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Sodium
Symbol: Na Atomic number: 11 Atomic weight: 22.99 Melting poim: 371.0 K Boiling point: 1154.6 K Density: 0.9680 g/cmg Compounds of this common element-the fifth most abundant metal after Al, Mg, Ca, and Fe have been known for manv "vears. While this element is not found free in nature, it is-after chlorine-the second most abundant element in solution in sea water. Lavoisier reaarded the alkalies as simple substances which "with increasing knowledge, may prove to he complex". No lesser man than John Dalton considered potash and soda to be simple elements, and the metals potassium and sodium to he compounds of these substances with hydrogen. In October 1807, Humphry Davy first isolated potassium by electrolyzing molten potash (KOH). A few days later he performed a similar experiment with soda-producing sodium. Davy named the elemenr afe at in word sodanum (headache remedv). The next ter ~ - the ~-~~ year Gay-Lussac and L. J. Thenard producedsodium by reducing sodium hydroxide with iron a t high temperatures. In 1824 Oersted discovered that metallic sodium would reduce aluminum chloride to elemental aluminum. In 1855 H. Sainte-Claire Deville developed the first commercial process for production of the metal by reducing sodium carhonate with carbon a t temperatures greater than 1100 OC. H. Y. Castner in 1890 produced the metal by electrolysis of fused sodium hydroxide. A process involving the electrolysis of a mixture of fused NaCl and CaClz in the Downs cell was introduced in 1921. This process produces the metal and elemental chlorine. Laree deoosits of sodium salts abound worldwide. In the unite; states deposits of sodium borate (borax), sodium carbonate (trona), sodium nitrate (saltpetre), and sodium chloride (rocksalt) are found in California, Michigan, New York, Utah, Virginia, and the Gulf Coast. The element is used to reduce beryllium, thorium, titanium. and zirconium halides. Sodium plaved a vital role in the of ( C Z H S ) ~ aP role ~ , that until recently accounted for 60% of the total sodium usage. The elimination of leaded gasoline will diminish this specific use of the metal.
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1046
Journal of Chemical Education
ALTON BANKS Soulhrmst Texas State Universily SBn Mamas, TX 78666
The element is used in trace amounts (less than 1%) to produce fine-grained aluminumlsilicon alloys. An extremely visible application of elemental sodium is in sodium vapor lamps, in which a small piece of the metal is placed in a sealed arc tube with neon. The familiar yellow glow of these lamps is areminder of the importanceof the sodium D line in the solar spectrum. Additionally the metal is used with potassium as an excellent heat-transfer agent in some nuclear reactors. The com~oundsof sodium are a vital part of industry. NaCl is moie widely used in manufacturing other inorganic chemicals than is any other substance. NaOH is an important industrial chemical, with about 30% of its uses being directed toward producing other chemicals. Another 25% of YaOH producti'n goes toward manufacture of cellulose film and rayon. Fifty percent of the annual sodium carbonate nrodurtion consumed bv ~ the elass industry. This salt also r..-. ~ .is~ - - ~ ~ plays a role in the manuf&turcof textiles, nonferrous metals. and oetroleum oroducts. As an aside, the carbonate is also known as soda ash, owing to its presence in the ashes of plants-from which the salt was formerly extracted. Indeed the ancients used plant ashes as a cleaning material. The carbonate is also assuming a larger role in reducing pollution from stack gases. The powdered salt reacts with sulfur dioxide in these eases to produce sodium sulfite. Another sodium salt, the sufate-alio known as salt cake-plays a vital role in the Kraft pulp process for producing brown wrapping paper and corrugated boxes. Finally, a vital but perhaps not as visible role for sodium in its ionic form is that of a regulator of hody fluids in higher animals. The sodiumlpotassium balance in hody fluids is essential for maintaining proper muscular contraction. Some of these applications are shown on "The Periodic Table Videodisc" in frames 36435-36440. ~~
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General References "KC? Oismverer: Exploring the Properties of the Chemical Elements", JCE: Soflwarr
19R8,IB(1).
Banks, A. J. "The PeriodicTableVideodisc";JCE: Softmare 1989, Special Issue 1. Handbook o/ Chemistry & Phyairs, 46th cd.; Weast. Robcn C., Ed.; Chemical Rubber: Cleveland. OH. 1965-1966; p 8.137. Kirk-Ofhmer Eneyclopedio o/ Chemical Technology, 2nd ed.; Intemience: New Yark. 1369; Vol. 16,p 432. G r e e n w d . N. N.: Eernshaw. A. Chemisfryo/fhe Elements; Pergamon: New York, 1984: "" "
