Iron(III) chloride

  • Ferric chloride
  • Ferric chloride
  • Eisensesquichlorid
  • 7705-08-0 (anhydrous)
  • 10025-77-1 (hexahydrate )
  • Anhydrous: dark, hexagonal, green in the plan, red in the review papers
  • Hexahydrate: dirty yellow, deliquescent crystalline pieces


2.90 g · cm -3

304 ° C

319 ° C, from 120 ° C sublimation

1 hPa (20 ° C)

  • In water: 920 g · l-1 (20 ° C)
  • Well in ethanol, acetone and diethyl ether


Template: Infobox chemical / molecular formula search is not possible

Iron (III ) chloride is a chemical compound of iron ( III) - and chloride ions. The Roman numeral III is the oxidation number of the iron ion (in this case, 3). Iron (III ) chloride belongs to the group of iron halides.

Under the name of ferric chloride and the compound precipitated iron (II ) chloride ( FeCl2 ).

  • 6.1 on Fe3 ions


In nature, iron exists (III ) chloride in the form of minerals Molysit (anhydrous ) and Hydromolysit (hexahydrate ) ago.

Production and representation

Of anhydrous iron ( III) chloride obtained in the laboratory by at temperatures of 250 to 400 ° C over iron wire -wool or the like chlorine passes. Then the product for cleaning in a current of chlorine at 220 is sublimated to a maximum of 300 ° C. It is important to ensure that equipment and chemicals are substantially water -free.

Crystal water -containing ferric chloride can also be prepared by dissolving iron powder in hydrochloric acid

And subsequent introduction of chlorine are produced, the first resulting iron (II ) chloride goes into iron ( III) chloride:

This can then be recovered by evaporation of the solution.

The technical production, chlorine is introduced at about 650 ° C for iron scrap.

Anhydrous iron (III ) chloride ( eg, nitrogen) mount for protection against water under inert gas or air.


Anhydrous iron (III ) chloride is a black, slightly pungent smelling of hydrochloric acid substance. When anhydrous compound is extremely hygroscopic, so cut off the air water. With increasing water content, the hygroscopic nature decreases and the color changed to red - brownish to yellowish, it creates iron (III ) chloride hexahydrate ( FeCl 3 · 6H 2 O ). This reacts by hydrolysis strongly acidic. On heating the hydrate decomposes with elimination of water and hydrogen chloride; So it is not possible in this way to obtain therefrom anhydrous iron (III ) chloride again. However, water- free iron (III ) chloride hexahydrate that is available on, when it is placed under a protective gas atmosphere with an excess of thionyl chloride ( 10 eq.). The resulting gases are overcooked and by introducing into a chilled sodium hydroxide solution ( ca. 0.5 - 1.0 M) neutralized.

Iron (III ) chloride is a compound having a layer structure mainly covalent. Above the sublimation point it is present mainly as gaseous Fe2Cl6 which dissociates with increasing temperature increasing to FeCl3. Anhydrous iron (III ) chloride behaves chemically similar to anhydrous aluminum chloride. Just like this, it is a moderately strong Lewis acid.

Iron (III ) chloride is formed with iron ( II) chloride in a 297.5 ° C melting eutectic with 13.4 mol% of iron (II ) chloride.


Iron (III ) chloride can oxidize and remove the copper; Therefore, one can use aqueous iron ( III) chloride solutions for careful etching of printed circuit boards:

Iron (III ) chloride is also used for binding hydrogen sulphide, and as a precipitating agent for phosphate precipitation in the simultaneous precipitation and generally in biological waste water treatment as a flocculant. In the chemical industry, it is used as a selectively acting catalytic converter in many Friedel -Crafts reactions. Many phenols arise with iron ( III ) chloride green or blue colored complexes and can thus be detected. By the addition of potassium hexacyanoferrate (II ), the Prussian blue pigment can be produced (see below).

In aqueous solution, it is used in textile printing as an oxidizing agent and dye mordant, in medicine for intravenous replacement in severe deficiency states, and as a styptic ( haemostatic and astringent, in Germany no longer commercially available ) for corrosion tests (according to ASTM G48A ) and for etching metals ( for example, in gravure printing ) and printed circuit boards for printed circuits, and in the production of dyes ( for example, aniline black ).


Iron (III ) chloride is harmful if swallowed and irritating to the skin. There is a danger of serious damage to eyes. In conjunction with alkali metals, allyl chloride and ethylene oxide may explode.


The LD50 in rats for oral administration is 450 mg · kg -1.


On Fe3 ions

Is added to iron (III ) chloride solution of potassium hexacyanoferrate (II ), produces a deep blue precipitate the pigment Prussian blue:

Another very sensitive detection is done by means of thiocyanate ions ( SCN ):

The complex formed Pentaaquathiocyanatoeisen (III ) ions appear intensely red.

Further evidence would be the red - brown precipitate of iron ( III ) oxide hydrate ( " iron (III ) hydroxide "), which upon reaction with OH - ions produced.