POTASH, originally a vegetable alkali (so called), obtained by leaching wood-ashes, evap orating and calcining, commonly called car bonate of potash or pearl-ash, KICO2. Soda and potash were not distinguished by old-time chemists, but in 1807 Davy separated them. Various plants take up potash salts, and the refuse of beet-roots has been utilized as a source of potash. After the electrolytic pro duction by Davy and others, it came to be understood that a metallic element was being dealt with and potassium (q.v.) was developed.
Commercial Potash.— Previous to the outbreak of the World War nearly the whole potash supply of the United States market was imported from Germany. A glance at the im portations of 1913 shows the various forms in which the potash came in and the amounts consumed normally by the industries of the country. The figures are as follows: Kainit, 521,176 tons; manure salts, 250,529 tons; muri ate of potash, 237,630 tons; sulphate of potash, 44,349 tons; argot or bitartrate of potash (mainly from France and Italy), 14,499 tons; carbonate of potash, 11,003 tons; nitrate of potash, 4,826 tons; ferrocyanide of potash, 1,706 tons; and much smaller quanties of other potash salts — cyanide, chlorate, permanganate, etc., a grand total of 1,092,588 short tons, having a con tent of actual potash amounting to 270,720 tons and valued at $18,073,865. Beside these. the figures of the imports of potash for 1917 indi cate the remarkable change of conditions and values —8,100 tons, valued at $7,788,406.
Although the world's supply of commercial potash had come almost wholly from mines in Germany and Austria, it was a matter of com mon knowledge to geologists everywhere that potash occurs very extensively in nature, being a component of granites and most other igneous rocks, and occurring in smaller amounts in the various sedimentary strata and soils. It is esti mated to form 3 per cent of the earth's crust. In the dry saline matter from evaporated river waters there is generally about 2 per cent of K20 (potassium oxide) and in the ocean from 1 to 2 per cent. Where these waters evaporate and the other saline components crystallize out, the potash accumulates in the remaining solu tion so that on the evaporation of the final theproportion of Ki0 may be high. There are deposits of this kind in various lake basins, both recent and of various older geo logic periods. Alunite, a hydrous ootassium aluminum sulphate (1(20.3Al202.4S02.61120.), contains when pure 11.4 per cent of K20 which
is made soluble by roasting.
The orthoclase feldspars which are of wide spread occurrence in granite and gneiss contain from 16.8 per cent of K20 in combination with silicic acid and some processes for separating this ingredient appear to be commercially prac ticable, especially when the residue can be util ized for making brick. Some of the younger igneous rocks contain much potash notably the rhyolites, trachytes and phonolites, some of which carry 8 per cent. The mineral leucite KAlSi202 contains a large amount of K20, the rock in Leucite Hills, Sweetwater County, Wyo., carrying from 9 to 11 per cent of potash. Sericite or altered mica schist in the southern Appalachians carries 10 per cent or more. Glauconite or grecnsand, which occurs in beds, notably in southern New Jersey, Maryland and Virginia, Kentucky, Tennessee and Georgia, contains up to 9 per cent, and in some cases 11 per cent of K20 in form of silicate. These deposits are from five to 20 feet thick and easily worked. These various silicates are ex ceedingly difficult to resolve, but heat and ad mixture with lime and other agents liberates most of the potash.
The largest known potash deposits exist in the Permian in central Germany, the Oligocene in Alsace, the lower Miocene in Galicia, in the early Tertiary near Sauria in northeastern Spain and in beds of unknown age in India. They are associated with the great deposits of common salt, dolomite and gypsum such as occur in the Permian beds of the central United States, and it is hoped that domestic supplies may be de rived from these beds. The potash deposits in central Germany have been very extensively de veloped by numerous mines, some of great depth. The annual production under ordinary conditions is about 7,000,000 metric tons valued at more than $30,000,000 and sold at a profit of about $4,000,000. The potash occurs in various compounds, the principal one being Kainite, MgS02.KC1.3H20, which is in the midst of a 3,500 foot succession of common salt and an hydrite, the products of long-continued desicca tion of a water body. The potash salt was deposited at or near the end of one stage of desiccation, but there was a later incursion of waters from which finally there were deposited anhydrite and common salt. Fortunately a thin overlying sheet of clay was deposited which protected the potash from solution by the water which brought the anhydrite and salt now covering the potash.