Uses of hydrofluoric acid with health effect.

Important Uses of hydrofluoric acid in chemistry

Hydrofluoric acid is a concentrated aqueous solution of hydrogen chloride, with chemical formula, HF. Density of hydrofluoric acid 1.15 g/c.c.

 It is a polar covalent compound. The dipole moment of H–F bond is 1.86 D. Hydrofluoric acid is a colorless, highly poisonous mono basic weak acid.

The melting and boiling point of hydrofluoric acid are, –83.6 ᵒC and 19.5 ᵒC respectively.

Although, hydrofluoric acid is a poisonous acid yet it has many chemical. Most amount of HF acid is used in industrialproduction.

Some important uses of hydrofluoric acid in chemistry is discussed below.

Use of hydrofluoric acid as non aqueous solvent

Hydrofluoric acid is one of the most water like solvents because, it is liquid at temperatures below 19.5 ᵒC upto –89.5 ᵒC.

The boiling point of hydrofluoric acid is very high with respect to other non aqueous solvent. Because of its high dielectric constant, it is used as a excellent ionizing solvent.

But the use of hydrofluoric acid as non aqueous solvent is limited due its high poisonous nature.Few important chemical reaction taking place in hydrofluoric acid medium are,

Use of hydrofluoric acid as neutralizer

The high value of specific conductance of hydrofluoric acid indicates that it under goes auto ionization to H₂F⁺ and HF₂^–ion.

Hence, any substance which can yield H₂F⁺ would behave as an acid and any substance which produce HF₂^–or F^– ion would behave as a base.

There are many acid-base reactions where hydrofluoric acid acts as a neutralizer. 

For example, in reaction with HNO₃, H₂SO₄, hydrofluoric acid behave as an acid and HNO₃, H₂SO₄ act as base.

There are another few acid-base reactions where hydrofluoric acid acts as a base and the other participating substance act as Lewis base.

Use of hydrofluoric acid as a precursor of fluorine and metal fluorides

HF is the pioneer of elemental fluorine. F₂ is produced by electrolysis of a solution of HF and anhydrous KHF₂.In this method a large amount of F₂ is prepared per every year.  

HF forms few addition compound with metal fluorides, such as, with KF, it form KHF₂, KF.2HF, KF.3HF and NH₄F.HF etc.    

Use of hydrofluoric acid as a precursor of fluorocarbon

Hydrogen fluoride is used to prepare fluorocarbons from chloro-carbons.An important reaction of HF to form  chloro carbon is the production tetra fluoro ethylene or Teflon .

Again, HF reacts with acetylene in the presence of ‘Hg’ catalyst and form 1,1-difluoroethane.

Use of hydrofluoric acid as an organic catalyst

HF acid is used as an organic catalyst. It is used in Friedel craft alkylation reaction to prepare ethyl benzene from benzene.

It is also used in production of cyclohexylbenzene from cyclohexene.

Use of hydrofluoric acid as an important chemical in industry

About 60% of entire hydrofluoric acid is used as different industrial purpose. For example, hydrofluoric acid is used in production of refrigerants, herbicides,

pharmaceuticals, gasoline, stainless steel kitchen products, plastics, electrical components incandescent light bulbs etc.

 Hydrofluoric acid is also used for etching glass and enamel, removing rust, and cleaning brass and crystal in manufacturing silicon semiconductor chips.

Others use of hydrofluoric acid

Due to its strong corrosive qualities, a diluted form of hydrofluoric acid is used in some commercial automotive cleaners, rust and stain removers and water-spot removers.

HF is used in the production of artificial cryolite [ AlF₃. 3NaF ] from which aluminium metal is extracted. 

It is also used for separation of sand from graphite and rote iron and analysis of silicate ores.

Health effects

Hydrogen fluoride is a poisonous gas. It has a bad impact on human organism.

When hydrogen fluoride come in contact with moisture, including tissue, it immediately converts to hydrofluoric acid which is highly corrosive and very toxic.

Hydrofluoric acid effected persons requires immediate medical attention.  Because, it can cause blindness due to rapid destruction of corneas.

Besides, breathing in hydrogen fluoride at high levels or in combination with skin contact can cause death.

• Important Uses of hydrofluoric acid in chemistry
• Use of hydrofluoric acid as non aqueous solvent
• Use of hydrofluoric acid as neutralizer
• Use of hydrofluoric acid as a precursor of fluorine and metal fluorides
• Use of hydrofluoric acid as an organic catalyst
• Use of hydrofluoric acid as an important chemical in industry

Read more: activating and non activating groups