Fluorosilicic acid

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  • Identifiers

    CAS number
    16961-83-4

    Molecular formula
    F6H2Si

    SMILES
    [H+].[H+].F[Si-2](F)(F)(F)(F)F

    Safety labels

    Corrosive
    Corrosive

  • Odor profile

  • Properties

    pKa est.
    22.06 (strong base)

    Molecular weight
    144.091 g/mol

    Melting point expt.

    • -4 °F (USCG, 1999)

    Boiling point

    • 212 °F at 760 mmHg (water) approx. (USCG, 1999)
    • Decomposes. (USCG, 1999)

    Flash point

    • -96.1 ˚C est.

    Solubility expt.

    • DECOMP AT MP; DELIQUESCENT; WHITE CRYSTALS; SOL IN ALKALI; SOL IN COLD AND HOT WATER /DIHYDRATE/
    • SOL IN COLD & HOT WATER; SLIGHTLY IN ALKALI /60.97% SOLN/
    • Solubility in water: miscible

  • Synonyms

    • Hexafluorosilicic acid
    • Fluorosilicic acid
    • Hydrofluosilicic acid
    • Hydrofluorosilicic acid
    • Silicon hexafluoride dihydride
    • Fluorosilicic acid (H2SiF6)
    • Silicate(2-), hexafluoro-, dihydrogen
    • FLUOROSILIC ACID
    • 53V4OQG6U1
    • DTXSID2029741
    • Dihydrogen hexafluorosilicate(2-)
    • NSC-16894
    • Hexafluosilicic acid
    • HYDROGEN HEXAFLUOROSILICATE (H2SIF6)
    • Silicofluoric acid
    • Sand acid
    • Acido fluosilicico
    • Acide fluosilicique
    • Hexafluorokiezelzuur
    • Acide fluorosilicique
    • Hexafluorokieselsaeure
    • Hexafluorokieselsaiure
    • Hydrosilicofluoric acid
    • Kiezelfluorwaterstofzuur
    • Silicate (2-), hexafluoro-, dihydrogen
    • RefChem:599447
    • DTXCID909741
    • 241-034-8
    • 16961-83-4
    • Fluosilicic acid
    • Silicofluoride
    • Dihydrogen hexafluorosilicate
    • MFCD00036289
    • hexafluorosilicon(2-);hydron
    • hexafluorosilicon(2-); hydron
    • F6Si
    • Kieselfluorwasserstoffsaure
    • FLUOSILICIC ACID [MI]
    • Dihydrogen hexafluoridosilicate(2-)
    • hexakis(fluoranyl)silicon(2-); hydron
    • DB-064742
    • HEXAFLUOROSILICATE(2-)HYDROGEN (1:2)
    • FLUOSILICIC ACID (HYDROFLUOSILICIC ACID)
    • A811126
    • Q411250
    • 16961-83-4

  • Applications

    Fluorosilicic acid (CAS 16961-83-4) is widely used as a fluoride source for municipal water fluoridation. It is also employed in the glass and ceramics industries as a fluoride flux and surface-etching agent for glazes and surfaces. In electronics and semiconductor processing, it serves as a fluoride source for specialty etchants and cleaning solutions. It functions as a fluoride feedstock for the production of hydrofluoric acid–based chemistries and other fluoride-containing formulations. It may be used as a component in coatings, inks, or other fluoride-containing formulations where controlled fluoride delivery is required.

    gpt-5-nano

  • Solubility @25˚C

    Solvent Solubility (g/L)
    ethanol 5.79
    methanol 6.59
    isopropanol 3.92
    water 0.11
    ethyl acetate 1.79
    n-propanol 4.25
    acetone 3.29
    n-butanol 3.7
    acetonitrile 2.72
    DMF 6.74
    toluene 0.45
    isobutanol 3.08
    1,4-dioxane 3.6
    methyl acetate 2.08
    THF 4.06
    2-butanone 2.32
    n-pentanol 2.41
    sec-butanol 3.28
    n-hexane 0.56
    ethylene glycol 2.91
    NMP 5.18
    cyclohexane 0.33
    DMSO 6.12
    n-butyl acetate 2.24
    n-octanol 1.83
    chloroform 2.49
    n-propyl acetate 1.24
    acetic acid 5.48
    dichloromethane 2.01
    cyclohexanone 2.82
    propylene glycol 3.01
    isopropyl acetate 1.06
    DMAc 3.48
    2-ethoxyethanol 2.66
    isopentanol 2.89
    n-heptane 0.46
    ethyl formate 1.41
    1,2-dichloroethane 1.39
    n-hexanol 3.91
    2-methoxyethanol 5.06
    isobutyl acetate 0.87
    tetrachloromethane 0.55
    n-pentyl acetate 1.11
    transcutol 8.53
    n-heptanol 1.7
    ethylbenzene 0.42
    MIBK 1.32
    2-propoxyethanol 4.28
    tert-butanol 4.41
    MTBE 2.35
    2-butoxyethanol 2.36
    propionic acid 3.72
    o-xylene 0.48
    formic acid 2.61
    diethyl ether 2.07
    m-xylene 0.47
    p-xylene 0.55
    chlorobenzene 0.86
    dimethyl carbonate 0.83
    n-octane 0.19
    formamide 2.56
    cyclopentanone 3.68
    2-pentanone 1.91
    anisole 1.12
    cyclopentyl methyl ether 2.12
    gamma-butyrolactone 4.33
    1-methoxy-2-propanol 3.71
    pyridine 1.85
    3-pentanone 1.35
    furfural 3.06
    n-dodecane 0.17
    diethylene glycol 3.47
    diisopropyl ether 0.68
    tert-amyl alcohol 3.45
    acetylacetone 1.57
    n-hexadecane 0.18
    acetophenone 1.04
    methyl propionate 1.78
    isopentyl acetate 1.9
    trichloroethylene 2.43
    n-nonanol 1.47
    cyclohexanol 2.24
    benzyl alcohol 1.1
    2-ethylhexanol 2.0
    isooctanol 1.33
    dipropyl ether 1.67
    1,2-dichlorobenzene 0.87
    ethyl lactate 0.97
    propylene carbonate 2.23
    n-methylformamide 3.59
    2-pentanol 2.46
    n-pentane 0.46
    1-propoxy-2-propanol 3.17
    1-methoxy-2-propyl acetate 1.73
    2-(2-methoxypropoxy) propanol 2.17
    mesitylene 0.38
    ε-caprolactone 2.47
    p-cymene 0.49
    epichlorohydrin 3.03
    1,1,1-trichloroethane 1.34
    2-aminoethanol 4.28
    morpholine-4-carbaldehyde 4.01
    sulfolane 5.26
    2,2,4-trimethylpentane 0.3
    2-methyltetrahydrofuran 3.4
    n-hexyl acetate 1.94
    isooctane 0.24
    2-(2-butoxyethoxy)ethanol 3.06
    sec-butyl acetate 0.82
    tert-butyl acetate 1.4
    decalin 0.25
    glycerin 3.44
    diglyme 4.16
    acrylic acid 3.47
    isopropyl myristate 0.77
    n-butyric acid 3.55
    acetyl acetate 0.99
    di(2-ethylhexyl) phthalate 0.84
    ethyl propionate 1.07
    nitromethane 4.81
    1,2-diethoxyethane 2.1
    benzonitrile 1.3
    trioctyl phosphate 0.73
    1-bromopropane 1.09
    gamma-valerolactone 3.94
    n-decanol 1.13
    triethyl phosphate 0.64
    4-methyl-2-pentanol 1.49
    propionitrile 2.15
    vinylene carbonate 1.79
    1,1,2-trichlorotrifluoroethane 2.81
    DMS 1.2
    cumene 0.42
    2-octanol 1.14
    2-hexanone 1.46
    octyl acetate 1.08
    limonene 0.86
    1,2-dimethoxyethane 3.26
    ethyl orthosilicate 0.65
    tributyl phosphate 0.85
    diacetone alcohol 2.36
    N,N-dimethylaniline 0.92
    acrylonitrile 2.69
    aniline 1.19
    1,3-propanediol 4.14
    bromobenzene 0.7
    dibromomethane 1.44
    1,1,2,2-tetrachloroethane 2.22
    2-methyl-cyclohexyl acetate 1.11
    tetrabutyl urea 1.11
    diisobutyl methanol 1.08
    2-phenylethanol 1.5
    styrene 0.51
    dioctyl adipate 1.02
    dimethyl sulfate 1.34
    ethyl butyrate 1.29
    methyl lactate 1.53
    butyl lactate 1.18
    diethyl carbonate 0.82
    propanediol butyl ether 2.63
    triethyl orthoformate 0.92
    p-tert-butyltoluene 0.51
    methyl 4-tert-butylbenzoate 1.35
    morpholine 4.34
    tert-butylamine 2.92
    n-dodecanol 0.86
    dimethoxymethane 2.45
    ethylene carbonate 1.4
    cyrene 1.55
    2-ethoxyethyl acetate 1.4
    2-ethylhexyl acetate 1.42
    1,2,4-trichlorobenzene 1.05
    4-methylpyridine 1.82
    dibutyl ether 1.41
    2,6-dimethyl-4-heptanol 1.08
    DEF 2.54
    dimethyl isosorbide 2.61
    tetrachloroethylene 1.55
    eugenol 1.55
    triacetin 1.49
    span 80 2.1
    1,4-butanediol 1.82
    1,1-dichloroethane 1.54
    2-methyl-1-pentanol 2.11
    methyl formate 2.17
    2-methyl-1-butanol 2.82
    n-decane 0.26
    butyronitrile 2.14
    3,7-dimethyl-1-octanol 1.64
    1-chlorooctane 0.83
    1-chlorotetradecane 0.36
    n-nonane 0.27
    undecane 0.2
    tert-butylcyclohexane 0.31
    cyclooctane 0.14
    cyclopentanol 2.84
    tetrahydropyran 2.9
    tert-amyl methyl ether 1.78
    2,5,8-trioxanonane 3.05
    1-hexene 1.37
    2-isopropoxyethanol 1.95
    2,2,2-trifluoroethanol 1.56
    methyl butyrate 1.51

    Scent© AI

1 4

IFRA standard 51

Recommendation
No restriction
Maximum acceptable concentrations in the finished product (%)
Category 1
Products applied to the lips
 No restriction Category 7A
Rinse-off products applied to the hair with some hand contact
 No restriction
Category 2
Products applied to the axillae
 No restriction Category 7B
Leave-on products applied to the hair with some hand contact
 No restriction
Category 3
Products applied to the face/body using fingertips
 No restriction Category 8
Products with significant anogenital exposure
 No restriction
Category 4
Products related to fine fragrance
 No restriction Category 9
Products with body and hand exposure, primarily rinse off
 No restriction
Category 5A
Body lotion products applied to the body using the hands (palms), primarily leave on
 No restriction Category 10A
Household care products with mostly hand contact
 No restriction
Category 5B
Face moisturizer products applied to the face using the hands (palms), primarily leave on
 No restriction Category 10B
Household care products with mostly hand contact, including aerosol/spray products (with potential leave-on skin contact)
 No restriction
Category 5C
Hand cream products applied to the hands using the hands (palms), primarily leave on
 No restriction Category 11A
Products with intended skin contact but minimal transfer of fragrance to skin from inert substrate without UV exposure
 No restriction
Category 5D
Baby Creams, baby Oils and baby talc
 No restriction Category 11B
Products with intended skin contact but minimal transfer of fragrance to skin from inert substrate with potential UV exposure
 No restriction
Category 6
Products with oral and lip exposure
 No restriction Category 12
Products not intended for direct skin contact, minimal or insignificant transfer to skin
 No restriction