592 POTASH 



In 1000 parts Potasaa 



6-00 

 6-26 

 7-22 



Dry beech-bark 

 Fern . 

 Large rush . 

 Stalk of maize 

 Bean-stalks . 



17-5 

 20-0 



In 1000 parts Potassa 



Bastard chamomilo 

 (Anthemis cotula, ~L.) 19'6 

 Sunflower-stalks . 20-00 

 Common nettle . 25'03 

 Vetch plant . . 27'50 



In 1000 parts. Potasaa 



Thistles in full growth 35'37 

 Dry straw of wheat 



before earing . . 47'0 

 Wormwood. . . 73'0 

 Fumitory . . . 79'0 



Stalks of tobacco, potatoes, chestnuts, chestnut-husks, broom, heath, furze, tansy, 

 sorrel, vine-leaves, beet-leayes, orach, and many other plants, abound in potash salts. 

 In Burgundy, the well-known cendres gravities are made by incinerating the lees of 

 wine pressed into cakes, and dried in the sun ; the ashes contain fully 16 per cent, of 

 potash. See ASHES OF PLANTS. 



The purification of pearlash is founded upon the fact of its being more soluble in 

 water than the neutral salts which debase it. Upon any given quantity of that sub- 

 stance, in an iron pot, let one and a half times its weight of water be poured, and let 

 n gentle heat be applied for a short time. When the whole has again cooled, the 

 bottom will be encrusted with the salts, while a solution of nearly pure carbonate of 

 pol-ash will be found floating above, which may be drawn off clear by a syphon. The 

 salts may be afterwards thrown upon a filter of gravel. If this lye be diluted with 

 six times its bulk of water mixed with as much slaked lime as there was pearlash 

 employed, and the mixture be boiled for an hour, the potash will become caustic, by 

 giving up its carbonic acid to the lime. If the clear, settled lixivium be now syphoned 

 off, and concentrated by boiling in a covered iron pan, till it assumes the appearance 

 of oil, it will constitute the common ' caustic' of tie surgeon, the potassa fusa of the 

 shops. But to obtain potash chemically pure, recourse must be had to the bicar- 

 bonate, nitrate, or tartrate of potash, salts which, when carefully crystallised, are 

 exempt from anything to render the potash derived from them impure. The bicar- 

 bonate having been gently ignited in a silver basin, is to be dissolved in six times its 

 weight of water, and the solution is to be boiled for an hour, along with 1 Ib. of 

 slaked lime for every pound of the bicarbonate used. The whole must be left to 

 settle without contact of air. The supernatant lye is to be drawn off by a syphon, and 

 evaporated in an iron or silver vessel, provided with a small orifice in its close cover 

 for the escape of the steam, till it assumes, as above, the appearance of oil, or till it 

 be nearly red-hot. Let the fused potash be now poured out upon a bright plate of 

 iron, cut into pieces as soon as it concretes, and put up immediately in a bottle fur- 

 nished with a well-ground stopper. It is a hydrate of potash, being composed of 

 1 atom of potash 48, + 1 atom of water 9 = 57 ; or KO.HO (XHO). 



A pure carbonate of potash may be also prepared by fusing pure nitre in an 

 earthen crucible, and projecting charcoal into it by small bits at a time, till it ceases 

 to cause deflagration. Or a mixture of 10 parts of nitre and 1 of charcoal may be 

 deflagrated in small successive portions in a red-hot deep crucible. When a mixture 

 of 2 parts of tartrate of potash, or crystals of tartar, and 1 of nitre is deflagrated, 

 pure carbonate of potash remains mixed with charcoal, which by lixiviation, and the 

 agency of quicklime will afford a pure hydrate. Crystals of tartar calcined alone 

 yield also a pure carbonate. 



In addition to the ashes of plants, other sources of potash are now utilized. The 

 most important of these sources are the potash-minerals occurring in the upper part 

 of the great salt-deposits of Stassfurt in Prussian Saxony and Kalucz in Galicia. 

 These salts are sylvine, or chloride of potassium ; carnallite, or chloride of potassium 

 and magnesium ; and kainite, a sulphate of potash and magnesia, with chloride of 

 magnesium. See ABBAUM SALTS. 



Potash has also been extracted from certain felspars, from sea-water, from beet-root 

 molasses, from the ash of sea-weeds, and from the suint of wool. But these sources 

 are insignificant when compared with the great deposits of potash salts occurring natu- 

 rally at Stassfurt, which have of late years been worked on a very extensive scale. 



The Production of Potash Salts at Stassfurt. A few details on these mines, which 

 have produced so great a revolution in the manufacture of potash salts, will be useful. 

 Stassfurt is situate about 20 kilos from Magdeburg, on the Anhalt frontier. The 

 geological formation on which it lies is the Bunter Sandstone. The presence of a bed 

 of rock-salt below this stratum was suspected in 1838. Borings were executed by 

 order of the Prussian Government, and in 1851 the presence of a deposit of rock-salt, 

 at least 330 meters in thickness, was ascertained. The formal working of the mines 

 began in 1857. Before reaching the salt it was necessary to sink 260 meters through 

 the sandstone, the gypsum, and the marl. 



The saline deposit does not consist exclusively of common salt, and may be divided 

 into four chief regions. The lowest bed is the largest, and consists entirely of rock- 

 salt, traversed by slender veins of karsteuite. It is about 240 meters in -thickness. 



