HEXAFLUOROSILICIC ACID

Hexafluorosilicic acid = FLUOROSILICIC ACID = FLUOSILICIC ACID = Sand acid = Silicofluoric acid

Applications of Hexafluorosilicic acid = Chemical Intermediate, Metal Surface Treatment, Water Fluoridation, Wood Preservation, Glass Additive, Ceramic Hardening
Hexafluorosilicic acid is a colorless, water-soluble fluid that is used in many in industrial and municipal operations. It has a pungent odor and is highly corrosive in nature. It is commonly used in applications such as water fluoridation, electroplating, and the manufacturing of cement and enamels. Its growing demand can be attributed to the use of hexafluorosilicic acid in water treatment plants, mainly in the fluoridation of public water supplies.


Hexafluorosilicic acid
EC Number: 241-034-8
EC Name: Hexafluorosilicic acid
CAS Number: 16961-83-4
Molecular formula: F6Si.2H
IUPAC Name: hexafluorosilicate


FLUOROSILICIC ACID    
Hexafluorosilicic acid
Dihydrogen hexafluorosilicate
Fluosilicic acid
Hydrosilicofluoric acid    
CAS #: 16961-83-4    
UN #: 1778
EC Number: 241-034-8


Hexafluorosilicic acid is an inorganic compound with the chemical formula H2SiF6 also written as (H3O)2[SiF6]. 
Hexafluorosilicic acid is a colorless liquid mostly encountered as diluted aqueous solution, from there, the second chemical notation also proposed. 
Hexafluorosilicic acid has a distinctive sour taste and pungent smell. It is produced naturally on a large scale in volcanoes.
Hexafluorosilicic acid is manufactured as a coproduct in the production of phosphate fertilizers. 
The resulting hexafluorosilicic acid is almost exclusively consumed as a precursor to aluminum trifluoride and synthetic cryolite, which are used in aluminium processing. 
Salts derived from hexafluorosilicic acid are called hexafluorosilicates.


Hexafluorosilicic acid is commonly used as a source of fluoride. It is converted to a variety of useful hexafluorosilicate salts. It is also used as an electrolyte in the Betts electrolytic process for refining lead. It is an important organic reagent for cleaving Si-O bonds of silyl ethers. Further, it is used as wood a preservation agent and also used in surface modification of calcium carbonate.


Hexafluorosilicic acid is incompatible in strong oxidizing agents, metals, alkalis, strong acids, stoneware and glass.

Fluosilicic acid, hexafluorosilicic acid
CAS: 16961-83-4
A colorless fuming liquid.

Other Known Names: fluosilicic acid, hexafluorosilicic acid, hydrogen hexafluorosilicate, hydrosilicofluoric acid

Molecular Formula: H2SiF6


The major use of sodium hexafluorosilicate and fluorosilicic acid is as fluoridation agents for drinking water. 
Sodium hexafluorosilicate has also been used for caries control as part of a silicophosphate cement, an acidic gel in combination with monocalcium phosphate monohydrate, and a two-solution fluoride mouth rinse. Both chemicals are also used as a chemical intermediate (raw material) for aluminum trifluoride, cryolite (Na3AlF6), silicon tetrafluoride, and other fluorosilicates and have found applications in commercial laundry. 
Other applications for sodium hexafluorosilicate include its use in enamels/enamel frits for china and porcelain, in opalescent glass, metallurgy (aluminum and beryllium), glue, ore flotation, leather and wood preservatives, and in insecticides and rodenticides. It has been used in the manufacture of pure silicon, as a gelling agent in the production of molded latex foam, and as a fluorinating agent in organic synthesis to convert organodichlorophosphorus compounds to the corresponding organodifluorophosphorus compound. 
In veterinary practice, external application of sodium hexafluorosilicate combats lice and mosquitoes on cattle, sheep, swine, and poultry, and oral administration combats roundworms and possibly whipworms in swine and prevents dental caries in rats. Apparently, all pesticidal products had their registrations cancelled or they were discontinued by the early 1990s. 
Fluorosilicic acid is used in the tanning of animal hides and skins, in ceramics and glass, in technical paints, in oil well acidizing, in the manufacture of hydrogen fluoride, for the sterilization of equipment (e.g., in brewing and bottling establishments and for copper and brass vehicles), and in electroplating. 
It is also employed as an impregnating ingredient to preserve wood and harden masonry and for the removal of mold as well as rust and stain in textiles.

Hexafluorosilicic acid Applications: water fluoridation, disinfecting copper and brass vessels, sterilizing bottling and brewing equipment

Fluorosilicic acid is one of the main products used in water fluoridation

Hydrofluorosilicic acid is a chemical often known by other names like fluorosilicic acid, fluosilicic acid, silicofluoride, and silicofluoric acid and is often abbreviated to HSA or FSA. It is a colorless chemical that is created when you take phosphoric rock from the ground and convert it to soluble fertilizer. In this process, two very toxic fluoride gases are released with hydrogen fluoride being one of them; the other is silicon tetrafluoride. The condensation from this hydrogen fluoride is collected, then scrubbed with water

Hydrofluorosilicic acid is a colorless liquid and inorganic compound that is rarely found undiluted. It has a pungent smell and a characteristic sour taste. Hydrofluorosilicic acid in its concentrated form is toxic and corrosive. It is mainly produced as a precursor to synthetic cryolite and aluminum trifluoride. It is also commonly used in water treatment to maintain the fluoride level in water.

What Industries and Applications Handle Hydrofluorosilicic Acid?
The most commonly known application of hydrofluorosilicic acid is water fluoridation at water treatment plants. It is up to 5 times less expensive than sodium fluoride, an alternative that can also be used to treat drinking water. As a result, hydrofluorosilicic acid has seen a major surge in demand in recent years. However, concentrations above 20 percent are more dangerous to store and handle than sodium fluoride and need adequate care and equipment.

The largest quantity of hydrofluorosilicic acid worldwide is converted to cryolite and aluminum fluoride. These materials are key in the process of converting aluminum ore into aluminum metal.

Hydrofluorosilicic acid is also used as an electrolyte in the Betts electrolytic process for refining lead and as the active compound in some rust removal cleaning products.


Fluorosilic Acid (H2SiF6), is an essential chemical in the following applications:

Water treatment
Surface treatment
Galvanotechnic
Lead refining
Glass industry
Potable water treatment
Ceramic
Chemical Industry
Enamel
Chemical synthesis

Fluorosilicic Acid
Fluorosilicic acid (also known as FSA) is used as a source of fluoride in drinkable water. This assists in preventing cavities in teeth. It is an inorganic compound with the chemical formula (H2SiF6).

Textile Chemicals & Dyes
Fluorosilicic Acid is used for pH adjustment in industrial textile processing or laundries
Textile processing is one of the largest application of fluorosilicic acid with a share of 12.67% in 2019. The product is witnessing increased demand in textile applications owing to its superior cleansing properties. It is used as a laundry chemical or laundry sour as it helps remove rust, stains, and mold from the fabric. The chemical also helps in pH regulation during the rinse cycle. It protects the fiber by forming a thin film coating around the fabric, which results in the reduction of surface tension. These factors are anticipated to fuel the demand from textile processing applications over the forecast period.

Laundry industry has been gaining traction in recent years owing to the changing lifestyle of people and increasing awareness about clean and hygienic clothes. 
This has created a high demand for clean and fragrant clothes. 
In addition, the rising prevalence of allergies and other skin diseases is expected to generate high demand for detergents in the near future. 
Detergent manufacturers are focused on developing high-quality products for efficient cleaning and increasing fabric life along with maintaining hygiene. 
Owing to these factors, fluorosilicic acid is expected to witness healthy demand in textile applications over the forecast period.
Hexafluorosilicic acid is used in removing rust and stains from the fabrics and tend to decrease the surface tension of the substrate by forming a thin film coating around the fiber. Moreover, it acts as a laundry chemical when added to clothes during the rinse cycle to lessen water pH and assist the removal of cleansers and corrosion stains, thereby stimulating the market demand.

Water Treatment
Fluorosilicic Acid is used as a source of fluoride for water fluoridation
Hexafluorosilicic acid is used in public water treatment plants for lessening in dental caries by regulating the fluoride content of public water supplies. 
Hexafluorosilicic acid is added to water treatment plants to give a total fluoride F level of which has been recognized as active component for reducing tooth decay, thereby fueling product demand. Governmental regulations in the U.S. and Europe are compelling the municipal corporations to use fluorosilicic acid as fluoridating agent for public drinking water. Researchers have identified that a controlled level of fluoride in the water effectively prevents cavities and tooth decay. Community water fluoridation is one of the most effective and economical methods to supplement water with fluoride to prevent tooth cavities. Moreover, fluorosilicic acid is predominantly used in the water fluoridation process as a fluoride additive


Others
Fluorosilicic Acid is used as an electrolyte in the Betts electrolytic process for refining lead

A metal surface treatment and cleaner
Fluorosilicic acid with a 40% concentration is highly used in metal surface treatment applications. Aluminum is treated with fluorides, such as fluorosilicic acid, to penetrate through the aluminum oxide layer that forms over the surface of the metal. The process enables fluoride ions to form a protective layer over the aluminum surface, which prevents further oxidation of the metal
Fluorosilicic acid is used by municipal corporation in water treatment process to maintain fluoride level. Hexafluorosilicic acid is widely used in metal surface treatment processes as it induces non-chromium surface passivation which may promote product demand.
Fluorosilicic acid acts as a non-hexavalent chromium formula component with low chlorine content and acts as a stable product during surface treatment process.
 

Hexafluorosilicic acid is used in various chemical industries which act as a catalyst to conventional chromium electrolyte. The product act as a reducing agent in electroplating process,
 

Hydrofluorosilicic acid is widely used in oral care products such as toothpaste, mouth wash, floss and teeth whitening. Global oral care products demand was valued at over USD 28.5 billion in 2018. Increasing consumer awareness for oral disorders such as gingivitis, denture irritation and bleeding gums is likely to boost the fluorosilicic acid market growth. It strengthens weak spots and exposed roots and aid in preventing the early stages of tooth decay.


Hydrofluorosilicic acid product offers excellent properties such as maintaining the fluoride levels when added in dental products. Moreover, increasing application in sterilization and fumigation technologies and increasing demand for animal hide and tanned glass is likely to foster the industry growth.

Hydrofluorosilicic acid is used for hardening masonry and ceramics


Hexafluorosilicic has been used in the manufacture of pure silicon, as a gelling agent in the production of molded latex foam, and as a fluorinating agent in organic synthesis to convert organodichlorophosphorus compounds to the corresponding organodifluorophosphorus compound. 
40 % grade fluorosilicic acid is used in the tanning of animal hides and skins, in ceramics and glass, in technical paints, in oil well acidizing, in the manufacture of hydrogen fluoride, for the sterilization of equipment, and in electroplating. 
Hexafluorosilicic is also employed as an impregnating ingredient to preserve wood and harden masonry and for the removal of mold as well as rust and stain in textiles. 


Fluorosilicic acid is one of the widely used abrasive compounds in the glass industry for glass etching applications. Etched glass products are commonly used in the building and construction industry. A major factor encouraging the growth of the global decorative glass market is the increase in the demand for glass products in commercial and residential buildings. Hence, etched glass products are gaining popularity due to their aesthetic appearance as well as energy savings from reduced electricity consumption. Also, glass provides thermal and sound insulation and allows the control of solar radiation.

 It is used in public water treatment plants for lessening in dental caries by regulating the fluoride content of public water supplies. It is added to water treatment plants to give a total fluoride F level of which has been recognized as active component for reducing tooth decay, thereby fueling product demand. Governmental regulations in the U.S. and Europe are compelling the municipal corporations to use fluorosilicic acid as fluoridating agent for public drinking water. Researchers have identified that a controlled level of fluoride in the water effectively prevents cavities and tooth decay. Community water fluoridation is one of the most effective and economical methods to supplement water with fluoride to prevent tooth cavities. Moreover, fluorosilicic acid is predominantly used in the water fluoridation process as a fluoride additive

LEATHER TANNING APPLICATION OF Hexafluorosilicic acid 
Hexafluorosilicic acid is added in an aqueous dispersion layer form to tanning bath during leather tanning process, making it soft and compliant, which may enhance the product growth.


APPLICATIONS OF HEXAFLUOROSILICIC ACID
Wood Preservatives
Electroplating
Fur Dressing and Dyeing
Glass Manufacturing
Leather Tanning and Processing
Metal Preparation and Pouring
Painting (Pigments, Binders, and Biocides)
Petroleum Production and Refining
Sewer and Wastewater Treatment
Disinfectants and Biocides


Overview.
Fluorosilicic acid, as well as Phosphoric acid, are produced as co-products by acidulation of phosphate rock by sulphuric acid. Phosphate rock contains both calcium phosphate and calcium fluoride, and by acidulation both products are obtained.

Fluorosilicic Acid can only exist as a liquid. There is no solid form. It is rarely encountered undiluted and has a distinctive sour taste and pungent smell.

The largest quantity of hydrofluorosilicic acid worldwide is converted to cryolite and aluminum fluoride. These materials are key in the process of converting aluminium ore into aluminium metal.

CAS Number:
16961-83-4
EC Number:
241-034-8
Appearance:
Colourless
Other Names:
Hexafluorosilicic Acid

Preferred IUPAC name: Hexafluorosilicic acid
Systematic IUPAC name: Dihydrogen hexafluorosilicate
Other names: Fluorosilicic acid, fluosilic acid, hydrofluorosilicic acid, silicofluoride, silicofluoric acid, oxonium hexafluorosilanediuide, oxonium hexafluoridosilicate(2−)

Identifiers
CAS Number: 16961-83-4 
EC Number: 241-034-8
UN number: 1778

Properties
Chemical formula: F6H2Si
Molar mass: 144.091 g·mol−1
Appearance: transparent, colorless, fuming liquid
Odor: sour, pungent

Density    
1.22 g/cm3 (25% soln.)
1.38 g/cm3 (35% soln.)
1.46 g/cm3 (61% soln.)

Melting point
ca. 19 °C (66 °F; 292 K) (60–70% solution)
< −30 °C (−22 °F; 243 K) (35% solution) 

Boiling point: 108.5 °C (227.3 °F; 381.6 K) (decomposes)
Solubility in water: miscible
Refractive index (nD): 1.3465
Structure
Molecular shape    Octahedral SiF62−

Flash point: Non-flammable
Lethal dose or concentration (LD, LC):LD50 (median dose): 430 mg/kg 


Structure
Hexafluorosilicic acid is generally assumed to consist of oxonium ions charge balanced by hexafluorosilicate dianions as well as water. In aqueous solution, the hydronium cation (H3O+) is traditionally equated with a solvated proton, and as such, the formula for this compound is often written as H
2SiF6. Extending that metaphor, the isolated compound is then written as H2SiF6·2H2O, or (H3O)2SiF6.
The situation is similar to that for chloroplatinic acid, fluoroboric acid, and hexafluorophosphoric acid. 
Hexafluorosilicate is an octahedral anion; the Si–F bond distances are 1.71 Å.
Hexafluorosilicic acid is only available commercially as solution

Production and principal reactions
The commodity chemical hydrogen fluoride is produced from fluorite by treatment with sulfuric acid.[5] As a by-product, approximately 50 kg of (H3O)2SiF6 is produced per tonne of HF owing to reactions involving silica-containing mineral impurities. (H3O)2SiF6 is also produced as a by-product from the production of phosphoric acid from apatite and fluorapatite. Again, some of the HF in turn reacts with silicate minerals, which are an unavoidable constituent of the mineral feedstock, to give silicon tetrafluoride. Thus formed, the silicon tetrafluoride reacts further with HF. The net process can be described as:[6]

SiO2 + 6 HF → SiF2−6 + 2 H3O+

Hexafluorosilicic acid can also be produced by treating silicon tetrafluoride with hydrofluoric acid.

In water, hexafluorosilicic acid readily hydrolyzes to hydrofluoric acid and various forms of amorphous and hydrated silica ("SiO2"). 
At the concentration usually used for water fluoridation, 99% hydrolysis occurs and the pH drops. The rate of hydrolysis increases with pH. 
At the pH of drinking water, the degree of hydrolysis is essentially 100%.

H2SiF6 + 2 H2O → 6 HF + "SiO2"
Neutralization of solutions of hexafluorosilicic acid with alkali metal bases produces the corresponding alkali metal fluorosilicate salts:

(H3O)2SiF6 + 2 NaOH → Na2SiF6 + 4 H2O
The resulting salt Na2SiF6 is mainly used in water fluoridation. Related ammonium and barium salts are produced similarly for other applications.

Near neutral pH, hexafluorosilicate salts hydrolyze rapidly according to this equation:

SiF2−6 + 2 H2O → 6 F− + SiO2 + 4 H+

Uses
The majority of the hexafluorosilicic acid is converted to aluminium fluoride and synthetic cryolite.
These materials are central to the conversion of aluminium ore into aluminium metal. The conversion to aluminium trifluoride is described as:

H2SiF6 + Al2O3 → 2 AlF3 + SiO2 + H2O
Hexafluorosilicic acid is also converted to a variety of useful hexafluorosilicate salts. The potassium salt, Potassium fluorosilicate, is used in the production of porcelains, the magnesium salt for hardened concretes and as an insecticide, and the barium salts for phosphors.

Hexafluorosilicic acid is also used as an electrolyte in the Betts electrolytic process for refining lead.

Hexafluorosilicic acid (identified as hydrofluorosilicic acid on the label) along with oxalic acid are the active ingredients used in Iron Out rust-removing cleaning products, which are essentially varieties of laundry sour.

Niche applications
H2SiF6 is a specialized reagent in organic synthesis for cleaving Si–O bonds of silyl ethers. 
It is more reactive for this purpose than HF. It reacts faster with t-butyldimethysilyl (TBDMS) ethers than triisopropylsilyl (TIPS) ethers.

Hexafluorosilicic acid and the salts are used as wood preservation agents.

Natural salts
Some rare minerals, encountered either within volcanic or coal-fire fumaroles, are salts of the hexafluorosilicic acid. Examples include ammonium hexafluorosilicate that naturally occurs as two polymorphs: cryptohalite and bararite.

Safety
Hexafluorosilicic acid can release hydrogen fluoride when evaporated, so it has similar risks. Inhalation of the vapors may cause lung edema. 
Like hydrogen fluoride, it attacks glass and stoneware.
The LD50 value of hexafluorosilicic acid is 430 mg/kg.


Hexafluorosilicic acid Chemical Properties,Uses and Production

Description
Hexafluorosilicic acid is a kind of inorganic acid. It is majorly used for the fluoridation of water in United State to minimize the incidence of dental caries and dental fluorosis. For chemical synthesis, it is majorly used for the manufacturing of aluminum fluoride and cryolite as well as many kinds of hexafluorosilicate salts. It can also be used for the production of silicon and silicon dioxide. It can also be used as an electrolyte in the Betts electrolytic process for refining lead. It is also a specialized reagent in organic synthesis for cleaving Si–O bonds of silyl ethers.

Chemical Properties
Fluosilicic acid,H2SiF6, also known as hydrofluorosilicic acid,is a colorless liquid that is soluble in water. It is highly corrosive and toxic,attacking glass and stoneware. Fluosilicic acid is used in water fluoridation, electroplating, and in manufacturing enamels and cement.

Chemical Properties
Fluorosilicic acid is a transparent, colorless fuming liquid.

Uses
A 1-2% solution is used widely for sterilizing equipment in brewing and bottling establishments. Other concentrations are used in the electrolytic refining of lead, in electroplating, for hardening cement, crumbling lime or brick work, for the removal of lime from hides during the tanning process, to remove molds, as preservative for timber.

General Description
A colorless fuming liquid with a penetrating pungent odor. Corrosive to metals and tissue. Both the fumes and very short contact with the liquid can cause severe and painful burns. Used in water fluoridation, in hardening cement and ceramics, as a wood preservative.

Air & Water Reactions
Fumes in air. Soluble in water with release of heat and corrosive fumes.

Reactivity Profile
Hexafluorosilicic acid can react with strong acids (such as sulfuric acid) to release fumes of toxic hydrogen fluoride. Attacks glass and materials containing silica. Reacts exothermically with chemical bases (examples: amines, amides, inorganic hydroxides). Reacts with active metals, including iron and aluminum to dissolve the metal and liberate hydrogen and/or toxic gases. Can initiate polymerization in certain alkenes. Reacts with cyanide salts and compounds to release gaseous hydrogen cyanide. Flammable and/or toxic gases are also often generated by reactions with dithiocarbamates, isocyanates, mercaptans, nitrides, nitriles, sulfides, and weak or strong reducing agents. Additional gas-generating reactions may occur with sulfites, nitrites, thiosulfates (to give H2S and SO3), dithionites (SO2), and carbonates. Can catalyze (increase the rate of) chemical reactions. Decomposes when heated to the boiling point to produce very toxic and corrosive hydrogen fluoride gas.

Hazard
Extremely corrosive by skin contact and inhalation.

Health Hazard
Inhalation of vapor produces severe corrosive effect on mucous membrane. Ingestion causes severe burns of mouth and stomach. Contact with liquid or vapor causes severe burns of eyes and skin.

Fire Hazard
Special Hazards of Combustion Products: Irritating fumes of hydrogen fluoride may form in fire.

Industrial uses
Hydrofluorosilicic acid (H2SiF6) is a colorless to light brown liquid. It is also manufactured from calcium fluoride or other fluoride-containing products. Hydrofluorosilic acid is a strong depressant for many silicates during flotation of a number of oxidic minerals. It is used for gangue depression during flotation of tin, columbite and tantalite.

Safety Profile
Poison by subcutaneous route. A corrosive irritant to sktn, eyes, and mucous membranes. Will react with water or steam to produce toxic and corrosive fumes. When heated to decomposition it emits toxic fumes of F-. See also FLUORIDES.

Potential Exposure
A solution of fluorosilicic acid is used for sterilization in the brewing and bottling industry, elec trolytic refining of lead; electroplating, hardening cement; removing mold, and others.

Shipping
UN1778 Fluorosilicic acid, Hazard class: 8; Labels: 8-Corrosive material.

Incompatibilities
The aqueous solution is a strong acid. Reacts with water or steam to produce toxic and corrosive fumes of hydrogen fluoride. Incompatible, and may react violently with: bases, aliphatic amines; alkanolamines, alkylene oxides; aromatic amines; amides, ammonia, ammonium hydroxide; calcium oxide; epichlorohydrin, iso cyanates, oleum, organic anhydrides; sulfuric acid; strong oxidizers; vinyl acetate; water. Attacks glass, concrete, and ceramics. The anhydrous form dissociates almost instantly into silicon tetrafluoride and hydrogen fluoride.

Waste Disposal
Add slowly to a large amount of soda ash in solution. Discharge to sewer with large volumes of water


Industry Uses

Agricultural chemicals (non-pesticidal)
Corrosion inhibitors and anti-scaling agents
Flame retardants
Fluorinating agent
Oxidizing/reducing agents
Plating agents and surface treating agents
Processing aids, not otherwise listed
Surface active agents
Water Fluoridation
Water Treatment Processing and other miscellaneous uses
Water treatment
Water treatment chemical - fluoridation
water treatment - fluoridation
water treatment processing

Substance Identifiers
 Trade name
•  Acide fluorosilicique
•  Acide fluosilicique
•  Acide fluosilicique
•  Acido fluosilicico
•  DIHYDROGEN HEXAFLUOROSILICATE(2-)
•  Dihydrogen hexafluorosilicate
•  FLUOROSILICIC ACID
•  FLUOROSILICIC ACID (H2SIF6)
•  FLUOROSILICIC ACID 40% (Solvay Specialty Polymers)
•  FLUOSILICIC ACID
•  FSA
•  Fluorosilicic Acid
•  Fluorosilicic acid
•  HEXAFLUORKIESELSAEURE
•  HEXAFLUOROSILICIC ACID
•  HFS
•  HYDROFLUOROSILICIC ACID
•  HYDROGEN HEXAFLUOROSILICATE
•  Hexafluorosilicic Acid
•  Hexafluosilicic acid
•  Hydrofluorosilicic acid
•  Hydrofluosilicic acid
•  Hydrofluosilicic acid
•  Hydrogen fluorosilicate
•  Hydrogen hexafluorosilicate
•  Hydrogen hexafluorosilicate
•  Hydrosilicofluoric acid
•  Hydrosilicofluororic acid
•  KIESELFLUORWASSERSTOFFSAEURE
•  SILICATE(2-), HEXAFLUORO-, DIHYDROGEN
•  Sand acid
•  Silicate(2-), hexafluoro-, dihydrogen
•  Silicic acid
•  Silicofluoric Acid
•  Silicofluoric acid
•  Silicofluoride
•  Silicofluoride
•  Silicon hexafluoride dihydride
•  Silicon hexafluoride dihydride
•  fluorosilicic acid
•  fluosilicic acid
•  hexafluorosilicic acid
•  hexafluorosilicic acid
•  hydrofluosilicic acid
•  kwas fluorokrzemowy
•  silicofluoric acid

Hexafluorosilicic acid
Fluorosilicic acid
16961-83-4
Dihydrogen hexafluorosilicate
Silicate(2-), hexafluoro-, dihydrogen
MFCD00036289
hexafluorosilicon(2-);hydron
Fluosilicic acid, 25 wt.% aqueous solution
UNII-53V4OQG6U1
hexafluorosilicon(2-); hydron
Kieselfluorwasserstoffsaure
53V4OQG6U1
DTXSID2029741
hexakis(fluoranyl)silicon(2-); hydron
DB-064742
FT-0626488
A811126
Q411250
J-521443


FLUOSILICIC ACID
tetrafluorosilane;dihydrofluoride
Hydrogen hexafluorosilicate
Fluorosilicic acid solution
Sand acid
Silicofluoric acid
Hexafluosilicic acid
Hydrofluosilicic acid
Hydrofluorosilicic acid
Hydrosilicofluoric acid
FLUOROSILIC ACID
H2SiF6
AKOS015903679
Fluorosilicic acid, 22-25% in water
Fluosilicic acid, purum, 33.5-35%
GF10035
SILICATE(2-),HEXAFLUORO-,DIHYDROGEN
Fluorosilicic acid solution, AR,30.0-32.0%
Fluorosilicic acid solution, GR,30.0-32.0%
Fluorosilicic acid solution, 20-25 wt. % in H2O

Chemical dangers
Decomposes on heating. This produces toxic fumes including hydrogen fluoride. The solution in water is a strong acid. It reacts violently with bases and is corrosive. Reacts with water and steam. This produces toxic and corrosive fumes. Attacks glass and stoneware. Attacks many metals. This produces flammable/explosive gas (hydrogen - see ICSC 0001). This substance (anhydrous form) dissociates almost instantly into silicon tetrafluoride and corrosive and toxic hydrogen fluoride. 

Marketed only as aqueous solution.
Solidification point for 60-70% solution: solidifies at about 19°C, forming a crystalline dihydrate.
Other melting points: <-30°C (35% solution).
Relative density for a 61% solution is 1.46 and for 35% solution is 1.38.
Vapour pressure for a 35% solution is about 3 kPa.
The symptoms of lung oedema often do not become manifest until a few hours have passed and they are aggravated by physical effort. Rest and medical observation are therefore essential.
Temperature of decomposition is unknown in the literature.
Immediate administration of an appropriate inhalation therapy by a doctor, or by an authorized person, should be considered. 


Hydrofluorosilicic acid, or H2SiF6, is a challenging chemical because it has properties that pose danger and specific storage concerns. With its common use in water treatment, it’s important that you’re aware of the risks that storing this chemical improperly carries.


How is Hydrofluorosilicic Acid Used
The most commonly discussed application for this chemical is water fluoridation at water treatment plants. This process helps prevent periodontal problems and is added to drinking water. Another common chemical added to drinking water for the same purpose is sodium fluoride, but it can be five times as expensive. Hydrofluorosilicic acid can, however, be more dangerous to store, so it’s important to have a reliable and safe storage solution.

Another use of FSA is to etch glass; the extremely corrosive nature of the chemical is effective for this desired application. We’ll get into storage options in the next section but for this reason, glass or fiberglass tanks are not good storage solutions when eating glass is “not” the intent. 

Hydrofluorosilicic acid is also used in the production of the salts that can contain porcelains


Storage Concerns and Solutions
Hydrofluorosilicic acid is easily the most dangerous chemical at your local water treatment plant. It can release hydrogen fluoride when it evaporates, is corrosive, and can damage the lungs if breathed in, making it especially dangerous for plant employees if stored incorrectly.

FSA also interacts negatively with metals to produce a flammable hydrogen gas, meaning a stainless steel chemical storage tank is not a viable option. It attacks glass, eats through concrete, and poses a serious storage concern. Before rotomolded plastic became a viable storage option, fiberglass tanks, constructed with a resin-rich veil, was often used for storage. The resin-rich veil, however, is often only ⅛” of chemical barrier protection from the incompatible fiberglass (chopped glass) structure itself. Since FSA eats glass, it’s actually incredibly dangerous to store FSA in something that only provides a minimal barrier of safety from a glass-made structural support container.

In these cases, a high-density cross-linked polyethylene (XLPE) storage tank is the safest option, and it’s best to choose one with secondary containment in the event of an issue. With linear polyethylene (HDPE), unzipping (or a catastrophic tear down the side of the tank) is possible, but with XLPE, the structural integrity of the tank will endure even if compromised. An XLPE tank with secondary containment, like Poly Processing’s SAFE-Tank®, can contain the chemical as well as the outlet to the pump transition from the primary tank. Not containing your fitting, the most vulnerable part of an otherwise robust system, is like having no containment in the first place. Another option is to place the pump fitting on top of the tank where chemical can not escape if a fitting fails. This, however, requires special design in the pumping system.

With the popularity of fluoridation occurring in most American water treatment plants, a tank with NSF-61 certification (and specifically for hydrofluorosilicic acid and not just potable water) should be included from the tank manufacturer. XLPE tanks are available with this certification. Always be sure NSF61 designations are for the specific chemical tested (not just water), as NSF offers certification by exact chemical according to Maximum Allowable Levels (MAL).

Hydrofluorosilicic Acid Storage Tank Requirements
The tank needs a reliable shut-off valve to isolate the pump skid, for regular pump inspection. The tank’s pump needs to be checked several times per year to ensure there is no line corrosion that could break and expose workers to the harmful effects of FSA.

An XLPE tank with a full drain is also a good choice for storage of FSA because it can help prevent build-up of deposits. One concern in storing FSA is arsenic build-up, and accumulated lead as discussed above. Some local EPA authorities will dictate special removal procedures of these tanks because of this. A full drain tank, however, will prevent these deposits from building.

Be sure that the full drain is flush with the bottom of the tank and contains no metal inserts for reasons discussed above. Precipitation of silica is a potential problem if dilution ranges get above 10:1. Again, a full drain or IMFO fitting will eliminate this concern.

Is Corrosion A Problem?
Many operators are concerned about HF gas released from concentrated H2SiF6 storage resulting in corrosion since water fluoridation will corrode pipes. Temperatures and concentrations for water fluoridation, however, ensure FSA achieves complete dissociation to fluoride, hydrogen, and silica (sand) and cannot produce HF. Silicates are actually used as a stabilizer for water corrosion. So, in solution, corrosion is not a concern- but venting is.

FLUOROSILICIC ACID

fluorosilicic acid
fluorosilicic acid ... %
Fluosilicic acid
Hexafluorosilicic acid
hexafluorosilicic acid


Translated names
...% fluorsilicio rūgštis (lt)
acid fluorosilicic…% (ro)
acide fluorosilicique à … % (fr)
acide fluosilicique ... % (fr)
acido fluosilicico ... % (it)
Fluoripiihappo...% (fi)
Fluororänihape …% (et)
fluorosilicijska kiselina ... % (hr)
fluskiselsyre ... % (da)
heksafluorkiselsyre ... % (no)
heksafluorosilicijeva kislina...% (sl)
hexafluorkiezelzuur (nl)
Hexafluorokieselsäure ... % (de)
hexafluorokiselsyra ... % (sv)
hexafluorosilicato de hidrógeno ... % (es)
hidrogén-szilícium-hexafluorid …% (hu)
hydrogensilicimhexafluorid ... % (da)
hydrogensilisiumfluorid ... % (no)
Kieselfluorwasserstoffsäure ... % (de)
kiezelfluorwaterstof ... % (nl)
kwas heksafluorokrzemowy ...% (pl)
kyselina hexafluorokremičitá ... % (sk)
kyselina hexafluorokřemičitá .....% (cs)
 … % fluorsilīcijskābe (lv)
ácido fluorosilícico (es)
ácido fluorossilícico em solução ... % (pt)
εξαφθοροπυριτικό οξύ ... % (el)
флуоросилициева киселина % (bg)

CAS names
Silicate(2-), hexafluoro-, hydrogen (1:2)

IUPAC names
Dihydrogen hexafluorosilicate
dihydrogen hexafluorosilicate
Dihydrogen hexafluorosilicate(2-)
fluorosilicic acid
Fluorosilicic acid
fluorosilicic acid ... %
H2SiF6
hexafluoro-kovasav
hexafluorosilcate
hexafluorosilicate
Hexafluorosilicic acid
hexafluorosilicic acid 
Hexafluorosilicic acid
hexafluorosilicic acid
hexafluorosilicic-acid-
hexafluorosilicon(2-); hydron
hexafluorosilicon(2-);hydron


Trade names
Acide fluorosilicique
Acide fluosilicique
Acido fluosilicico
Dihydrogen hexafluorosilicate
DIHYDROGEN HEXAFLUOROSILICATE(2-)
FLUOROSILICIC ACID
Fluorosilicic Acid
Fluorosilicic acid
fluorosilicic acid
FLUOROSILICIC ACID (H2SIF6)
FLUOROSILICIC ACID 40% (Solvay Specialty Polymers)
FLUOSILICIC ACID
fluosilicic acid
FSA
HEXAFLUORKIESELSAEURE
HEXAFLUOROSILICIC ACID
Hexafluorosilicic Acid
hexafluorosilicic acid
Hexafluosilicic acid
HFS
HYDROFLUOROSILICIC ACID
Hydrofluorosilicic acid
Hydrofluosilicic acid
hydrofluosilicic acid
Hydrogen fluorosilicate
HYDROGEN HEXAFLUOROSILICATE
Hydrogen hexafluorosilicate
Hydrosilicofluoric acid
Hydrosilicofluororic acid
KIESELFLUORWASSERSTOFFSAEURE
kwas fluorokrzemowy
Sand acid
SILICATE(2-), HEXAFLUORO-, DIHYDROGEN
Silicate(2-), hexafluoro-, dihydrogen
Silicic acid
Silicofluoric Acid
Silicofluoric acid
silicofluoric acid
Silicofluoride
Silicon hexafluoride dihydride

Other Names

Corticotropin
Dihydrogen hexafluorosilicate
FKS
Fluosilicic acid (6CI)
Fluorosilicic acid
Hexafluorosilicic acid
Hexafluorosilicate (2 - ), dihydrogen
Hexafluosilicic acid
Hydrofluorosilicic acid
Hydrofluosilicic acid
Hydrogen hexafluorosilicate
Hydrogen hexafluorosilicic
Hydrosilicofluoric acid
Sand acid
Silicate (2 - ), hexafluoro-, dihydrogen (8CI, 9CI)
Silicic acid (H2SiF6)
Silicofluoric acid
Silicofluoride Silicon hexafluoride dihydride
UN1778 (DOT)


Hexafluorosilicic Acid is a water insoluble Silicon source for use in oxygen-sensitive applications, such as metal production. In extremely low concentrations (ppm), fluoride compounds are used in health applications. 
Fluoride compounds also have significant uses in synthetic organic chemistry. They are commonly also used to alloy metal and for optical deposition. Certain fluoride compounds can be produced at nanoscale and in ultra high purity forms

Reactivity Profile
FLUOROSILICIC ACID can react with strong acids (such as sulfuric acid) to release fumes of toxic hydrogen fluoride. 
FLUOROSILICIC ACID attacks glass and materials containing silica. 
FLUOROSILICIC ACID reacts exothermically with chemical bases (examples: amines, amides, inorganic hydroxides). 
FLUOROSILICIC ACID reacts with active metals, including iron and aluminum to dissolve the metal and liberate hydrogen and/or toxic gases. 
FLUOROSILICIC ACID can initiate polymerization in certain alkenes. 
FLUOROSILICIC ACID reacts with cyanide salts and compounds to release gaseous hydrogen cyanide. 
FLUOROSILICIC ACID is flammable and/or toxic gases are also often generated by reactions with dithiocarbamates, isocyanates, mercaptans, nitrides, nitriles, sulfides, and weak or strong reducing agents. Additional gas-generating reactions may occur with sulfites, nitrites, thiosulfates (to give H2S and SO3), dithionites (SO2), and carbonates. Can catalyze (increase the rate of) chemical reactions. Decomposes when heated to the boiling point to produce very toxic and corrosive hydrogen fluoride gas.

DIHYDROGEN HEXAFLUOROSILICATE
DIHYDROGEN HEXAFLUOROSILICATE(2-)
FLUOROSILIC ACID
FLUOROSILICIC ACID
FLUOROSILICIC ACID (H2SIF6)
FLUOSILICIC ACID
HEXAFLUOROSILICIC ACID
HEXAFLUOSILICIC ACID
HYDROFLUOROSILICIC ACID
HYDROFLUOSILIC ACID
HYDROFLUOSILICIC ACID
HYDROGEN HEXAFLUOROSILICATE
HYDROGEN HEXAFLUOROSILICATE (H2SIF6)
SAND ACID
SILICOFLUORIC ACID
SILICON HEXAFLUORIDE DIHYDRIDE

•    SILICOFLUORIC ACID
•    HYDROGEN HEXAFLUOROSILICATE
•    HYDROFLUOROSILICIC ACID
•    HYDROFLUOSILICIC ACID
•    HYDROSILICOFLUORIC ACID
•    HEXAFLUOROSILICIC ACID
•    HEXAFLUOSILICIC ACID
•    FLUOSILICIC ACID
•    Fluorosilicic acid 35% 
    Fluorosilicic acid 
    Hexafluorosilicic acid 
    Fluosilicic acid
•    CORTICOTROPHIN
•    CORTICOTROPIN (HUMAN)
•    DIHYDROGEN HEXAFLUOROSILICATE
•    Hexafluorkieselsure
•    Silicate(2-), hexafluoro-, dihydrogen
•    fluorosilicic acid solution
•    Hexafluorosilicic acid, 23% aqueous solution
•    FLUOROSILICIC ACID: 35% IN WATER
•    HEXAFLUOROSILICIC ACID: 35% W/W AQUEOUS SOLUTION
•    ACTH
•    ACTH 1-39
•    ACTH (1-39), HUMAN
•    ADRENOCORTICOTROPIC HORMONE (1-39) (HUMAN)
•    ADRENOCORTICOTROPIC HORMONE HUMAN
•    hexafluorosilicicacid23%solution
•    Sand acid
•    FLUOROSILICIC ACID, 20-25 WT. % SOLUTION IN WATER
•    Hexafluorosilicic acid 25 %
•    HEXAFLUOROSILICIC ACID 34 %, PURE
•    HEXAFLUOROSILICIC ACID 34 %, TECHNICAL
•    HEXAFLUOROSILICIC ACID APPROX. 25 %
•    Hexafluorosilicic acid, 35% aqueous solution
•    Fluorsilicic acid
•    Hexafluorosilicicacid,2aqueoussolution
•    FLUOROSILICIC ACID, 20-25% SOLUTION
•    Silicofluoric acid (35%)
•    Silicate(2-), hexafluoro-, hydrogen (1:2)
•    Fluorosilicic acid, Hexafluorosilicic acid, Hydrogen hexafluorosilicate
•    Hexafluorosilic acid
•    FLUOROSILIC ACID
•    FLUOROSILICIC ACID
•    CORTICOTROPIN A
•    Hexafluorosilicic acid, 35% w/w aq. soln.
•    Hexafluorosilicic acid, 23% w/w aq. soln.
•    Silicofluoric acid: (Fluorosilicic acid)
•    FLUOROSILICIC ACID, 25% in water
•    SER-TYR-SER-MET-GLU-HIS-PHE-ARG-TRP-GLY-LYS-PRO-VAL-GLY-LYS-LYS-ARG-ARG-PRO-VAL-LYS-VAL-TYR-PRO-ASN-GLY-ALA-GLU-ASP-GLU-SER-ALA-GLU-ALA-PHE-PRO-LEU-GLU-PHE: SYSMEHFRWGKPVGKKRRPVKVYPNGAEDESAEAFPLEF
•    Hexafluorosilicic Acid w/w aq. Soln.
•    Fluorosilicic acid 35%
•    Fluorosilicic acid s
•    Hexafluorosilicic acid (HFS)
•    Fluosilicic acid, 25 wt % aqueous solution 500GR
•    Fluosilicic acid, 25 WT % aqueous solution
•    Hydrosillicofluoric acid
•    FLUOROSILICIC ACID, 22-25% in water

Acide fluorosilicique [French]
Acido fluosilicico [Italian]
Dihydrogen hexafluorosilicate [ACD/IUPAC Name]
Dihydrogenhexafluorosilicat [German] [ACD/IUPAC Name]
Hexafluorosilicate de dihydrogène [French] [ACD/IUPAC Name]
Hexafluorosilicic acid [Wiki]
Silicate(2-), hexafluoro-, dihydrogen [ACD/Index Name]
Acide fluosilicique [French]
Caswell No. 463
CCRIS 2296
DIHYDROGEN HEXAFLUOROSILANEDIUIDE
Dihydrogen hexafluorosilicate (2-)
Dihydrogen hexafluorosilicate(2-)
Fluorosilicic acid
Fluorosilicic acid [UN1778] [Corrosive]
Fluosilicic acid
Hexafluorokieselsaeure [German]
Hexafluorokiezelzuur [Dutch]
Hexafluorosilic acid
Hexafluorosilicic acidaqueous
hexafluorosilicon(2-); hydron
Hexafluosilicic acid
HSDB 2018
Hydrofluorosilicic acid
Hydrofluosilicic acid
Hydrogen hexafluorosilicate
Hydrosilicofluoric acid
Kiezelfluorwaterstofzuur [Dutch]
MFCD00036289 [MDL number]
NSC 16894
Sand acid
SILICOFLUORIC ACID
Silicofluoride
Silicon hexafluoride dihydride
UN1778
氟硅酸 [Chinese]

Hexafluorosilicic acid is sold as a concentrated solution that contains a significant concentration of HF(aq) to prevent dissociation and hydrolysis of the H2SiF6.


The Europe fluorosilicic acid market size was estimated at USD 52.38 million in 2019 and is expected to expand at a compound annual growth rate (CAGR) of 4.5% from 2020 to 2027. High consumption of the product for manufacturing hydrogen fluoride-primarily used as an industrial raw material for manufacturing aluminum, gasoline, and refrigerants-is anticipated to drive the growth of the market. Fluorosilicic acid is a key byproduct obtained from the production process of phosphate fertilizer; wherein sulfuric acid is treated with phosphate rock. This substance is widely used across multiple industries and is preliminarily consumed to formulate various herbicides, refrigerants, gasoline, pharmaceuticals, kitchen utensils, electrical components, plastic products, and others.

Fluorosilicic acid finds numerous applications across several industries; however, its primary application is in the synthesis of hydrogen fluoride. However, in Europe, due to stringent regulations on fluoridation agents used in water, the chemical finds its major application in formulating hydrogen fluoride, aluminum fluoride, and others.

Hydrogen fluoride which is one of the major application industries catered by fluorosilicic acid is used to manufacture hydrofluorocarbons used in refrigerants The consumption for fluorosilicic acid is driven by the rising demand for refrigerants. European countries have reflected high penetration of FMCG companies into the market space, which has resulted in parallelly high consumption of various industrial refrigerants in the region. High sales of packaged food products, canned beverages, and more have resulted in the construction of multiple supermarkets and organized groceries across all European countries. This resulted in higher demand for refrigerants and, therefore, subsequently higher hydrogen fluoride demand in Europe.


Synonyms:
     dihydrogen hexafluorosilicate
     hexafluorosilicic acid
     hexafluorosilicon(2-);hydron
     hydrogen hexafluorosilicate
     silicate(2-), hexafluoro-, dihydrogen


Fluorosilicic acid

Agent Name
Fluorosilicic acid

Alternative Name
Fluosilicic acid

CAS Number
16961-83-4

Formula
F6-Si.2H

Major Category
Toxic Gases & Vapors
Fluorosilicic acid formula graphical representation

Synonyms
Fluosilicic acid; Acide fluorosilicique [French]; Acide fluosilicique [French]; Acido fluosilicico [Italian]; Dihydrogen hexafluorosilicate; Dihydrogen hexafluorosilicate (2-); FKS; Hexafluorokieselsaeure [German]; Hexafluorokieselsaiure [German]; Hexafluorokiezelzuur [Dutch]; Hexafluorosilicic acid; Hexafluosilicic acid; Hydrofluorosilicic acid; Hydrofluosilicic acid; Hydrogen hexafluorosilicate; Hydrosilicofluoric acid; Kiezelfluorwaterstofzuur [Dutch]; Sand acid; Silicate (2-), hexafluoro-, dihydrogen; Silicofluoric acid; Silicofluoride; Silicon hexafluoride dihydride; Silicate(2-), hexafluoro-, hydrogen (1:2); [ChemIDplus] UN1778

Category
Acids, Inorganic

Description
Colorless liquid with a sour, pungent odor; [HSDB] Aqueous solution (<=35% fluorosilicic acid): Clear light yellow liquid; [Aldrich MSDS]

Sources/Uses
Used as a chemical intermediate, a disinfectant, a water fluoridating agent, a wood preservative, a masonry and ceramic hardener, and a glass additive; it is also used to treat hides and skins, to electroplate chromium, and to electrolytically refine lead; [HSDB] Used in technical paints, oil well acidizing, and to remove mold, rust, and stains from textiles; [NTP]

Comments
Corrosive to skin; [Quick CPC] High inhalation exposure may cause pulmonary edema; Potential for fluorosis after chronic ingestion or inhalation of aerosol; [ICSC] Marketed strictly as an aqueous solution; Anhydrous form dissociates almost instantly into silicon tetrafluoride and hydrofluoric acid; 60-70% solutions solidify at about 19 deg C, forming a crystalline dihydrate; [Merck Index] Fumes in air; Evolves heat and corrosive fumes on mixing with water; [CAMEO] Causes burns to eyes and skin (second-degree after contact of several minutes); Chronic exposure hazards include osteofluorosis, respiratory impairment, and injury to liver and kidneys; [CHRIS] Chronic exposure may cause changes in bone, corrosion of mucous membranes, coughing, shock, pulmonary edema, fluorosis, coma, and death; [NTP] Causes burns; Inhalation may cause corrosive injuries to upper respiratory tract and lungs; Toxic by ingestion; [Aldrich MSDS] See "FLUORIDES."

APPLICATIONS OF HEXAFLUOROSILICIC ACID
Wood Preservatives
Electroplating
Fur Dressing and Dyeing
Glass Manufacturing
Leather Tanning and Processing
Metal Preparation and Pouring
Painting (Pigments, Binders, and Biocides)
Petroleum Production and Refining
Sewer and Wastewater Treatment
Disinfectants and Biocides


Fluorosilicic Acid, Hexafluorosilicic Acid, Fluosilicic Acid or FSA is also an involuntary byproduct of the phosphoric acid industry that is normally being neutralized and disposed with the phosphogypsum or in a dedicated area.

 

FSA can be of a very beneficial use, it can be used in water fluoridation a normal practice in water treatment industry, it can be also used in the manufacturing of Sodium Fluoride or Aluminium Fluoride which both are used in Aluminium industry to decrease the melting point of Aluminium ore.

 

FSA can be also a source of active silica which is a valuable product that can be used in the phosphoric acid industry itself to neutralize the highly corrosive Hydrofluoric Acid (HF), it can be also used in many other industries.


Synonyms: Hydrofluorosilicic Acid, Hydrofluosilicic Acid, Hydrtosilicofluodie Acid, Fluorosilicic Acid, Silicofluoric Acid, Fluosilicic Acid Raw materials Calcium fluoride, Hydrofluoric acid, Silicon dioxide, Sulphuric acid, Celite Preparation Products Ammonium hexafluorosilicate, Sodium fluoroaluminate, Magnesium fluorosilicate, Potassium tetrafluoroborate, Potassium fluoride, Sodium tetrafluoroborate, MAGNESIUM HEXAFLUOROACETYLACETONATE DIHYDRATE, Chromic acid, Potassium fluorosilicate, Magnesium fluosilicate, Magnesium hexafluorosilicate hexahydrate, Sodium tripolyphosphate, Aluminium fluoride, Sodium fluorosilicate, CUPRIC FLUOROSILICATE, Trisodium hexafluoroaluminate, Ammonium fluoborate, Sodium fluoride, ZINC SILICOFLUORIDE, Lead. 1 FLUORSPAR AND WATER FLUORIDATION CHEMICALS Fluorspar (CaF2) is the most important fluoric containing mineral. About 52% of fluorspar consumption worldwide is used as starting material for the production of hydrofluoric acid; another 18% is used for aluminium fluoride, the fluxing agent in the aluminium industry; and 25 % for the steel industry as a flux to improve the fluidity of slag in steelmaking. 
Fluorspar is the commercial name for the mineral fluorite (calcium fluorite) and it is a major raw material source of fluorine. 
25% of the fluorspar consumption of the European Union is produced by EU member states, mainly by Spain. 
A much larger amount is imported from states like China. 2 Fluorspar deposits are primarly a byproduct of precious and base metal ores, such as lead, silver or zinc. 
Fluorspar deposits vary in mineral composition and are not pure. 
They contain large quantities of silica. 
Small quantities of rare earth elements (REE), strontium and other elements may substitute for calcium within the fluorspar crystal structure. Fluorspar is used directly or indirectly to manufacture such products as aluminium, gasoline, insulating foams, refrigerants, steel, and uranium fuel. 
It is used in the manufacture of Fluorocarbon chemicals, including fluoropolymers, chlorofluorocarbons (CFC's) , hydrochlorofluorocarbons (HCFC's), and hydrofluorocarbons (HFC's). CFC's, HCFC's, HFC's and Hydrofluoric acid (HF).

HF is used as the feedstock in the manufacture of a host of fluorine chemicals used in dielectrics, metallurgy, wood preservatives, herbicides, mouthwashes, dentifrices, plastics and water fluoridation. 
One of its most common end-products is fluorosilicic acid or hexafluorosilicic acid also known as hydrofluosilicic acid, which is used in water fluoridation. 
HF is the primary feedstock for the manufacture of virtually all organic and inorganic fluorine-bearing chemicals and is also a key ingredient in the processing of aluminium and uranium. 
The remaining use of fluorspar consumption is as a flux in steelmaking, in iron and steel foundries, primary aluminium production, glass manufacture, enamels, welding rod coatings, cement production, and other uses or products such as the manufacture of Hexafluorosilicic acid. Trace elements such as lead and arsenic are present in finished products. Hexafluorosilicic acid is sold as a concentrated solution that contains a significant concentration of HF(aq) to prevent dissociation and hydrolysis of the H2SiF6. 
In North America many municipal authorities source the same product using recovered sulphuric acid from acid scrubbers to react with either fluorspar or phosphate rock. 

How is it manufactured? 
Before fluorspar can be used to make hydrofluoric acid, the raw ore must be physically concentrated and purified. Fluorspar is crushed, ground up and purified by froth flotation. First the lead and zinc sulphides are separated and the fluorspar treated with sulphuric acid forming hydrofluoric acid gas (HF). 
The acid grade fluorspar typically contains at least 97 percent calcium fluoride, as well as silica, mixed metal oxides and a trace amounts of arsenic. 
The HF gas then begins a purification process involving the gas being cooled, purified by scrubbing and condensed. 
The crude product may be diluted and sold as an approximately 70 percent hydrofluoric acid solution, or distilled to remove any remaining water and further reduce impurities, and sold as hexafluorosilicic acid (hydrofluorosilicic acid) typically made up to a concentration of 37 to 42 per cent. 
The manufacturing process generates tailing waste consisting of lead and zinc sulfides, spent flotation reagents and corrosive process wastewater

Applications
Cement
Ceramics
Chemical intermediate
Electroplating
Laundry sour
Ore extraction
Sterilizing bottling equipment
Water fluoridation

Hydrofluorosilicic acid can be the most dangerous chemical at a particular facility. In the case of evaporation, it releases hydrogen fluoride that is extremely corrosive and will harm the lungs if it is breathed. In addition, hydrofluorosilicic acid interacts with metals and produces a flammable hydrogen gas. These dangers, along with potential corrosion or leakage, can cause imminent harm to working personnel and equipment. Safety precautions should be a key consideration when choosing the right pump for handling hydrofluorosilicic acid.


When pumping hydrofluorosilicic acid at room temperature, it is strongly recommended to choose a sealless magnetic drive chemical pump made out of Polypropylene. Hydrofluorosilicic acid is extremely corrosive and interacts with all kinds of metals. An Encapsulated Impeller, Carbon Bushing, and Viton O-ring will prevent all forms of leakage and ensure the safety of your working personnel and equipment.


Hydrofluorosilicic Acid; Hydrosilicofluoric acid;
Sand acid; Silicofluoric acid; Fluosilicic acid; Hydrofluorosilicic acid; Hydrofluosilic Acid; Hexafluorosilicic acid; Dihydrogen hexafluorosilicate; 氟硅酸; Hexafluorokieselsäure (Dutch); ácido hexafluorosilicico (Spanish); Acide hexafluorosilicique (French); Silicofluoric acid; Silicofluoride; Silicon hexafluoride dihydride; Fluorosilicic acid; H2SiF6; Hydrogen hexafluorosilicate;


Fluorosilicic acid is a translucent, straw-colored, corrosive liquid comprising the H2SiF6 chemical formulation. It is produced in modern rubber lined equipment containing high industrial purity acid. Fluorosilicic acid is an organic liquid formed by the synthesis of fluoride hydrogen and phosphoric acid. It is commonly used for water fluoridation to control the amount of fluoride in water by municipal corporations and toothpaste. Maintaining fluoride levels helps prevent tooth decay.

MARKET DYNAMICS

Increased consumer demand for water fluoridation, electroplating, and well acidifying oils may boost the size of the market for fluorosilicic acid. 
It is used by municipal corporations in the process of water treatment to control the amount of fluoride. 
Hexafluorosilic acid is commonly used in metal surface treatment processes as it causes non-chromium surface passivation that can stimulate product demand. 
Moreover, increasing demand for products from the textile industry for the removal of stain and rust from textiles is likely to fuel the growth of the hydrofluorosilic industry. 
Further, the product is used for pH adjustment in industrial textile processing or laundry services, thereby driving product growth. Hydrofluorosilic acid is commonly used in oral care products such as toothpaste, mouthwash, floss, and teeth whitening. Growing consumer awareness of oral disorders such as gingivitis, denture irritation, and bleeding gums is likely to fuel industry development. 
It strengthens weak spots and exposed roots and helps prevent early tooth decay, which may stimulate demand for the product. 
Thus all these factors are expected to positively affect the demand of the product.


Water fluoridation is an important preventative measure carried out in much of the western world. 
It results in some of the hydroxyapatite, Ca5(PO4)3OH, of which human tooth enamel is made being replaced by fluoroapatite, Ca5(PO4)3F - a substance significantly more resistant to decay. Thus to protect the teeth of the population, water is often fluoridated. This is usually done with one of three fluorine-containing chemicals (sodium fluoride, sodium fluorosilicate and hydrofluorosilicic acid), but this article focuses on hydrofluorosilicic acid as that is the chemical most commonly used in New Zealand for this purpose. Hydrofluorosilicic acid manufacture can be viewed as a two-step process, although in reality it is carried out in four steps to ensure that the right concentration of acid is obtained. 
Step 1 - Production of SiF4 The superphosphate production process results in the evolution of carbon dioxide, steam and SiF4. 
This SiF4 is an environmental pollutant and so is removed from the gas stream and used to produce fluorosilicic acid. 
Step 2 - Hydrolysis of SiF4 The SiF4 is removed from the gas stream by contacting the gas with water droplets. 
This water hydrolyses the SiF4 as follows: 3SiF4 + 2H2O → 2H2SiF6 + SiO2 The resultant hydrofluorosilicic acid (H2SiF6) is used for fluoridating drinking water.

INTRODUCTION In many cities in the western world, drinking water is fluoridated to help prevent peopleís teeth from decaying. 
Fluorine achieves this by replacing hydroxyapatite (Ca5(PO4)3OH) with fluoroapatite (Ca5(PO4)3F). 
Fluoroapatite is more resistant to acid attack and thus teeth which contain even a small proportion of fluoroapatite are less likely to decay. 
The relevant reactions are as follows: Tooth decay: Ca5(PO4)3OH(s) + 4H3O+ (aq) → 5Ca2+(aq) + 3HPO4 2-(aq) + 5H2O(l) Fluoridation: Ca5(PO4)3OH(s) + F- (aq) → Ca5(PO4)3F(s) + OH- (aq) Fluoridation of water in New Zealand is largely accepted, and there are only two major cities that do not adjust the fluoride level of their water supply. Referendum is becoming the norm for determining public opinion on whether to fluoridate or not. Three chemicals are in common use for this purpose, namely sodium fluoride, sodium fluosilicate and hydrofluorosilicic acid (HFA). Sodium fluoride Sodium fluoride is a white powder, moderately soluble in water (about 3% w/w). 
For water I-Chemicals-C-Hydrofluorosilicic acid-2 fluoridation purposes it is usual to prepare a saturated solution in water and inject this solution into the bulk water. 
However, sodium fluoride is the most expensive of the three and for this reason is not widely used. 
Sodium fluorosilicate Sodium fluorosilicate is a white powder sparingly soluble in water (about 0.6% w/w). This low solubility means that it is not feasible to use a saturated solution so dry solid is fed into bulk water at the appropriate rate. However, it can be difficult to control small flows of solid and this aspect of fluoridation equipment must be well designed and carefully monitored. Nevertheless, the fluorosilicate is widely used as it is significantly cheaper than the fluoride salt. 
Hydrofluorosilicic acid Hydrofluorosilicic acid has several advantages. Being a liquid, it is easy to handle and to meter accurately into the bulk water. Plant operators do not have to manually handle fine powders. The acid is also the cheapest source of fluorine. 
However, it is corrosive and tends to fume, particularly at concentrations of above 20%. 
Its main drawback is that it is a comparatively dilute source of fluoride. 15% acid contains just under 12% fluorine by mass, whereas sodium fluoride contains 47% and sodium fluorosilicate 60%. Over long distance transport costs can make solid chemicals more attractive. 
All manufacturers of superphosphate produce hydrofluorosilicic acid as a by-product. 
THE HYDROFLUOROSILICIC ACID MANUFACTURING PROCESS 
Step 1 - Production of SiF4 Superphosphate is manufactured by mixing together finely ground phosphate rock and sulfuric acid. 
A vigorous reaction occurs with considerable gas evolution. The gases given off are mainly steam and carbon dioxide, but there is also a small quantity of silicon tetrafluoride released (seeprevious article). 
Uncontrolled release of this gas to atmosphere could cause significant pollution so every fertiliser works has a gas scrubber as an integral part of its manufacture plant. 
Step 2 - Hydrolysis of SiF4 Silicon tetrafluoride reacts readily with water, so it is removed from the other gases by a gas scrubber that is essentially a means of contacting the gas stream with finely divided droplets of water. 
The reaction with water hydrolyses the silicon tetrafluoride according to the equation: 3SiF4 + 2H2O → 2H2SiF6 + SiO2
 In this way 99% of the fluoride is removed from the gas stream, leaving only a very small quantity to be emitted. 
These emissions are covered by a discharge permit and less than 0.1 g s-1 fluoride is discharged to the atmosphere. 
The liquid from the scrubber is usually a dilute solution of hydrofluorosilicic acid, with a small amount of solid silica suspended in it. 
This dilute hydrofluorosilicic acid can be partially substituted for sulfuric acid in the production of superphosphate. 
In the New Plymouth works of Farmers Fertiliser Ltd the scrubbing process has been modified so as to produce an acid suitable for water fluoridation. 
In this works the scrubbing I-Chemicals-C-Hydrofluorosilicic acid-3 process is divided into three stages with acid of different concentration in each. 
This yields an acid containing about 20% H2SiF6 which is acceptable to local authorities. The superphosphate article has a flowsheet showing a typical scrubber installation for hydrofluorosilicic acid production. 
Water and gas are made to flow ëcountercurrentí to each other so that gas rich in fluoride is contacted by strong acid and gas weak in fluoride meets very dilute acid. 
Strong acid is pumped away from the first scrubber and settled to remove silica before being sold. 
ENVIRONMENTAL AND FINANCIAL CONSIDERATIONS 
This process removes fluoride from the gas stream, thus preventing an environmental hazard, but it does have its problems. 
The 20% acid is very corrosive to most metals, so scrubbing equipment is more costly than that used with plain water sprays. 
However, the demand in the North Island is sufficient to justify economic recovery.

It is used in mixing, preparation or repackaging, as an interim product in the synthesis of chemicals, as a process auxiliary means for cleaning and disinfection. It is also applied in water fluorination, the treatment of the surfaces of metals, production of basic metals, acid decomposition of minerals, professional cleaning and disinfection as well as a laboratory chemical.

Hydroflurosilicic acid, also known as fluorosilicic acid and hexaflurosilicic acid, is a clear, colorless liquid that is used in a variety of industrial applications. Due to its ease of use over competing technologies, hydroflurosilic acid is commonly used in water fluoridation applications. Hydroflurosilicic acid is also used for hardening masonry and ceramics, as a metal surface treatment and cleaner, pH adjustment in industrial textile processing or laundries, and as an intermediate in the manufacturing of chemicals.

Compatibility:

Hydroflurosilicic acid is incompatible with metals, glass, alkali, ceramics, and strong concentrated acids. Strong concentrated acids will cause the release of poisonous hydrogen fluoride. Hydrofluorosilicic acid will attack glass and ceramics and metals will corrode and liberate hydrogen gas.

Hydrofluorosilicic acid is very corrosive. An inorganic acid, it is classified as a “strong” acid, as are all inorganic acids. (An acid’s strength is defined as the percentage of ionization the acid undergoes when dissolved in water: it has nothing to do with the concentration (the amount of acid dissolved in water) of the acid.] Inorganic acids are highly hazardous even at low concentrations; their degree of ionization is nearly 100 percent. Other inorganic acids include sulfuric acid, hydrochloric acid, hydrofluoric acid, chromic acid, nitric acid, and phosphoric acid (among numerous others).

Organic acids, on the other hand, are classified as weak acids since their degree of ionization in water is extremely low. often considerably less than one percent. Examples of organic acids include acetic acid (present in vinegar), formic acid (the painful substance injected by most stinging insects), lactic acid (present in sour milk), and acrylic acid, a monomer for many plastics. Again, these four organic acids are taken from a list of thousands.

The strength of an acid commonly is erroneously associated with its corrosiveness. Generally speaking, while it is true that strong acids are more corrosive than weak acids, concentrated weak acids can be very corrosive to human tissue and other materials. Do not try to classify the danger an acid poses to human tissue or other materials on the basis of its “strong” or “weak” designation. To be sure of the danger posed, you must know exactly what the acid is and its level of concentration.

If hydrofluorosilicic acid’s concentration is high enough, it will severely damage any human tissue it contacts. Pure hydrofluorosilicic acid and most concentrations of this acid in water are extremely corrosive: Even relatively low concentrations can severely damage human tissue. The damage can range from simple first-degree bums to very deep, tissue-destroying third-degree burns. Chemical burns are always many times more severe than thermal burns, so severe harm (to the point of causing death) can occur with relatively small areas of tissue damage. Eyes and skin will be severely damaged by contact with concentrated hydrofluorosilicic acid fumes or vapors; the hazards are more far-reaching than those posed by contact with the liquid. If very low concentrations of the acid contact the skin, the damage may be as light and simple as reversible irritation of the tissue involved.


 

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