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Joan Hess, age 11, of Santa Rosa, Calif., for her question:

WHAT EXACTLY IS BORAX?

Borax is an important chemical compound of the element boron. Its chemical name is sodium borate or sodium tetraborate. Borax is 65 a white, soft, many sided crystal that dissolves easily and quickly  in water. Borax crystals will clump together if they are exposed to moist air, much as salt crystals will.

Perhaps borax is best known for its use in washing powders, water softeners and soaps. It is also used extensively in medicines, for ointments and eye washes. Manufacturers also mix borax with clay and other substances to      make enamel glazes for sinks, stoves, refrigerators and metal tiles.

Potters use borax to add strength to their products and to make a hard glaze for dishes. In addition, glassmakers mix borax with sand so that it will melt easily and give strong, brilliant glass. Glass cooking utensils and thermometers are made from glass that contains borax.

Borax is also used as a food preservative and in the textile industries, in tanning leather and making paper. It is indeed a very versatile compound.

Most of the world's supply of borax comes from Southern California. It has been estimated that there is more than a 100 year supply of borax in one California mine alone.

Borax may be taken from open pit mines, as in California's Mojave Desert. In these, miners strip away the covering ground to expose the borax bed. Workers then use dynamite to blast loose the solid borax. The large chunks of borax are crushed and dissolved. This solution goes through many purification steps until borax crystals are obtained.

Borax is also obtained from dry lake beds. A solution is made and then allowed to stand in vats to separate the borax from the heavier salts, which sink to the bottom.

Kernite is 75 percent pure sodium borate. It was discovered in the Mojave Desert in 1926, and is a major source of commercial borax. It is dissolved in water, and, after the impurities are filtered off, it is allowed to recrystalize. This is a cheap and easy way to produce borax.

Tibet is said to have been the first important source of borax. Since the 1920s, however, the United States and California have produced most of the world's borax.

When borax crystals are heated in a loop of platinum wire, 'they swell because the water in them evaporates. When all of the water is gone, a clear, glassy liquid remains. This liquid combines with many metallic oxides to produce borax beads of various colors.

In mineral and chemical analyses, the borax beads are used to detect the presence of certain metals. If cobalt is present, a dark blue bead appears. For copper, a light blue bead appears. The presence of nickel will produce a brown bead while manganese comes out amethyst.

Boric acid is prepared in the United States by treating borax with hydrochloric or sulfuric acid. It forms colorless, odorless crystals or a white powder that dissolves in water.

 

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