Fluosilicic acid
CAS No. 16961-83-4

Return to Fluosilicic acid Adverse Effects

ACTIVITY: Wood Preservative


Adverse Effects:

Gastrointestinal tract

Regulatory Information
(only comprehensive for the US)
US EPA Registered: No for pesticides
Yes as an agent for fluoridating US public drinking water. It is a highly toxic waste product from the phosphate fertilizer industry.
US EPA PC Code: 075305 
Old US EPA PC Code: 075303 
Banned in Austria
Other Information
Molecular Formula: F6-Si.2H  

Farmland Industries
Gardinier Inc.
IMC Fertilizer
Pelham Phosphate
Weaver Fertilizer

-- see box below for more information, including production sites.

Other Names

Dihydrogen hexafluorosilicate
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)

Of special interest:
PAN Data 
October 2001 - Toxicological Summary for Sodium Hexafluorosilicate [CASRN 16893-85-9] and Fluorosilicic Acid [CASRN 16961-83-4]. Review of Toxicological Literature. Prepared for Scott Masten, Ph.D., National Institute of Environmental Health Sciences. Also available at:
TOXNET profile from Hazardous Substances Data Bank 

The major use of sodium hexafluorosilicate and fluorosilicic acid is as fluoridation agents for drinking water. 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. 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.
-- Fluorosilicic acid is mainly produced as a byproduct of the manufacture of phosphate fertilizers... In the manufacture of phosphate fertilizer in Central Florida, fluorides and radionuclides
(radium and uranium) are released as toxic pollutants.
During the acidulation process, radon gas can be released and carried into the fluorosilicic acid, while polonium can be captured during the
scrubbing process and combined with fluoride.

Ref: Toxicological Summary for Sodium Hexafluorosilicate [CASRN 16893-85-9] and Fluorosilicic Acid [CASRN 16961-83-4]. Review of Toxicological Literature. October 2001. Prepared for Scott Masten, Ph.D. National Institute of Environmental Health Sciences.


Chemtech Industries, Inc, Hq, 1655 Des Peres Road, PO Box 31000, St Louis, MO 63131, (314) 966-9900; Fluoride Manufacturing Division;
Production site: East, St Louis, IL 62202

Dow Chemical USA, Hq, 2020 Dow Center, Midland, MI 48674, (517) 636-1000; Subsidiary: Essex Chemical Corp, 1401 Broad St, Clifton, NJ 07015, (201) 773-6300; Essex Industrial Chemicals, Inc, subsidiary;
Production site: 100 Thomas Ln, Paulsboro, NJ 08066

Farmland Industries, Inc, Hq, 3315 N Oak Trafficway, PO Box 7305, Kansas City, MO 64116, (816) 459-6000;
Production site: Green Bay, FL 33830

Freeport-McMoran Resource Partners, Hq, 1615 Poydras, New Orleans, LA 70112, (504) 582-4000; Agrico Chemical Company, PO Box 60031, New Orleans, LA 70160;
Production sites: Bartow, FL 33830; Uncle Sam, LA 70792

Gardinier Inc, Hq, PO Box 3269, Tampa, FL 33601, (813) 677-9111;
Production site: Tampa, FL 33601

IMC Fertilizer Group, Inc, Hq, 2315 Sanders Rd, Northbrook, IL 60062, (312) 564-8600;
Production sites: Americus, GA 31709; Florence, AL 35650; Hartsville, SC 29550

Maxxam Group Inc, Hq, 1088 O Wilshire Blvd, Los Angeles, CA 90024, (213) 474-6264; Kaiser Tech Limited, Harshaw/Filtrol Partnership, 30100 Chagrin Boulevard, Cleveland, OH 44124;
Production site: 1000 Harvard Avenue, Cleveland, OH 44109

Nu-West Industries Inc, Hq, 8400 E Prentice Ave, Suite 1320, Englewood, CO 80111, (303) 721-1396;
Production site: Conda, ID 83230; Nu-South, Pascagoula, MS 39568; Production site: Pascagoula, MS 39567

Occidental Petroleum Corporation, Hq, 10889 Wilshire Blvd, Suite 1500, Los Angeles, CA 90024, (213) 879-1700; Subsidiary: Occidental Chemical Corp, 5005 LBJ Freeway, Dallas, TX 75244, (214) 404-3800; Agricultural Products Division, 4830 W Kennedy Blvd, Suite 950, Tampa, FL 33609; Feed Products Group;
Production site: Highway 22, Montepelier, IA 52759

Pelham Phosphate Co, Hq, West Railroad St, Pelham, GA 31779, (912) 294-2081

Texasgulf Inc, Hq, PO Box 30321, Raleigh, NC 27622, (919) 881-2700;
Production site: Aurora, NC 27806

Weaver Fertilizer Company, Inc, Hq, First Virginia Tower, Norfolk, VA 23510, (804) 622-6591;
Production site: Norfolk, VA 23510

Ref: Hazardous Substances Data Bank for FLUOSILICIC ACID CASRN: 16961-83-4. http://www.fluorideaction.org/pesticides/fluosilicic.acid.toxnet.hsd.htm

US Federal Register
Date Published  Details
June 19, 1995 Technical Amendments for coloration are deleted as they are "no longer registered and not sold for pesticide use." FINAL RULE.

Material Safety Data Sheets (MSDS):
Name of Product Manufacturer / Distributor MSDS
Fluorosilicic Acid Pelchem (South Africa) MSDS
Hydrofluosilicic Acid Incitec Pivot Limited (Australia) [supplier] MSDS
Laundry PackSour - LPS 750  Americlean Systems, Inc.  MSDS
Rialto Antisale Harpo S.p.A. (Italy) MSDS
Soft Finish Hillyard, Inc. MSDS
Fluoride Action Network | Pesticide Project | 315-379-9200 | pesticides@fluoridealert.org