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| Synonyms:Iron trichloride Ferric chloride anhydrous Ferric chloride hexahydrate Ferric chloride liquid solution Iron(3+) chloride Molecular Formula:FeCl3 Molecular Weight: 162.2 HS Code: 2827399090 Grade: Industrial grade40% 96% Hazard Class:8 | |||||||||
7705-08-0
bosschem
7705-08-0
Ferric chloride (iron(III) chloride; FeCl₃, CAS 7705-08-0) is one of the most important and widely used iron compounds. The anhydrous salt is a hygroscopic, dark green-black crystalline solid (appearing purple-red in transmitted light) that melts at 307.6 °C, while the hexahydrate (FeCl₃·6H₂O, CAS 10025-77-1) is a yellow, deliquescent solid that liquefies near 37 °C. Both forms dissolve readily in water — up to about 912 g/L at 25 °C — giving strongly acidic brown solutions. Chemically, ferric chloride combines Lewis acidity with mild oxidizing power, and this dual character drives its three major industrial roles: as the leading coagulant/flocculant for drinking water and wastewater treatment (its largest use), as the classic etchant for copper in printed-circuit-board manufacturing, and as a Lewis-acid catalyst in chlorination and organic synthesis. It also serves in hydrometallurgical leaching, analytical testing, and specialty chemical production. Supplied as anhydrous powder, hexahydrate crystals or liquid solution to match application and logistics.
Core value propositions:
● Water Treatment Workhorse (Largest Application): effective coagulant/flocculant for drinking water, sewage and industrial wastewater;
● Proven Copper Etchant: the standard chemistry for PCB and metal etching with clean, controllable results;
● Lewis Acid Catalyst: drives chlorination and electrophilic substitution reactions at industrial scale;
● Multi-Form Supply: anhydrous, hexahydrate and liquid grades to match your process.
Item | Specification |
Chemical Name | Iron(III) chloride (ferric chloride) |
Synonyms | Ferric chloride; iron trichloride; molysite; Flores martis |
CAS No. | 7705-08-0 (anhydrous); 10025-77-1 (hexahydrate) |
EC No. (EINECS) | 231-729-4 |
Molecular Formula | FeCl₃ (anhydrous); FeCl₃·6H₂O (hexahydrate) |
Molecular Weight | 162.20 g/mol (anhydrous); 270.30 g/mol (hexahydrate) |
Appearance | Anhydrous: dark green-black crystalline solid (purple-red in transmitted light); hexahydrate: yellow deliquescent solid; aqueous solution: brown |
Solubility | Highly soluble in water (≈ 912 g/L at 25 °C); soluble in acetone, ethanol, methanol and diethyl ether |
Assay | ≥ 96% (anhydrous, per COA); also supplied as 40% aqueous solution |
Ferric chloride is an ionic iron(III) halide in which iron carries the +3 oxidation state. The anhydrous solid adopts a layer-type structure (BiI₃ motif) built from octahedral Fe(III) centers bridged by chloride ions, and its vapor consists of the dimer Fe₂Cl₆, which dissociates to monomeric FeCl₃ at higher temperature. With five unpaired d-electrons (high-spin d⁵), all forms are strongly paramagnetic. The anhydrous compound is a hard Lewis acid — it accepts electron pairs from bases such as ethers, phosphine oxides and chloride, forming adducts and tetrachloroferrate salts — and a mild one-electron oxidant (Fe³⁺ → Fe²⁺). In water the salt hydrolyzes: the octahedral aquo complexes make the solution strongly acidic, and polymerization of the hydrolysis products generates the Fe-O-Fe networks and Fe(OH)₃/FeO(OH) (ferrihydrite) flocs that are the active species in water treatment. The hydrated form behaves as a Brønsted acid rather than a Lewis acid, and its affinity for oxygen donors underlies the classic ferric chloride colorimetric test for phenols.
●Leading coagulant/flocculant: forms heavy Fe(OH)3 flocs, which clarify the water and extract suspended solids.
● Phosphorus and odour control: Precipitate soluble phosphate and oxidise (deodorise) hydrogen sulphide.
●Standard copper etchant: For PCB and metal patterning – clean, well-controlled copper dissolution.
●Lewis acid catalyst. Allows chlorination and electrophilic aromatic substitution on industrial scale.
● Very high water solubility (≈912 g/L at 25 °C) and strongly acidic solutions to allow fast reaction kinetics.
● Dual Chemistry : Oxidising agent and acid catalyst in one versatile, low cost iron salt.
The largest application of ferric chloride is water treatment, where it acts as a coagulant and flocculant:
● Drinking water production: flocculation removes turbidity, color and suspended solids before filtration.
● Sewage and industrial wastewater treatment: separates suspended matter and clarifies effluent.
● Phosphorus removal: precipitates insoluble iron(III) phosphate, cutting nutrient loading.
● Odor control: oxidizes hydrogen sulfide in wastewater, reducing sulfide odors.
● Sludge conditioning: improves dewatering of treatment sludges.
Ferric chloride's oxidizing reaction with metals makes it the standard etchant for copper and other materials:
● PCB manufacture: removes copper foil by etching to leave circuit patterns (2 FeCl₃ + Cu → 2 FeCl₂ + CuCl₂)
● Metal etching and engraving: Patterning of metal surfaces for hobby and industrial use.
● Hydrometallurgy of chlorides: leaching agent for metal recovery (e.g. production of silicon from ferrosilicon).
● Metallography and restoration: etches iron meteorites and archaeological metal objects.
As a Lewis acid and oxidant, ferric chloride catalyzes and drives key industrial and laboratory reactions:
● Ethylene dichloride (EDC) production: catalyst for ethylene chlorination — the route to vinyl chloride/PVC.
● Chlorination and electrophilic aromatic substitution: Lewis-acid catalysis similar to aluminum chloride.
● Oxidative transformations: oxidizes naphthols to naphthoquinones and promotes C-C coupling.
● Supported reagents: FeCl₃ on silica gel or alumina for dehydration, rearrangement and ene reactions.
Long-established laboratory uses exploit the affinity of Fe(III) for oxygen donors and its color chemistry:
● Ferric chloride test: classic colorimetric detection of phenols.
● Trinder spot test and histology staining (e.g., Verhoeff elastic stain).
● General laboratory oxidant and chlorinating reagent.
Additional established uses:
● Oxidative polymerization of thiophenes to conductive polythiophenes.
● Feedstock for iron(III) salts, iron oxide pigments and specialty inorganics.
● Printmaking (intaglio etching) and metal-finishing formulations.
Packaging (customizable):
● 25 kg / 50 kg moisture-barrier drums or bags with PE liner ;
● 1,000 kg IBC totes or ISO tank for 40% liquid solution; small packs on request;
Storage:
● Store in a cool, dry, well-ventilated area; keep containers tightly closed.
● Protect from moisture and humidity (deliquescent salt); keep away from alkalis and oxidizable materials.
● Contain spills promptly — solutions are strongly acidic and corrosive to metals.
Handling & Safety (per SDS):
● Wear chemical goggles, acid-resistant gloves and protective clothing; use dust/acid-mist control;
● On skin/eye contact, rinse immediately with plenty of water and seek medical attention.
● Factory-direct supply: own production and sourcing capability, transparent pricing, no middleman markup.
● Stable quality: strict internal control; every batch tested (assay, iron content, appearance), COA with every shipment.
● Fast response: quotations and technical support (COA, SDS, application advice); small trial orders accepted.
Ferric chloride's largest use is water treatment: as a coagulant/flocculant it clarifies drinking water and wastewater, removes phosphorus, and controls sulfide odors. It is also the classic etchant for copper in printed circuit board production and metal etching, a Lewis-acid catalyst in chlorination and organic synthesis (including ethylene dichloride production for PVC), a leaching agent in hydrometallurgy, and a long-standing laboratory reagent for phenol testing.
Because it hydrolyzes in water to form positively charged iron hydroxide species that neutralize the negative charge on suspended particles, causing them to aggregate into settleable flocs. The resulting Fe(OH)₃/FeO(OH) floc enmeshes turbidity, color and colloids for easy removal by settling and filtration. In parallel, ferric ion precipitates soluble phosphate as insoluble iron(III) phosphate, and it oxidizes hydrogen sulfide — eliminating both nutrients and odors in one treatment step.
Ferric chloride oxidizes metallic copper to soluble copper(II) chloride while the iron is reduced to the ferrous state: 2 FeCl₃ + Cu → 2 FeCl₂ + CuCl₂. The copper(II) chloride dissolves and is rinsed away, leaving the protected copper pattern behind. This simple, well-controlled reaction is the basis of printed circuit board etching and of many metal-etching and engraving applications.
