A green-gray precipitate is reversibly formed.
name: Insoluble iron (II) hydroxide is formed when iron (II) sulfate is treated with alkali. The acid dissolves the precipitate.
Iron (II) sulfate reacts with potassium hydroxide producing iron (II) hydroxide and potassium sulfate. The exchange reaction between soluble salt and alkali is the common way to obtain insoluble hydroxides. The iron (II) sulfate under the action of alkali forms a green-gray precipitate. The addition of hydrochloric acid dissolves the precipitate turning iron (II) hydroxide back to iron (II) chloride.