What is ferric chloride used for?

Mainly as a coagulant in drinking water and wastewater treatment, removing suspended solids, phosphorus and turbidity, and conditioning sludge. It is also used in etching and metal surface treatment.

Is iron chloride FeCl₂ or FeCl₃?

Both exist. FeCl₃ is ferric chloride, iron in the +3 state, and is the grade used for water treatment coagulation. FeCl₂ is ferrous chloride, +2. Different products, different applications, not interchangeable.

Why use FeCl₃ in water treatment?

It hydrolyses to iron hydroxide flocs that bind fine particles into settleable aggregates, works across a wide pH range, removes phosphorus, and improves sludge dewatering.

What is the formula of ferric chloride?

Ferric chloride is FeCl₃ — one iron atom in the +3 oxidation state bonded to three chlorine atoms. It is also written as iron(III) chloride. Ferrous chloride is FeCl₂, iron in the +2 state.

What colour is ferric chloride?

As supplied for water treatment it is a dark brown to reddish-brown liquid. In solid anhydrous form the crystals are dark, greenish-black with a metallic sheen; the hydrated crystalline form is yellow to orange-brown. Ferrous chloride (FeCl₂) is visibly different — pale green — which is the quickest way to tell the two apart.

Is ferric chloride soluble in water?

Yes, highly soluble. It dissolves readily and the resulting solution is strongly acidic because FeCl₃ hydrolyses in water.

Does ferric chloride form a precipitate?

FeCl₃ itself dissolves rather than precipitating. What precipitates is iron(III) hydroxide, Fe(OH)₃ — the brown floc formed when FeCl₃ hydrolyses. That precipitate is precisely the mechanism that makes it useful as a coagulant.

Ferric Chloride (FeCl₃)

Ferric chloride (FeCl₃), also called iron(III) chloride, is one of the most widely used coagulants in municipal and industrial water treatment. It is supplied most often as a dark brown aqueous solution, and it works by destabilising the fine suspended particles that will not settle out of water on their own.

This page explains what ferric chloride is, how it behaves in treatment, the grades it is supplied in, and what to consider when buying it. For our own product specification, see CHIMIFLOC FR 4014.

What it is

Ferric chloride is an iron salt in which iron carries a +3 charge. It is distinct from ferrous chloride (FeCl₂), where iron carries a +2 charge — the two are different products with different uses and are not interchangeable. Ferric chloride is strongly acidic in solution and highly soluble in water.

How it works as a coagulant

When ferric chloride is dosed into water, it hydrolyses and forms iron hydroxide. Three things follow:

Charge neutralisation. Most suspended particles carry a negative surface charge that keeps them apart. The positively charged iron species neutralise it so particles can approach each other.
Floc formation. Iron hydroxide precipitates and sweeps fine particles into larger aggregates (flocs) heavy enough to settle or be filtered.
Phosphorus removal. Iron binds phosphate into an insoluble form, removing it from the water.

Ferric chloride works across a relatively wide pH band and is effective in cold water, which is why it is often chosen over alternatives. It consumes alkalinity, so pH correction is a normal part of dosing design.

Where it is used

Drinking water treatment — turbidity, colour and organic-matter removal.
Municipal wastewater — primary treatment, phosphorus removal, sludge conditioning ahead of dewatering.
Industrial effluent — solids and metals removal across food, textile and process industries.
Sludge dewatering — improves the water release of sludge on belt presses and centrifuges.
Industrial etching and metal surface treatment — a separate, non-water-treatment use.

Grades, concentration and supply

Ferric chloride is supplied as a solution at various concentrations and as an anhydrous solid. Concentration matters commercially: you are buying iron content, so compare on active basis rather than on volume.

Concentration and how it is stated.
Whether they manufacture or resell. This determines batch consistency and whether anyone can answer a technical question about the material.
Batch documentation — a certificate of analysis for the batch you receive.
Delivery format and turnaround.

CHIMI ART is a leading manufacturer of ferric chloride in Egypt. We produce it ourselves — we are not a reseller — and we have manufactured continuously since 1977. A certificate of analysis is supplied with every delivery.

Ferric chloride: formula, colour and solubility

What is the formula of ferric chloride?: Ferric chloride is FeCl₃ — one iron atom in the +3 oxidation state bonded to three chlorine atoms. It is also written as iron(III) chloride. Ferrous chloride is FeCl₂, iron in the +2 state.
What colour is ferric chloride?: As supplied for water treatment it is a dark brown to reddish-brown liquid. In solid anhydrous form the crystals are dark, greenish-black with a metallic sheen; the hydrated crystalline form is yellow to orange-brown. Ferrous chloride (FeCl₂) is visibly different — pale green — which is the quickest way to tell the two apart.
Is ferric chloride soluble in water?: Yes, highly soluble. It dissolves readily and the resulting solution is strongly acidic because FeCl₃ hydrolyses in water.
Does ferric chloride form a precipitate?: FeCl₃ itself dissolves rather than precipitating. What precipitates is iron(III) hydroxide, Fe(OH)₃ — the brown floc formed when FeCl₃ hydrolyses. That precipitate is precisely the mechanism that makes it useful as a coagulant.

Frequently asked questions

What is ferric chloride used for?: Mainly as a coagulant in drinking water and wastewater treatment, removing suspended solids, phosphorus and turbidity, and conditioning sludge. It is also used in etching and metal surface treatment.
Is iron chloride FeCl₂ or FeCl₃?: Both exist. FeCl₃ is ferric chloride, iron in the +3 state, and is the grade used for water treatment coagulation. FeCl₂ is ferrous chloride, +2. Different products, different applications, not interchangeable.
Why use FeCl₃ in water treatment?: It hydrolyses to iron hydroxide flocs that bind fine particles into settleable aggregates, works across a wide pH range, removes phosphorus, and improves sludge dewatering.

Our ferric chloride

For our ferric chloride specification, see CHIMIFLOC FR 4014. For pricing, delivery or technical support, request a quote and our technical team will respond.

CHIMIFLOC FR 4014 specification

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