Water & Air / Compounds / Ferric chloride

Ferric chloride in water and air: safety profile

Moderate risk

(People-specific data is limited; this page draws from human adult context.) Ferric chloride is used as a coagulant in drinking water and wastewater treatment, PCB etching, and as a hemostatic agent. Corrosive (pH <2 in solution). Causes severe skin burns, serious eye damage, and GI damage on ingestion. Oral LD50 rat 450-900 mg/kg. Occupational exposure is the primary concern — handling concentrated solutions (40-45% FeCl3) without PPE causes chemical burns. Iron overload toxicity possible with massive ingestion.

What is ferric chloride?

Also known as: Iron(III) chloride, FeCl3, Iron trichloride, Flores martis.

CAS number: 7705-08-0
Molecular formula: Cl3Fe
Molecular weight: 162.2 g/mol
SMILES: Cl[Fe](Cl)Cl
PubChem CID: 24380

Risk for people

Moderate risk

Ferric chloride is used as a coagulant in drinking water and wastewater treatment, PCB etching, and as a hemostatic agent. Corrosive (pH <2 in solution). Causes severe skin burns, serious eye damage, and GI damage on ingestion. Oral LD50 rat 450-900 mg/kg. Occupational exposure is the primary concern — handling concentrated solutions (40-45% FeCl3) without PPE causes chemical burns. Iron overload toxicity possible with massive ingestion.

Regulatory consensus

2 regulatory and scientific bodies have classified Ferric chloride. The classifications differ — that's the data.

Agency	Year	Classification	Notes
NSF International	2000	NSF/ANSI 60 certified for drinking water treatment chemicals
ECHA	2010	Registered under REACH; classified as corrosive

Regulators apply different standards of evidence — animal-data weighting, exposure-pattern assumptions, epidemiological power thresholds — which is why two scientific bodies can review the same data and reach different conclusions. The disagreement is the data.

Where you encounter ferric chloride

Water Treatment
Industrial
Medicine

Safer alternatives

Lower-risk approaches that achieve a similar outcome to Ferric chloride:

Polyaluminium chloride (PAC)
Trade-offs: Less corrosive. Effective at wider pH range. Lower sludge volume. Aluminum residual concerns.

Relative cost: Higher
Chitosan-based coagulants
Trade-offs: Natural polymer from shrimp shells. Limited efficacy at high turbidity. No metal residual.

Relative cost: 3-5x higher

Frequently asked questions

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Sources (1)

ECHA Registration Dossier — Ferric chloride — echa

Reference data, not professional advice. Aggregates publicly available regulatory and scientific data; not a substitute for veterinary, medical, legal, or regulatory advice. Why we built ALETHEIA →