Sodium

Properties, occurrence, and uses. Sodium is a very soft, silvery-white metal. It occurs abundantly in nature in compounds, especially common salt sodium chloride (NaCl)—which forms the mineral halite and comprises about 80 percent of the dissolved constituents of seawater. Sir Humphry Davy first prepared sodium in its elemental form (1807) by the electrolysis of fused sodium hydroxide (NaOH). Sodium is the most common alkali metal and the sixth most abundant element on Earth, comprising 2.8 percent of the Earth's crust; it also occurs in more than trace amounts in the stars and Sun. Lighter than water, it can be cut with a knife at room temperature and is brittle at low temperatures. It conducts heat and electricity easily and exhibits to a marked degree the photoelectric effect (emission of electrons when exposed to light). Sodium reacts vigorously with water to give hydrogen (which may ignite from the heat of the reaction) and sodium hydroxide. The metal is extremely active chemically, easily unites with oxygen of the air, and usually must be kept immersed in an inert atmosphere such as nitrogen or in inert liquids such as kerosene or naphtha. Because sodium is so reactive, it never occurs in the free state in nature. It is commercially produced by electrolyzing sodium chloride.

Kerosene is a complex mixture of hydrocarbons from a variety of chemical processes blended to meet standardized product specifications. Composition varies greatly and includes C9 to C16 hydrocarbons with a boiling range of about degrees Fahrenheit A petroleum distillate, from the same "middle distillates" as kerosene and "mineral spirits", but is somewhat more volatile than kerosene. Naphtha is the "first cut", coming off in fractional distillation BEFORE Kerosene. Today used as a solvent, and paint thinner (not recommended as such!). Has been sold in a blended form by Coleman as "white gas" or "Coleman Fuel" for years.

Inexpensive and available in tank-car quantities, sodium is widely used in the manufacture of chemicals and pharmaceuticals, in metallurgy, as a heat exchanger in atomic reactors and certain types of engines, and in sodium vapour lamps. Natural sodium is the stable isotope of mass 23. Of the six radioactive, artificial isotopes, sodium-22 (2.6-year half-life) is used as a radioactive tracer for natural sodium, sodium-24 (15-hour half-life) is limited in use by its short life, and the rest have half-lives of a minute or less. The yellow colour of the sodium vapour lamp and the sodium flame (the basis of an analytical test for sodium) is identified with two prominent lines in the yellow portion of the light spectrum.

Principal compounds. Sodium is highly reactive, forming a wide variety of compounds with nearly all inorganic and organic anions. It has a valence of +1, and its single valence electron is lost with great ease, yielding the colourless sodium ion (Na + ).

Sodium hydroxide (NaOH) is a corrosive, white crystalline solid that readily absorbs moisture until it liquefies. Commonly called caustic soda, or lye, sodium hydroxide is the most widely used industrial alkali. It is highly corrosive to animal and vegetable tissue. The alkaline solutions it forms when dissolved in water neutralize acids in various commercial processes: in petroleum refining, it removes sulfuric and organic acids; in soapmaking, it reacts with fatty acids. In the making of cellophane, paper, viscose rayon, and other products, its alkaline solutions enter into the treatment of cellulose and into the manufacture of many chemicals.

The most important and familiar sodium compound is sodium chloride, or common salt, NaCl. Most other sodium compounds are prepared either directly or indirectly from sodium chloride, which occurs in seawater, in natural brines, and as rock salt. Other major commercial applications of sodium chloride include its use in the manufacture of chlorine and sodium hydroxide by electrolytic decomposition and in the production of sodium carbonate (Na 2 CO 3 ) by the Solvay process. The electrolysis of sodium chloride produces sodium hypochlorite, NaOCl, a compound of sodium, oxygen, and chlorine used in large quantities in household chlorine bleach. Sodium hypochlorite is also utilized as an industrial bleach for paper pulp and textiles, for chlorination of water, and in certain medicinal preparations as an antiseptic and a fungicide. It is an unstable compound known only in aqueous solution.

Sodium nitrate, or soda nitre, NaNO 3, is commonly called Chile saltpetre after its mineral deposits in northern Chile, the principal source. Sodium nitrate is used as a nitrogenous fertilizer and as a component of dynamite.

Sodium sulphate, Na 2 SO 4, is a white crystalline solid or powder employed in the manufacture of kraft paper, paperboard, glass, and detergents and as a raw material for the production of various chemicals. It is obtained either from deposits of the sodium sulfate minerals mirabilite and thenardite or synthetically by the treatment of sodium chloride with sulfuric acid. The crystallized product is a hydrate, Na 2 SO 4 ×10H 2 O, commonly known as Glauber's salt. Sodium thiosulphate (sodium hyposulfite), Na 2 S 2 O 3, is used by photographers to fix developed negatives and prints; it acts by dissolving the unchanged silver salts

Other familiar sodium compounds are the carbonates, which contain the carbonate ion (CO 3 2- ). Sodium bicarbonate, also called sodium hydrogencarbonate, or bicarbonate of soda, NaHCO 3, is a source of carbon dioxide and so is used as an ingredient in baking powders, in effervescent salts and beverages, and as the main constituent of dry-chemical fire extinguishers. Its slight alkalinity makes it useful in treating gastric or urinary hyperacidity and acidosis. It is also employed in certain industrial processes, as in tanning and the preparation of wool.

Sodium carbonate, or soda ash, Na 2 CO 3, is widely distributed in nature, occurring as constituents of mineral waters and as the solid minerals natron, trona. Large quantities of this alkaline salt are used in making glass, detergents, and cleansers. Sodium carbonate is treated with carbon dioxide to produce sodium bicarbonate. The monohydrate form of sodium carbonate, Na 2 CO 3 ×H 2 O, is employed extensively in photography as a constituent in developers. Washing soda (sal soda) consists of sodium carbonate decahydrate, Na 2 CO 3.10H 2 O; it serves as a bleach for cotton and linen