Ferric Chloride - FeCl3

What is Ferric Chloride?

Ferric Chloride is a chemical compound where the oxidation state of iron is +3. It is also called Iron (III) chloride or Molysite. It is an iron coordination entity which functions as an astringent and Lewis acid. The chemical formula of Ferric Chloride is FeCl3.

Molysite solution is colourless to light brown in colour and has a faint hydrochloric acid (HCl) smell. It is corrosive to most metals and tissues. It is non-combustible and is widely used in water purification and sewage treatment.

In its anhydrous form, it is deliquescent. Also, partial hydrolysis takes place as it absorbs water from the air and liberates hydrogen chloride (HCl) that forms mists in moist air. It is a strong Lewis acid.

Properties of Ferric Chloride – FeCl3

Ferric Chloride FeCl3
Molecular Weight of Ferric Chloride 162.204 g/mol (anhydrous)
Density of Ferric Chloride 2.90 g/cm3 (anhydrous)
Melting Point of Ferric Chloride 307.6 °C
Boiling Point of Ferric Chloride 316 °C

Structure of Ferric Chloride (FeCl3)

Uses of Ferric Chloride (FeCl3)

  • Ferric Chloride is used in organic synthesis as a catalyst.
  • It is used to treat overcropping of animal claws especially when the overcropping leads to bleeding.
  • It is used as drying reagent in some reactions in its anhydrous form.
  • It has wide applications in energy storage systems.

Production of Ferric Chloride

Anhydrous Iron (III) chloride is prepared as follows:

Ferric Chloride solution preparation

    • By dissolving iron ore in HCl (hydrochloric acid)

    • By oxidizing iron (II) chloride with chlorine (Cl)

    • By oxidizing iron (II) chloride with oxygen

Ferric chloride test

This test is conducted to determine the presence or absence of phenol in a given sample. Compounds such as enols, hydroxamic acids, sulfinic acids, and oximes give positive results. The quantity of phenol in the sample can be measured by Folin-Ciocalteau assay.

Step 1: Dissolve the sample in water plus ethanol.

Step 2: Add drops of a dilute solution of ferric chloride (FeCl3).

Step 3: If the sample turns to red, green, purple, or blue colouration then it indicates the presence of phenols.

Step 4: In case the sample is insoluble in water, it can be dissolved in dichloromethane (CH2Cl2) with a small quantity of pyridine (C5H5N).