Borax
To begin with, Borax, also known as sodium tetraborate, may look like an ordinary white powder, but it holds fascinating properties far beyond a common salt. It is the most important of all borates. Widely used in laboratories, households, and industries, Borax is valued for its cleansing power and unique chemical behaviour and structure. Borax is formed by NaOH ( a strong base) and H₂B₄O₇ ( a weak acid), so it is a basic salt.) Borax occurs as a natural deposit called tincal in the dried-up lakes of Tibet and California
H₂B₄O₇ + 2NaOH + 10H₂O → Na₂B₄O₇·10H₂O
From glass-making to metallurgy, and from laundry boosters to laboratory reagents, its applications are deeply rooted in its physical and chemical nature. But what exactly makes this compound so special? In this article, we’ll explore the physical characteristics, chemical properties, and manufacturing process of Borax to uncover whether it’s truly a chemical wonder in disguise.
Manufacturing of Borax
After that, here are three ways that we discussed to manufacture borax.
- From Soda ash/ Old method
- Colemantie
- From Tincal
From Soda ash/ Old method
Formally, borax was manufactured by treating a hot solution of boric acid with the proper amount of soda ash ( Na₂CO₃).
4H₃BO₃ + Na₂CO₃ → Na₂B₄O₇ + CO₂ + 6H₂O
Na₂B₄O₇ + 10H₂O → Na₂B₄O₇·10H₂O
Colemanite
Nowadays, borax is almost exclusively obtained from calcium borate. Finally, powdered Colemanite is boiled with Na₂CO₃ solution, when CaCO3 precipitates out and a mixture of borax and sodium metaborate is formed.
Ca₂B₆O₁₁·5H₂O + Na₂CO₃ → Na₂B₄O₇·10H₂O + CaCO₃ ↓ + By-products
The clear solution from the top is taken off and is then allowed to crystallize, when crystals of borax separate out. To get more borax, CO2 is blown through the mother liquor. The sodium metaborate is decomposed into borax, which separates in the form of fine crystals.
4NaBO₂ + CO₂ + → Na₂B₄O₇ + 2Na₂CO₃
From Tincal
Borax may also be obtained from tincal(Na₂B₄O₇·10H₂O). By treating tincal with water and subsequently evaporating the clear solution, the crystals of borax separate.
Properties of Borax
Each element shows two types of properties: physical properties and chemical properties. Here we discussed the physical and chemical properties of Borax.
Physical Properties
- Borax is a white crystalline solid.
- It is sparingly soluble ( very soluble)in cold water but more soluble in hot water. In 100g of water at 10 degrees, only 3g of borax is soluble, but at 100 degrees, its solubility is 99.3 g.
- If a saturated solution of borax is allowed to crystallise above 62 degrees, octahedral crystals of pentahydrateNaBO₂·5H₂O separate, but if temperatures of below 62 degrees, decahydrate crystals Na₂B₄O₇·10H₂O are formed.
Chemical Properties
1. Hydrolysis
Aqueous solution of borax is alkaline in nature due to hydrolysis.
Na₂B₄O₇ + 7H₂O → 4H₃BO₃ + 2NaOH
Aqueous solution of borax turns red litmus blue due to the presence of alkali.
- Borax, when dissolved in water, ionises as:
Na₂B₄O₇ → 2Na⁺ + B₄O₇²⁻
- Hydrolysis of B₄O₇²⁻ ions occurs as follows:
B₄O₇²⁻ + 7H₂O → 4H₃BO₃ + 2OH⁻
So, a strong alkali ( NaOH) is formed, which is highly ionised. On the other hand, boric acid is ionized to a litlle extent becauses it is a weak acid. Hence, solution of borax as a whole is alkaline in nature.
- Hydrolysis is prevented in the presence of glycerol.
2. Effect of Heat
When borax is heated, it loses water and swells up into a white porous mass due to the expulsion of water. On further heating, it melts into a clear, transparent glass, which dissolves many metallic oxides, forming coloured beads. This reaction forms the basis of the borax bead test.
Na₂B₄O₇·10H₂O → 2NaBO₂ + B₂O₃ + 10H₂O
3. Action of Strong Acid
It’s an aqueous solution that reacts with HCl or H₂SO₄ to form boric acid:
Na₂B₄O₇ + 2HCl + 5H₂O → 4H₃BO₃ + 2NaCl
Na₂B₄O₇ + H₂SO₄ + 5H₂O → 4H₃BO₃ + Na₂SO₄
4. Reaction with Ammonium Chloride
When borax is heated with ammonium chloride, boron nitride is produced.
Na₂B₄O₇ + 2NH₄Cl + 3H₂O → 4H₃BO₃ + 2NaCl + 2NH₃
Borax Bead Test
This test is used for the identification of coloured ions of the salt, e.g., Co²⁺, Cu², Fe³⁺, and Ni²⁺ , etc.
Procedure
Prepare a loop at the end of the platinum wire. Heat the wire and take a little powder box on the hot loop. Heat again, borax first swells up and then melts into colourless, glass-like beads on the loop.
Na₂B₄O₇·10H₂O → Na₂B₄O₇ + 10H₂O
Na₂B₄O₇ → 2NaBO₂ + B₂O₃
Now put a few grains of the substance, under examination, on the beads and reheat it first in he oxidizing flame and then in the reducing flame.
Chemistry of Borax Bead Test
Borax, when fused, decomposes into sodium metaborate and boric anhydride.
Na₂B₄O₇ → 2NaBO₂ + B₂O₃
The metallic oxide formed by the substance, under examination, combines with B₂O₃, giving the coloured metallic borates. With cupric oxide, the beads are coloured blue in the oxidising flame because cupric borates are blue.
CuSO₄ → CuO + SO₃
3CuO + B₂O₃ → Cu₃(BO₃)₂
similarliy 3CoO + B₂O₃ ⟶ 2Co₃(BO₃)₂
Uses of Borax
- It is used to prepare borate glass, which is heat-resistant.
- Borax is used in the softening of water.
- It is employed in the borax and bead test for the detection of metallic cations.
- Borax is used as a flux in welding and metallurgy.
- It is employed in making washing powders.
- It is used in the leather industry for tanning and dying.
- Borax was also used in cosmetics, soaps, textiles, paints, medicine, and the match industry and as a preservative.
Concluion
To sum up, Borax is a vital boron compound with diverse applications, from laboratory bead tests to industrial uses. Its unique chemical behaviour, especially in reactions with acids and metal oxides, highlights its importance in analytical chemistry and material science. Understanding its structure and reactions provides a solid foundation for further study in inorganic chemistry.
