Chemical Reactivity of Borax

Borax is a hydrate salt of boric acid that is also known as sodium borate, sodium borate decahydrate, or sodium tetraborate decahydrate. It dissolves in water to generate a basic, aqueous solution and is commonly available in powder or granular form. It is soluble and has a wide range of industrial and home uses as a component in a variety of goods.

IUPAC Name:- disodium;3,7-dioxido-2,4,6,8,9-pentax a-1,3,5,7-tetra borabicyclo[3.3.1]nonane; decahydrate.

Names used for the Borax:-

• borax decahydrate

• sodium borate decahydrate

• sodium tetraborate decahydrate.

Chemical Formula:-   B4O7Na2 . 10H2O

                                       B4H20Na2O17

  Fig :- Structure of  Borax.

Uses

Borax is used in several cosmetic products and detergents. 

1. Borax preparation from Tincal.

Tincal  can be made into borax Na2B4O7 by dissolving it in hot water. The resulting solution is filtered to eliminate insoluble impurities such as sand, clay, and other contaminants. The resultant solution can be concentrated to obtain pure borax crystals ( Na2B4O7).

2. Preparation of Borax from Colemanite (Ca2B6O11):-

In this method , The colemanite mineral is finely powdered and boiled with a solution of sodium carbonate solution. As a result, borax and sodium metaborate are formed. The chemical Equation for the Reaction can be given as:-

Ca2B6O11 +  2Na2CO3   →    2CaCO3 +  Na2B4O7 +  2NaBO2

White precipitate of CaCO3 is formed in this Reaction. 

The White calcium carbonate precipitate formed during the reaction is removed by filtration, and the fluid is concentrated and then cooled to provide pure borax crystals. It is possible to convert carbon dioxide gas to borax by passing it through sodium metaborate, which is found in the mother liquor. The reaction’s chemical equation is as follows:

4NaBO2 + CO2   →   Na2B4O7 +  Na2CO3

3. Boric acid is used to make borax  (H3BO3):-

Small amounts of borax can be made by reacting boric acid (H3BO3) with sodium carbonate. This is a neutralisation reaction in action. The reaction’s chemical equation is as follows:

4H3BO3 +  Na2CO3 →   Na2B4O7  +  6H2O +  CO2      .

Borax’s Physical Characteristics

Borax is a crystalline white substance. It is only slightly soluble in cold water, but it dissolves rapidly in hot water. When crystallised at room temperature, borax creates transparent crystals with 10 molecules of water of crystallisation. Borax crystallises as pentahydrate crystals (Na2B4O7.5H2O) when heated above 338 degrees Fahrenheit. Jeweller’s borax is the name for this type of borax. It is more difficult to work with than conventional borax.

Borax Chemical Properties

1. Reaction of Borax with Halogen group:-

             Hydrochloric acid  reacts with Borax to form Boric acid. Reaction is given Below:-

Na2B4O7.10H2O  +  2HCl  →   4B(OH)3  +  2NaCl +  5H2O   

2. When borax is hydrolyzed, it produces an alkaline solution. This is due to the fact that when it is hydrolyzed, it produces a mild acid (H3BO3) and a strong base  (NaOH) The following are the chemical equations for hydrolysis:

Na2B4O7 + 3H2O → 2NaBO2 + 2H3BO3

2NaBO2  +  4H2O→  2NaOH +  2H3BO3

  Na2B4O7+7H2O→2Na++2OH–+4H3BO3 

The phenolphthalein indicator lends a pink colour to the aqueous solution of borax due to its alkaline nature, which is expelled when glycerol is added to the aqueous solution. This is because the boric acid created during the hydrolysis reacts with the glycerol to form a complex, releasing a proton (H+). This proton neutralises NaOH, restoring the solution’s neutrality. As a result, the solution has lost its colour.

    3  . Heat Action – Borax Bead Test

Borax expands when heated due to the escape of crystallisation water (as steam).

     Na2B4O5OH4.8H2O→  Na2B4O7+ 10H2O

It eventually transforms into a colourless glassy bead when heated further (made of Na2BO2 and B2O3). The borax bed is the name for this type of bed. When cooked in the presence of colored   salt, this bead takes on a distinct colour. 

Borax’s Applications

Borax has numerous applications in a variety of industries. They are as follows:

• Soldering, welding, and other metallurgical activities employ borax as a flux.

• Enamelling and glazes for pottery and tiles are made with it.

• In the leather business, borax is used to clean hides and skins as well as to colour leather.

• Because it hydrolyzes to generate a mildly alkaline solution, borax is a good cleansing agent.

• It’s a softening agent for water.

• The cations of colored salts are detected using the borax bead test.

• It is used to prevent afterglow in match sticks by impregnating them with it.

• It’s a moderate antiseptic that’s been used for a long time.

• Fire retardants contain borax.

• It’s used to make candle wicks stiffer.

Conclusion

Borax is a name that refers to a group of minerals or chemical compounds that are  closely related. Their crystal water content differs. Anhydrous sodium tetraborate (Na2B4O7) and sodium tetraborate pentahydrate (Na2B4O7.5H2O) are two types of borax discovered. The octahydrate (Na2B4O5OH4.8H2O) is the same as the octahydrate (Na2B4O5(OH)4.H2O)  .