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16961-83-4 Usage


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

Different sources of media describe the Chemical Properties of 16961-83-4 differently. You can refer to the following data:
1. 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.
2. Fluorosilicic acid is a transparent, colorless fuming liquid.

Physical properties

d 1.220 g cm?3 for a 25% aq solution.


Different sources of media describe the Uses of 16961-83-4 differently. You can refer to the following data:
1. A fluoride source with both protic and Lewis acid properties providing efficient cleavage of silicon–oxygen bonds, e.g. silyl ether deprotection.
2. 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.
3. 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.


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.

Flammability and Explosibility


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.


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


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


Robinson, Tim. "Innovative Processes in Electrometallurgy." Innovative Process Development in Metallurgical Industry. Springer International Publishing, 2016. 385- 392. Sarawade, Pradip B., et al. "Recovery of high surface area mesoporous silica from waste hexafluorosilicic acid (H 2 SiF 6) of fertilizer industry." Journal of hazardous materials 173.1 (2010): 576-580. Kauffman, Joel M. "Water fluoridation: a review of recent research and actions." Journal of American Physicians and Surgeons 10.2 (2005): 38. Krot, V. V., et al. "ChemInform Abstract: Preparation of Amorphous Silicon Dioxide from Hexafluorosilicic Acid." Cheminform 23.48(1992):no-no. Zorya, L., and V. Krot. "Method of high-purity silica production from hexafluorosilicic acid." Reaction Kinetics & Catalysis Letters 50.1-2(1993):349-354.

Check Digit Verification of cas no

The CAS Registry Mumber 16961-83-4 includes 8 digits separated into 3 groups by hyphens. The first part of the number,starting from the left, has 5 digits, 1,6,9,6 and 1 respectively; the second part has 2 digits, 8 and 3 respectively.
Calculate Digit Verification of CAS Registry Number 16961-83:
134 % 10 = 4
So 16961-83-4 is a valid CAS Registry Number.

16961-83-4 Well-known Company Product Price

  • Brand
  • (Code)Product description
  • CAS number
  • Packaging
  • Price
  • Detail
  • Alfa Aesar

  • (69109)  Hexafluorosilicic acid, 23% w/w aq. soln.   

  • 16961-83-4

  • 100g

  • 286.0CNY

  • Detail
  • Alfa Aesar

  • (69109)  Hexafluorosilicic acid, 23% w/w aq. soln.   

  • 16961-83-4

  • 500g

  • 495.0CNY

  • Detail
  • Alfa Aesar

  • (69109)  Hexafluorosilicic acid, 23% w/w aq. soln.   

  • 16961-83-4

  • 2.5kg

  • 1519.0CNY

  • Detail
  • Alfa Aesar

  • (L14829)  Hexafluorosilicic acid, 35% w/w aq. soln.   

  • 16961-83-4

  • 100g

  • 289.0CNY

  • Detail
  • Alfa Aesar

  • (L14829)  Hexafluorosilicic acid, 35% w/w aq. soln.   

  • 16961-83-4

  • 500g

  • 500.0CNY

  • Detail
  • Alfa Aesar

  • (L14829)  Hexafluorosilicic acid, 35% w/w aq. soln.   

  • 16961-83-4

  • 2500g

  • 880.0CNY

  • Detail
  • Sigma-Aldrich

  • (01302)  Fluosilicicacid  purum, 33.5-35%

  • 16961-83-4

  • 01302-1L

  • 622.44CNY

  • Detail
  • Sigma-Aldrich

  • (01302)  Fluosilicicacid  purum, 33.5-35%

  • 16961-83-4

  • 01302-6X1L

  • 3,113.37CNY

  • Detail
  • Aldrich

  • (372757)  Fluorosilicicacidsolution  20-25 wt. % in H2O

  • 16961-83-4

  • 372757-500G

  • 617.76CNY

  • Detail



According to Globally Harmonized System of Classification and Labelling of Chemicals (GHS) - Sixth revised edition

Version: 1.0

Creation Date: Aug 12, 2017

Revision Date: Aug 12, 2017


1.1 GHS Product identifier

Product name Hexafluorosilicic acid

1.2 Other means of identification

Product number -
Other names Fluorosilicic acid

1.3 Recommended use of the chemical and restrictions on use

Identified uses For industry use only. CBI,Oxidizing/reducing agents,Plating agents and surface treating agents,Processing aids, not otherwise listed,Solvents (for cleaning or degreasing)
Uses advised against no data available

1.4 Supplier's details

1.5 Emergency phone number

Emergency phone number -
Service hours Monday to Friday, 9am-5pm (Standard time zone: UTC/GMT +8 hours).

More Details:16961-83-4 SDS

16961-83-4Related news

Interaction of Hexafluorosilicic acid (cas 16961-83-4) with sulfa drugs. Bis(sulfathiazolium) hexafluorosilicate: Spectral data and crystal structure08/08/2019

Interaction of hexafluorosilicic acid with sulfa drugs sulfathiazole (stz) and sulfalen (2-sulfanilamido-3-methoxypyrazine, sl) results in the crystalline salts of the compositions [stzH]2[SiF6] (I) and [4-H2NO2SPhNH3]2[SiF6] (II). Complex I is characterized by IR, mass spectrometry data and sin...detailed

Recovery of high surface area mesoporous silica from waste Hexafluorosilicic acid (cas 16961-83-4) (H2SiF6) of fertilizer industry08/07/2019

In this article we report recovery of mesoporous silica from the waste material (hexafluorosilicic acid) of phosphate fertilizer industry. The process involves the reaction of hexafluorosilicic acid (50 ml, 24 wt% H2SiF6) and 100 ml, 0.297 M Na2CO3 to generate the alkaline aqueous slurry. Silica...detailed

Synthesis of titanium containing MCM-41 from industrial Hexafluorosilicic acid (cas 16961-83-4) as epoxidation catalyst08/06/2019

The industrial by-product hexafluorosilicic acid was investigated as silicate source for titanium containing MCM-41 (Si/Ti–MCM-41) synthesis. An extended and detailed study, which includes the effects of several factors such as the state and content of Ti, surfactant/Si ratio and template remov...detailed

Synthesis of ZSM-5 with the silica source from industrial Hexafluorosilicic acid (cas 16961-83-4) as transalkylation catalyst08/05/2019

A new effective process to improve the utilization of industrial fluorosilicic acid of phosphate fertilizer by-product has been investigated to comprehensive application of the silicon and fluorine source. Two-step ammoniation was applied to recover high-quality silica. The recovered silica can ...detailed

16961-83-4Relevant articles and documents

Heimann, Robert B.

, (1984)

Worthington, K. K.,Haring, M. M.

, p. 7 - 7 (1931)

Temperature dependence of photoluminescence spectra and dynamics of the red-emitting K2SiF6:Mn4+phosphor

Shao, Qiyue,Wang, Lin,Song, Li,Dong, Yan,Liang, Chao,He, Jinhua,Jiang, Jianqing

, p. 221 - 226 (2017)

Investigating and understanding temperature-dependent photoluminescence (PL) properties of inorganic phosphors are of vital importance to optimize their performance and expand their application. Recently, K2SiF4:Mn4+phosphors have attracted intense attention as a red phosphor candidate for white LED applications because of their extremely narrow emission peaks in the red spectral region. Here, temperature-dependent (20–200?°C) diffuse reflection spectra and steady and transient PL spectra of K2SiF4:Mn4+were systematically investigated. Both the emission intensities and spectral characteristics of the phosphor showed excellent thermal stability at temperatures from 20 to 150?°C, ensuring its great potential for practical white LED applications. An abnormal PL enhancement was found at elevated temperatures that differed from the thermal quenching behavior of common phosphors and could be attributed to enhanced phonon-assisted radiative transitions at higher temperatures. We further successfully tested and verified that the intensity ratio of anti-Stokes and Stokes emission peaks of Mn4+ions was sensitive to temperature and followed a Boltzmann-type distribution function very well, making the K2SiF4:Mn4+phosphor a good candidate for temperature sensing, especially for investigating the thermal distribution of white LEDs.

Synthesis, properties, sintering and microstructure of sphene, CaTiSiO5: A comparative study of coprecipitation, sol-gel and combustion processes


, p. 655 - 661 (1998)

Sphene (CaTiSiO5), a titanosilicate ceramic considered as a host material for the immobilization of radioactive waste from nuclear power reactors, has been prepared using coprecipitation, sol-gel, and solution combustion methods. All these processes initially yielded amorphous powders, which on further calcination, crystallized to yield sphene along with perovskite, titania, and cristobalite. The coprecipitation-derived powder calcined at 1000 °C for 2 h showed the formation of single phase sphene; whereas, the sol-gel-derived and combustion-derived powders required higher temperature (1200 °C for 2 h) for single phase sphene to form. Coprecipitation-derived sphene powder achieved 96% theoretical density when sintered at 1300 °C for 2 h, and the microstructure of the sintered body showed a uniform grain size of ≈1 μm.

Sulfuric acid breakdown of fluorite in the presence of silica


, p. 1876 - 1879 (2010/05/01)

We study the reaction of CaF2 with concentrated sulfuric acid in the presence of silica at 120 and 140°C using fluorite mineral, fluorite concentrate, and mica-fluorite ore samples. When steam is fed to the reaction mixture, fluorosilicic acid

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