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Annex II Entry 1330 13/08/2020

4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products

4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products is listed in Annex II as a prohibited substance for cosmetic products placed on the EU market.

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Prohibited substance— Annex II, EU Regulation 1223/2009
Entry: 1330

Chemical identity and properties

PubChem 2D chemical structure for CAS 2050-34-2
CAS 2050-34-2PubChem CID 11035

4-[2-(2,4-Dihydroxyphenyl)diazenyl]benzenesulfonic acid

4-[(2,4-Dihydroxyphenyl)azo]benzenesulfonic acid is a member of azobenzenes. — ChEBI

IUPAC name
4-[(2,4-dihydroxyphenyl)diazenyl]benzenesulfonic acid
Molecular formula
C12H10N2O5S
Molecular weight
294.29 g/mol
Exact mass
294.03104260 Da
XLogP3
1.7
Topological polar surface area
128.0 Ų
Hydrogen-bond donors
3
Hydrogen-bond acceptors
7
Covalent units
1
Defined stereocentres
0

Also known as

4-(2-(2,4-Dihydroxyphenyl)diazenyl)benzenesulfonic acidRefChem:1985464-((2,4-Dihydroxyphenyl)azo)benzenesulphonic acidAcid Orange 6 free acidChrysoine SResorcinol yellowTropaeolineChrysoine
16 more reported names
Resorcin yellowC.I. Food Yellow 8Chrysoine ExtraTropaeoline OChrysonine STropaeolin RChrysoine NChrysonis SGold YellowResorcine YellowTropaelin-OTropeolin OChrysoin GYellow TCurol Orange GDermina Yellow G
Open full PubChem recordPubChem annotations3D structure image
External database identifiers

Retrieved from NIH PubChem on 2026-09-02 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

PubChem 2D chemical structure for CAS 547-57-9
CAS 547-57-9PubChem CID 2728027

C.I. Acid Orange 6

IUPAC name
sodium 4-[(2,4-dihydroxyphenyl)diazenyl]benzenesulfonate
Molecular formula
C12H9N2NaO5S
Molecular weight
316.27 g/mol
Exact mass
316.01298685 Da
Topological polar surface area
131.0 Ų
Hydrogen-bond donors
2
Hydrogen-bond acceptors
7
Covalent units
2
Defined stereocentres
0

Also known as

RefChem:1080549Tropaeolin OACID ORANGE 6Resorcinol yellowChrysoineTropaeolinOChrysoine STropaeoline
16 more reported names
Resorcin yellowChrysoine ExtraTropaeoline OChrysonine STropaeolin RChrysoine NChrysonis SGold YellowResorcine YellowTropaelin-OTropeolin OChrysoin GSodium azoresorcinolsulfanilateYellow TCurol Orange GDermina Yellow G
Open full PubChem recordPubChem annotations3D structure image
External database identifiers

Retrieved from NIH PubChem on 2026-09-02 by checksum-valid CAS matching. Chemical properties do not replace the regulatory decision on this page.

Record details

Chemical name

4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products

Chemical / IUPAC name

4-(2,4-Dihydroxyphenylazo)benzensulphonic acid

Regulatory information

Regulation

(EC) 2013/344

See every entry this act set

Identified ingredients

Key data

CAS
2050-34-2 -- 547-57-9
EC
218-087-0 -- 208-924-8
Annex
II
Entry number
1330

Inventory links for 4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products

Inventory Restriction reference
Ref 31619

ACID ORANGE 6

CAS: 547-57-9
EC: 208-924-8
Inventory Restriction reference
Ref 32710

CI 14270

CAS: 547-57-9
EC: 208-924-8

Direct matches are limited for this record, so nearby entries from Annex II are shown as well.

Annex IV 17
Shared CAS number

CI 14270

CAS: 547-57-9
EC: 208-924-8

What Annex II means for 4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products

4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products is listed as a prohibited substance under Annex II of EU Cosmetics Regulation 1223/2009 and must not be intentionally added. Article 17 separately addresses unintended small quantities that are technically unavoidable under good manufacturing practice and compatible with the Article 3 safety requirement.

Formulators must screen their ingredients and raw materials to ensure none contain this substance. Suppliers should provide documentation confirming absence when requested.

This record is linked to 2 CosIng inventory ingredients for name and identifier cross-reference. The page also surfaces 12 related annex records with overlapping identifiers, annex logic or naming patterns.

Compliance checklist

  • Verify this substance is absent from all raw materials and finished formulations.
  • Request absence confirmation or CoA from raw material suppliers.
  • Document the screening result in the Product Information File (PIF).

Frequently asked questions

Yes. 4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products is listed in Annex II of EU Cosmetics Regulation 1223/2009 and is prohibited as an intentionally added cosmetic ingredient. Article 17 provides a narrow exception for unintended small quantities that are technically unavoidable under good manufacturing practice, provided the product remains safe under Article 3.

CAS 2050-34-2 -- 547-57-9 is the unique numerical identifier assigned to 4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products by the Chemical Abstracts Service. In cosmetic compliance work, the CAS number is used to cross-reference the substance across regulatory databases, raw material specifications and safety assessment reports. Multiple EU annex entries may share the same CAS number if the same substance appears under different conditions or in different annexes.

Use the INCI Checker tool on this site to paste your full ingredient list (INCI) and scan it against all Annex II–VI entries. The tool highlights any ingredients that match restricted, prohibited or allergen-flagged records. This is useful for rapid compliance screening of finished product formulas or raw material declarations.
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Source note for Annex II record 4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products

This page summarizes one Annex II record for 4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products from public European Commission cosmetic materials and adds linked inventory or identifier matches when available.

Use this record page to review Annex II conditions for 4-(2,4-Dihydroxyphenylazo)benzensulphonic acid (CAS 2050-34-2; EINECS 218-087-0) and its sodium salt (Acid Orange 6; CI 14270) (CAS 547-57-9; EINECS 208-924-8) when used as substance in hair dye products, but confirm any final regulatory decision against the current official annex wording and source files.

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