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Borax

Borax Powder Chemical Formula

Borax powder, chemical name sodium tetraborate decahydrate having chemical formula Na2B4O7, 10H2O, or Na2[B4O5(OH)4], 8H2O widely uses in India, Egipt, Rome, and other ancient civilization for the preparation of flux, glazes, and hard glass. Therefore, borax is an important chemical compound of chemical element boron isolated in the nineteenth century by Davy, Gay-Lussc, and Thenard in 1808. Heating of borax crystals first swells due to losing the hydrated water but on further heating anhydrous substance gives meta-borate and boron trioxide. The physical properties are of borax very similar to boric acid and obtained on heating boric acid solution with sodium carbonate. Borax powder is an important chemical of boron compound widely uses in pesticide or insecticide to killing ant or roach, antiseptics or mouthwash in medicine, cleaner solution or water softener, and enamel or fertilizer preparation.

Chemical Structure of Borax Crystal

The ionic structure of borax contains two covalent tetrahedral units of BO4 and two covalent planners units of BO3 and each BO4 shares two oxygen with two BO3 units but one oxygen with the second BO4 unit given below the picture. The fourth oxygen bonding with the BO4 unit of boron and hydrogen atom.

Borax powder crystals or sodium tetra-borate decahydrate chemical formula and compound structure

Therefore, the planner BO3 unit is sp2 hybridized but the tetrahedral BO4 unit is sp3 hybridized with an additional electron from sodium. These hybrid orbital overlap with suitable orbitals of the oxygen atom.

Preparation of Sodium tetraborate decahydrate

Boiling the mineral colemanite with an alkaline solution of sodium carbonate uses for the preparation of sodium tetraborate decahydrate or crystalline solid borax powder. The produced calcium carbonate filtered out and concentration filtrate deposits as the crystals solid. Another solution containing NaBO2 again uses for the conversation of Na2B4O7, 10H2O by passing carbon dioxide.

2CaO,3B2O3+2Na2CO3=Na2B4O7+2CaCO3+2NaBO2
NaBO2 + CO2 = Na2B4O7 + Na2CO3

Borax is also obtained by chemical reaction or heating the boric acid solution with sodium carbonate and specific heat. It can be crystalline by cooling the solution.

4H3BO3 + Na2CO3 → Na2B4O7 + 6H2O + CO2

Physical and Chemical Properties of Borax

The base properties and structure of boron compounds like crystalline borax powder and boric acid are very much similar that dissolved in liquid mainly hot water solution. At normal temperature, the crystalline borax powder contains ten molecules of hydrated water in its molecular formula but at 62°C, it contains five molecules of hydrating water in molecular structure.

An aqueous solution shows alkaline properties due to hydrolysis. Because of the chemical reaction of water (H2O) with borax form the substitute boric acid (H3BO3), a weak acid tritiated against strong acids using methyl orange as an indicator (pH scale 3.1 to 4.4).

Color of Borax Bead Test in Chemistry

When we heating borax first swells due to the loss of hydrating water but on further heating produced metaborate and boron trioxide.

Na2B4O7, 10H2O → 2NaBO2 + B2O3 + 10H2O

The fusion of borax with metal oxide forms a bead of metal borate that look like a characteristic glossy color uses in chemistry for the quantitative chemical analysis of metal salts, known as the bead test. When fusion with metal salts heated in oxidation flame forms ic-metaborate with a characteristic glossy color. But when fusion with metal salts heated in reduction flame forms us-metaborate with a characteristic glossy color.

Metal compound Color of the bead
Oxidizing flame Reducing flame
Copper Green, blue Dull red
Iron Yellow Dark green
Cobalt Dark blue Dark blue
Nickel Brown colorless
Chromium Green Green

Therefore, the fusion of borax with metal ingredients like CuO in an oxidizing flame define blue cupric metaborate but in reducing flame it define dull red cuprous metaborate.

CuO + B2O3 → Cu(BO2)2
2Cu(BO2)2 + C → Cu2(BO2) + CO + B2O3

Uses of Borax Powder

  1. A soft, light, colorless crystalline substance, sodium tetraborate decahydrate, or borax is used mainly in the manufacture of optical and hard glass, as a solvent in metallurgy for metal-oxide slags, as a flux in welding and soldering, and as a fertilizer for the cultivation.
  2. Borax is also used as a soap supplement for the carpet cleaner in the laundry, antiseptic in medicine, manufacturing of enamel, and toxic poisonous pest or insecticide control chemicals using for ants or roach killer.
  3. Due to the facts of the low solubility of calcium and magnesium borates, borax is used as a cleaner or softener of water.
  4. Borax powder uses for the preparation of glaze to pottery, stiffening candle-wicks, and laundering.