Magnesium fluosilicate
CAS No. 16949-65-8

ACTIVITY: Insecticide (Inorganic)


Regulatory Information
(only comprehensive for the US)
US EPA Registered: No 
US EPA PC Code: 075304 
Other Information
Molecular Formula:


Other Names:  

Farmoz X-Lice Washdown
Instant wetting sheep dip

Magnesium hexafluorosilicate
Magnesium hexafluorosilicate(2-)
Magnesium silicofluoride

Fluosilicate de magnesium [French]
Fluosilicic acid magnesium salt
Hexafluorosilicate(2-) magnesium (1:1)
Silicon fluoride magnesium salt
Silicate(2-), hexafluoro-, magnesium (1:1)

Of special interest:
PAN Data 
Material Safety Data Sheet: Farmoz X-Lice Washdown; Instant wetting sheep dip   

October 2002 - Guidelines for producing EU eco-label wool

If lice are present, use an OP off-shears backliner; OP or magnesium fluorosilicate dip no later than 2-3 weeks after shearing. If an IGR backliner is used, eco-label eligibility will have to be foregone.

Ref: Factsheet. Guidelines for producing European eco-label and nil residue wool. Western Australia Department of Agriculture. Also available at

Sheep dip;
Used as a moothrproofer in the US
(manufactured by Herters Inc.,
Waseca MN) from 1968-1989

Adverse Effects:

As of February 2005: very little data available

Related Chemicals for Ammonium fluosilicate on silica gel
Ref: Pesticide Action Network (PAN)
CAS No. Relation Chemical Name PAN & FAN data Some Notes from FAN:
16893-85-9 Parent * Sodium fluosilicate



US EPA List 3 inert

Registered in:
Australia, Canada, India, South Africa, Tanzania, Vietnam

UK: Cancelled

16919-19-0 Related (1)

Ammonium fluosilicate



US EPA List 3 inert

SYN: Ammonium silicofluoride

62449-69-8 Related (1) Ammonium fluosilicate on silica gel



SYN: Barium hexafluorosilicate
17125-80-3 Related (1)

Barium fluosilicate



Registered in:

EU: Not allowed to be used as an active ingredient after July 25, 2003

SYN: Barium hexafluorosilicate

12062-24-7 Related (1)

Cupric fluosilicate



Copper silicofluoride,
Cupric hexafluorosilicate
1327-43-1 Related (1) Magnesium aluminum fluosilicate



US EPA List 3 inert  
16949-65-8 Related (1) Magnesium fluosilicate


53404-77-6 Related (1) Sodium aluminum fluosilicate



16871-71-9 Related (1)

Zinc fluosilicate



PAN Bad Actor Chemical:
Developmental or Reproductive Toxin

SYN: Zinc silicofluoride

Explanation from PAN:
* Parent: Compounds labeled with a "P" are the parent compound of the group. The parent chemical was chosen on the basis of available toxicity information, where chemicals with the maximum amount of toxicity information assigned to parent status. Where no toxicity information was available for any member of a group, we assigned parent status to the least derivatized member of the group for organic compounds (e.g., benzoic acid would be the parent instead of methyl benzoate), the sodium salt (for compounds with a common anion), or the chloride salt (for compounds with a common cation). These are general guidelines and not hard and fast rules, because the groups are rarely so easy to categorize. For some groups with no obvious parent, assignment of parent status was arbitrary.

Group 1: Salts, esters and/or complexes of the parent chemical, e.g., glyphosate and glyphosate, isopropylamine salt; 2,4-D and 2,4-D, butoxyethyl ester. Alternatively, the parent compound itself is an ester or salt, and related compounds are other esters or salts.

Toxicology Letters Volume 88 , October 1996, Pages 53-54

 A case of intoxication with household products containing fluorosilicates

José M. Torrecill, Rosa Martínez, Emilio Mencías and Salomé Ballesteros

Servicio de Información Toxicológica, Instituto Nacional de Toxicologíca Madrid Spain

Although only a few reports of poisoning by fluosilicates have lately appeared in literature, 43 accidental cases, 2 of them fatal have been communicated to our center in the period 1991-1995. One of them is presented here.

A 17-month-year old girl was admitted to the hospital 60 min after the ingestion of a probably small amount of floor polish containing 20% of Mg2SiF6. On admission, she showed continual vomiting and a crisis of generalyzed muscle spasms. Hypertonus, arreflexia, hypoesthesia and other signs of neurological damage were also present. Fluoride has been associated with a wide variety of neurotoxicity, ranging from confusion to coma. Shock and coma were significant aspects of a suicidal case previously reported to our center. On autopsy edematosous areas in pharynx, larynge, trachea and esophagus compatible with caustic lessions by fluorosilicates were found. Hypocalcemia that leaded to a ventricular fibrillation and cardiac arrest was rapidly insatured. Although early endovenously 10% calcium gluconate were applied, by itself it does not always prevent arrhythmias. In fact, her condition continued to deteriorate and 45 minutes after initiation of the resuscitation measures she died of cardiac failure. Hyperkaliemia was observed and could be implicated in contributing to fluoride-induced arrhythmias. Analysis of blood and serum showed a fluor concentration of 38.4 mg/L and 419 mg/L respectively far above the lethal level.

The fatal dose of fluoride has been reported to be 30 mg/kg. Therefore, the ingestion of a small amount of the floor polish such as 2 ml can be lethal for a 2-year-old baby. Due to the riskiness of magnesium fluorosilicate containing products restrictions in marketing and sales are justified.

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