Iron(III) chloride is a yellow solid. It dissolves in water to make a colloid of iron(III) oxide, making the water look muddy. When it is dissolved in an acidic solution, it is bright yellow. When it is very concentrated in a solution, it is dark brown. It is corrosive to skin and metals. It reacts with iron to produce iron(II) chloride. It fumes hydrochloric acid in moist air. It is a weak oxidizing agent. It reacts with copper(I) chloride to make copper(II) chloride. It breaks down when heated to make chlorine and iron(II) chloride.
It can be made by mixing hydrochloric acid and iron(III) oxide. It can be made by mixing iron and chlorine. It can also be made by reacting iron(II) chloride with chlorine at a low temperature.
It is used in sewage processing. It reacts with slightly basic water to make a "floc" that can remove things from the water. It used to react with copper in circuit boards; iron(III) nitrate is sometimes used too. It is used as a catalyst in making plastics. It is used in certain tests as a reagent.