Ferric Chloride

Ferric chloride is an inorganic compound with formula FeCl3 which has numerous industrial, pharmaceutical and laboratorial uses. In this article we will discuss ferric chloride structure with its physical and chemical properties, ferric chloride test for phenols and applications in various fields. 

What is Ferric Chloride?

Ferric chloride is a common compound of iron and chlorine in which iron possesses +3 oxidation state. It’s IUPAC name is Iron(III) chloride or Iron trichloride. Apart from ferric chloride it has several common names such as molysite and flores martis. It possesses various colours such as in its anhydrous form it appears black-green or purple while in its hydrous form it appears yellow solid. 

It is a covalent compound although iron is a metal and chlorine is a non-metal. In  ferric chloride, iron gets partial positive charge and chlorine atoms get partial negative charge as chlorine is more electronegative than iron so it pulls a shared electron pair towards itself. 

Properties of Ferric Chloride 

Physical properties 

  • Its chemical formula is FeCl3.

  • Its molar mass is 162.2 g/mol (anhydrous).

  • It looks purple - red or green – black in its anhydrous form while yellow solid as hexahydrate. 

  • Its aqueous solution looks brown in color.

  • It has a faint HCl odor.

  • Its melting point is 307.6 in its anhydrous form. 

  • It shows 316 boiling point in its anhydrous form. 

  • It is highly soluble in methanol and diethyl ether. 

Chemical Properties 

Ferric chloride shows following chemical reactions –

  • Reaction with iron (III) oxide 

             FeCl3 + Fe2O3 🡪 3FeOCl 

  • Reaction with copper (I) chloride

             FeCl3 + CuCl 🡪 FeCl2 + CuCl2

  • Reaction with chlorobenzene to give ferrous chloride 

            2FeCl3 + C6H5Cl 🡪 2FeCl2 + C6H4Cl2 + HCl

  • Reaction with organometallic compound LiCH3 

           2FeCl3 + LiCH3 🡪 FeCl2 + LiFeCl4 + .CH3

Preparation of Ferric Chloride 

Anhydrous ferric chloride can be prepared by reaction of iron and chlorine. The reaction is given below –

2Fe(s) + 3Cl2(g) 🡪 2FeCl3(s)

Preparation of Aqueous Ferric Chloride –

Aqueous ferric chloride can be prepared by following three methods –

  • By dissolving iron ore in HCl 

            Fe3O4(s) + 8HCl(aq) 🡪 FeCl2(aq) + 2FeCl3(aq) + 4H2O(l)

  • By oxidation of ferrous chloride with chlorine 

            2FeCl2(aq) + Cl2(g) 🡪 2FeCl3(aq)

  • By oxidation of ferrous chloride with oxygen 

            4FeCl2(aq) + O2 + 4HCl 🡪 4FeCl3(aq) + 2H2O(l)

Ferric Chloride Test 

Ferric chloride test is performed to know the presence or absence of phenol in a sample. It is a traditional colorimetric test for phenols. It is performed by following steps –

  • Take 1% ferric chloride solution that has been neutralized with sodium hydroxide until a slight precipitate of FeO(OH) is formed. It is filtered before use.

  • The organic substance or sample is dissolved in water, methanol or ethanol in a test tube. 

  • Now the above taken neutralized ferric chloride solution is added in the test containing the solution of the sample. 

  • If transient or permanent purple, green or blue coloration occurs then it indicates the presence of phenol or enol group in the sample. 

Applications of Ferric Chloride  

Ferric chloride is used in various fields. Few of its uses are given below –

  • It is used in sewage treatment. 

  • It is used in production of printed circuit boards. 

  • It is used as a catalyst in many reactions. 

  • It is frequently used in laboratories. 

  • It is used for colorimetric tests for phenols.

  • It can also be used to test gamma-hydroxybutyric acid and gamma -butyrolactone. 

  • It is used as drying reagent in many reactions. 

  • It is used by bladesmiths and artisans in pattern welding.

  • It is used to strip aluminum coating from mirrors. 

  • It is used to etch intricate medical devices. 

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