| In some ways, potassium is a strange substance, as | | | | causing a state of permanent relaxation known as |
| evidenced by its behavior in response to water. As | | | | potassium inhibition. Since plants depend on potassium |
| everyone knows, water tends to put out a fire, and | | | | for growth, it was only logical that potassium, in the |
| most explosives, when exposed to sufficient | | | | form of potassium chloride, was eventually applied as |
| quantities of water, become ineffective. Potassium, | | | | a fertilizer. This, at least, distinguishes it from its sister |
| on the other hand, explodes in contact with water | | | | element: sodium, or sodium chloride, which can kill |
| and reacts violently with ice at temperatures as low | | | | plants if administered to the soil in large enough |
| as ?148°F (?100°C). In a complete reversal of the | | | | quantities. Another application of potassium is in the |
| procedures normally followed for most substances, | | | | area pioneered by the Chinese about 800 years ago: |
| potassium is stored in kerosene, because it might | | | | the manufacture of fireworks and gunpowder from |
| burst into flames if exposed to moist air. Many | | | | potassium nitrate. Like ammonium nitrate, made |
| aspects of potassium mirror those with regard to | | | | infamous by its use in the 1993 World Trade Center |
| sodium. The two have a number of the same | | | | bombing and the Oklahoma City bombing in 1995, |
| applications, and in certain situations, potassium is | | | | potassium nitrate doubles as a fertilizer. |
| used as a sodium substitute. Like sodium, potassium | | | | The three heaviest alkali metals are hardly household |
| is never found alone in nature; instead, it comes | | | | names, though one of them, cesium, does have |
| primarily from sylvinite and carnalite, two ores | | | | several applications in industry. Rubidium and cesium, |
| containing potassium chloride. Also, like sodium, | | | | discovered in 1860 by German chemist R. W. Bunsen |
| potassium was first isolated in 1807 by Davy, using | | | | (1811-1899) and German physicist Gustav Robert |
| the process of electrolysis. A few years later, a | | | | Kirchhoff (1824-1887), were the first elements ever |
| German chemist dubbed the newly isolated element | | | | found using a spectroscope. Matter emits |
| "kalium," apparently a derivation of the Arabic qali, for | | | | electromagnetic radiation along various spectral lines, |
| "alkali"; hence the use of K as the chemical symbol | | | | which can be recorded using a spectroscope and |
| for potassium. | | | | then analyzed to discern the particular "fingerprint" of |
| Potassium has another similarity with sodium; although | | | | the substance in question. When Bunsen and |
| it was not isolated until the early nineteenth century, | | | | Kirchhoff saw the bluish spectral lines emitted by one |
| its compounds have been in use for many centuries. | | | | of the two elements, they named it cesium, after a |
| The Romans, for instance, used potassium | | | | Latin word meaning "sky blue." Cesium, which is very |
| carbonate, or potash, obtained from the ashes of | | | | rare, appears primarily in compounds such as pollucite. |
| burned wood, to make soap. During the Middle Ages, | | | | It is used today in photoelectric cells, military infrared |
| the Chinese applied a form of saltpeter, potassium | | | | lamps, radio tubes, and video equipment. During the |
| nitrate, in making gunpowder. And in colonial America, | | | | 1940s, American physicist Norman F. Ramsey, Jr. built |
| potash went into the production of soap, glass, and | | | | a highly accurate atomic clock based on the natural |
| other products. The production of just one ton of | | | | frequencies of cesium atoms. Rubidium, by contrast, |
| potash required the burning of several acres' worth | | | | has far fewer applications, and those are primarily in |
| of trees, a wasteful practice in more ways than one. | | | | areas of scientific research. On Earth it is found in |
| Though there was no environmentalist movement in | | | | pollucite, lepidolite, and carnallite. It is considerably |
| those days, financial concerns never go out of style. | | | | more abundant than cesium, and vastly more so than |
| In order to save the money lost by using up vast | | | | francium. Indeed, it is estimated that if all the |
| acres of timber, American industry in the nineteenth | | | | francium in Earth's crust were combined, it would |
| century sought another means of making potash. | | | | have a mass of about 25 grams. Francium was |
| The many similarities between sodium and potassium | | | | discovered in 1939 by French physicist Marguerite |
| provided a key, and the substitution of sodium | | | | Perey (1909-1975), student of the famous |
| carbonate for potassium carbonate saved millions of | | | | French-Polish physicist and chemist Marie Curie |
| trees. | | | | (1867-1934). For about four decades, scientists had |
| In 1847, German chemist Justus von Lie big | | | | been searching for the mysterious Element 87, and |
| (1803-1873) discovered potassium in living tissues. As | | | | while studying the decay products of an actinium |
| a result, scientists became aware of the role this | | | | isotope, actinium-227, Perey discovered that one out |
| alkali metal plays in sustaining life: indeed, potassium is | | | | of 100 such atoms decayed to form the |
| present in virtually all living cells. In the human body, | | | | undiscovered element. She named it francium, after |
| potassium which accounts for only 0.4% of the | | | | her home-land, France. Though the discovery of |
| body's mass is essential to the functioning of muscles. | | | | francium solved a mystery, the element has no |
| In larger quantities, however, it can be dangerous, | | | | known uses outside of its applications in research. |