Calcium ferrocyanide

E number E538INS 538CAS 13821-08-4

Used as an anticaking agent.

Calcium ferrocyanide is an anticaking agent for salt. The name alarms people, but the cyanide here is locked into an iron complex so stable that it does not behave as cyanide at all — it is the same chemistry as the pigment Prussian blue.

Where it is and isn’t permitted

Status of Calcium ferrocyanide by jurisdiction. Every jurisdiction this site covers is listed, including those where the substance does not appear.
JurisdictionStatusScope and limitsCitation
United StatesFood and Drug AdministrationNot listedDoes not appear on this jurisdiction’s permitted list. That is not the same as being prohibited.
Codex AlimentariusCodex Alimentarius Commission / JECFAPermitted, with conditions

3 food categories

highest permitted level 20 mg/kg

Show every food category
  • 12.1.1 Salt — 14 mg/kg
  • 12.1.2 Salt substitutes — 20 mg/kg
  • 12.2.2 Seasonings and condiments — 20 mg/kg
CXS 192-1995 Table One, INS 538and 2 further provisionsretrieved 2026-09-07

What it is made from

Produced synthetically from a ferrocyanide salt and a calcium source. It is used at a few parts per million in salt, enough to change how the crystals grow.

  • Vegan
  • Vegetarian
CAS registry number
13821-08-4
InChIKey
BAZQCHGUTMBXBU-UHFFFAOYSA-N
PubChem
CID 166920

Every name it appears under

23 recorded names. A label may use any of them.

E number

  • E538

INS number

  • 538

CAS registry number

  • 13821-08-4

Other names

  • 906D36VLZG
  • BAZQCHGUTMBXBU-UHFFFAOYSA-N
  • Calcium ferrocyanide
  • Calcium hexacyanoferrate
  • calcium hexacyanoferrate(II)
  • Dicalcium hexacyanoferrate
  • DICALCIUM HEXACYANOFERRATE(4-)
  • dicalcium;iron(2+);hexacyanide
  • E 538
  • Ferrate(4), hexakis(cyanokappaC), calcium (1:2), (OC611)
  • FERRATE(4-), HEXACYANO-, DICALCIUM
  • Ferrate(4-), hexakis(cyano-.kappa.C)-, calcium (1:2), (OC-6-11)-
  • FERRATE(4-), HEXAKIS(CYANO-C)-, CALCIUM (1:2), (OC-6-11)-
  • Ferrate(4-), hexakis(cyano-kappaC)-, calcium (1:2), (OC-6-11)-
  • HEXACYANOFERRATE OF CALCIUM
  • INS NO.538
  • INS-538
  • Yellow prussiate of lime
  • Yellow prussiate of limeCalcium hexacyanoferrate

Systematic names

  • dicalcium;iron(2+);hexacyanide

Hazard reference values

Values set by assessing bodies. A body that has not set a value is not listed here.
TypeValuePopulationAssessed byOpinion
ADI0.03 mg/kg bw/dayconsumersEFSA ANS2018

Evidence and how bodies read it

Studies, and the differing conclusions regulators drew from them, are curated by hand rather than machine-read, and none has been written for this substance yet.

Sources for this page

  • gsfa retrieved 2026-09-07

Full licence terms and publisher details on Sources. How this page is built and updated: Method.

Machine-readable:/api/v1/additives/calcium-ferrocyanide.json