Production of an aqueous solution of ferric chloride which can be produced in various concentrations and therefore subsequently used for different purposes. The ferric chloride solution is produced in an array of three reaction chambers. In the first chamber (C1) a mainly ferrous chloride containing solution reacts under a chlorine atmosphere with a heated solid iron surface to increase its concentration. A second chamber (C2) then neutralizes the pre-concentrated ferrous/ferric chloride solution, which contains small amounts of hydrochloric acid. The third and final reaction chamber (C3) ensures the transformation of ferrous-into ferric chloride solution by the reaction of ferrous chloride under a chlorine atmosphere until the product achieves the final quality of its desired application.