Difference between revisions of "Iron(III) chloride"

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[[Category:Iron compounds]]
 
[[Category:Iron compounds]]
 
[[Category:Chlorides]]
 
[[Category:Chlorides]]
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[[Category:Lewis acids]]
 
[[Category:PCB etchants]]
 
[[Category:PCB etchants]]
 
[[Category:Irritants]]
 
[[Category:Irritants]]
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[[Category:Readily available chemicals]]

Revision as of 15:24, 26 July 2017

Iron(III) chloride
Iron(III) chloride hexahydrate.jpg
Hydrated crystals of ferric chloride.
Names
IUPAC name
Iron(III) chloride
Other names
Ferric chloride
Flores martis
Iron trichloride
Molysite
Properties
FeCl3
Molar mass 162.204 g/mol (anhydrous)
270.295 g/mol (hexahydrate)
Appearance Black hygroscopic solid (anhydrous)
Yellow hygroscopic solid (hydrated)
Odor Slight acidic
Density 2.90 g/cm3 (anhydrous)
1.82 g/cm3 (hexahydrate)
Melting point 307.6 °C (585.7 °F; 580.8 K) (anhydrous)
37 °C (99 °F; 310 K) (hexahydrate)
Boiling point 316 °C (601 °F; 589 K) (anhydrous, decomposes)
280 °C (536 °F; 553 K) (hexahydrate, decomposes)
91.2 g/100 ml (anh. or hexahydrate, 25 °C)
Hazards
Safety data sheet Sigma-Aldrich (anhydrous)
Sigma-Aldrich (hexahydrate)
Flash point Non-flammable
Related compounds
Related compounds
Iron(II) chloride
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
Infobox references

Iron(III) chloride, also known as ferric chloride, is a compound of iron and chlorine with the formula FeCl3. It is a moderately strong Lewis acid and many of its applications exploit this property. It normally exists as a hexahydrate salt. When heated or anhydrous, it tends to hydrolyze, producing hydrogen chloride gas. It is a popular catalyst for organic synthesis, and the most common printed circuit board etchant (though there are better ones).

Properties

Physical properties

Iron(III) chloride is a yellow solid as the common hexahydrate form, but undergoes many different color changes when the anhydrous form is viewed under different light sources at different angles. Aqueous solutions tend to be dark brown in color. The material resembles aluminum chloride due to its covalent character, and has a narrow liquid range when anhydrous, ranging from only 306 to 315 °C, and dimerizes as a vapor.  

Chemical properties

As a strong Lewis acid, iron(III) chloride is corrosive and readily forms adducts with Lewis bases, such as triphenylphosphine oxide. It will also dissolve in methanol and ethanol quite readily. It is also highly soluble in acetone. Strong heating will convert the hexahydrate form, or the anhydrous form in the presence of water, to iron(III) oxychloride and hydrogen chloride, and the anhydrous form to iron(II) chloride and chlorine gas. It is a mild oxidizing agent. It is capable of reacting with copper yielding copper(II) chloride and ferrous chloride.

Iron(III) chloride hydrates cannot be dehydrated to anhydrous, because it decomposes to iron(III) oxychloride and hydrogen chloride, or iron hydroxide and hydrogen chloride.

When solutions of iron(III) chloride are presented with metallic iron, they are slowly reduced back to iron(II) chloride, which can be reverted back to iron(III) chloride by the addition of more hydrochloric acid and oxygen or hydrogen peroxide.

Iron (III) chloride produces colorful insoluble compounds with several common reagents. These reactions can be used to determine the presence of trivalent iron; they can also be used to produce pigments and inks.

Availability

Iron(III) chloride is a popular printed circuit board (PCB) etchant. It is available as a solution at many electronics store, such as RadioShack.

Preparation

Iron (III) chloride hydrate may be produced by adding steel wool (which is relatively pure iron) to a mixture of hydrogen peroxide and hydrochloric acid, and then filtering off the carbon. Boiling the solution al low pH will yield hydrated crystals of ferric chloride.[1] Anhydrous iron (III) chloride can be produced by combining pure iron metal to dry chlorine gas at high temperature.

Solutions of green iron(II) chloride slowly oxidize in air or on heating to form iron(III) chloride, provided there are excess chloride ions in solution. This is a somewhat reversible reaction, as the addition of more iron to ferric chloride solutions reverts it back to iron(II) chloride.

Projects

  • Detecting phenol compounds
  • Etch PCBs
  • Separate gold from electronic fingers and pins
  • Etching widmanstätten patterns into meteorites
  • Making iron complexes
  • Producing ferrocene
  • Producing ferrofluid[2]

Handling

Safety

Iron(III) chloride is corrosive and will stain many surfaces dark brown. If it touches the skin, it will turn it brown-yellowish and may cause burns if the pH is low enough. It is also extremely irritant to sensitive tissues.

Storage

Ferric chloride should be stored in closed plastic or glass bottles, at a low pH.

Disposal

Ferric chloride can be neutralized with calcium hydroxide. This yields calcium chloride and iron oxide/hydroxide, which can be safely disposed of.

References

  1. https://www.youtube.com/watch?v=43Xsh9J7S-g
  2. https://www.youtube.com/watch?v=LlQw9dfexBQ

Relevant Sciencemadness threads