Preparation of iron hydroxide (III) and its reaction with acid

A brown-red precipitate is reversibly formed.

Scientific name: Insoluble iron (III) hydroxide is formed when iron (III) chloride is treated with alkali. The acid turns the product to the initial salt dissolving the precipitate.


iron(III) hydroxide precipitate

Получение гидроксида железа III и взаимодействие его с кислотами

How to Make Iron Hydroxide

by Chemsitry Alchemist


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Reaction formula

FeCl3 + 3KOH → Fe(OH)3 + 3KCl

Fe(OH)3 + 3HCl → FeCl3 + 3H2O

Step-by-step instruction

  1. To obtain iron (III) hydroxide mix the solutions of iron (III) chloride and potassium hydroxide in a flask
  2. A red-brown precipitate is formed
  3. To test the action of an acid on iron (III) hydroxide put a few drops of hydrochloric acid solution to the flask. The solution become yellow and clear as it was at the beginning of the experiment.

Scientific background

Iron (III) chloride reacts with potassium hydroxide producing iron (III) hydroxide and potassium chloride. The exchange reaction between soluble salt and alkali is the common way to obtain insoluble hydroxides. The iron (III) chloride forms the red-brown precipitate. The addition of hydrochloric acid reverses the reaction turning iron (III) hydroxide back to iron (III) chloride. The precipitate dissolves.


Published on 09 September 2015

  • Fire
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  • Poisoned gas
  • Organic
  • Electricity
  • Solution
  • Oxidation reduction
  • Color change
  • Precipitate
  • Gassing
  • Catalyst