Abstract: The invention provides a process for the production of ferrous sulphate monohydrate which comprises: (a) reacting a source of iron with an aqueous solution of sulphuric acid in at least a first reaction vessel, to obtain a process liquor comprising ferrous sulphate and acid solution; and then (b) combining the process liquor with concentrated sulphuric acid in a mixing vessel, causing the solution to self crystallize, thus forming a slurry comprising crystalline ferrous sulfate monohydrate. The slurry can, if desired, then be converted to ferric sulphate.