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.
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.
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.
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
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 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.
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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