[Dr.Jim]

[Unknown008]

Well, the simplest/cheapest thing I can think of is adding an excess of Fe2O3 (s) (powdered better because it's faster) to relatively concentrated HCl (aq).

Wait until there is no more reaction, then filter off the excess Fe2O3.



You since Fe2O3 is in excess, you don't have any HCl left.

Evaporate and heat to dryness over a bunsen flame.

[Dr.Jim]

Nice try, but no cigar. An aqueous solution of FeCl3 heated to dryness produces the hydrate. Further heating will decompose the hydrate back to Fe2O3 and HCl. Cannot get anhydrous FeCl3 by heating the hydrate.

[Unknown008]

Well, then do the direct reaction then:

React hot Fe with Cl2 (g).



Cl2 is also an oxidiser, so you'll get FeCl3 all right.

[Dr.Jim]

That's the only way!

[ajkoer]

Dissolve Iron in even dilute HClO (Hypochlorous acid).

My best guess on the reaction chain of Fe in HClO is as follows:

Fe + HClO --> FeO + HCl

HCl + HClO <--> Cl2 + H20

Hence, the observed chlorine creation. Continuing:

2 FeO + HClO + 3 H2O --> HCl + 2 Fe(OH)3

This is the oxidation of Ferrous Oxide mentioned in the Mellor (source cited below). Continuing with the hypothetical (but very temporary) creation of Iron Hypochlorite:

Fe(OH)3 + 3 HClO --> Fe(OCl)3 + 3 H20

And, the possible immediate reaction is Fe(OCl)3 oxidizing more iron and decomposing (which is similar to the bleaching ability of aluminum hypochlorite followed by its immediate decomposition and depositing of Al2O3 into the bleached fabric):

Fe(OCl)3 + 2 Fe --> Fe2O3 + FeCl3

Thus, FeCl3 (reddish brown solution) is formed without the benefit (or danger) of concentrated HCl or a high temperature reaction involving Cl2 gas (also hazardous).

Source: "A comprehensive treatise on inorganic and theoretical chemistry, Volume 2 By Joseph William Mellor, page 275. Quote: "Iron filings immediately decompose hypochlorous acid with a brisk effervescence produced by the evolution of chlorine; the iron is partly oxidized and in part dissolved as chloride without the formation of any chlorate."

[Dr.Jim]

Sorry! Anhydrous means "not a water solution". A water solution is easy. Just dissolve Fe metal in 6M hydrochloric acid. The only way is by direct oxidation. Fe metal + Cl2 gas. This was a question on a Ph.D. inorganic exam.

[ajkoer]

To make the anhydrous, add ethanol (FeCl3 dissolves in ethanol) and filter out the Fe2O3. This should prevent the formation of the hydrated salt. Let evaporate.