Sodium Borate: Overview, Questions, Preparation

1)      It is completely soluble in water and ethylene glycol

2)      Moderately soluble in methanol and diethylene glycol

3)      Slightly soluble in acetone

4)      Less soluble in cold water but more soluble in hot water

5)      With an increase in temperature, solubility also increases

Structure:

• Molecular Formula – H20B4Na2O17
• Molecular Weight – 201.22 g/mol (anhydrate)
• Boiling Point- 1,575 °C
• Melting Point- 743 °C
• Density: 1.73 g/dm3

1)      From Colemanite: Finely powdered colemanite is boiled with sodium carbonate solution. The precipitate of calcium carbonate thus formed is removed by filtration. The filtrate is concentrated and the crystals of borax separate out.

2)      From Tincal: Tincal is naturally occurring borax. Tincal obtained from dried up lakes contains 50% borax. It is boiled with water and filtered to remove the insoluble impurities. The filtrate is concentrated and the crystals of borax separate out.

3)      From Boric acid: When boric acid is neutralized with sodium carbonate, borax crystals separate out on cooling.

Uses of Borax:

1)      In softening of water- removes both the temporary and permanent hardness of water

2)      As a stiffening agent for candle wicks

3)      It is used as a flux in certain metallurgical processes

4)      It can also serve as a flame retardant

5)      In the manufacturing of heat resistant borosilicate glass

6)      To make peroxoborate which is an important cleansing and bleaching agent present in washing powder

7)      In the preparation of medicinal soaps due to its antiseptic properties

8)      It also acts as an antifungal agent

9)      It serves as a cross-linking agent in the preparation of slime

10)  It is used as an ingredient in vitamin supplements

11)  It is used as a food additive

12)  It is used in laundry cleaning and household cleaning products

13)  It is used as a flame retardant

14)  It is used by blacksmiths for forge welding

Reactions of Sodium Borate:

1)      Action of Heat – Borax bead test

On heating, it loses its water of crystallization and swells up to form a puffy mass. On further heating, it melts into a clear liquid and then solidifies into a glass like bead known as borax bead.

2)      Action of NaOH

On adding a certain quantity of NaOH, Sodium metaborate is formed.

3)      Action of Sulphuric Acid

To a hot concentrated solution of borax to concentrated sulphuric acid, boric acid is produced.

Class 11 and Class 12 NCERT have a chapter on p-block elements which includes Sodium Borate (Borax)

Q. What is sodium borate used for?

Q. Is sodium borate harmful to humans?

Q. What is the pH of Sodium borate?

Q. What is the IUPAC name of Borax?

Q. Can it be used as a disinfectant?