Why does CAS 2809-21-4 appear in more than one EU cosmetic annex?

A substance identified by CAS 2809-21-4 may appear in multiple EU cosmetic regulation annexes when it is subject to different conditions in different contexts — for example, restricted under Annex III with specific conditions, while also appearing in Annex IV as an approved colorant under separate entry conditions. Each entry must be reviewed individually.

How do I check if my formula contains a substance with CAS 2809-21-4?

Use the INCI Checker on CosIng Checker with INCI names, CAS numbers or EC numbers. Paste CAS 2809-21-4 to screen it directly, then review every linked annex record and supplier document.

CAS 1 record

CAS 2809-21-4

Q: How do I use CAS 2809-21-4 for compliance screening?

Cross-reference CAS 2809-21-4 against your raw material specification sheets and CoA documents. When it appears in Annex II, verify absence. When it appears in Annex III, verify that concentration limits and product type conditions are met. All annex entries sharing this CAS number are listed on this page.

CAS 2809-21-4 matches 1 EU annex record across Annex II–VI of Regulation 1223/2009.

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Chemical identity and properties

PubChem 2D chemical structure for CAS 2809-21-4

CAS 2809-21-4PubChem CID 3305

Etidronic Acid

Etidronic acid is a 1,1-bis(phosphonic acid) that is (ethane-1,1-diyl)bis(phosphonic acid) having a hydroxy substituent at the 1-position. It inhibits the formation, growth, and dissolution of hydroxyapatite crystals by chemisorption to calcium phosphate surfaces. It has a role as an antineoplastic agent, a chelator and a bone density conservation agent. It is a conjugate acid of an etidronic acid(2-). — ChEBI

IUPAC name: (1-hydroxy-1-phosphonoethyl)phosphonic acid

Molecular formula: C2H8O7P2
Molecular weight: 206.03 g/mol
Exact mass: 205.97452659 Da
XLogP3: -3.7
Topological polar surface area: 135.0 Å²
Hydrogen-bond donors: 5
Hydrogen-bond acceptors: 7
Covalent units: 1
Defined stereocentres: 0

Also known as

HEDP1-Hydroxyethylidene-1,1-diphosphonic acidEHDPEtidronsaeureTurpinal SLAcetodiphosphonic acidHydroxyethanediphosphonic acidAcido etidronico

16 more reported names

Acide etidroniqueOxyethylidenediphosphonic acidDequest 2015Dequest Z 010Ferrofos 510Dequest 20101-Hydroxyethane-1,1-diphosphonic acidDiphosphonate (base)1-Hydroxyethanediphosphonic acidPhosphonic acid, (1-hydroxyethylidene)bis-(1-Hydroxyethylidene)diphosphonic acidAcidum etidronicum(Hydroxyethylidene)diphosphonic acid1-Hydroxyethane-1,1-bisphosphonic acidEthane-1-hydroxy-1,1-diphosphonic acid(1-Hydroxyethylidene)bisphosphonic acid

Open full PubChem record PubChem annotations 3D structure image

External database identifiers

ChEBI:CHEBI:4907
ChEMBL:CHEMBL871
EPA DTXSID:DTXSID6023028
PubMed:23022200
PubMed:22988612
PubMed:22966908
PubMed:22951500
PubMed:22797188
PubMed:22733953
PubMed:22717979
PubMed:22678684
PubMed:22675556
PubMed:22654798
PubMed:22639712
PubMed:22629613

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

Records for CAS 2809-21-4

1 total

Annex

III

Entry

Etidronic acid

(1-Hydroxyethylidene)diphosphonic acid and its salts

(a) Hair product (b) Soap

220-552-8

Max concentration

How CAS 2809-21-4 is used on this site

CAS 2809-21-4 is the Chemical Abstracts Service identifier used to pin this page to a specific substance. In the current dataset, 1 EU annex record shares this identifier, which helps you cross-check whether the same substance appears under one regulatory context or several.

Use this page when a supplier specification, SDS or raw-material dossier gives you CAS 2809-21-4 and you need to see every linked Annex II–VI record in one place. The entry cards above are the quickest route to concentration limits, warnings, annex placement and product-type conditions.

Frequently asked questions

A substance identified by CAS 2809-21-4 may appear in multiple EU cosmetic regulation annexes when it is subject to different conditions in different contexts. For example, a substance might be restricted under Annex III with specific conditions, and the same CAS might also appear in Annex IV as an approved colorant under separate entry conditions. Each entry must be reviewed individually.

Cross-reference the CAS number against your raw material specification sheets and CoA documents. When a CAS appears in Annex II, verify absence. When it appears in Annex III, verify that concentration limits and product type conditions are met in your formulation. All annex entries sharing this CAS number are listed above.

A CAS number is assigned by the Chemical Abstracts Service (USA) and is globally recognised. An EC number is a European Commission identifier from inventories such as EINECS, ELINCS or the NLP list. Both identifiers may appear in EU cosmetic annex entries. Some substances have both, some have only one, and some older entries may have neither.

The INCI Checker accepts ingredient names, CAS numbers and EC numbers. Check this CAS number directly, then verify the result against supplier specification sheets and every linked annex condition.

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