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sodium tetraborate decahydrate

(sō`dēəm tĕ'trəbôr`āt dĕk'əhī`drāt), chemical compound, Na2B4O7·10H2O; sp. gr. 1.73; slightly soluble in cold water; very soluble in hot water; insoluble in acids. Borax is a colorless, monoclinic crystalline salt; it also occurs as a white powder. It readily effloresces, especially on heating. It loses all water of hydration when heated above 320°C; and fuses when heated above 740°C;; a "borax bead" so formed is used in chemical analysis (see bead testbead test,
test used in the identification of certain metals. Some metallic ions that cannot be identified by a flame test are identified by a bead test. The test can also be used to confirm the results of a flame test. The borax bead test is the most common.
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). Borax is widely and diversely used, e.g., as a mild antiseptic, a cleansing agent, a water softener, a corrosion inhibitor for antifreeze, a flux for silver soldering, and in the manufacture of enamels, shellacs, heat-resistant glass (e.g., Pyrex), fertilizers, pharmaceuticals, and other chemicals. It is sometimes used as a preservative but is toxic if consumed in large doses. Naturally occurring borax (sometimes called tincal) is found in large deposits in the W United States (Borax Lake in Death Valley, Calif.; Nevada; and Oregon) and in the Tibet region of China. Borax can also be obtained from borate minerals such as kernite, colemanite, or ulexite. California is the chief source of borate minerals in the United States.
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The following article is from The Great Soviet Encyclopedia (1979). It might be outdated or ideologically biased.



sodium tetraborate, Na2B4O7·IOH2O, crystal hydrate of the sodium salt of tetraboric acid. It is found in nature in the form of the mineral borax (or tincal), which is white or, less frequently, gray and yellow in color; its density is 1, 690-1, 720 kg/m3. Borax is soluble in water (1.6 g of the anhydrous salt in 100 g of H2O at 10° C). Aqueous solutions of borax are alkaline and absorb CO2 from the air. Borax is decomposed by strong acids. It is used in soldering, since fused borax dissolves oxides of metals and in that way cleans the metallic surfaces to be soldered. Borax is used in the production of special kinds of glass (mainly optical), enamels, glazes, for tanning leather, for making substances borated, and in agriculture as a trace-element fertilizer.

Borax is a medicinal preparation that has antiseptic action. It is used in the form of a 3-5 percent solution for irrigation and lubrication of the buccal cavity, nose, and nasopharynx in various infectious diseases (tracheitis, head cold, stomatitis, and others). Borax is prescribed internally for treatment of epilepsy (especially in children).

The Great Soviet Encyclopedia, 3rd Edition (1970-1979). © 2010 The Gale Group, Inc. All rights reserved.


Na2B4O7·10H2O A white, yellow, blue, green, or gray borate mineral that is an ore of boron and occurs as an efflorescence or in monoclinic crystals; when pure it is used as a cleaning agent, antiseptic, and flux. Also known as diborate; pyroborate; sodium (1:2) borate; sodium tetraborate; tincal.
McGraw-Hill Dictionary of Scientific & Technical Terms, 6E, Copyright © 2003 by The McGraw-Hill Companies, Inc.


1. a soluble readily fusible white mineral consisting of impure hydrated disodium tetraborate in monoclinic crystalline form, occurring in alkaline soils and salt deposits. Formula: Na2B4O7.10H2O
2. pure disodium tetraborate
Collins Discovery Encyclopedia, 1st edition © HarperCollins Publishers 2005