Dhristi JEE 2022-24

What is Sodium Borate?

What is Sodium Borate?


Sodium borate is a white solid boron compound, composed of borate ions and sodium ions.  It can be in a crystalline or amorphous state. Sodium borate is a mineral, which naturally occurs in the earth’s crust. It is also known as Borax. The most important boron compounds are sodium tetraborate, disodium tetraborate, and Borax. 


Occurrence of Sodium Borate

Sodium borate naturally occurs in seasonal lakes as a deposit due to evaporation. Sodium borate is commonly found in California, Tibet, Romania, the southwestern United States, Turkey, etc. 


Chemical Formula of Sodium Borate

Sodium borate exists in two states, hydrated form, and dehydrated form. Hydrated forms of sodium borate are the states in which the water of hydration is present, while in dehydrated forms of sodium borate there is no water of hydration present. The chemical formula of sodium borate in the hydrated state is \[ Na_{2}B_{4}O_{7}.10H_{2}O \] and in the dehydrated state is \[ Na_{2}B_{4}O_{7}\]. Its molecular weight is 381.4 g/mol. The International Union of Pure and Applied Chemistry (IUPAC) name of sodium borate is sodium tetraborate decahydrate.


Structure of Sodium Borate

In sodium borate structure three positively charged sodium ions are attracted by the negatively charged borate ion. They form ionic bonds. Borate is a covalent compound of boron and oxygen that forms boron oxyanion. Its shape can be trigonal or tetrahedral.


Properties of Sodium Borate

  1. Physical Properties of Sodium Borate

  • The molecular weight or molar mass of dehydrated sodium borate is 201.22 g/mol, while that of hydrated form is 381.38 g/mol.

  • The color of sodium borate is white and it can be in a crystalline or amorphous state.

  • The density of sodium borate is 1.73 g/dm3.

  • The boiling point of sodium borate is 1,575℃.

  • The melting point of sodium borate is 743℃.

  • Sodium borate is soluble in water.

  1. Chemical Properties of Sodium Borate

  • The hydrated form of sodium borate is highly reactive with acids. On reacting with acids, sodium borate forms boric acid. 

  • Sodium borate is a  flammable compound. It produces a greenish-yellow flame when burned.

  • It shows very high solubility towards ethylene glycol.

  • It is sparingly soluble in acetone.

  • It shows reactivity with bases.

Preparation Method of Sodium Borate

  1. \[Ca_{2}B_{6}O_{11} + 2Na_{2}CO_{3} \rightarrow  Heat \rightarrow  Na_{2}B_{4}O_{7} + 2NaBO_{2} + 2CaCO_{3} \downarrow\]

Colemanite is a borate mineral, which in reaction with sodium carbonate in the presence of heat forms sodium borate and calcium carbonate.

  1. \[ 4NaBO_{2} + CO_{2} \rightarrow Na_{2}B_{4}O_{7} + Na2CO_{3}\]

Sodium metaborate on reaction with carbon dioxide leads to the formation of sodium borate.

  1. \[ 4H_{3}BO_{3} + Na2CO_{3} \rightarrow  Na_{2}B_{4}O_{7} + 6H_{2}O +CO_{2} \uparrow \]

Boric acid on reacting with sodium carbonate forms sodium borate and water and carbon dioxide are formed as byproducts.


Reactions of Sodium Borate

  1. \[ Na_{2}B_{4}O_{7} + 7H_{2}O \rightarrow  4Na[B(OH)_{4}] \]

Amorphous borax Na2B4O7 forms tetrahydroxoborate on reacting with concentrated sodium hydroxide solution.

  1. \[ Na_{2}B_{4}O_{7} + 2NaOH_{2} \rightarrow  4NaBOH_{2} + H_{2}O \] (At high temperature around 700-750)

The fusion of sodium borate leads to the formation of sodium metaborate.

  1. \[Na_{2}B_{4}O_{7} + 2NaOH_{2} + 4H_{2}O_{2} + 11H_{2}O \rightarrow  2Na_{2}[B_{2}(O_{2})_{2} + O_{4}] . 6H_{2}O\]

When sodium borate reacts with hydrogen peroxide it forms peroxoborate.

  1. \[Na_{2}[B_{4}O_{5}(OH)_{4}] . 8H_{2}O \rightarrow  2Na^{+} + B_{4} O_{5}(OH) {_{4}}^{2-} + . 8H_{2}O (1)\]

\[2Na + 2Na^{+} + B_{4} O_{5} (OH) {_{4}}^{2-} + 5H_{2}O \rightleftharpoons 2Na^{+} (aq) + 4B(OH)_{3} + 2OH^{-}\] 

\[2Na^{+} + B_{4} O_{5} (OH) {_{4}}^{2-} + 2HCl + 5H_{2}O \rightarrow 4B(OH)_{3} + 2Na^{+} + Cl^{-}\]

Sodium borate, when dissolved in water, dissociates completely, and then, hydrolyzes to orthoboric acid hydroxyl ions, which leads to the basic solution. Therefore, borax reacts with strong acid solutions. 


Uses of Sodium Borate

  • It is used as a buffer in various reactions.

  • A 10 percent solution of sodium borate is used as an insect killer, for roach killing, and as a moth-preventative. 

  • It can also be used as a fungicide and herbicide.

  • In many industries and treatment plants, it is used as a water softening agent.

  • It is used as a food additive as a preservative.


Is Sodium Borate Safe?

Sodium borate is not acutely toxic, which means at low amounts or at low concentration it does not show any harmful effects, but when it is inhaled or ingested in large amounts it would have harmful effects on health. As far as pesticides go, it is one of the safest chemical compounds available. A 2006 survey of the chemical by the U.S. The Environment Protection Act finds no signs of toxicity from exposure and no evidence of cell toxicity in humans. However, this does not make sodium borate categorically safe. Intake of large amounts of sodium borate can cause vomiting, nausea, and diarrhea. While the findings are rather contradictory, it's advisable children and pregnant women limit their exposure to sodium borate if possible.


Harmful Effects of Sodium Borate

  • Organ system toxicity 

  • Fertility damage 

  • Damage to an unborn child 

  • Endocrine and hormone disruption 

  • Skin allergy 

  • Eye irritation

  • Damage to the male reproductive system 

  • Respiratory irritation 


Cleaning Agents used Other than Borax

The substances used to remove the dirt, stain, and bad smells are known as cleaning agents. These cleaning agents can be liquids, solids or sprays, and some even kill the bacteria. The cleaning agents used to clean oil stains contain degreasers.

There are many types of cleaning agents.


Acidic Cleaning Agents

The acidic type of cleaning agent is usually used for inorganic deposits such as scaling. The active ingredients used in such agents are usually mineral acids and chelants. The commonly used acids are hydrochloric acids and sulphuric acid. Vinegar is also used to clean surfaces to get rid of calcium stains, and also helps to maintain a bacteria-free environment.


Sulphuric acid cleaners are often used to clean the drain and clogged pipes to dissolve grease.


Alkaline Cleaning Agents

The alkaline cleaning agents are strong bases. They are usually used to remove stubborn oil or protein-based stains and dirt.


The strong bases used are sodium hydroxide and potassium hydroxide. The most commonly used alkaline cleaning agents are bleach and ammonia.


Dispersants and chelants to avoid the redeposition of dirt and prevent rusting are added to alkaline cleaning agents.


Neutral Cleaning Agents

There is this third type of cleaning agent that is pH neutral and is neither acidic nor basic. These are non-ionic surfactants and are used in day-to-day cleaning agents.

The other commonly used cleaning agents are as follows:

  • Acetic acid or vinegar

  • Ammonia solution

  • Acetone

  • Alcohol

  • Chromic acid

  • Citric acid

  • Saltwater soap( potassium-based soap)

  • Soap or detergent

  • Sodium bicarbonate (Baking soda)

  • Sodium hydroxide(Lye)

  • Sodium hypochlorite(liquid bleach)


The Difference Between Borax and Boric Acid

The two compounds namely borax and boric acid are often confused, even though both are completely different compounds. Both the compounds are produced with a common element called boron. So, sometimes both of them are referred to as borates.


Boric acid comes from borax. It is created by mixing borax with other minerals such as colemanite and boracite. The adding of hydrogen or another acid creates the boric acid.


The chemical composition of boric acid is H3 BO3


Boric acid is also referred to as hydrogen borate.


The Difference Between Borax and Washing Soda

Washing soda is also referred to as soda ash. Its chemical composition is \[Na_{2}CO_{3}\]. Since its pH level is 11, washing soda is quite extremely alkaline. That is why it is effective in removing grease and deep cleaning the clothes. It is not recommended to touch the washing soda with bare hands as it may be caustic.


Even though borax is alkaline just like washing soda, it has a slightly different chemical composition to that of washing soda.


The chemical composition of borax is \[Na_{2}B_{4}O_{7}\], also known as sodium tetraborate.


The other difference between washing soda and borax is that the molecules of borax aren't sharp. Hence, they dissolve in the water easily.


Both are effective in cleaning the dirt and other stubborn stains.


The Difference Between Borax and Baking Soda

There might be a lot of confusion when it comes to using borax or baking soda for cleaning. Many get confused between the two compounds.


Baking soda is commonly known as sodium bicarbonate. The chemical composition for baking soda is \[NaHCO_{3}\]. Borax and baking soda are naturally occurring compounds.


The key difference between baking soda and borax is that the latter is more alkaline. The pH of borax is 9.5 and the pH of baking soda is 8. Because borax is more alkaline than baking soda, that also makes it harsh.


Other Uses of Borax

  • Borax is used as an ingredient in the making of enamel.

  • Borax is used in fire retardants.

  • It is used in woodworm treatment.

  • It is used as a neutron absorber

  • Borax is used as a micronutrient fertilizer, for soils that lack boron.

  • It is used as a curing agent.

  • Borax is used by the blacksmiths in forge welding.

  • It is used to make indelible ink for the dipping pens.

  • To control the pH of a swimming pool, borax is used.

  • Borax is a component in glass, pottery and also in ceramics.

  • Borax is used in various adhesives.

  • It is also used as a flux.

  • It is used as the main component in many house cleaning products.


Did You know?

  • Most of the sodium borate is found in the United States. It comes from the seasonal lakes through the erosion process in the Mojave Desert in California.

  • Sodium borate is used in cosmetics, cleaning products and personal care products.

  • Sodium borate offers many health benefits like maintaining bone health, maintaining the hormonal balance, improving the nervous system and reducing inflammation.

  • Commercially sold borax is usually partially dehydrated.

  • Sodium borate is used as a fire retardant, as it can release water from its crystalline structure. 

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FAQs (Frequently Asked Questions)

1. What is the IUPAC name of sodium borate?

Sodium tetraborate decahydrate is the IUPAC name of the sodium borate.

2. Name some of the borate minerals that naturally occur in the earth's crust.

Colemanite, kernite, boracite, painite are some borate minerals, which naturally occurs in the earth’s crust. This mineral is used for the formation of sodium borate.

3. Is sodium borate an ionic compound or covalent compound?

In the sodium borate structure, three positively charged sodium ions are electrostatically attracted by the negatively charged borate ion. These types of compounds are called ionic compounds.

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