Congo red

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  • Identifiers

    CAS number
    573-58-0

    Molecular formula
    C32H22N6Na2O6S2

    SMILES
    C1=CC=C2C(=C1)C(=CC(=C2N)N=NC3=CC=C(C=C3)C4=CC=C(C=C4)N=NC5=C(C6=CC=CC=C6C(=C5)S(=O)(=O)[O-])N)S(=O)(=O)[O-].[Na+].[Na+]

    Safety labels

    Health Hazard
    Health

  • Odor profile

    Fragrance
    Odorless 65.43%
    Cooked 25.35%
    Grape 25.11%
    Fruity 23.27%
    Bitter 21.78%
    Savory 20.35%
    Burnt 17.94%
    Meaty 16.98%
    Roasted 16.58%
    Fatty 15.14%

     

    Flavor
    Bitter 90.91%
    Odorless 30.65%
    Nitrile 20.3%
    Very strong 18.72%
    Indole 18.36%
    Bland 18.0%
    Bread crust 17.83%
    Taco 17.78%
    Moth ball 17.51%
    Rotten 17.3%

     

    Odor impact est.
    Odorless

  • Properties

    pKa est.
    3.1 (weak acid)

    Molecular weight
    696.7 g/mol

    Flash point

    • 438.03 ˚C est.

  • Synonyms

    • Congo red
    • 573-58-0
    • DIRECT RED 28
    • C.I. Direct Red 28
    • Congo Red 4B
    • Congazone sodium
    • Benzo Congo Red
    • Haemomedical
    • Haemonorm
    • Hemorrhagyl
    • Solucongo
    • Sugai Congo Red
    • Atul Congo Red
    • Vondacel Red CL
    • Kayaku Congo Red
    • Mitsui Congo Red
    • Cotton Red L
    • Direct Red K
    • Azocard Red Congo
    • Congo Red H
    • Congo Red L
    • Congo Red M
    • Congo Red N
    • Congo Red R
    • Congo Red W
    • Congo Red CR
    • Congo Red WS
    • Atlantic Congo Red
    • Cotton Red 4BC
    • Cotton Red 5B
    • Erie Congo 4B
    • Tertrodirect Red C
    • Hispamin Congo 4B
    • Congo Red 4BX
    • Red K
    • Diacotton Congo Red
    • Peeramine Congo Red
    • Trisulfon Congo Red
    • Direct Red DC-CF
    • Brasilamina congo 4B
    • Direct Red C
    • C.I. 22120
    • Kongorot
    • CCRIS 2277
    • Congo Red ICI
    • C.I. Direct Red 28, disodium salt
    • MFCD00004028
    • AI3-63036
    • Congo Red (C.I. 22120)
    • CI Direct Red 28
    • 3U05FHG59S
    • DTXSID4022816
    • NSC-7232
    • sodium diphenyldiazo-bis-alpha-naphthylaminesulfonate
    • NSC-56651
    • Disodium 3,3'-((1,1'-biphenyl)-4,4'-diylbis(azo))bis(4-aminonaphthalene-1-sulphonate)
    • Cosmos Red
    • Cotton Red B
    • Cotton Red C
    • Direct Red R
    • Direct Red Y
    • Congo Red (90%)
    • Congo Red RS
    • Kongorot [German]
    • 1-Naphthalenesulfonic acid,3,3'-[[1,1'-biphenyl]-4,4'-diylbis(azo)]bis[4-amino-, disodium salt
    • DTXCID502816
    • Cerven kongo [Czech]
    • Cerven kongo
    • Cerven prima 28 [Czech]
    • DirectRed28
    • disodium 3,3'-(biphenyl-4,4'-diyldidiazene-2,1-diyl)bis(4-aminonaphthalene-1-sulfonate)
    • Cerven prima 28
    • CAS-573-58-0
    • Sodium 3,3'-([1,1'-biphenyl]-4,4'-diylbis(diazene-2,1-diyl))bis(4-aminonaphthalene-1-sulfonate)
    • Congo red [USP]
    • HSDB 4225
    • NCGC00159364-02
    • NSC 7232
    • EINECS 209-358-4
    • NSC 56651
    • UNII-3U05FHG59S
    • congo-red
    • Direct Congo Red
    • Congo Red K
    • 1-NAPHTHALENESULFONIC ACID, 3,3'-((1,1'-BIPHENYL)-4,4'-DIYLDIAZO)BIS(4-AMINO-, DISODIUM SALT
    • 1-naphthalenesulfonic acid, 3,3'-([1,1'-biphenyl]-4,4'-diyldiazo)bis[4-amino-, disodium salt
    • disodium 3,3'-[biphenyl-4,4'-diyldi(E)diazene-2,1-diyl]bis(4-aminonaphthalene-1-sulfonate)
    • Congo Red sodium salt
    • C.I.Direct Red 28
    • CONGO RED [MI]
    • CONGO RED [HSDB]
    • Congo Red, indicator grade
    • Natrium-salz der diphenyl-bis-azo-bis-naphthylamin-4-sulfonsaeure [German]
    • CONGO RED [MART.]
    • CONGO RED [WHO-DD]
    • Congo Red, certifiable grade
    • SCHEMBL25635
    • 1-Naphthalenesulfonic acid, 3,3'-((1,1'-biphenyl)-4,4'-diylbis(azo))bis(4-amino-, disodium salt
    • Congo Red, JIS special grade
    • Congo Red, analytical standard
    • CHEMBL429694
    • C32H22N6O6S2.2Na
    • CHEBI:34653
    • IQFVPQOLBLOTPF-UHFFFAOYSA-L
    • GLXC-20473
    • Congo Red, Dye content >=35 %
    • Natrium-salz der diphenyl-bis-azo-bis-naphthylamin-4-sulfonsaeure
    • Tox21_111605
    • Tox21_202934
    • HB0737
    • AKOS000282971
    • AKOS016368576
    • AKOS024285600
    • FD03839
    • 1-Naphthalenesulfonic acid, 3,3'-(4,4'-biphenylenebis(azo))bis(4-amino-, disodium salt
    • NCGC00260480-01
    • DA-52047
    • disodium 4-amino-3-[[4-[4-[(1-amino-4-sulfonatonaphthalen-2-yl)diazenyl]phenyl]phenyl]diazenyl]naphthalene-1-sulfonate
    • SY010430
    • C.I. Direct Red 28, disodium salt (8CI)
    • NS00020843
    • Congo Red, High Purity - CAS 573-58-0
    • D89267
    • Q114391
    • Congo Red, BioXtra, certified by the Biological Stain Commission
    • Congo Red, for microscopy (Bact., Bot., Hist.), indicator (pH 3.0-5.2), Reag. Ph. Eur.
    • 1-Naphthalenesulfonic acid, 3,3'-((1,1'-biphenyl)-4,4'-diylbis(2,1-diazenediyl))bis(4-amino-, sodium salt (1:2)
    • 1-Naphthalenesulfonic acid, 3,3'-[[1,1'-biphenyl]-4,4'-diylbis(azo)]bis[4-amino-, disodium salt (9CI)

  • Applications

    Congo red (CAS 573-58-0) is an azo dye used primarily as a textile dye for cellulose and protein fibers such as cotton and silk; it is also employed in dyeing and finishing paper and leather. In histology and research, Congo red serves as a staining agent for microscopy to detect amyloid deposits, providing characteristic coloration and aiding structural assessment of tissues. Additionally, it is used as a dye component in coatings and inks and functions as an intermediate in the synthesis of other azo dyes in the dye manufacture industry.

    gpt-5-nano

  • Solubility @25˚C

    Solvent Solubility (g/L)
    ethanol 0.13
    methanol 0.33
    isopropanol 0.06
    water 0.0
    ethyl acetate 0.09
    n-propanol 0.1
    acetone 0.29
    n-butanol 0.05
    acetonitrile 0.1
    DMF 4.31
    toluene 0.03
    isobutanol 0.04
    1,4-dioxane 0.79
    methyl acetate 0.24
    THF 2.11
    2-butanone 0.34
    n-pentanol 0.03
    sec-butanol 0.05
    n-hexane 0.0
    ethylene glycol 0.2
    NMP 3.87
    cyclohexane 0.0
    DMSO 1.89
    n-butyl acetate 0.07
    n-octanol 0.02
    chloroform 0.29
    n-propyl acetate 0.07
    acetic acid 0.54
    dichloromethane 0.3
    cyclohexanone 0.36
    propylene glycol 0.23
    isopropyl acetate 0.06
    DMAc 3.96
    2-ethoxyethanol 0.45
    isopentanol 0.03
    n-heptane 0.0
    ethyl formate 0.18
    1,2-dichloroethane 0.14
    n-hexanol 0.02
    2-methoxyethanol 1.28
    isobutyl acetate 0.03
    tetrachloromethane 0.02
    n-pentyl acetate 0.09
    transcutol 0.77
    n-heptanol 0.03
    ethylbenzene 0.01
    MIBK 0.05
    2-propoxyethanol 0.43
    tert-butanol 0.04
    MTBE 0.05
    2-butoxyethanol 0.33
    propionic acid 0.24
    o-xylene 0.02
    formic acid 0.85
    diethyl ether 0.06
    m-xylene 0.01
    p-xylene 0.01
    chlorobenzene 0.04
    dimethyl carbonate 0.33
    n-octane 0.0
    formamide 1.2
    cyclopentanone 1.34
    2-pentanone 0.13
    anisole 0.08
    cyclopentyl methyl ether 0.15
    gamma-butyrolactone 1.77
    1-methoxy-2-propanol 0.68
    pyridine 0.8
    3-pentanone 0.12
    furfural 1.95
    n-dodecane 0.0
    diethylene glycol 0.47
    diisopropyl ether 0.01
    tert-amyl alcohol 0.04
    acetylacetone 0.29
    n-hexadecane 0.0
    acetophenone 0.11
    methyl propionate 0.21
    isopentyl acetate 0.04
    trichloroethylene 0.51
    n-nonanol 0.03
    cyclohexanol 0.04
    benzyl alcohol 0.1
    2-ethylhexanol 0.01
    isooctanol 0.02
    dipropyl ether 0.06
    1,2-dichlorobenzene 0.04
    ethyl lactate 0.12
    propylene carbonate 0.34
    n-methylformamide 1.27
    2-pentanol 0.02
    n-pentane 0.0
    1-propoxy-2-propanol 0.26
    1-methoxy-2-propyl acetate 0.21
    2-(2-methoxypropoxy) propanol 0.29
    mesitylene 0.01
    ε-caprolactone 0.39
    p-cymene 0.01
    epichlorohydrin 1.32
    1,1,1-trichloroethane 0.04
    2-aminoethanol 0.24
    morpholine-4-carbaldehyde 3.9
    sulfolane 2.55
    2,2,4-trimethylpentane 0.0
    2-methyltetrahydrofuran 0.29
    n-hexyl acetate 0.07
    isooctane 0.0
    2-(2-butoxyethoxy)ethanol 0.4
    sec-butyl acetate 0.03
    tert-butyl acetate 0.06
    decalin 0.0
    glycerin 0.83
    diglyme 1.09
    acrylic acid 0.53
    isopropyl myristate 0.02
    n-butyric acid 0.16
    acetyl acetate 0.09
    di(2-ethylhexyl) phthalate 0.05
    ethyl propionate 0.07
    nitromethane 1.56
    1,2-diethoxyethane 0.17
    benzonitrile 0.08
    trioctyl phosphate 0.03
    1-bromopropane 0.04
    gamma-valerolactone 3.5
    n-decanol 0.02
    triethyl phosphate 0.04
    4-methyl-2-pentanol 0.01
    propionitrile 0.09
    vinylene carbonate 0.43
    1,1,2-trichlorotrifluoroethane 2.32
    DMS 0.16
    cumene 0.01
    2-octanol 0.02
    2-hexanone 0.08
    octyl acetate 0.04
    limonene 0.01
    1,2-dimethoxyethane 0.9
    ethyl orthosilicate 0.04
    tributyl phosphate 0.03
    diacetone alcohol 0.16
    N,N-dimethylaniline 0.06
    acrylonitrile 0.26
    aniline 0.1
    1,3-propanediol 0.27
    bromobenzene 0.03
    dibromomethane 0.09
    1,1,2,2-tetrachloroethane 0.4
    2-methyl-cyclohexyl acetate 0.04
    tetrabutyl urea 0.09
    diisobutyl methanol 0.01
    2-phenylethanol 0.06
    styrene 0.02
    dioctyl adipate 0.07
    dimethyl sulfate 0.75
    ethyl butyrate 0.07
    methyl lactate 0.44
    butyl lactate 0.15
    diethyl carbonate 0.05
    propanediol butyl ether 0.3
    triethyl orthoformate 0.08
    p-tert-butyltoluene 0.01
    methyl 4-tert-butylbenzoate 0.16
    morpholine 1.09
    tert-butylamine 0.01
    n-dodecanol 0.01
    dimethoxymethane 1.14
    ethylene carbonate 0.22
    cyrene 0.52
    2-ethoxyethyl acetate 0.27
    2-ethylhexyl acetate 0.03
    1,2,4-trichlorobenzene 0.08
    4-methylpyridine 0.3
    dibutyl ether 0.03
    2,6-dimethyl-4-heptanol 0.01
    DEF 0.37
    dimethyl isosorbide 0.6
    tetrachloroethylene 0.22
    eugenol 0.22
    triacetin 0.22
    span 80 0.24
    1,4-butanediol 0.08
    1,1-dichloroethane 0.08
    2-methyl-1-pentanol 0.02
    methyl formate 1.04
    2-methyl-1-butanol 0.03
    n-decane 0.0
    butyronitrile 0.05
    3,7-dimethyl-1-octanol 0.01
    1-chlorooctane 0.01
    1-chlorotetradecane 0.0
    n-nonane 0.0
    undecane 0.0
    tert-butylcyclohexane 0.0
    cyclooctane 0.0
    cyclopentanol 0.13
    tetrahydropyran 0.2
    tert-amyl methyl ether 0.04
    2,5,8-trioxanonane 0.66
    1-hexene 0.01
    2-isopropoxyethanol 0.18
    2,2,2-trifluoroethanol 0.32
    methyl butyrate 0.11

    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