash and magnesia with chlorid of magnesium) are found in abundance, and mined on a large scale. From these naturally occurring potassiferous compounds all the various salts of potash used in the arts are manufactured, and it is by using the potash-salts obtained at Stassfurt that the Chili saltpeter (nitrate of soda) is converted into common saltpeter or niter (nitrate of potash), a substance important as the principal ingredient in the manufacture of gunpowder.
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• • n Potash pot′ash a powerful alkali, obtained from the ashes of plants—also Potass′
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