Borax is a natural mineral and a salt of boric acid. It is also known as sodium borate, sodium tetraborate or disodium tetraborate. It is an important boron compound. Several closely related minerals that differ in their crystal water content such as decahydrate, pentahydrate and octahydrate salts are also referred to as borax. Even its anhydrous form is also referred to as borax.
Formula of Borax – As we know the term borax is used for many closely related crystals. So, it has various formulae depending upon its water of crystallization –
Physical Properties of Borax –
Its molar mass is 202.22 (anhydrous) and 381.38 (decahydrate).
It is white colored solid substance.
Its density is 2.4g/cm3 (anhydrous) and 1.73 g/cm3 (decahydrate).
Its melting point is 743 ℃ (anhydrous) and 75 ℃ (decahydrate).
It is soluble in water.
Its boiling point is 1,575℃ (anhydrous).
Chemical properties of Borax –
Borax reacts with acids and can be easily converted into boric acids which is a highly useful compound. Reaction is given below –
Na2B4O7·10H2O + 2HCl → 4B(OH)3 + 2NaCl + 5H2O
It is flammable and produces yellow green flame.
It is very soluble in ethylene glycol and slightly soluble in acetone.
Reaction with sodium hydroxide –
Na2B4O7 + 7H2O + 2NaOH 🡪 4Na[B(OH)4]
Borax occurs naturally as deposits in seasonal lakes by their repeated evaporation. It is most commonly found in Turkey, Boron (California), Searles lake, southwestern united states, Atacama Desert in Chile, Bolivia, Tibet and Romania etc.
Few of the Uses of Borax are Listed Below –
As Cleaning Agent – Various properties of borax help to increase its cleaning power. It converts water into hydrogen peroxide during cleaning. It is highly basic so it makes the hot water basic which enhances the effectiveness of bleach or other cleaners.
As an Insect Killer – Borax stops the metabolic process of many organisms. This property of borax makes it a better disinfectant.
It is used in the test of diabetes mellitus.
It is used as a water softening agent.
For welding of iron and steel mixture of borax and ammonium chloride is used as flux.