How dangerous is ferric chloride

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

The term iron chloride also includes the compound iron (II) chloride (FeCl2).

Extraction and presentation

Anhydrous iron (III) chloride is obtained in the laboratory by passing chlorine at temperatures of 250 ° C to 400 ° C over iron wire, wool or the like. The product is then sublimed for cleaning in a stream of chlorine at 220 ° C to a maximum of 300 ° C. It is important to ensure that both the equipment used and the chemicals are as free of water as possible.

The iron chloride containing water of crystallization can also be obtained by dissolving iron powder in hydrochloric acid

and the subsequent introduction of chlorine can be produced, with the initially formed iron (II) chloride being converted into iron (III) chloride:

This can then be obtained by evaporating the solution.

For technical production, chlorine is passed over scrap iron at around 650 ° C.

Anhydrous iron (III) chloride is stored under protective gas (e.g. nitrogen) in the absence of air to protect it from water.


Anhydrous iron (III) chloride is a black substance with a slightly pungent odor of hydrochloric acid. As an anhydrous compound, it is extremely hygroscopic, i.e. it attracts water in the air. With increasing water content, the hygroscopic nature decreases and the color changes from red-brownish to yellowish, iron (III) chloride hexahydrate (FeCl3 · 6 H.2O). This reacts strongly acidic through hydrolysis.

Iron (III) chloride is a predominantly covalent compound with a layered structure. Above the sublimation point, it is mainly in the form of gaseous Fe2Cl6 before, the increasing temperature to FeCl3 dissociated. Anhydrous ferric chloride behaves chemically in a similar way to anhydrous aluminum chloride. Just like this, it is a moderately strong Lewis acid.


Iron (III) chloride is used to bind hydrogen sulfide, for phosphate precipitation and generally as a flocculant in biological wastewater treatment. By adding potassium hexacyanoferrate (II), the color Prussian blue can be produced (see below). As a solution with water, it is used in textile printing as an oxidizing agent and stain, in medicine as a hemostatic agent (hemostyptic or astringent, no longer available in Germany), for etching metals (e.g. in copper gravure printing) and circuit boards printed circuits and in the manufacture of dyes (aniline black). In the chemical industry it is used as a selective catalyst in many Friedel-Crafts reactions. Iron (III) chloride is still a precipitant in simultaneous precipitation. Furthermore, most phenols are detected with iron (III) chloride.

safety instructions

Iron (III) chloride is harmful if swallowed and irritates the skin. There is a risk of serious damage to eyes. In connection with alkali metals there is a risk of explosion.


The LD50 in rats it is 450 mg kg after oral administration−1.


about Fe3+-Ions

If you add potassium hexacyanoferrate (II) to iron (III) chloride solution, a deep blue precipitate of the pigment Berlin blue is produced:


Another very sensitive detection is done using thiocyanate ions (SCN-):


The complex pentaaquathiocyanato iron (III) ions formed appear intensely red.

Another proof would be the red-brown precipitate that is formed when reacting with OH ions.


  1. abcdefG BGIA-Gstis hazardous substance database


  • Gerhart Jander, Ewald Blasius et al .: Introduction to the inorganic-chemical internship. 14. re-edit Ed. Hirzel, Stuttgart, 1995. ISBN 3777606723
  • Michael Binnewies, Manfred Jäckel et al .: General and Inorganic Chemistry. Spectrum Academic Publishing House, 2003. ISBN 3827402085
  • ChemDAT® Germany - The Merck Chemistry Databases

Categories: Harmful Substance | Iron compound | chloride