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POTASSIUM [symbol K (from kalium), atomic weight 39.114 0=16)] , a metallic chemical element, belonging to the group termed the metals of the alkalis. Although never found free in nature, in combination the metal is abundantly and widely distributed. In the oceans alone there are estimated to be 1141,X 1012 tons of sulphate, K2SO4, but this inexhaustible store is not much drawn upon; and the " salt gardens " on the coast of France lost their industrial importance as potash-producers since the deposits at Stassfurt in Germany have come to be worked. These deposits, in addition to common salt, include the following minerals: sylvine, KCI; carnallite, KClMgC12.6H2O (transparent, deliquescent crystals, often red with diffused oxide of iron); kainite, K2SO4MgSO4MgC126H2O (hard crystalline masses, permanent in the air); kieserite MgSO4H20 (only very slowly dissolved by water); besides polyhalite, MgSO4K2SO4.2CaSO4.2H2O- anhydrite, CaSO4; salt, NaCl, and some minor components. These potassium minerals are not con-fined to Stassfurt; larger quantities of sylvine and kainite are met with in the salt mines of Kalusz in the eastern Carpathian Mountains. The Stassfurt minerals owe their industrial importance to their solubility in water and consequent ready amenability to chemical operations. In point of absolute mass they are insignificant compared with the abundance and variety of potassiferous silicates, which occur everywhere in the earth's crust; orthoclase (potash felspar) and potash mica may be quoted as prominent examples. Such potassiferous silicates are found in almost all rocks, both as normal and as accessory components; and their disintegration furnishes the soluble potassium salts which are found in all fertile soils. These salts are sucked up by the roots of plants, and by taking part in the process of nutrition are partly converted into oxalate, tartrate, and other organic salts, which, when the plants are burned, are converted into the carbonate, K2CO3. It is a remarkable fact that, although in a given soil the soda-content may predominate largely over the potash salts, the plants growing in the soil take up the latter: in the ashes of most land plants the potash (calculated as K20) forms upwards of 90% of the total alkali. The proposition holds, in its general sense, for sea plants likewise. In ocean water the ratio of soda (Na2O) to potash (K20) is loo : 3.23 (Dittmar); in kelp it is, on the average, too : 5.26 (Richardson). Ashes particularly rich in potash are those of burning nettles, wormwood (Artemisia absinthium), tansy (Tanacetum vulgare), fumitory (Fumaria officinalis), and tobacco. In fact, the ashes of herbs generally are richer in potash than those of the trunks and branches of trees; yet, for obvious reasons, the latter are of greater industrial importance as sources of potassium carbonate. According to Liebig , potassium is the essential alkali of the animal body; and it may be noted that sheep excrete most of the potassium which they take from the land as sweat, one-third of the weight of raw merino consisting of potassium compounds.
To Sir Humphry Davy belongs the merit of isolating this element from potash, which itself had previously been considered an element. On placing a piece of potash on a platinum plate, connected to the negative of a powerful electric battery, and
ordinary merit. Curious if not very artistic bills have been produced in Russia; and in Austria good work has been done by Orlik, Schliessmann, Oliva and Hynais.
In the United States of America, however, with the exception of some designs by Matt Morgan, few posters of artistic interest were produced before 1.889, in which year Louis J. Rhead commenced a notable series of decorative placards. Will H. Bradley began to produce his curious decorative grotesque posters a little later. If American artists are behind Europeans in the artistic designing of large posters they have no rivals in the production of small illustrated placards for publishers of books and magazines. Chief among those who have devoted themselves to this branch of poster design is Edward Penfield. Others who have achieved success in it include Maxfield Parrish, Ethel Reed, Will Carqueville, J. J. Gould, J. C. Leyendecker, Frank Hazenplug, Charles Dana Gibson, Will Denslow, Florence Lundbourg and Henry Mayer.
Exhibitions of artistic posters have been held in the chief cities of Europe and America, and the illustrated placard has already a literature of its own. In England a monthly magazine (The Poster) was for a time specially devoted to its interests, and col-lectors are numerous and enthusiastic.
See Ernest Maindron, Les Afches illustrees (Paris, 1895); Les Maitres de l'affcche (Paris) ; Les Affiches etrangeres illustrees (Belgium, Austria, Great Britain, United States, Germany and Japan) (Paris, 1897) ; Charles Hiatt, Picture Posters (London, 1895) ; J. L. Spousel, Das Moderne Plakat (Dresden, 1897) ; Arsene Alexandre, M. H. Spielmann, H. C. Bunner and A. Jaccacci, The Modern Poster (New York . 1895). ' (C. HI.)
End of Article: POTASSIUM [symbol K (from kalium), atomic weight 39.114 0=16)]
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