Preparation and Usage of Hydrofluoric Acid

A highly corrosive acid, Hydrofluoric acid is the inorganic acid of elemental fluorine and is denoted chemically by HF. This fuming, colorless solution is miscible with water, benzene, toluene, and concentrated sulfuric acid. A water solution of hydrogen fluoride, hydrofluoric acid contains 35.35% hydrogen fluoride by weight and is known for its ability of dissolving many materials, especially oxides. It also exhibits extreme reactivity with glass, reacting with the silica, SiO2, to form the gas silicon tetra fluoride, SiF4, and water; which leaves the surface of the glass etched. Owing to this, it is usually stored in steel tanks, cylinders, or drums, or, in small amounts, in plastic bottles.

Hydrofluoric Acid is quite possibly the most dangerous chemical to deal with in Power Labs and hence have to be handled with extreme caution. It is a is a severe poison and possesses unique ability to penetrate tissue by non-ionic diffusion. A contact poison, it is known to inflict deep, initially painless burns, with later tissue death. Even a 70% spill over 2% body area can prove to be fatal, as the concentrated acid may cause systemic toxicity and eventual cardiac arrest after interfering with the body calcium metabolism. The high concentration acid also out gases pure HF extensively, and inhalation of as much as a single lungful of that gas will result in almost certain death by pulmonary edema.

HF ID identified as:

CAS number (7664-39-3 Yes)
ChemSpider (14214 Yes)
UNII (RGL5YE86CZ Yes)
EC number (231-634-8)
ChEBI (CHEBI:29228 Yes)
RTECS number (MW7875000)

Chemically it can be summarized as:

Molecular formula - HF (aq)

Molar mass (Not applicable)
Appearance (Colorless solution)
Density (1.15 g/mL (for 48% soln.))
Melting point (–83.37°C)
Boiling point (19.43°C)
Solubility in water (Miscible.)
Acidity (pKa) (3.17 )

Preparation

On a commercial level, Hydrogen fluoride is produced by treating fluorspar (calcium fluoride) with concentrated sulfuric acid. This solution is heated to to a temperature of 256*C and the produced gas is condensed by cooling or dissolved in water. Chemically the reaction can be detailed by the following reaction:

CaF2 + H2SO4 â 2 HF + CaSO4

Alte
atively, a very pure form can also be produced by passing hydrogen fluoride gas through a Teflon filter and freeze it in a Kel-F tankand by cooling it with liquid nitrogen and subsequently introduce the gas into pure distilled water in a Teflon bottle.

Usage

Although a potentially fatal acid, HF acid enjoys a wide range of industrial uses such as etching and polishing glass, cleaning stone, brick and marble, and in the manufacture of pesticides, plastics and high octane fuels. Moreover, it is also employed in the vital etching of semiconductors to make microchips. Hydrofluoric acid is also present in rust removers, aluminum brighteners and heavy duty cleaners, used in homes.

HF is an inalienable part in the synthesis of fluorocarbons, and production of aluminum fluoride and synthetic coprolite for use in aluminum refining. It is also employed in refining uranium for use as a nuclear fuel, in manufacturing various organic chemicals, in producing stainless steel, and for various other applications.